| Common Name | Scientific Name | Code |
|---|
| n/a | ?Solidaster H. R. Wehrh. | SOLID2 |
| n/a | ?Solidaster luteus (Everett) M. L. Green ex Dress | SOLU10 |
| n/a | Achillea aegyptiaca L. | ACAE2 |
| n/a | Achillea biserrata M. Bieb. | ACBI6 |
| n/a | Achillea cartilaginea Ledeb. ex Rchb. | ACCA29 |
| n/a | Achillea chrysocoma Friv. | ACCH6 |
| n/a | Achillea clavennae L. | ACCL3 |
| n/a | Achillea clusiana Tausch | ACCL4 |
| n/a | Achillea clypeolata Sm. | ACCL5 |
| n/a | Achillea collina Becker ex Rchb. | ACCO19 |
| n/a | Achillea conferta DC. | ACCO20 |
| n/a | Achillea crithmifolia Waldst. & Kit. | ACCR3 |
| n/a | Achillea distans Waldst. & Kit. ex Willd. ssp. tanacetifolia Janch. | ACDIT |
| n/a | Achillea erba-rotta All. | ACER7 |
| n/a | Achillea erba-rotta All. ssp. rupestris (Porta) I. Richardson | ACERR |
| n/a | Achillea grandifolia Friv. | ACGR12 |
| n/a | Achillea impatiens L. | ACIM6 |
| n/a | Achillea lingulata Waldst. & Kit. | ACLI7 |
| n/a | Achillea macrocephala Rupr. | ACMA15 |
| n/a | Achillea macrophylla L. | ACMA13 |
| n/a | Achillea odorata L. | ACOD2 |
| n/a | Achillea pannonica Scheele | ACPA11 |
| n/a | Achillea pyrenaica Sibth. ex Godr. | ACPY5 |
| n/a | Achillea setacea Waldst. & Kit. | ACSE10 |
| n/a | Achillea umbellata Sm. | ACUM |
| n/a | Acmella uliginosa (Sw.) Cass. [excluded] | ACUL |
| n/a | Adenostemma berteroi DC. [excluded] | ADBE3 |
| n/a | Adenostemma lanceolatum Miq. | ADLA4 |
| n/a | Ageratum domingense Spreng. [excluded] | AGDO3 |
| n/a | Agnorhiza (Jepson) W.A. Weber | AGNOR |
| n/a | Ambrosia ?helenae Rouleau [artemisiifolia ? trifida] | AMHE3 |
| n/a | Ambrosia ?intergradiens Wagner [artemisiifolia ? psilostachya] | AMIN |
| n/a | Anisocarpus Nutt. | ANISO5 |
| n/a | Antennaria ?foliacea Greene (pro sp.) [microphylla ? racemosa] | ANFO |
| n/a | Antennaria ?macounii Greene (pro sp.) [media ? umbrinella] | ANMA6 |
| n/a | Antennaria ?oblancifolia E. Nels. (pro sp.) [racemosa ? umbrinella] | ANOB3 |
| n/a | Antennaria caucasica Boriss. | ANCA39 |
| n/a | Antennaria chilensis Remy | ANCH11 |
| n/a | Argyroxiphium ?kai (Forbes) Keck [caliginis ? grayanum] | ARKA |
| n/a | Arnica alpina (L.) Olin [excluded] | ARAL29 |
| n/a | Artemisia argentea L'Her. | ARAR25 |
| n/a | Artemisia aucheri Boiss. | ARAU6 |
| n/a | Artemisia campestris L. ssp. glutinosa (J. Gay ex Besser) Batt. | ARCAG2 |
| n/a | Artemisia caucasica Willd. | ARCA44 |
| n/a | Artemisia chamaemelifolia Vill. | ARCH15 |
| n/a | Artemisia gorgonum Webb | ARGO4 |
| n/a | Artemisia krushiana Bess [excluded] | ARKR2 |
| n/a | Artemisia norvegica Fries [excluded] | ARNO7 |
| n/a | Artemisia rupestris L. ssp. rupestris L. [excluded] | ARRUR3 |
| n/a | Artemisia rupestris L. [excluded] | ARRU14 |
| n/a | Artemisia thuscula Cav. | ARTH5 |
| n/a | Aster alpinus L. var. serpentimontanus (Tamamsch.) Ling | ASALS3 |
| n/a | Aster amellus L. ssp. ibericus (Steven) V. E. Avet. | ASAMI |
| n/a | Aster bietii Franch. | ASBI12 |
| n/a | Aster brachytrichus Franch. | ASBR17 |
| n/a | Aster caucasicus Willd. | ASCA42 |
| n/a | Aster diplostephioides (DC.) C. B. Clarke | ASDI13 |
| n/a | Aster farreri W. W. Sm. & Jeffrey | ASFA6 |
| n/a | Aster flaccidus Bunge | ASFL6 |
| n/a | Aster flaccidus Bunge var. flaccidus | ASFLF2 |
| n/a | Aster glehnii F. Schmidt | ASGL12 |
| n/a | Aster himalaicus C. B. Clarke | ASHI6 |
| n/a | Aster maackii Regel | ASMA21 |
| n/a | Aster oreophilus Franch. | ASOR7 |
| n/a | Aster pyrenaeus Desf. ex DC. | ASPY3 |
| n/a | Aster sedifolius L. | ASSE16 |
| n/a | Aster sedifolius L. ssp. dracunculoides (Lam.) Merxm. | ASSED |
| n/a | Aster thomsonii C. B. Clarke | ASTH3 |
| n/a | Aster tongolensis Franch. | ASTO8 |
| n/a | Aster yunnanensis Franch. | ASYU3 |
| n/a | Baccharis concava (Ruiz & Pav.) Pers. | BACO9 |
| n/a | Balsamorhiza ?bonseri St. John (pro sp.) [rosea ? sagittata] | BABO |
| n/a | Balsamorhiza ?terebinthacea (Hook.) Nutt. (pro sp.) [deltoidea ? hookeri] | BATE3 |
| n/a | Balsamorhiza ?tomentosa Rydb. (pro sp.) [incana ? sagittata] | BATO2 |
| n/a | Berlandiera ?humilis Small (pro sp.) [pumila ? subacaulis] | BEHU |
| n/a | Berlandiera pumila (Michx.) Nutt. var. scabrella Nesom & B.L. Turner | BEPUS |
| n/a | Bidens ?multiceps Fassett [connata ? eatonii] | BIMU |
| n/a | Bidens bigelovii Gray var. angustiloba (DC.) Ballard ex T.E. Melchert | BIBIA |
| n/a | Bidens squarrosa Kunth [excluded] | BISQ2 |
| n/a | Boltonia lautureana Debeaux | BOLA5 |
| n/a | Bombycilaena DC. | BOMBY |
| n/a | Borrichia ?cubana Britt. & Blake (pro sp.) [arborescens ? frutescens] | BOCU2 |
| n/a | Bracteantha A. Anderb. & Heagi | BRACT |
| n/a | Brickellia diffusa (Vahl) Gray [excluded] | BRDI61 |
| n/a | Carduus ?orthocephalus Wallr. [acanthoides ? nutans] | CAOR8 |
| n/a | Carlquistia B.G. Baldwin | CARLQ |
| n/a | Catananche caerulea L. | CACA94 |
| n/a | Catananche L. | CATAN |
| n/a | Celmisia spectabilis Hook. f. | CESP8 |
| n/a | Centaurea ?pouzinii DC. [aspera ? calcitrapa] | CEPO8 |
| n/a | Centaurea orientalis L. | CEOR8 |
| n/a | Centaurea ovina Pallas ex Willd. ssp. besseriana (DC.) Dost?l [excluded] | CEOVB2 |
| n/a | Centaurea ovina Pallas ex Willd. [excluded] | CEOV3 |
| n/a | Centromadia Greene | CENTR8 |
| n/a | Chorisiva Rydb. | CHORI5 |
| n/a | Chrysanthellum americanum (L.) Vatke [excluded] | CHAM8 |
| n/a | Chrysanthellum Rich. | CHRYS17 |
| n/a | Chrysogonum virginianum L. var. brevistolon Nesom | CHVIB2 |
| n/a | Cineraria multiflora L'Herit. | CIMU3 |
| n/a | Cirsium ?canalense Petrak [excluded] | CICA22 |
| n/a | Cirsium ?crassum Petrak [excluded] | CICR4 |
| n/a | Cirsium ?iowense (Pammel) Fern. (pro sp.) [altissimum ? discolor] | CIIO2 |
| n/a | Cirsium ochrocentrum Gray ssp. martinii P. Barlow | CIOCM |
| n/a | Cirsium validus Greene [excluded] | CIVA5 |
| n/a | Clibadium surinamense L. [excluded] | CLSU21 |
| n/a | Constancea B.G. Baldwin | CONST |
| n/a | Coreopsis grandiflora Hogg ex Sweet var. inclinata J. Allison | COGRI |
| n/a | Crassocephalum vitellinum (Benth.) S. Moore | CRVI15 |
| n/a | Crepis foetida L. var. rhoeadifolia (Bieb.) Celak. | CRFOR |
| n/a | Crepis kotschyana Boiss. | CRKO2 |
| n/a | Crepis paludosa (L.) Moench | CRPA23 |
| n/a | Crupina vulgaris Cass. var. brachypappa Beauv. | CRVUB |
| n/a | Cyclachaena Fresen. | CYCLA4 |
| n/a | Deinandra Greene | DEINA2 |
| n/a | Dendranthema indicum (L.) Des Moulins [excluded] | DEIN61 |
| n/a | Doellingeria scabra (Thunb.) Nees | DOSC |
| n/a | Doronicum austriacum Jacq. | DOAU2 |
| n/a | Dubautia ?demissifolia (Sherff) Keck (pro sp.) [menziesii ? reticulata] | DUDE |
| n/a | Dubautia ?fallax Sherff [plantaginea ? scabra] | DUFA2 |
| n/a | Dubautia ?media Sherff [laevigata ? laxa] | DUME |
| n/a | Dubautia ?molokaiensis (Hbd.) Keck (pro sp.) [linearis ? scabra] | DUMO |
| n/a | Dubautia ?montana (Mann) Keck (pro sp.) [arborea ? linearis] | DUMO2 |
| n/a | Dubautia ?thyrsiflora (Sherff) Keck (pro sp.) [dolosa ? scabra] | DUTH |
| n/a | Echinops bannaticus Rochel ex Schrad. | ECBA5 |
| n/a | Elephantopus angustifolius Sw. [excluded] | ELAN5 |
| n/a | Elephantopus scaber L. [excluded] | ELSC10 |
| n/a | Encelia resinifera C. Clark ssp. tenuifolia C. Clark | ENRET |
| n/a | Epaltes australis Less. | EPAU2 |
| n/a | Epaltes Cass. | EPALT |
| n/a | Ericameria ?bolanderi (Gray) Nesom & Baird [discoidea ? nauseosa] | ERBO9 |
| n/a | Ericameria ?uintahensis (L.C. Anders.) Nesom & Baird [nauseosa ? parryi] | ERUI2 |
| n/a | Ericameria ?viscosa (Keck) Nesom & Baird [cuneata ? nauseosa] | ERVI21 |
| n/a | Erigeron acris L. ssp. decoloratus (H. Lindb.) Hiitonen | ERACD3 |
| n/a | Erigeron acris L. ssp. droebachiensis (O. F. Mull.) Arcang. | ERACD4 |
| n/a | Erigeron alpinus L. | ERAL20 |
| n/a | Erigeron alpinus L. ssp. intermedius (Schleich.) Pawl. | ERALI2 |
| n/a | Erigeron atticus Vill. | ERAT8 |
| n/a | Erigeron candidus Widder | ERCA36 |
| n/a | Erigeron caucasicus Steven | ERCA40 |
| n/a | Erigeron caucasicus Steven ssp. venustus (Botsch.) Grierson | ERCAV |
| n/a | Erigeron clokeyi Cronquist var. pinzliae G.L. Nesom | ERCLP |
| n/a | Erigeron gaudinii Brugger | ERGA4 |
| n/a | Erigeron glabratus Hoppe & Hornsch. ex Bluff & Fingerh. | ERGL10 |
| n/a | Erigeron myosotis Pers. | ERMY2 |
| n/a | Erigeron naudinii (Bonnet) Humbert | ERNA9 |
| n/a | Erigeron orientalis Boiss. | EROR8 |
| n/a | Erigeron polymorphus Scop. | ERPO12 |
| n/a | Erigeron roylei DC. | ERRO12 |
| n/a | Erigeron strigosus Muhl. ex Willd. var. calcicola J. Allison | ERSTC2 |
| n/a | Erigeron strigosus Muhl. ex Willd. var. dolomiticolor J. Allison | ERSTD3 |
| n/a | Erigeron thunbergii Gray | ERTH5 |
| n/a | Erigeron thunbergii Gray ssp. glabratus Gray | ERTHG3 |
| n/a | Espeletia Mutis ex Bonpl. | ESPEL |
| n/a | Espeletia schultzii Wedd. | ESSC |
| n/a | Eupatoriadelphus King & H.E. Robins. | EUPAT3 |
| n/a | Eupatorium ?pinnatifidum Ell. [capillifolium ? perfoliatum] | EUPI3 |
| n/a | Eupatorium ?truncatum Muhl. ex Willd. (pro sp.) [perfoliatum ? serotinum] | EUTR5 |
| n/a | Eupatorium sordidum Less. [excluded] | EUSO3 |
| n/a | Eurybia ?herveyi (Gray) Nesom [macrophylla ? spectabilis] | EUHE9 |
| n/a | Felicia amoena (Sch. Bip.) Levyns | FEAM2 |
| n/a | Felicia Cass. | FELIC |
| n/a | Felicia fruticosa (L.) G. Nicholson | FEFR3 |
| n/a | Felicia uliginosa (J. M. Wood & M. S. Evans) Grau | FEUL |
| n/a | Filifolium Kitam. | FILIF |
| n/a | Filifolium sibiricum (L.) Kitam. | FISI4 |
| n/a | Gaillardia ?grandiflora Van Houtte [aristata ? pulchella] | GAGR11 |
| n/a | Galatella Cass. | GALAT |
| n/a | Galatella punctata (Waldst. & Kit.) Nees | GAPU9 |
| n/a | Glebionis Cass. | GLEBI |
| n/a | Glossogyne Cass. | GLOSS3 |
| n/a | Glossogyne tenuifolia Cass. ex. Less. | GLTE6 |
| n/a | Harmonia B.G. Baldwin | HARMO |
| n/a | Hedosyne Strother | HEDOS |
| n/a | Helenium ?polyphyllum Small (pro sp.) [autumnale ? flexuosum] | HEPO2 |
| n/a | Helenium apterum (Blake) Bierner [excluded] | HEAP4 |
| n/a | Helenium lanciniatum Gray [excluded] | HELA26 |
| n/a | Helianthus ?ambiguus (Gray) Britt. (pro sp.) [divaricatus ? giganteus] | HEAM7 |
| n/a | Helianthus ?brevifolius E.E. Wats. (pro sp.) [grosseserratus ? mollis] | HEBR5 |
| n/a | Helianthus ?cinereus Torr. & Gray (pro sp.) [mollis ? occidentalis] | HECI3 |
| n/a | Helianthus ?divariserratus R.W. Long [divaricatus ? grosseserratus] | HEDI5 |
| n/a | Helianthus ?doronicoides Lam. (pro sp.) [giganteus ? mollis] | HEDO |
| n/a | Helianthus ?glaucus Small (pro sp.) [divaricatus ? microcephalus] | HEGL10 |
| n/a | Helianthus ?intermedius R.W. Long [grosseserratus ? maximiliani] | HEIN2 |
| n/a | Helianthus ?kellermanii Britt. (pro sp.) [grosseserratus ? salicifolius] | HEKE2 |
| n/a | Helianthus ?luxurians E.E. Wats. (pro sp.) [giganteus ? grosseserratus] | HELU4 |
| n/a | Helianthus ?orgyaloides Cockerell (pro sp.) [maximiliani ? salicifolius] | HEOR |
| n/a | Helianthus ?verticillatus E.E. Wats. (pro sp.) [angustifolius ? grosseserratus] | HEVE3 |
| n/a | Heliomeris multiflora Nutt. var. macrocephala Heiser | HEMUM2 |
| n/a | Hemizonella (Gray) Gray | HEMIZ2 |
| n/a | Hertia cheirifolia Kuntze | HECH4 |
| n/a | Hertia Neck. | HERTI |
| n/a | Heteropappus altaicus (Willd.) Novopokr. | HEAL15 |
| n/a | Heteropappus Less. | HETER21 |
| n/a | Hieracium ?alleghaniense Britt. (pro sp.) [gronovii ? paniculatum] | HIAL4 |
| n/a | Hieracium ?atramentarium (Naegeli & Peter) Zahn ex Engl. (pro sp.) [aurantiacum ? piloselloides] | HIAT |
| n/a | Hieracium ?brachiatum Berth. ex DC. [pilosella ? piloselloides] | HIBR3 |
| n/a | Hieracium ?fassettii Lepage var. fassettii | HIFAF |
| n/a | Hieracium ?fassettii Lepage var. mendicum Lepage (pro nm.) | HIFAM |
| n/a | Hieracium ?fassettii Lepage var. wisconsinense Lepage (pro nm.) | HIFAW |
| n/a | Hieracium ?fassettii Lepage [kalmii ? scabrum] | HIFA2 |
| n/a | Hieracium ?fernaldii Lepage [canadense ? scabrum] | HIFE2 |
| n/a | Hieracium ?flagellare Willd. (pro sp.) var. cernuiforme (Naegeli & Peter) Lepage (pro nm.) | HIFLC |
| n/a | Hieracium ?flagellare Willd. (pro sp.) var. flagellare | HIFLF |
| n/a | Hieracium ?flagellare Willd. (pro sp.) var. glatzense (Naegeli & Peter) Lepage [excluded] | HIFLG3 |
| n/a | Hieracium ?flagellare Willd. (pro sp.) [caespitosum ? pilosella] | HIFL2 |
| n/a | Hieracium ?floribundum Wimmer & Grab. (pro sp.) [caespitosum ? lactucella] | HIFL3 |
| n/a | Hieracium ?fuscatrum Naegeli & Peter (pro sp.) [aurantiacum ? caespitosum] | HIFU2 |
| n/a | Hieracium ?grohii Lepage var. farwellii Lepage | HIGRF2 |
| n/a | Hieracium ?grohii Lepage var. grohii | HIGRG2 |
| n/a | Hieracium ?grohii Lepage [canadense ? lachenalii] | HIGR7 |
| n/a | Hieracium kalmii L. var. subintegrum (Lepage) Lepage | HIKAS2 |
| n/a | Hieracium scouleri Hook. var. albertinum (Farr) G.W. Douglas & G.A. Allen | HISCA |
| n/a | Hulteniella Tzvelev | HULTE |
| n/a | Hymenopappus flavomarginatus I.M.Johnst. [excluded] | HYFL7 |
| n/a | Hymenoxys ambigens (Blake) Bierner var. neomexicana W.L. Wagner | HYAMN |
| n/a | Isocoma veneta (Kunth) Greene [excluded] | ISVE5 |
| n/a | Iva ambrosiifolia (Gray) Gray ssp. lobata (Rydb.) R.C. Jackson [excluded] | IVAML2 |
| n/a | Jensia B.G. Baldwin | JENSI |
| n/a | Kalimeris mongolica (Franch.) Kitam. | KAMO |
| n/a | Keysseria Lauterb. | KEYSS2 |
| n/a | Kleinia anteuphorbium (L.) Haw. | KLAN |
| n/a | Kleinia P. Mill. | KLEIN2 |
| n/a | Kyhosia B.G. Baldwin | KYHOS |
| n/a | Lactuca ?morssii B.L. Robins. (pro sp.) [biennis ? canadensis] | LAMO4 |
| n/a | Launaea cornuta (Hochst. ex Oliv. & Hiern) C. Jeffrey | LACO14 |
| n/a | Leucanthemum ?superbum (Bergmans ex J.W. Ingram) Berg. ex Kent. [maximum ? lacustre] | LESU49 |
| n/a | Leuciva Rydb. | LEUCI |
| n/a | Liatris ?boykinii Torr. & Gray (pro sp.) [elegans ? tenuifolia] | LIBO7 |
| n/a | Liatris ?fallacior (Lunell) Rydb. (pro sp.) [ligulistylis ? punctata] | LIFA |
| n/a | Liatris ?freemaniana J. Allison [cylindracea ? oligocephala] | LIFR6 |
| n/a | Liatris ?frostii Gaiser [aspera ? pycnostachya] | LIFR |
| n/a | Liatris ?gladewitzii (Farw.) Farw. ex Shinners [cylindracea ? spheroidea] | LIGL3 |
| n/a | Liatris ?macdanieliana J. Allison [cylindracea ? squarrosa] | LIMA19 |
| n/a | Liatris ?ridgwayi Standl. [pycnostachya ? squarrosa] | LIRI2 |
| n/a | Liatris ?steelei Gaiser [aspera ? spicata] | LIST6 |
| n/a | Liatris ?weaveri Shinners [aspera ? punctata] | LIWE2 |
| n/a | Liatris aestivalis Nesom & R. O'Kennon | LIAE3 |
| n/a | Liatris gholsonii L.C. Anderson | LIGH |
| n/a | Ligularia Cass. | LIGUL |
| n/a | Lipochaeta ?procumbens O. Deg. & Sherff [integrifolia ? lobata] | LIPR4 |
| n/a | Machaeranthera asteroides (Torr.) Greene var. glandulosa B.L. Turner | MAASG |
| n/a | Machaeranthera asteroides (Torr.) Greene var. lagunensis (Keck) B.L. Turner | MAASL |
| n/a | Malacothrix insularis Greene [excluded] | MAIN20 |
| n/a | Malacothrix polycephala W.S. Davis, sp. nov. ined. [excluded] | MAPO17 |
| n/a | Malacothrix xanthii Gray [excluded] | MAXA |
| n/a | Micropus dasycarpa (Griseb.) Beauv. [excluded] | MIDA3 |
| n/a | Nipponanthemum (Kitam.) Kitam. | NIPPO |
| n/a | Oclemena ?blakei (Porter) Nesom [acuminata ? nemoralis] | OCBL |
| n/a | Oligoneuron ?bernardii (Boivin) Nesom [album ? riddellii] | OLBE |
| n/a | Oligoneuron ?krotkovii (Boivin) Nesom [album ? ohioensis] | OLKR |
| n/a | Oligoneuron ?lutescens (Lindl. ex DC.) Nesom [album ? rigidum] | OLLU |
| n/a | Osteospermum muricatum E. Mey. ex DC. | OSMU2 |
| n/a | Osteospermum sinuatum (DC.) Norl. [excluded] | OSSI2 |
| n/a | Osteospermum spinescens Thunb. | OSSP2 |
| n/a | Oxytenia Nutt. | OXYTE3 |
| n/a | Palafoxia linearis (Cav.) Lag. [excluded] | PALI15 |
| n/a | Pectis ?floridana Keil [glaucescens ? prostrata] | PEFL14 |
| n/a | Pectis coulteri Harvey & Gray [excluded] | PECO39 |
| n/a | Pentzia lanata Hutch. | PELA25 |
| n/a | Pentzia sphaerocephala DC. | PESP10 |
| n/a | Perezia Lagasca | PEREZ2 |
| n/a | Perezia multiflora (Humb. & Bonpl.) Less. | PEMU16 |
| n/a | Perezia multiflora (Humb. & Bonpl.) Less. ssp. sonchifolia (Baker) Vuilleum | PEMUS2 |
| n/a | Perityle californica Benth. [excluded] | PECA38 |
| n/a | Petasites frigidus (L.) Fries var. vitifolius (Greene) Cherniawsky | PEFRV |
| n/a | Phymaspermum Less. | PHYMA2 |
| n/a | Phymaspermum parvifolium (DC.) Benth. & Hook. f. | PHPA22 |
| n/a | Picris hieracioides L. ssp. hieracioides var. alpina Koidzumi [excluded] | PIHIA2 |
| n/a | Plateilema (Gray) Cockerell | PLATE |
| n/a | Plateilema palmeri (Gray) Cockerell | PLPA9 |
| n/a | Pleiacanthus Rydb. | PLEIA |
| n/a | Pleurocoronis laphamioides (Rose) King & H.E. Robins. [excluded] | PLLA14 |
| n/a | Pluchea salicifolia (P. Mill.) S.F. Blake [excluded] | PLSA12 |
| n/a | Podocoma Cass. | PODOC3 |
| n/a | Podocoma hieracifolia (Poir.) Cass. [excluded] | POHI15 |
| n/a | Prenanthes ?mainensis Gray (pro sp.) [racemosa ? trifoliolata] | PRMA8 |
| n/a | Psathyrotopsis Rydb. | PSATH3 |
| n/a | Pseudognaphalium brachypterum (DC.) A. Anderb. [excluded] | PSBR11 |
| n/a | Rhodanthe chlorocephala (Turcz.) P. Wilson ssp. rosea (Hook.) P. Wilson | RHCHR |
| n/a | Rhodanthe Lindl. | RHODA |
| n/a | Rudbeckia laciniata L. var. heterophylla (Torr. & Gray) Fern. & Schub. | RULAH3 |
| n/a | Santolina neapolitana Jord. & Fourr. | SANE9 |
| n/a | Santolina rosmarinifolia L. | SARO13 |
| n/a | Sartwellia gypsophila Powell & B.L. Turner [excluded] | SAGY2 |
| n/a | Saussurea ?tschuktschorum Lipsch. (pro sp.) [angustifolia ? nuda] | SATS |
| n/a | Saussurea alpina (L.) DC. [excluded] | SAAL22 |
| n/a | Saussurea tilesii (Ledeb.) Ledeb. [excluded] | SATI4 |
| n/a | Scabrethia W.A. Weber | SCABR |
| n/a | Senecio aquaticus Hill ssp. barbareifolius (Wimmer & Grab.) S.M. Walters | SEAQB |
| n/a | Senecio grandifolius Less. | SEGR11 |
| n/a | Senecio integrifolius (L.) Clairv. | SEIN6 |
| n/a | Senecio murrayi Bornm. | SEMU10 |
| n/a | Senecio palmensis C. Sm. | SEPA9 |
| n/a | Senecio webbii (Sch. Bip.) H. Christ | SEWE7 |
| n/a | Sigesbeckia jorullensis Kunth [excluded] | SIJO2 |
| n/a | Silybum eburneum Coss. & Durieu | SIEB2 |
| n/a | Solidago ?asperula Desf. (pro sp.) [rugosa ? sempervirens] | SOAS2 |
| n/a | Solidago ?beaudryi Boivin [rugosa ? uliginosa] | SOBE |
| n/a | Solidago ?erskinei Boivin [canadensis ? sempervirens] | SOER3 |
| n/a | Solidago ?ovata Friesner (pro sp.) [sphacelata ? ulmifolia] | SOOV |
| n/a | Solidago ?ulmicaesia Friesner [caesia ? ulmifolia] | SOUL4 |
| n/a | Sonchus asper (L.) Hill ssp. glaucescens (Jord.) J. Ball [excluded] | SOASG2 |
| n/a | Symphyotrichum ?amethystinum (Nutt.) Nesom [ericoides ? novae-angliae] | SYAM3 |
| n/a | Symphyotrichum ?batesii (Rydb.) Nesom [ericoides ? oblongifolium] | SYBA |
| n/a | Symphyotrichum ?columbianum (Piper) Nesom [campestre ? ericoides] | SYCO2 |
| n/a | Symphyotrichum ?finkii (Rydb.) Nesom (pro sp.) [cordifolium ? shortii] | SYFI4 |
| n/a | Symphyotrichum ?gravesii (Burgess) Nesom [dumosum ? laeve] | SYGR6 |
| n/a | Symphyotrichum ?longulum (Sheldon) Nesom [boreale ? puniceum] | SYLO4 |
| n/a | Symphyotrichum ?salignum (Willd.) Nesom [excluded] | SYSA8 |
| n/a | Symphyotrichum ?schistosum (Steele) Nesom [cordifolium ? laeve] | SYSC2 |
| n/a | Symphyotrichum ?versicolor (Willd.) Nesom [excluded] | SYVE2 |
| n/a | Symphyotrichum ?woldenii (Rydb.) Nesom [laeve ? praealtum] | SYWO3 |
| n/a | Symphyotrichum vahlii (Gaudich.) G. L. Nesom | SYVA3 |
| n/a | Symphyotrichum vahlii (Gaudich.) G. L. Nesom var. vahlii | SYVAV |
| n/a | Tephroseris atropurpurea (Ledeb.) Holub ssp. frigida (Richards.) A.& D. L?ve | TEATF2 |
| n/a | Tragopogon ?crantzii Dichlt. [dubius ? pratensis] | TRCR10 |
| n/a | Tragopogon ?neohybridus Farw. [porrifolius ? pratensis] | TRNE7 |
| n/a | Tragopogon pratensis pratensis ssp. orientalis (L.) Celak. [excluded] | TRPRO2 |
| n/a | Verbesina hastata Kellogg ex Curran [excluded] | VEHA6 |
| n/a | Vernonia ?concinna Gleason (pro sp.) [angustifolia ? gigantea] | VECO2 |
| n/a | Vernonia ?dissimilis Gleason (pro sp.) [angustifolia ? glauca] | VEDI3 |
| n/a | Vernonia ?georgiana Bartlett (pro sp.) [acaulis ? angustifolia] | VEGE |
| n/a | Vernonia ?guadalupensis Heller (pro sp.) [baldwinii ? lindheimeri] | VEGU |
| n/a | Vernonia ?illinoensis Gleason [gigantea ? missurica] | VEIL3 |
| n/a | Vernonia ?peralta Daniels [baldwinii ? missurica] | VEPE5 |
| n/a | Vernonia ?vulturina Shinners (pro sp.) [baldwinii ? marginata] | VEVU |
| n/a | Vesicarpa Rydb. | VESIC2 |
| n/a | Viguiera deltoidea Gray [excluded] | VIDE6 |
| n/a | Wollastonia biflora (l.) Dc. | WOBI |
| n/a | Wollastonia DC. ex Decaisne | WOLLA |
| n/a | Wyethia ?cusickii Piper (pro sp.) [amplexicaulis ? helianthoides] | WYCU |
| n/a | Wyethia ?magna A. Nels. (pro sp.) [amplexicaulis ? arizonica] | WYMA |
| n/a | Xanthium ambrosioides Hook. & Arn. [excluded] | XAAM5 |
| 'ena'ena | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. | PSSA8 |
| 'ena'ena | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. var. hawaiiense (O. Deg. & Sherff) W.L. Wagner | PSSAH2 |
| 'ena'ena | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. var. kilaueanum (O. Deg. & Sherff) W.L. Wagner | PSSAK2 |
| 'ena'ena | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. var. molokaiense (O. Deg. & Sherff) W.L. Wagner | PSSAM2 |
| 'ena'ena | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. var. sandwicensium | PSSAS4 |
| ?Solidaster luteus | Aster hybridus hort. var. luteus hort. | ASHYL |
| Abajo fleabane | Erigeron abajoensis Cronq. | ERAB3 |
| absinthium | Artemisia absinthium L. | ARAB3 |
| Acamptopappus sphaerocephalus var. sphaerocephalus | Aplopappus sphaerocephalus Harvey & Gray ex Gray | APSP2 |
| Acanthospermum australe | Acanthospermum xanthioides DC. | ACXA |
| Acanthospermum australe | Melampodium australe Loefl. | MEAU |
| Acanthospermum humile | Melampodium humile Sw. | MEHU5 |
| Acevedo's velvetshrub | Piptocoma acevedoi Pruski | PIAC6 |
| achicoria azul | Launaea intybacea (Jacq.) Beauv. | LAIN7 |
| Achillea aegyptiaca | Achillea taygetea Boiss. & Heldr. | ACTA3 |
| Achillea distans | Achillea dentifera DC. | ACDE10 |
| Achillea distans ssp. tanacetifolia | Achillea tanacetifolia All. | ACTA2 |
| Achillea erba-rotta ssp. rupestris | Achillea rupestris Porta | ACRU13 |
| Achillea macrocephala | Achillea ptarmica L. ssp. macrocephala (Rupr.) Heimerl | ACPTM |
| Achillea millefolium | Achillea magna auct. | ACMA14 |
| Achillea millefolium var. alpicola | Achillea alpicola (Rydb.) Rydb. | ACAL11 |
| Achillea millefolium var. alpicola | Achillea fusca Rydb. | ACFU |
| Achillea millefolium var. alpicola | Achillea lanulosa Nutt. ssp. alpicola (Rydb.) Keck | ACLAA |
| Achillea millefolium var. alpicola | Achillea lanulosa Nutt. var. alpicola Rydb. | ACLAA2 |
| Achillea millefolium var. alpicola | Achillea millefolium L. var. fusca (Rydb.) G.N. Jones | ACMIF |
| Achillea millefolium var. alpicola | Achillea subalpina Greene | ACSU3 |
| Achillea millefolium var. arenicola | Achillea arenicola Heller | ACAR6 |
| Achillea millefolium var. arenicola | Achillea borealis Bong. ssp. arenicola (Heller) Keck | ACBOA |
| Achillea millefolium var. arenicola | Achillea borealis Bong. var. arenicola (Heller) J.T. Howell | ACBOA2 |
| Achillea millefolium var. arenicola | Achillea millefolium L. var. maritima Jepson | ACMIM4 |
| Achillea millefolium var. borealis | Achillea borealis Bong. | ACBO |
| Achillea millefolium var. borealis | Achillea borealis Bong. ssp. typica Keck | ACBOT |
| Achillea millefolium var. borealis | Achillea millefolium L. ssp. atrotegula Boivin | ACMIA3 |
| Achillea millefolium var. borealis | Achillea millefolium L. ssp. borealis (Bong.) Breitung | ACMIB2 |
| Achillea millefolium var. borealis | Achillea millefolium L. var. fulva Boivin | ACMIF2 |
| Achillea millefolium var. borealis | Achillea millefolium L. var. parviligula Boivin | ACMIP3 |
| Achillea millefolium var. borealis | Achillea millefolium L. var. parvula Boivin | ACMIP4 |
| Achillea millefolium var. californica | Achillea borealis Bong. ssp. californica (Pollard) Keck | ACBOC |
| Achillea millefolium var. californica | Achillea borealis Bong. var. californica (Pollard) J.T. Howell | ACBOC2 |
| Achillea millefolium var. californica | Achillea californica Pollard | ACCA7 |
| Achillea millefolium var. gigantea | Achillea gigantea Pollard | ACGI2 |
| Achillea millefolium var. nigrescens | Achillea nigrescens (E. Mey.) Rydb. | ACNI4 |
| Achillea millefolium var. occidentalis | Achillea angustissima Rydb. | ACAN7 |
| Achillea millefolium var. occidentalis | Achillea aspleniifolia auct. non Vent. [misapplied] | ACAS2 |
| Achillea millefolium var. occidentalis | Achillea eradiata Piper | ACER2 |
| Achillea millefolium var. occidentalis | Achillea gracilis Raf. | ACGR5 |
| Achillea millefolium var. occidentalis | Achillea lanulosa Nutt. | ACLA5 |
| Achillea millefolium var. occidentalis | Achillea lanulosa Nutt. ssp. typica Keck | ACLAT |
| Achillea millefolium var. occidentalis | Achillea lanulosa Nutt. var. arachnoidea Lunell | ACLAA3 |
| Achillea millefolium var. occidentalis | Achillea lanulosa Nutt. var. eradiata (Piper) M.E. Peck | ACLAE |
| Achillea millefolium var. occidentalis | Achillea laxiflora Pollard & Cockerell | ACLA3 |
| Achillea millefolium var. occidentalis | Achillea millefolium L. ssp. lanulosa (Nutt.) Piper | ACMIL |
| Achillea millefolium var. occidentalis | Achillea millefolium L. ssp. occidentalis (DC.) Hyl. | ACMIO2 |
| Achillea millefolium var. occidentalis | Achillea millefolium L. ssp. pallidotegula Boivin | ACMIP5 |
| Achillea millefolium var. occidentalis | Achillea millefolium L. var. aspleniifolia (Vent.) Farw. | ACMIA4 |
| Achillea millefolium var. occidentalis | Achillea millefolium L. var. gracilis Raf. ex DC. | ACMIG2 |
| Achillea millefolium var. occidentalis | Achillea millefolium L. var. lanulosa (Nutt.) Piper | ACMIL3 |
| Achillea millefolium var. occidentalis | Achillea millefolium L. var. rosea (Desf.) Torr. & Gray | ACMIR |
| Achillea millefolium var. occidentalis | Achillea millefolium L. var. russeolata Boivin | ACMIR2 |
| Achillea millefolium var. occidentalis | Achillea occidentalis (DC.) Raf. ex Rydb. | ACOC |
| Achillea millefolium var. occidentalis | Achillea rosea Desf. | ACRO4 |
| Achillea millefolium var. occidentalis | Achillea tomentosa Pursh, non L. | ACTO3 |
| Achillea millefolium var. pacifica | Achillea pacifica Rydb. | ACPA5 |
| Achillea millefolium var. puberula | Achillea puberula Rydb. | ACPU2 |
| Achillea sibirica | Achillea multiflora Hook. | ACMU3 |
| Acmella decumbens | Spilanthes americana (Mutis ex L. f.) Hieron. var. stolonifera (DC.) A.H. Moore | SPAMS |
| Acmella decumbens | Spilanthes stolonifera DC. | SPST4 |
| Acmella iodiscaea | Spilanthes iodiscaea A.H. Moore | SPIO |
| Acmella oppositifolia var. repens | Acmella repens (Walt.) L.C. Rich. | ACRE6 |
| Acmella oppositifolia var. repens | Spilanthes americana (Mutis ex L. f.) Hieron. var. repens (Walt.) A.H. Moore | SPAMR3 |
| Acmella oppositifolia var. repens | Spilanthes americana auct. p.p., non Hieron. | SPAM3 |
| Acmella pusilla | Spilanthes pusilla Hook. & Arn. | SPPU5 |
| Acmella uliginosa | Spilanthes uliginosa Sw. [excluded] | SPUL3 |
| Acourtia microcephala | Perezia microcephala (DC.) Gray | PEMI11 |
| Acourtia nana | Perezia nana Gray | PENA5 |
| Acourtia runcinata | Perezia runcinata (Lag. ex D. Don) Lag. ex Gray | PERU7 |
| Acourtia thurberi | Perezia thurberi Gray | PETH6 |
| Acourtia wrightii | Perezia wrightii Gray | PEWR4 |
| Acroptilon repens | Centaurea picris Pallas ex Willd. | CEPI3 |
| Acroptilon repens | Centaurea repens L. | CERE6 |
| Acton's brittlebush | Encelia actonii Elmer | ENAC |
| Adenophyllum cooperi | Dyssodia cooperi Gray | DYCO2 |
| Adenophyllum porophylloides | Dyssodia porophylloides Gray | DYPO |
| Adenophyllum porophyllum | Dyssodia porophylla (Cav.) Cav. | DYPO3 |
| Adenophyllum porophyllum | Pteronia porophylla Cav. | PTPO2 |
| Adenophyllum wrightii | Dyssodia neomexicana (Gray) B.L. Robins. | DYNE |
| Adenophyllum wrightii | Hymenatherum neomexicanum Gray | HYNE2 |
| Adenostemma lavenia | Adenostemma viscosum J.R. & G. Forst. | ADVI2 |
| Adenostemma lavenia | Verbesina lavenia L. | VELA4 |
| Adenostemma verbesina | Cotula verbesina L. | COVE7 |
| African bonebract | Sclerocarpus africanus Jacq. | SCAF |
| African daisy | Arctotis stoechadifolia Berg. | ARST2 |
| African sheepbush | Pentzia incana (Thunb.) Kuntze | PEIN4 |
| Ageratina adenophora | Eupatorium adenophorum Spreng. | EUAD2 |
| Ageratina adenophora | Eupatorium glandulosum Kunth, non Michx. | EUGL8 |
| Ageratina altissima var. altissima | Ageratum altissimum L., non Eupatorium altissimum L. | AGAL9 |
| Ageratina altissima var. altissima | Eupatorium rugosum Houtt. | EURU6 |
| Ageratina altissima var. altissima | Eupatorium rugosum Houtt. var. chlorolepis Fern. | EURUC |
| Ageratina altissima var. altissima | Eupatorium rugosum Houtt. var. tomentellum (B.L. Robins.) Blake | EURUT |
| Ageratina altissima var. altissima | Eupatorium rugosum Houtt. var. villicaule (Fern.) Blake | EURUV |
| Ageratina altissima var. altissima | Eupatorium urticifolium Reichard var. tomentellum B.L. Robins. | EUURT |
| Ageratina altissima var. angustata | Eupatorium rugosum Houtt. var. angustata (Gray) Blake | EURUA |
| Ageratina altissima var. roanensis | Eupatorium roanense Small | EURO8 |
| Ageratina altissima var. roanensis | Eupatorium rugosum Houtt. var. roanense (Small) Fern. | EURUR |
| Ageratina altissima var. roanensis | Eupatorium urticifolium Reichard | EUUR4 |
| Ageratina aromatica var. aromatica | Eupatorium aromaticum L. | EUAR7 |
| Ageratina aromatica var. aromatica | Eupatorium latidens Small | EULA11 |
| Ageratina aromatica var. incisa | Eupatorium aromaticum L. var. incisum Gray | EUARI3 |
| Ageratina havanensis | Eupatorium havanense Kunth | EUHA5 |
| Ageratina havanensis | Eupatorium texense (Torr. & Gray) Rydb. | EUTE9 |
| Ageratina herbacea | Eupatorium herbaceum (Gray) Greene | EUHE7 |
| Ageratina jucunda | Eupatorium juncundum Greene | EUJU |
| Ageratina lemmonii | Eupatorium lemmonii B.L. Robins. | EULE7 |
| Ageratina luciae-brauniae | Eupatorium luciae-brauniae Fern. | EULU3 |
| Ageratina occidentalis | Eupatorium occidentale Hook. | EUOC5 |
| Ageratina paupercula | Eupatorium pauperculum Gray | EUPA10 |
| Ageratina resiniflua | Eupatorium resinifluum Urban | EURE11 |
| Ageratina riparia | Eupatorium riparium Regel | EURI4 |
| Ageratina rothrockii | Eupatorium rothrockii Gray | EURO9 |
| Ageratina shastensis | Eupatorium shastense Taylor & Stebbins | EUSH |
| Ageratina wrightii | Eupatorium wrightii Gray | EUWR3 |
| Ageratum corymbosum | Ageratum guatemalense M.F. Johnson | AGGU |
| Agnorhiza bolanderi | Balsamorhiza bolanderi Gray | BABO3 |
| Agnorhiza bolanderi | Wyethia bolanderi (Gray) W.A. Weber | WYBO |
| Agnorhiza elata | Wyethia elata Hall | WYEL |
| Agnorhiza invenusta | Wyethia invenusta (Greene) W.A. Weber | WYIN |
| Agnorhiza ovata | Wyethia ovata Torr. & Gray ex Torr. | WYOV |
| Agnorhiza reticulata | Wyethia reticulata Greene | WYRE |
| agoseris | Agoseris Raf. | AGOSE |
| Agoseris apargioides var. apargioides | Agoseris hirsuta (Hook.) Greene | AGHI4 |
| Agoseris apargioides var. apargioides | Troximon apargioides Less. | TRAP2 |
| Agoseris apargioides var. eastwoodiae | Agoseris eastwoodiae Fedde | AGEA |
| Agoseris apargioides var. maritima | Agoseris apargioides (Less.) Greene ssp. maritima (Sheldon) Q. Jones | AGAPM2 |
| Agoseris apargioides var. maritima | Agoseris maritima Sheldon | AGMA4 |
| Agoseris aurantiaca var. aurantiaca | Agoseris graminifolia Greene | AGGR7 |
| Agoseris aurantiaca var. aurantiaca | Agoseris rostrata Rydb. | AGRO2 |
| Agoseris aurantiaca var. aurantiaca | Troximon aurantiacum Hook. | TRAU8 |
| Agoseris aurantiaca var. purpurea | Agoseris aurantiaca (Hook.) Greene ssp. purpurea (Gray) G.W. Douglas | AGAUP2 |
| Agoseris elata | Stylopappus elatus Nutt. | STEL4 |
| Agoseris glauca var. agrestis | Agoseris agrestis Osterhout | AGAG |
| Agoseris glauca var. dasycephala | Agoseris glauca (Pursh) Raf. ssp. scorzonerifolia (Schrad.) Piper | AGGLS |
| Agoseris glauca var. dasycephala | Agoseris glauca (Pursh) Raf. var. asper (Rydb.) Cronq. | AGGLA2 |
| Agoseris glauca var. dasycephala | Agoseris glauca (Pursh) Raf. var. pumila (Nutt.) Garrett | AGGLP2 |
| Agoseris glauca var. dasycephala | Agoseris scorzonerifolia (Schrad.) Greene | AGSC7 |
| Agoseris glauca var. dasycephala | Troximon glaucum Pursh var. dasycephalum Torr. & Gray | TRGLD |
| Agoseris glauca var. glauca | Agoseris turbinata Rydb. | AGTU3 |
| Agoseris glauca var. glauca | Troximon glaucum Pursh | TRGL7 |
| Agoseris glauca var. laciniata | Agoseris arizonica Greene | AGAR5 |
| Agoseris glauca var. laciniata | Agoseris glauca (Pursh) Raf. var. parviflora (Nutt.) Rydb. | AGGLP |
| Agoseris glauca var. laciniata | Agoseris parviflora (Nutt.) Greene | AGPA14 |
| Agoseris glauca var. laciniata | Macrorhynchus glaucus (Pursh) D.C. Eat. var. laciniatus D.C. Eat. | MAGLL |
| Agoseris glauca var. laciniata | Troximon parviflorum Nutt. | TRPA12 |
| Agoseris glauca var. monticola | Agoseris monticola Greene | AGMO5 |
| Agoseris grandiflora | Agoseris laciniata (Nutt.) Greene | AGLA6 |
| Agoseris grandiflora | Agoseris plebeja (Greene) Greene | AGPL3 |
| Agoseris grandiflora | Troximon grandiflorum Nutt. | TRGR13 |
| Agoseris heterophylla var. heterophylla | Agoseris heterophylla (Nutt.) Greene ssp. californica (Nutt.) Piper | AGHEC2 |
| Agoseris heterophylla var. heterophylla | Agoseris heterophylla (Nutt.) Greene ssp. normalis Piper | AGHEN |
| Agoseris heterophylla var. heterophylla | Agoseris heterophylla (Nutt.) Greene var. cryptopleura Jepson | AGHEC3 |
| Agoseris heterophylla var. heterophylla | Agoseris heterophylla (Nutt.) Greene var. kymapleura Greene | AGHEK |
| Agoseris heterophylla var. heterophylla | Macrorhynchus heterophyllus Nutt. | MAHE4 |
| Agoseris retrorsa | Macrorhynchus retrorsus Benth. | MARE7 |
| Ajo rockdaisy | Perityle ajoensis T.K. Todsen | PEAJ |
| Alabama blazing star | Liatris squarrosa (L.) Michx. var. alabamensis (Alexander) Gaiser | LISQA |
| Alabama warbonnet | Jamesianthus alabamensis Blake & Sherff | JAAL |
| Alakai Swamp island-daisy | Keysseria erici (Forbes) Cabrera | KEER |
| Alameda County thistle | Cirsium quercetorum (Gray) Jepson | CIQU2 |
| Alaska arnica | Arnica unalaschcensis Less. | ARUN |
| Alaska hawkweed | Hieracium gracile Hook. var. alaskanum Zahn | HIGRA |
| Alaska wormwood | Artemisia alaskana Rydb. | ARAL5 |
| Albert's creeping zinnia | Sanvitalia abertii Gray | SAAB |
| alcove rockdaisy | Perityle specuicola Welsh & Neese | PESP5 |
| Aleutian ragwort | Senecio cannabifolius Less. | SECA7 |
| Aleutian wormwood | Artemisia aleutica Hult | ARAL6 |
| Alexander's rock aster | Eurybia avita (Alexander) Nesom | EUAV |
| Algodones sunflower | Helianthus niveus (Benth.) Brandeg. ssp. tephrodes (Gray) Heiser | HENIT |
| Alice Eastwood's fleabane | Erigeron aliceae T.J. Howell | ERAL3 |
| alkali goldenbush | Isocoma acradenia (Greene) Greene | ISAC2 |
| alkali goldenbush | Isocoma acradenia (Greene) Greene var. acradenia | ISACA2 |
| alkali goldenbush | Isocoma acradenia (Greene) Greene var. bracteosa (Greene) Nesom | ISACB |
| alkali goldenbush | Isocoma acradenia (Greene) Greene var. eremophila (Greene) Nesom | ISACE2 |
| alkali goldfields | Lasthenia platycarpha (Gray) Greene | LAPL2 |
| alkali marsh aster | Almutaster A.& D. L?ve | ALMUT2 |
| alkali marsh aster | Almutaster pauciflorus (Nutt.) A.& D. L?ve | ALPA14 |
| alkali sunflower | Helianthus laciniatus Gray | HELA8 |
| alkali yellowtops | Flaveria campestris J.R. Johnston | FLCA |
| alkalisink goldfields | Lasthenia chrysantha (Greene ex Gray) Greene | LACH2 |
| Allegheny hawkweed | Hieracium paniculatum L. | HIPA2 |
| Almutaster pauciflorus | Aster hydrophilus Greene ex Woot. & Standl. | ASHY6 |
| Almutaster pauciflorus | Aster pauciflorus Nutt. | ASPA8 |
| alpine arctic cudweed | Omalotheca supina (L.) DC. | OMSU |
| alpine aster | Aster alpinus L. | ASAL3 |
| alpine aster | Aster alpinus L. var. alpinus | ASALA12 |
| alpine dustymaiden | Chaenactis douglasii (Hook.) Hook. & Arn. var. alpina Gray | CHDOA2 |
| alpine false goldenaster | Heterotheca pumila (Greene) Semple | HEPU14 |
| alpine feverfew | Parthenium alpinum (Nutt.) Torr. & Gray | PAAL6 |
| alpine groundsel | Packera pauciflora (Pursh) A.& D. L?ve | PAPA19 |
| alpine hymenopappus | Hymenopappus filifolius Hook. var. nudipes (Maguire) B.L. Turner | HYFIN2 |
| alpine knapweed | Centaurea transalpina Schleich. ex DC. | CETR6 |
| alpine lake prairie-dandelion | Nothocalais alpestris (Gray) Chambers | NOAL2 |
| alpine leafybract aster | Symphyotrichum foliaceum (Lindl. ex DC.) Nesom | SYFO2 |
| alpine leafybract aster | Symphyotrichum foliaceum (Lindl. ex DC.) Nesom var. apricum (Gray) Nesom | SYFOA |
| alpine leafybract aster | Symphyotrichum foliaceum (Lindl. ex DC.) Nesom var. foliaceum | SYFOF |
| alpine pussytoes | Antennaria alpina (L.) Gaertn. | ANAL4 |
| alpine rattlesnakeroot | Prenanthes boottii (DC.) Gray | PRBO2 |
| alpine sagebrush | Artemisia scopulorum Gray | ARSC |
| alpine serpentweed | Tonestus alpinus (L.C. Anders. & Goodrich) Nesom & D. Morgan | TOAL2 |
| alpine tetramolopium | Tetramolopium humile (Gray) Hbd. | TEHU |
| alpine tetramolopium | Tetramolopium humile (Gray) Hbd. ssp. humile | TEHUH2 |
| alpine tetramolopium | Tetramolopium humile (Gray) Hbd. ssp. humile var. humile | TEHUH3 |
| alpine tetramolopium | Tetramolopium humile (Gray) Hbd. ssp. humile var. sublaeve Sherff | TEHUS2 |
| alpine yellow fleabane | Erigeron aureus Greene | ERAU |
| alpine yellow fleabane | Erigeron aureus Greene var. aureus | ERAUA3 |
| alpineflames | Pyrrocoma apargioides (Gray) Greene | PYAP2 |
| alpinegold | Hulsea Torr. & Gray | HULSE |
| Alps wormwood | Artemisia umbelliformis Lam. | ARUM |
| Alps yarrow | Achillea distans Waldst. & Kit. ex Willd. | ACDI6 |
| amberboa | Amberboa (Pers.) Less. | AMBER |
| Amberboa moschata | Centaurea moschata L. | CEMO3 |
| amblyolepis | Amblyolepis DC. | AMBLY |
| Amblyolepis setigera | Helenium setigerum (DC.) Britt. & Rusby | HESE2 |
| amblyopappus | Amblyopappus Hook. & Arn. | AMBLY2 |
| Ambrosia acanthicarpa | Franseria acanthicarpa (Hook.) Coville | FRAC2 |
| Ambrosia acanthicarpa | Gaertneria acanthicarpa (Hook.) Britt. | GAAC2 |
| Ambrosia ambrosioides | Franseria ambrosioides Cav. | FRAM3 |
| Ambrosia artemisiifolia var. elatior | Ambrosia elatior L. | AMEL2 |
| Ambrosia artemisiifolia var. paniculata | Ambrosia glandulosa Scheele | AMGL5 |
| Ambrosia artemisiifolia var. paniculata | Ambrosia monophylla (Walt.) Rydb. | AMMO2 |
| Ambrosia artemisiifolia var. paniculata | Ambrosia paniculata Michx. | AMPA8 |
| Ambrosia chamissonis | Ambrosia chamissonis (Less.) Greene var. bipinnatisecta (Less.) J.T. Howell | AMCHB |
| Ambrosia chamissonis | Franseria chamissonis Less. | FRCH4 |
| Ambrosia chamissonis | Franseria chamissonis Less. ssp. bipinnatisecta (Less.) Wiggins & Stockwell | FRCHB |
| Ambrosia chamissonis | Franseria chamissonis Less. var. bipinnatisecta Less. | FRCHB2 |
| Ambrosia chenopodiifolia | Franseria chenopodiifolia Benth. | FRCH5 |
| Ambrosia confertiflora | Franseria confertiflora (DC.) Rydb. | FRCO3 |
| Ambrosia confertiflora | Franseria strigulosa Rydb. | FRST3 |
| Ambrosia confertiflora | Gaertneria tenuifolia Harvey & Gray | GATE6 |
| Ambrosia cordifolia | Franseria cordifolia Gray | FRCO4 |
| Ambrosia deltoidea | Franseria deltoidea Torr. | FRDE3 |
| Ambrosia dumosa | Franseria dumosa Gray | FRDU2 |
| Ambrosia eriocentra | Franseria eriocentra Gray | FRER2 |
| Ambrosia grayi | Franseria tomentosa Gray | FRTO2 |
| Ambrosia grayi | Gaertnera tomentosa (Gray) Kuntze | GATO2 |
| Ambrosia grayi | Gaertneria grayi A. Nels. | GAGR7 |
| Ambrosia ilicifolia | Franseria ilicifolia Gray | FRIL2 |
| ambrosia leaf burr ragweed | Ambrosia ambrosioides (Cav.) Payne | AMAM2 |
| Ambrosia linearis | Franseria linearis Rydb. | FRLI4 |
| Ambrosia psilostachya | Ambrosia californica Rydb. | AMCA10 |
| Ambrosia psilostachya | Ambrosia coronopifolia Torr. & Gray | AMCO5 |
| Ambrosia psilostachya | Ambrosia cumanensis auct. non Kunth [misapplied] | AMCU2 |
| Ambrosia psilostachya | Ambrosia psilostachya DC. var. californica (Rydb.) Blake | AMPSC |
| Ambrosia psilostachya | Ambrosia psilostachya DC. var. coronopifolia (Torr. & Gray) Farw. | AMPSC2 |
| Ambrosia psilostachya | Ambrosia psilostachya DC. var. lindheimeriana (Scheele) Blank. | AMPSL |
| Ambrosia psilostachya | Ambrosia rugelii Rydb. | AMRU2 |
| Ambrosia pumila | Franseria pumila Nutt. | FRPU5 |
| Ambrosia tomentosa | Franseria discolor Nutt. | FRDI3 |
| Ambrosia tomentosa | Franseria tomentosa (Nutt.) A. Nels., non Gray | FRTO3 |
| Ambrosia tomentosa | Gaertneria discolor (Nutt.) Kuntze | GADI3 |
| Ambrosia tomentosa | Gaertneria tomentosa (Nutt.) Heller | GATO3 |
| Ambrosia trifida var. texana | Ambrosia aptera DC. | AMAP |
| Ambrosia trifida var. texana | Ambrosia trifida L. var. aptera (DC.) Kuntze | AMTRA |
| Ambrosia trifida var. trifida | Ambrosia trifida L. var. integrifolia (Muhl. ex Willd.) Torr. & Gray | AMTRI |
| American burnweed | Erechtites hieraciifolia (L.) Raf. ex DC. | ERHI2 |
| American burnweed | Erechtites hieraciifolia (L.) Raf. ex DC. var. cacalioides (Fisch. ex Spreng.) Less. ex Griseb. | ERHIC |
| American burnweed | Erechtites hieraciifolia (L.) Raf. ex DC. var. hieraciifolia | ERHIH |
| American burnweed | Erechtites hieraciifolia (L.) Raf. ex DC. var. megalocarpa (Fern.) Cronq. | ERHIM |
| American everlasting | Gamochaeta americana (P. Mill.) Weddell | GAAM3 |
| American saw-wort | Saussurea americana D.C. Eat. | SAAM3 |
| American star-thistle | Centaurea americana Nutt. | CEAM2 |
| American tarwort | Flourensia cernua DC. | FLCE |
| American threefold | Trixis californica Kellogg | TRCA8 |
| American trailplant | Adenocaulon bicolor Hook. | ADBI |
| Ampelaster carolinianus | Aster carolinianus Walt. | ASCA20 |
| Ampelaster carolinianus | Lasallea caroliniana (Walt.) Semple & L. Brouillet | LACA11 |
| Ampelaster carolinianus | Virgulus carolinianus (Walt.) Reveal & Keener | VICA10 |
| Amphiachyris amoena | Xanthocephalum amoenum Shinners | XAAM4 |
| Amphiachyris amoena | Xanthocephalum amoenum Shinners var. intermedium Shinners | XAAMI |
| Amphiachyris dracunculoides | Brachyris dracunculoides DC. | BRDR |
| Amphiachyris dracunculoides | Gutierrezia dracunculoides (DC.) Blake | GUDR2 |
| Amphiachyris dracunculoides | Xanthocephalum dracunculoides (DC.) Shinners | XADR |
| Amphipappus fremontii | Amphipappus fremontii Torr. & Gray var. fremontii Torr. & Gray [superfluous autonym] | AMFRF2 |
| Amphipappus fremontii ssp. spinosus | Amphiachyris spinosa A. Nels. | AMSP4 |
| Amphipappus fremontii ssp. spinosus | Amphipappus fremontii Torr. & Gray ex Gray var. spinosus (A. Nels.) C.L. Porter | AMFRS |
| anacyclus | Anacyclus L. | ANACY2 |
| Anacyclus | Anacylus L. [orthographic error] | ANACY |
| Anacyclus clavatus | Anacyclus tomentosus DC. | ANTO7 |
| Anacyclus clavatus | Anacylus clavatus (Desf.) Pers. [orthographic error] | ANCL |
| Anacyclus clavatus | Anacylus tomentosus DC. [orthographic error] | ANTO4 |
| Anaphalis margaritacea | Anaphalis margaritacea (L.) Benth. var. angustior (Miq.) Nakai | ANMAA |
| Anaphalis margaritacea | Anaphalis margaritacea (L.) Benth. var. intercedens Hara | ANMAI |
| Anaphalis margaritacea | Anaphalis margaritacea (L.) Benth. var. occidentalis Greene | ANMAO |
| Anaphalis margaritacea | Anaphalis margaritacea (L.) Benth. var. revoluta Suksdorf | ANMAR |
| Anaphalis margaritacea | Anaphalis margaritacea (L.) Benth. var. subalpina Gray | ANMAS |
| Anaphalis margaritacea | Anaphalis occidentalis (Greene) Heller | ANOC8 |
| Anaphalis margaritacea | Gnaphalium margaritaceum L. | GNMA2 |
| Ancistrocarphus filagineus | Stylocline filaginea (Gray) Gray | STFI |
| Ancistrocarphus filagineus | Stylocline filaginea (Gray) Gray var. depressa Jepson | STFID |
| Anderson's hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. andersonii (Gray) Babcock & Stebbins | CRRUA |
| anisescented goldenrod | Solidago odora Ait. | SOOD |
| anisescented goldenrod | Solidago odora Ait. var. odora | SOODO |
| Anisocarpus scabridus | Raillardella scabrida Eastw. | RASC |
| Anisocarpus scabridus | Raillardiopsis scabrida (Eastw.) Rydb. | RASC4 |
| anisocoma | Anisocoma Torr. & Gray | ANISO3 |
| annual agoseris | Agoseris heterophylla (Nutt.) Greene | AGHE2 |
| annual agoseris | Agoseris heterophylla (Nutt.) Greene var. crenulata Jepson | AGHEC |
| annual agoseris | Agoseris heterophylla (Nutt.) Greene var. heterophylla | AGHEH |
| annual agoseris | Agoseris heterophylla (Nutt.) Greene var. turgida (Hall) Jepson | AGHET |
| annual bushsunflower | Simsia lagasceiformis DC. | SILA11 |
| annual candyleaf | Stevia micrantha Lag. | STMI |
| annual marshelder | Iva annua L. | IVAN2 |
| annual marshelder | Iva annua L. var. ?macrocarpa (Blake) R.C. Jackson | IVANM |
| annual marshelder | Iva annua L. var. annua | IVANA |
| annual marshelder | Iva annua L. var. caudata (Small) R.C. Jackson | IVANC |
| annual monsterwort | Parthenice mollis Gray | PAMO2 |
| annual nehe | Lipochaeta remyi Gray | LIRE5 |
| annual psathyrotes | Psathyrotes annua (Nutt.) Gray | PSAN |
| annual ragweed | Ambrosia artemisiifolia L. | AMAR2 |
| annual ragweed | Ambrosia artemisiifolia L. var. artemisiifolia | AMARA2 |
| annual ragweed | Ambrosia artemisiifolia L. var. elatior (L.) Descourtils | AMARE |
| annual ragweed | Ambrosia artemisiifolia L. var. paniculata (Michx.) Blank. | AMARP |
| annual Townsend daisy | Townsendia annua Beaman | TOAN |
| annual trampweed | Facelis retusa (Lam.) Schultz-Bip. | FARE |
| Antelope Island skeletonplant | Lygodesmia dianthopsis (Eat. ex King) S. Tomb | LYDI4 |
| Antennaria alpina | Antennaria alpina (L.) Gaertn. var. canescens (Lange) Trautv. | ANALC |
| Antennaria alpina | Antennaria alpina (L.) Gaertn. var. compacta (Malte) Welsh | ANALC2 |
| Antennaria alpina | Antennaria alpina (L.) Gaertn. var. glabrata J. Vahl | ANALG |
| Antennaria alpina | Antennaria alpina (L.) Gaertn. var. intermedia Rosenv. | ANALI |
| Antennaria alpina | Antennaria alpina (L.) Gaertn. var. stolonifera (Porsild) Welsh | ANALS2 |
| Antennaria alpina | Antennaria alpina (L.) Gaertn. var. ungavensis Fern. | ANALU |
| Antennaria alpina | Antennaria arenicola Malte | ANAR11 |
| Antennaria alpina | Antennaria atriceps Fern. | ANAT2 |
| Antennaria alpina | Antennaria bayardii Fern. | ANBA7 |
| Antennaria alpina | Antennaria boecheriana Porsild | ANBO |
| Antennaria alpina | Antennaria borealis Greene | ANBO2 |
| Antennaria alpina | Antennaria brunnescens Fern. | ANBR11 |
| Antennaria alpina | Antennaria cana (Fern. & Wieg.) Fern. | ANCA30 |
| Antennaria alpina | Antennaria canescens (Lange) Malte | ANCA81 |
| Antennaria alpina | Antennaria canescens (Lange) Malte ssp. porsildii (Ekman) A.& D. L?ve | ANCAP2 |
| Antennaria alpina | Antennaria canescens (Lange) Malte var. pseudoporsildii B?cher | ANCAP |
| Antennaria alpina | Antennaria columnaris Fern. | ANCO16 |
| Antennaria alpina | Antennaria compacta Malte | ANCO5 |
| Antennaria alpina | Antennaria confusa Fern. | ANCO17 |
| Antennaria alpina | Antennaria crymophila Porsild | ANCR5 |
| Antennaria alpina | Antennaria foggii Fern. | ANFO3 |
| Antennaria alpina | Antennaria friesiana (Trautv.) Ekman ssp. compacta (Malte) Hult | ANFRC |
| Antennaria alpina | Antennaria glabrata (J. Vahl) Greene | ANGL7 |
| Antennaria alpina | Antennaria groenlandica Porsild | ANGR6 |
| Antennaria alpina | Antennaria hansii Kern. | ANHA3 |
| Antennaria alpina | Antennaria intermedia (Rosenv.) A.E. Pors. | ANIN6 |
| Antennaria alpina | Antennaria labradorica Nutt. | ANLA10 |
| Antennaria alpina | Antennaria longii Fern. | ANLO3 |
| Antennaria alpina | Antennaria media Greene ssp. compacta (Malte) Chmielewski | ANMEC2 |
| Antennaria alpina | Antennaria pallida E. Nels. | ANPA3 |
| Antennaria alpina | Antennaria pedunculata Porsild | ANPE8 |
| Antennaria alpina | Antennaria porsildii Ekman | ANPO80 |
| Antennaria alpina | Antennaria sornborgeri Fern. | ANSO3 |
| Antennaria alpina | Antennaria stolonifera Porsild | ANST3 |
| Antennaria alpina | Antennaria subcanescens Ostenf. ex Malte | ANSU5 |
| Antennaria alpina | Antennaria ungavensis (Fern.) Malte | ANUN3 |
| Antennaria alpina | Antennaria vexillifera Fern. | ANVE4 |
| Antennaria alpina | Antennaria wiegandii Fern. | ANWI |
| Antennaria alpina | Gnaphalium alpinum L. | GNAL |
| Antennaria anaphaloides | Antennaria pulcherrima (Hook.) Greene ssp. anaphaloides (Rydb.) W.A. Weber | ANPUA2 |
| Antennaria anaphaloides | Antennaria pulcherrima (Hook.) Greene var. anaphaloides (Rydb.) G.W. Douglas | ANPUA3 |
| Antennaria argentea | Antennaria luzuloides Torr. & Gray var. argentea (Benth.) Gray | ANLUA |
| Antennaria chilensis | Antennaria magellanica Sch. Bip. | ANMA20 |
| Antennaria corymbosa | Antennaria acuta Rydb. | ANAC6 |
| Antennaria corymbosa | Antennaria dioica (L.) Gaertn. var. corymbosa (E. Nels.) Jepson | ANDIC |
| Antennaria corymbosa | Antennaria hygrophila Greene | ANHY2 |
| Antennaria corymbosa | Antennaria nardina Greene | ANNA2 |
| Antennaria densifolia | Antennaria ellyae Porsild | ANEL3 |
| Antennaria dimorpha | Antennaria dimorpha (Nutt.) Torr. & Gray var. integra Henderson | ANDII |
| Antennaria dimorpha | Antennaria dimorpha (Nutt.) Torr. & Gray var. latisquama (Piper) M.E. Peck | ANDIL |
| Antennaria dimorpha | Antennaria dimorpha (Nutt.) Torr. & Gray var. macrocephala D.C. Eat. | ANDIM |
| Antennaria dimorpha | Antennaria latisquama Piper | ANLA6 |
| Antennaria dimorpha | Antennaria macrocephala (D.C. Eat.) Rydb. | ANMA8 |
| Antennaria dimorpha | Gnaphalium dimorphum Nutt. | GNDI |
| Antennaria dioica | Antennaria dioica (L.) Gaertn. var. hyperborea (D. Don) Greene | ANDIH |
| Antennaria dioica | Antennaria hyperborea D. Don | ANHY5 |
| Antennaria dioica | Antennaria insularis Greene | ANIN4 |
| Antennaria dioica | Gnaphalium dioicum L. | GNDI2 |
| Antennaria flagellaris | Antennaria dimorpha (Nutt.) Torr. & Gray var. flagellaris Gray | ANDIF |
| Antennaria friesiana ssp. alaskana | Antennaria alaskana Malte | ANAL5 |
| Antennaria friesiana ssp. friesiana | Antennaria alpina (L.) Gaertn. var. friesiana Trautv. | ANALF |
| Antennaria friesiana ssp. friesiana | Antennaria angustifolia Ekman, non Rydb. | ANAN7 |
| Antennaria friesiana ssp. friesiana | Antennaria ekmaniana Porsild | ANEK |
| Antennaria friesiana ssp. neoalaskana | Antennaria neoalaskana Porsild | ANNE6 |
| Antennaria geyeri | Gnaphalium alienum Hook. & Arn. | GNAL2 |
| Antennaria howellii ssp. canadensis | Antennaria canadensis Greene | ANCA38 |
| Antennaria howellii ssp. canadensis | Antennaria neglecta Greene var. canadensis (Greene) Cronq. | ANNEC5 |
| Antennaria howellii ssp. canadensis | Antennaria neglecta Greene var. randii (Fern.) Cronq. | ANNER |
| Antennaria howellii ssp. canadensis | Antennaria neodioica Greene ssp. canadensis (Greene) Bayer & Stebbins | ANNEC2 |
| Antennaria howellii ssp. canadensis | Antennaria neodioica Greene var. randii (Fern.) Boivin | ANNER2 |
| Antennaria howellii ssp. canadensis | Antennaria randii Fern. | ANRA4 |
| Antennaria howellii ssp. canadensis | Antennaria spathulata (Fern.) Fern. | ANSP3 |
| Antennaria howellii ssp. howellii | Antennaria callilepis Greene | ANCA31 |
| Antennaria howellii ssp. howellii | Antennaria eximia Greene | ANEX4 |
| Antennaria howellii ssp. howellii | Antennaria neglecta Greene ssp. howellii (Greene) Hult | ANNEH2 |
| Antennaria howellii ssp. howellii | Antennaria neglecta Greene var. howellii (Greene) Cronq. | ANNEH |
| Antennaria howellii ssp. howellii | Antennaria neodioica Greene ssp. howellii (Greene) Bayer | ANNEH3 |
| Antennaria howellii ssp. neodioica | Antennaria grandis (Fern.) House | ANGR9 |
| Antennaria howellii ssp. neodioica | Antennaria neglecta Greene var. attenuata (Fern.) Cronq. | ANNEA |
| Antennaria howellii ssp. neodioica | Antennaria neglecta Greene var. neodioica (Greene) Cronq. | ANNEN2 |
| Antennaria howellii ssp. neodioica | Antennaria neodioica Greene | ANNE80 |
| Antennaria howellii ssp. neodioica | Antennaria neodioica Greene var. attenuata Fern. | ANNEA3 |
| Antennaria howellii ssp. neodioica | Antennaria neodioica Greene var. chlorophylla Fern. | ANNEC3 |
| Antennaria howellii ssp. neodioica | Antennaria neodioica Greene var. grandis Fern. | ANNEG2 |
| Antennaria howellii ssp. neodioica | Antennaria neodioica Greene var. interjecta Fern. | ANNEI |
| Antennaria howellii ssp. neodioica | Antennaria neodioica Greene var. rupicola (Fern.) Fern. | ANNER3 |
| Antennaria howellii ssp. neodioica | Antennaria obovata E. Nels. | ANOB |
| Antennaria howellii ssp. neodioica | Antennaria rhodantha Fern. | ANRH2 |
| Antennaria howellii ssp. neodioica | Antennaria rupicola Fern. | ANRU2 |
| Antennaria howellii ssp. neodioica | Antennaria russellii Boivin | ANRU3 |
| Antennaria howellii ssp. petaloidea | Antennaria appendiculata Fern. | ANAP2 |
| Antennaria howellii ssp. petaloidea | Antennaria concolor Piper | ANCO21 |
| Antennaria howellii ssp. petaloidea | Antennaria neglecta Greene var. petaloidea (Fern.) Cronq. | ANNEP3 |
| Antennaria howellii ssp. petaloidea | Antennaria neodioica Greene ssp. petaloidea (Fern.) Bayer & Stebbins | ANNEP |
| Antennaria howellii ssp. petaloidea | Antennaria neodioica Greene var. petaloidea Fern. | ANNEP2 |
| Antennaria howellii ssp. petaloidea | Antennaria pedicellata Greene | ANPE6 |
| Antennaria howellii ssp. petaloidea | Antennaria petaloidea (Fern.) Fern. | ANPE11 |
| Antennaria howellii ssp. petaloidea | Antennaria petaloidea (Fern.) Fern. var. scariosa Fern. | ANPES |
| Antennaria howellii ssp. petaloidea | Antennaria petaloidea (Fern.) Fern. var. subcorymbosa (Fern.) Fern. | ANPES2 |
| Antennaria howellii ssp. petaloidea | Antennaria stenolepis Greene | ANST6 |
| Antennaria lanata | Antennaria carpathica (Wahlenb.) R. Br. var. lanata Hook. | ANCAL |
| Antennaria luzuloides ssp. aberrans | Antennaria argentea Benth. ssp. aberrans E. Nels. | ANARA4 |
| Antennaria luzuloides ssp. aberrans | Antennaria luzuloides Torr. & Gray var. microcephala (Gray) Cronq. | ANLUM |
| Antennaria luzuloides ssp. aberrans | Antennaria microcephala Gray | ANMI2 |
| Antennaria luzuloides ssp. aberrans | Antennaria pyramidata Greene | ANPY2 |
| Antennaria luzuloides ssp. luzuloides | Antennaria luzuloides Torr. & Gray var. oblanceolata (Rydb.) M.E. Peck | ANLUO |
| Antennaria luzuloides ssp. luzuloides | Antennaria oblanceolata Rydb. | ANOB4 |
| Antennaria marginata | Antennaria dioica (L.) Gaertn. var. marginata (Greene) Jepson | ANDIM2 |
| Antennaria marginata | Antennaria fendleri Greene | ANFE |
| Antennaria marginata | Antennaria peramoena Greene | ANPE10 |
| Antennaria media | Antennaria alpina (L.) Gaertn. var. media (Greene) Jepson | ANALM |
| Antennaria media | Antennaria austromontana E. Nels. | ANAU |
| Antennaria media | Antennaria candida Greene | ANCA24 |
| Antennaria media | Antennaria densa Greene | ANDE5 |
| Antennaria media | Antennaria gormanii St. John | ANGO |
| Antennaria media | Antennaria modesta Greene | ANMO4 |
| Antennaria media | Antennaria mucronata E. Nels. | ANMU5 |
| Antennaria microphylla | Antennaria bracteosa Rydb. | ANBR9 |
| Antennaria microphylla | Antennaria nitida Greene | ANNI5 |
| Antennaria microphylla | Antennaria parvifolia Nutt. var. bracteosa (Rydb.) A. Nels. | ANPAB |
| Antennaria microphylla | Antennaria parvifolia sensu Greene, non Nutt. | ANPA5 |
| Antennaria microphylla | Antennaria rosea Greene var. nitida (Greene) Breitung | ANRON |
| Antennaria microphylla | Antennaria solstitialis Lunell | ANSO4 |
| Antennaria monocephala ssp. angustata | Antennaria alpina (L.) Gaertn. var. megacephala (Fern.) Welsh | ANALM3 |
| Antennaria monocephala ssp. angustata | Antennaria angustata Greene | ANAN8 |
| Antennaria monocephala ssp. angustata | Antennaria burwellensis Malte | ANBU2 |
| Antennaria monocephala ssp. angustata | Antennaria congesta Malte | ANCO20 |
| Antennaria monocephala ssp. angustata | Antennaria fernaldiana Polunin | ANFE2 |
| Antennaria monocephala ssp. angustata | Antennaria friesiana (Trautv.) Ekman var. megacephala (Fern.) Hult | ANFRM |
| Antennaria monocephala ssp. angustata | Antennaria hudsonica Malte | ANHU2 |
| Antennaria monocephala ssp. angustata | Antennaria megacephala Fern. | ANME3 |
| Antennaria monocephala ssp. angustata | Antennaria pygmaea Fern. | ANPY |
| Antennaria monocephala ssp. angustata | Antennaria tansleyi Polunin | ANTA |
| Antennaria monocephala ssp. angustata | Antennaria tweedsmurii Polunin | ANTW |
| Antennaria monocephala ssp. monocephala | Antennaria exilis Greene | ANEX2 |
| Antennaria monocephala ssp. monocephala | Antennaria monocephala DC. ssp. philonipha (Porsild) Hult | ANMOP |
| Antennaria monocephala ssp. monocephala | Antennaria monocephala DC. var. exilis (Greene) Hult | ANMOE |
| Antennaria monocephala ssp. monocephala | Antennaria nitens Greene | ANNI2 |
| Antennaria monocephala ssp. monocephala | Antennaria philonipha Porsild | ANPH2 |
| Antennaria neglecta | Antennaria angustiarum Lunell | ANAN10 |
| Antennaria neglecta | Antennaria athabascensis Greene | ANAT3 |
| Antennaria neglecta | Antennaria campestris Rydb. | ANCA27 |
| Antennaria neglecta | Antennaria campestris Rydb. var. athabascensis (Greene) Boivin | ANCAA |
| Antennaria neglecta | Antennaria chelonica Lunell | ANCH5 |
| Antennaria neglecta | Antennaria erosa Greene | ANER3 |
| Antennaria neglecta | Antennaria howellii Greene var. athabascensis (Greene) Boivin | ANHOA |
| Antennaria neglecta | Antennaria howellii Greene var. campestris (Rydb.) Boivin | ANHOC2 |
| Antennaria neglecta | Antennaria longifolia Greene | ANLO4 |
| Antennaria neglecta | Antennaria lunellii Greene | ANLU4 |
| Antennaria neglecta | Antennaria nebraskensis Greene | ANNE7 |
| Antennaria neglecta | Antennaria neglecta Greene var. athabascensis (Greene) Taylor & MacBryde | ANNEA4 |
| Antennaria neglecta | Antennaria neglecta Greene var. campestris (Rydb.) Steyermark | ANNEC |
| Antennaria neglecta | Antennaria parvula Greene | ANPA6 |
| Antennaria neglecta | Antennaria wilsonii Greene | ANWI2 |
| Antennaria parlinii ssp. fallax | Antennaria ambigens (Greene) Fern. | ANAM2 |
| Antennaria parlinii ssp. fallax | Antennaria ampla Bush | ANAM3 |
| Antennaria parlinii ssp. fallax | Antennaria arkansana Greene | ANAR14 |
| Antennaria parlinii ssp. fallax | Antennaria arnoglossa Greene var. ambigens Greene | ANARA5 |
| Antennaria parlinii ssp. fallax | Antennaria bifrons Greene | ANBI2 |
| Antennaria parlinii ssp. fallax | Antennaria brainerdii Greene | ANBR10 |
| Antennaria parlinii ssp. fallax | Antennaria calophylla Greene | ANCA26 |
| Antennaria parlinii ssp. fallax | Antennaria fallax Greene | ANFA |
| Antennaria parlinii ssp. fallax | Antennaria fallax Greene var. calophylla (Greene) Fern. | ANFAC |
| Antennaria parlinii ssp. fallax | Antennaria farwellii Greene | ANFA4 |
| Antennaria parlinii ssp. fallax | Antennaria greenei Bush | ANGR4 |
| Antennaria parlinii ssp. fallax | Antennaria mesochora Greene | ANME4 |
| Antennaria parlinii ssp. fallax | Antennaria munda Fern. | ANMU6 |
| Antennaria parlinii ssp. fallax | Antennaria occidentalis Greene | ANOC4 |
| Antennaria parlinii ssp. fallax | Antennaria parlinii Fern. var. farwellii (Greene) Boivin | ANPAF2 |
| Antennaria parlinii ssp. fallax | Antennaria plantaginifolia (L.) Richards. var. ambigens (Greene) Cronq. | ANPLA |
| Antennaria parlinii ssp. fallax | Antennaria umbellata Greene | ANUM2 |
| Antennaria parlinii ssp. parlinii | Antennaria arnoglossa Greene | ANAR13 |
| Antennaria parlinii ssp. parlinii | Antennaria parlinii Fern. var. arnoglossa (Greene) Fern. | ANPAA |
| Antennaria parlinii ssp. parlinii | Antennaria plantaginifolia (L.) Richards. var. arnoglossa (Greene) Cronq. | ANPLA2 |
| Antennaria parlinii ssp. parlinii | Antennaria plantaginifolia (L.) Richards. var. parlinii (Fern.) Cronq. | ANPLP3 |
| Antennaria parvifolia | Antennaria aprica Greene | ANAP |
| Antennaria parvifolia | Antennaria aprica Greene var. minuscula (Boivin) Boivin | ANAPM |
| Antennaria parvifolia | Antennaria aureola Lunell | ANAU2 |
| Antennaria parvifolia | Antennaria holmii Greene | ANHO2 |
| Antennaria parvifolia | Antennaria latisquamea Greene | ANLA19 |
| Antennaria parvifolia | Antennaria minuscula Boivin | ANMI5 |
| Antennaria parvifolia | Antennaria obtusata Greene | ANOB5 |
| Antennaria parvifolia | Antennaria pumila Greene | ANPU9 |
| Antennaria parvifolia | Antennaria recurva Greene | ANRE4 |
| Antennaria parvifolia | Antennaria rhodanthus Suksdorf | ANRH3 |
| Antennaria plantaginifolia | Antennaria caroliniana Rydb. | ANCA25 |
| Antennaria plantaginifolia | Antennaria decipiens Greene | ANDE6 |
| Antennaria plantaginifolia | Antennaria denikeana Boivin | ANDE7 |
| Antennaria plantaginifolia | Antennaria nemoralis Greene | ANNE3 |
| Antennaria plantaginifolia | Antennaria petiolata Fern. | ANPE9 |
| Antennaria plantaginifolia | Antennaria pinetorum Greene | ANPI3 |
| Antennaria plantaginifolia | Antennaria plantaginifolia (L.) Richards. var. petiolata (Fern.) Heller | ANPLP2 |
| Antennaria plantaginifolia | Gnaphalium plantaginifolium L. | GNPL |
| Antennaria pulchella | Antennaria alpina (L.) Gaertn. var. scabra (Greene) Jepson | ANALS |
| Antennaria pulchella | Antennaria media Greene ssp. ciliata E. Nels. | ANMEC |
| Antennaria pulchella | Antennaria media Greene ssp. pulchella (Greene) Chmielewski | ANMEP |
| Antennaria pulchella | Antennaria scabra Greene | ANSC6 |
| Antennaria pulcherrima | Antennaria carpathica (Wahlenb.) R. Br. var. pulcherrima Hook. | ANCAP3 |
| Antennaria pulcherrima | Antennaria pulcherrima (Hook.) Greene var. angustisquama Porsild | ANPUA |
| Antennaria pulcherrima | Antennaria pulcherrima (Hook.) Greene var. sordida Boivin | ANPUS |
| Antennaria racemosa | Antennaria petasites Greene | ANPE18 |
| Antennaria racemosa | Antennaria piperi Rydb. | ANPI4 |
| Antennaria rosea ssp. arida | Antennaria arida E. Nels. | ANAR12 |
| Antennaria rosea ssp. arida | Antennaria arida E. Nels. ssp. viscidula E. Nels. | ANARV |
| Antennaria rosea ssp. arida | Antennaria scariosa E. Nels. | ANSC7 |
| Antennaria rosea ssp. confinis | Antennaria albicans Fern. | ANAL6 |
| Antennaria rosea ssp. confinis | Antennaria angustifolia Rydb. | ANAN9 |
| Antennaria rosea ssp. confinis | Antennaria arida E. Nels. var. humilis (Rydb.) E. Nels. | ANARH |
| Antennaria rosea ssp. confinis | Antennaria breitungii Porsild | ANBR8 |
| Antennaria rosea ssp. confinis | Antennaria brevistyla Fern. | ANBR14 |
| Antennaria rosea ssp. confinis | Antennaria concinna E. Nels. | ANCO18 |
| Antennaria rosea ssp. confinis | Antennaria confinis Greene | ANCO19 |
| Antennaria rosea ssp. confinis | Antennaria dioica (L.) Gaertn. var. kernensis Jepson | ANDIK |
| Antennaria rosea ssp. confinis | Antennaria elegans Porsild | ANEL4 |
| Antennaria rosea ssp. confinis | Antennaria foliacea Greene var. humilis Rydb. | ANFOH |
| Antennaria rosea ssp. confinis | Antennaria incarnata Porsild | ANIN5 |
| Antennaria rosea ssp. confinis | Antennaria laingii Porsild | ANLA12 |
| Antennaria rosea ssp. confinis | Antennaria leontopodioides Cody | ANLE9 |
| Antennaria rosea ssp. confinis | Antennaria leuchippii M.P. Porsild | ANLE8 |
| Antennaria rosea ssp. confinis | Antennaria rosea Greene var. angustifolia (Rydb.) E. Nels. | ANROA2 |
| Antennaria rosea ssp. confinis | Antennaria sedoides Greene | ANSE9 |
| Antennaria rosea ssp. confinis | Antennaria sordida Greene | ANSO5 |
| Antennaria rosea ssp. confinis | Antennaria straminea Fern. | ANST7 |
| Antennaria rosea ssp. confinis | Antennaria subviscosa Fern. | ANSU6 |
| Antennaria rosea ssp. confinis | Antennaria tomentella E. Nels. | ANTO5 |
| Antennaria rosea ssp. pulvinata | Antennaria affinis Fern. | ANAF |
| Antennaria rosea ssp. pulvinata | Antennaria albescens (E. Nels.) Rydb. | ANAL7 |
| Antennaria rosea ssp. pulvinata | Antennaria fusca E. Nels. | ANFU3 |
| Antennaria rosea ssp. pulvinata | Antennaria gaspensis (Fern.) Fern. | ANGA |
| Antennaria rosea ssp. pulvinata | Antennaria howellii Greene ssp. gaspensis (Fern.) Chmielewski | ANHOG |
| Antennaria rosea ssp. pulvinata | Antennaria isolepis Greene | ANIS2 |
| Antennaria rosea ssp. pulvinata | Antennaria maculata Greene | ANMA7 |
| Antennaria rosea ssp. pulvinata | Antennaria manicouagana Landry | ANMA9 |
| Antennaria rosea ssp. pulvinata | Antennaria media Greene ssp. fusca (E. Nels.) Chmielewski | ANMEF |
| Antennaria rosea ssp. pulvinata | Antennaria neglecta Greene var. gaspensis (Fern.) Cronq. | ANNEG |
| Antennaria rosea ssp. pulvinata | Antennaria neodioica Greene var. gaspensis Fern. | ANNEG3 |
| Antennaria rosea ssp. pulvinata | Antennaria peasei Fern. | ANPE12 |
| Antennaria rosea ssp. pulvinata | Antennaria pulvinata Greene | ANPU10 |
| Antennaria rosea ssp. pulvinata | Antennaria pulvinata Greene ssp. albescens E. Nels. | ANPUA4 |
| Antennaria rosea ssp. pulvinata | Antennaria sansonii Greene | ANSA4 |
| Antennaria rosea ssp. pulvinata | Antennaria umbrinella auct. non Rydb. [misapplied] | ANUM4 |
| Antennaria rosea ssp. rosea | Antennaria acuminata Greene | ANAC8 |
| Antennaria rosea ssp. rosea | Antennaria alborosea Porsild ex M.P. Porsild | ANAL3 |
| Antennaria rosea ssp. rosea | Antennaria chlorantha Greene | ANCH6 |
| Antennaria rosea ssp. rosea | Antennaria dioica (L.) Gaertn. var. rosea (Greene) D.C. Eat. | ANDIR2 |
| Antennaria rosea ssp. rosea | Antennaria formosa Greene | ANFO4 |
| Antennaria rosea ssp. rosea | Antennaria hendersonii Piper | ANHE7 |
| Antennaria rosea ssp. rosea | Antennaria imbricata E. Nels. | ANIM |
| Antennaria rosea ssp. rosea | Antennaria lanulosa Greene | ANLA11 |
| Antennaria rosea ssp. rosea | Antennaria neodioica Greene var. chlorantha (Greene) Boivin | ANNEC4 |
| Antennaria rosea ssp. rosea | Antennaria oxyphylla Greene | ANOX |
| Antennaria rosea ssp. rosea | Antennaria rosea Greene ssp. divaricata E. Nels. | ANROD |
| Antennaria rosea ssp. rosea | Antennaria rosea Greene var. imbricata (E. Nels.) E. Nels. | ANROI |
| Antennaria rosea ssp. rosea | Antennaria speciosa Greene | ANSP80 |
| Antennaria rosulata | Antennaria bakeri Greene | ANBA4 |
| Antennaria rosulata | Antennaria sierrae-blancae Rydb. | ANSI2 |
| Antennaria solitaria | Antennaria monocephala (Torr. & Gray) Greene | ANMO5 |
| Antennaria solitaria | Antennaria plantaginifolia (L.) Richards. var. monocephala Torr. & Gray | ANPLM |
| Antennaria stenophylla | Antennaria alpina (L.) Gaertn. var. stenophylla Gray | ANALS3 |
| Antennaria stenophylla | Antennaria leucophaea Piper | ANLE7 |
| Antennaria umbrinella | Antennaria aizoides Greene | ANAI |
| Antennaria umbrinella | Antennaria flavescens Rydb. | ANFL6 |
| Antennaria umbrinella | Antennaria reflexa E. Nels. | ANRE5 |
| Antennaria virginica | Antennaria neglecta Greene var. argillicola (Stebbins) Cronq. | ANNEA2 |
| Antennaria virginica | Antennaria virginica Stebbins var. argillicola Stebbins | ANVIA3 |
| Anthemis altissima | Cota altissima (L.) J. Gay | COAL11 |
| Anthemis arvensis | Anthemis arvensis L. var. agrestis (Wallr.) DC. | ANARA2 |
| Anthemis cotula | Maruta cotula (L.) DC. | MACO22 |
| Anthemis tinctoria | Cota tinctoria (L.) J. Gay | COTI4 |
| Antheropeas lanosum | Eriophyllum lanosum (Gray) Gray | ERLA15 |
| Antheropeas wallacei | Eriophyllum wallacei (Gray) Gray | ERWA7 |
| Antheropeas wallacei | Eriophyllum wallacei (Gray) Gray ssp. australe (Rydb.) Wiggins | ERWAA |
| Antheropeas wallacei | Eriophyllum wallacei (Gray) Gray var. calvescens Blake | ERWAC |
| Antheropeas wallacei | Eriophyllum wallacei (Gray) Gray var. rubellum (Gray) Gray | ERWAR |
| Anticosti Island aster | Symphyotrichum anticostense (Fern.) Nesom | SYAN3 |
| Antilles velvetshrub | Piptocoma antillana Urban | PIAN4 |
| Apache beggarticks | Bidens ferulifolia (Jacq.) DC. | BIFE2 |
| Apache Passe rubberweed | Hymenoxys ambigens (Blake) Bierner var. floribunda (Gray) W.L. Wagner | HYAMF |
| Apache plant | Guardiola platyphylla Gray | GUPL |
| Apalachicola aster | Eurybia spinulosa (Chapman) Nesom | EUSP4 |
| Apalachicola doll's daisy | Boltonia apalachicolensis L.C. Anders. | BOAP |
| apargidium | Microseris borealis (Bong.) Schultz-Bip. | MIBO |
| Aphanostephus ramosissimus var. humilis | Aphanostephus arizonicus Gray | APAR |
| Aphanostephus ramosissimus var. humilis | Aphanostephus humilis (Benth.) Gray | APHU2 |
| Aphanostephus ramosissimus var. humilis | Aphanostephus potosinus Shinners | APPO |
| Aphanostephus ramosissimus var. humilis | Leucopsidium humile Benth. | LEHU4 |
| Aphanostephus skirrhobasis var. kidderi | Aphanostephus kidderi Blake | APKI |
| Aphanostephus skirrhobasis var. skirrhobasis | Keerlia skirrhobasis DC. | KESK |
| Appalachian blazing star | Liatris squarrulosa Michx. | LISQ2 |
| Appalachian rosinweed | Silphium wasiotense M. Medley | SIWA |
| arctic alpine fleabane | Erigeron humilis Graham | ERHU |
| arctic aster | Eurybia sibirica (L.) Nesom | EUSI13 |
| arctic cudweed | Omalotheca Cass. | OMALO |
| Arctic daisy | Chrysanthemum arcticum L. | CHAR13 |
| Arctic daisy | Chrysanthemum arcticum L. ssp. arcticum | CHARA |
| arctic daisy | Chrysanthemum arcticum L. ssp. polare Hult | CHARP3 |
| arctic daisy | Dendranthema (DC.) Des Moulins | DENDR5 |
| arctic goldenrod | Solidago multiradiata Ait. var. arctica (DC.) Fern. | SOMUA |
| arctic groundsel | Tephroseris atropurpurea (Ledeb.) Holub | TEAT2 |
| arctic groundsel | Tephroseris atropurpurea (Ledeb.) Holub ssp. atropurpurea | TEATA |
| arctic sweet coltsfoot | Petasites frigidus (L.) Fries | PEFR5 |
| arctic sweet coltsfoot | Petasites frigidus (L.) Fries var. frigidus | PEFRF |
| arctic sweet coltsfoot | Petasites frigidus (L.) Fries var. palmatus (Ait.) Cronq. | PEFRP |
| arctic wormwood | Artemisia senjavinensis Bess. | ARSE5 |
| Arctium lappa | Lappa major Gaertner | LAMA13 |
| Arctium minus | Lappa minor Hill | LAMI7 |
| Arctium vulgare | Arctium minus Bernh. ssp. nemorosum (Lej. & Court.) Syme | ARMIN |
| Arctium vulgare | Arctium nemorosum Lej. & Court. | ARNE5 |
| arctotis | Arctotis L. | ARCTO4 |
| Arctotis stoechadifolia | Arctotis grandis Thunb. | ARGR10 |
| Arctotis stoechadifolia | Arctotis stoechadifolia Berg. var. grandis (Thunb.) Less. | ARSTG |
| Argyranthemum foeniculum | Argyranthemum anethifolium (Willd.) Webb | ARAN4 |
| Argyranthemum foeniculum | Pyrethrum anethifolium Willd. | PYAN4 |
| Argyranthemum frutescens | Chrysanthemum frutescens L. | CHFR5 |
| Argyroxiphium ?kai | Argyroxiphium caliginis Forbes var. kai Forbes | ARCAK |
| Argyroxiphium grayanum | Wilkesia grayana Hbd. | WIGR |
| Argyroxiphium kauense | Argyroxiphium sandwicense DC. var. kauense Rock & Neal | ARSAK |
| Argyroxiphium sandwicense ssp. macrocephalum | Argyroxiphium macrocephalum Gray | ARMA16 |
| Argyroxiphium virescens | Argyroxiphium forbesii St. John | ARFO |
| arhyrautia | ?Argyrautia Sherff | ARGYR4 |
| arid tansyaster | Machaeranthera arida B.L. Turner & Horne | MAAR5 |
| arid throne fleabane | Erigeron arisolius Nesom | ERAR22 |
| Arizona baccharis | Baccharis thesioides Kunth | BATH |
| Arizona beggarticks | Bidens aurea (Ait.) Sherff | BIAU |
| Arizona blackfoot | Melampodium longicorne Gray | MELO |
| Arizona blanketflower | Gaillardia arizonica Gray | GAAR2 |
| Arizona cottonrose | Logfia arizonica (Gray) Holub | LOAR12 |
| Arizona cudweed | Pseudognaphalium arizonicum (Gray) A. Anderb. | PSAR12 |
| Arizona false goldenaster | Heterotheca fulcrata (Greene) Shinners var. arizonica Semple | HEFUA |
| Arizona fleabane | Erigeron arizonicus Gray | ERAR4 |
| Arizona four-nerve daisy | Tetraneuris acaulis (Pursh) Greene var. arizonica (Greene) Parker | TEACA |
| Arizona gumweed | Grindelia arizonica Gray | GRAR2 |
| Arizona gumweed | Grindelia arizonica Gray var. arizonica | GRARA |
| Arizona gumweed | Grindelia arizonica Gray var. stenophylla Steyermark | GRARS |
| Arizona mule-ears | Wyethia arizonica Gray | WYAR |
| Arizona rabbitbrush | Chrysothamnus molestus (Blake) L.C. Anders. | CHMO2 |
| Arizona ragwort | Senecio arizonicus Greene | SEAR3 |
| Arizona rubberweed | Hymenoxys subintegra Cockerell | HYSU |
| Arizona skeletonplant | Lygodesmia arizonica S. Tomb | LYAR2 |
| Arizona snakeweed | Gutierrezia arizonica (Gray) M.A. Lane | GUAR |
| Arizona sneezeweed | Helenium arizonicum Blake | HEAR2 |
| Arizona sunflower | Helianthus arizonensis R.C. Jackson | HEAR8 |
| Arizona sunflowerweed | Tithonia thurberi Gray | TITH |
| Arizona thistle | Cirsium arizonicum (Gray) Petrak | CIAR3 |
| Arkansas dozedaisy | Aphanostephus skirrhobasis (DC.) Trel. | APSK |
| Arkansas dozedaisy | Aphanostephus skirrhobasis (DC.) Trel. var. kidderi (Blake) B.L. Turner | APSKK |
| Arkansas dozedaisy | Aphanostephus skirrhobasis (DC.) Trel. var. skirrhobasis | APSKS |
| Arkansas dozedaisy | Aphanostephus skirrhobasis (DC.) Trel. var. thalassius Shinners | APSKT |
| Arkansas ironweed | Vernonia arkansana DC. | VEAR3 |
| Arkansas leastdaisy | Chaetopappa asteroides Nutt. ex DC. | CHAS |
| Arkansas leastdaisy | Chaetopappa asteroides Nutt. ex DC. var. asteroides | CHASA |
| Arkansas leastdaisy | Chaetopappa asteroides Nutt. ex DC. var. grandis Shinners | CHASG |
| Arkansas River feverfew | Parthenium tetraneuris Barneby | PATE12 |
| arnica | Arnica L. | ARNIC |
| Arnica acaulis | Doronicum acaule Walt. | DOAC |
| Arnica amplexicaulis | Arnica amplexicaulis Nutt. ssp. genuina Maguire | ARAMG |
| Arnica amplexicaulis | Arnica amplexicaulis Nutt. ssp. prima (Maguire) Maguire | ARAMP |
| Arnica amplexicaulis | Arnica amplexicaulis Nutt. var. piperi St. John & Warren | ARAMP2 |
| Arnica amplexicaulis | Arnica amplexicaulis Nutt. var. prima (Maguire) Boivin | ARAMP3 |
| Arnica amplexicaulis | Arnica amplexifolia Rydb. | ARAM3 |
| Arnica amplexicaulis | Arnica mollis Hook. var. aspera (Greene) Boivin | ARMOA |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin ssp. angustifolia (Vahl) Maguire | ARALA4 |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin ssp. attenuata (Greene) Maguire | ARALA5 |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin ssp. sornborgeri (Fern.) Maguire | ARALS |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin var. angustifolia (Vahl) Fern. | ARALA6 |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin var. attenuata (Greene) Ediger & T.M. Barkl. | ARALA |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin var. linearis Hult | ARALL |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin var. plantaginea (Pursh) Ediger & T.M. Barkl. | ARALP |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin var. ungavensis Boivin | ARALU |
| Arnica angustifolia ssp. angustifolia | Arnica alpina (L.) Olin var. vestita Hult | ARALV |
| Arnica angustifolia ssp. angustifolia | Arnica angustifolia Vahl ssp. attenuata (Greene) G.W. Douglas | ARANA2 |
| Arnica angustifolia ssp. angustifolia | Arnica plantaginea Pursh | ARPL6 |
| Arnica angustifolia ssp. angustifolia | Arnica sornborgeri Fern. | ARSO3 |
| Arnica angustifolia ssp. angustifolia | Arnica terrae-novae Fern. | ARTE6 |
| Arnica angustifolia ssp. tomentosa | Arnica alpina (L.) Olin ssp. tomentosa (Macoun) Maguire | ARALT3 |
| Arnica angustifolia ssp. tomentosa | Arnica alpina (L.) Olin var. tomentosa (Macoun) Cronq. | ARALT2 |
| Arnica angustifolia ssp. tomentosa | Arnica angustifolia Vahl var. tomentosa (Macoun) Dorn | ARANT2 |
| Arnica angustifolia ssp. tomentosa | Arnica tomentosa Macoun | ARTO5 |
| Arnica cernua | Arnica chandleri Rydb. | ARCH6 |
| Arnica chamissonis ssp. chamissonis var. chamissonis | Arnica chamissonis Less. ssp. genuina Maguire | ARCHG |
| Arnica chamissonis ssp. foliosa var. andina | Arnica chamissonis Less. var. foliosa (Nutt.) Maguire | ARCHF2 |
| Arnica chamissonis ssp. foliosa var. andina | Arnica chamissonis Less. var. jepsoniana Maguire | ARCHJ |
| Arnica chamissonis ssp. foliosa var. andina | Arnica foliosa Nutt. | ARFO2 |
| Arnica chamissonis ssp. foliosa var. bernardina | Arnica bernardina Greene | ARBE4 |
| Arnica chamissonis ssp. foliosa var. incana | Arnica chamissonis Less. ssp. incana (Gray) Maguire | ARCHI5 |
| Arnica chamissonis ssp. foliosa var. incana | Arnica foliosa Nutt. var. incana Gray | ARFOI |
| Arnica cordifolia | Arnica cordifolia Hook. ssp. genuina Maguire | ARCOG2 |
| Arnica cordifolia | Arnica cordifolia Hook. var. humilis (Rydb.) Maguire | ARCOH |
| Arnica cordifolia | Arnica cordifolia Hook. var. pumila (Rydb.) Maguire | ARCOP2 |
| Arnica cordifolia | Arnica cordifolia Hook. var. whitneyi (Fern.) Maguire | ARCOW2 |
| Arnica cordifolia | Arnica hardinae St. John | ARHA5 |
| Arnica cordifolia | Arnica humilis Rydb. | ARHU7 |
| Arnica cordifolia | Arnica paniculata A. Nels. | ARPA12 |
| Arnica cordifolia | Arnica whitneyi Fern. | ARWH |
| Arnica dealbata | Whitneya dealbata Gray | WHDE |
| Arnica discoidea | Arnica discoidea Benth. var. alata (Rydb.) Cronq. | ARDIA2 |
| Arnica discoidea | Arnica discoidea Benth. var. eradiata (Gray) Cronq. | ARDIE |
| Arnica discoidea | Arnica grayi Heller | ARGR12 |
| Arnica discoidea | Arnica parviflora Gray | ARPA25 |
| Arnica discoidea | Arnica parviflora Gray ssp. alata (Rydb.) Maguire | ARPAA |
| Arnica frigida ssp. frigida | Arnica frigida C.A. Mey. ex Iljin var. glandulosa Boivin | ARFRG2 |
| Arnica frigida ssp. frigida | Arnica griscomii Fern. ssp. frigida (C.A. Mey. ex Iljin) S.J. Wolf | ARGRF |
| Arnica frigida ssp. frigida | Arnica louiseana Farr ssp. frigida (C.A. Mey. ex Iljin) Maguire | ARLOF |
| Arnica frigida ssp. frigida | Arnica louiseana Farr var. brevifolia (Rydb.) Maguire | ARLOB |
| Arnica frigida ssp. frigida | Arnica louiseana Farr var. frigida (C.A. Mey. ex Iljin) Welsh | ARLOF2 |
| Arnica frigida ssp. frigida | Arnica louiseana Farr var. illiamnae (Rydb.) Maguire | ARLOI |
| Arnica frigida ssp. frigida | Arnica louiseana Farr var. mendenhallii (Rydb.) Maguire | ARLOM |
| Arnica frigida ssp. frigida | Arnica louiseana Farr var. pilosa Maguire | ARLOP |
| Arnica frigida ssp. frigida | Arnica snyderi Raup | ARSN |
| Arnica gracilis | Arnica latifolia Bong. var. gracilis (Rydb.) Cronq. | ARLAG |
| Arnica lanceolata | Arnica mollis Hook. var. petiolaris Fern. | ARMOP |
| Arnica latifolia | Arnica latifolia Bong. var. angustifolia Herder | ARLAA3 |
| Arnica lessingii | Arnica lessingii Greene ssp. norbergii Hult?n & Maguire | ARLEN |
| Arnica lonchophylla ssp. arnoglossa | Arnica arnoglossa Greene | ARAR11 |
| Arnica lonchophylla ssp. arnoglossa | Arnica lonchophylla Greene var. arnoglossa (Greene) Boivin | ARLOA2 |
| Arnica lonchophylla ssp. lonchophylla | Arnica alpina (L.) Olin ssp. lonchophylla (Greene) Taylor & MacBryde | ARALL3 |
| Arnica lonchophylla ssp. lonchophylla | Arnica alpina (L.) Olin var. lonchophylla (Greene) Welsh | ARALL2 |
| Arnica lonchophylla ssp. lonchophylla | Arnica angustifolia Vahl ssp. lonchophylla (Greene) G.W. Douglas & G. Ruyle-Douglas | ARANL |
| Arnica lonchophylla ssp. lonchophylla | Arnica chionopappa Fern. | ARCH7 |
| Arnica lonchophylla ssp. lonchophylla | Arnica gaspensis Fern. | ARGA |
| Arnica lonchophylla ssp. lonchophylla | Arnica lonchophylla Greene ssp. chionopappa (Fern.) Maguire | ARLOC |
| Arnica longifolia | Arnica longifolia D.C. Eat. ssp. genuina Maguire | ARLOG5 |
| Arnica longifolia | Arnica longifolia D.C. Eat. ssp. myriadenia (Piper) Maguire | ARLOM2 |
| Arnica mollis | Arnica mollis Hook. var. silvatica (Greene) Maguire | ARMOS |
| Arnica nevadensis | Arnica tomentella Greene | ARTO4 |
| Arnica parryi ssp. parryi | Arnica parryi Gray ssp. genuina Maguire | ARPAG |
| Arnica parryi ssp. sonnei | Arnica parryi Gray var. sonnei (Greene) Cronq. | ARPAS |
| Arnica parryi ssp. sonnei | Arnica sonnei Greene | ARSO4 |
| Arnica rydbergii | Arnica cascadensis St. John | ARCA25 |
| Arnica sororia | Arnica fulgens Pursh var. sororia (Greene) G.W. Douglas & G. Ruyle-Douglas | ARFUS |
| Arnica spathulata | Arnica cusickii Rydb. | ARCU4 |
| Arnica spathulata | Arnica spathulata Greene ssp. eastwoodiae (Rydb.) Maguire | ARSPE2 |
| Arnica spathulata | Arnica spathulata Greene var. eastwoodiae (Rydb.) Ediger & T.M. Barkl. | ARSPE |
| Arnica viscosa | Chrysopsis shastensis Jepson | CHSH2 |
| Arnoglossum atriplicifolium | Cacalia atriplicifolia L. | CAAT |
| Arnoglossum atriplicifolium | Cacalia rotundifolia (Raf.) House | CARO21 |
| Arnoglossum atriplicifolium | Mesadenia atriplicifolia (L.) Raf. | MEAT |
| Arnoglossum diversifolium | Cacalia diversifolia Torr. & Gray | CADI26 |
| Arnoglossum diversifolium | Mesadenia diversifolia (Torr. & Gray) Greene | MEDI5 |
| Arnoglossum floridanum | Cacalia floridana Gray | CAFL12 |
| Arnoglossum floridanum | Mesadenia floridana (Gray) Greene | MEFL4 |
| Arnoglossum ovatum | Cacalia elliottii (Harper) Shinners | CAEL14 |
| Arnoglossum ovatum | Cacalia lanceolata Nutt. | CALA56 |
| Arnoglossum ovatum | Cacalia lanceolata Nutt. var. elliottii (Harper) Kral & R.K. Godfrey | CALAE |
| Arnoglossum ovatum | Cacalia lanceolata Nutt. var. virescens (Harper) Shinners | CALAV2 |
| Arnoglossum ovatum | Cacalia ovata Walt. | CAOV6 |
| Arnoglossum ovatum | Mesadenia elliottii Harper | MEEL4 |
| Arnoglossum ovatum | Mesadenia lanceolata (Nutt.) Raf. | MELA11 |
| Arnoglossum ovatum | Mesadenia lanceolata (Nutt.) Raf. var. virescens Harper | MELAV |
| Arnoglossum ovatum | Mesadenia maxima Harper | MEMA10 |
| Arnoglossum plantagineum | Cacalia paniculata Raf. | CAPA54 |
| Arnoglossum plantagineum | Cacalia plantaginea (Raf.) Shinners | CAPL |
| Arnoglossum plantagineum | Cacalia pteranthes Raf. | CAPT2 |
| Arnoglossum plantagineum | Cacalia tuberosa Nutt. | CATU10 |
| Arnoglossum plantagineum | Mesadenia tuberosa (Nutt.) Britt. | METU3 |
| Arnoglossum reniforme | Arnoglossum muehlenbergii (Schultz-Bip.) H.E. Robins. | ARMU3 |
| Arnoglossum reniforme | Cacalia muehlenbergii (Schultz-Bip.) Fern. | CAMU23 |
| Arnoglossum reniforme | Cacalia reniformis Muhl. ex Willd., non Lam. | CARE12 |
| Arnoglossum reniforme | Mesadenia reniformis Raf. | MERE5 |
| Arnoglossum reniforme | Senecio muehlenbergii Schultz-Bip. | SEMU6 |
| Arnoglossum sulcatum | Cacalia sulcata Fern. | CASU30 |
| Arnoglossum sulcatum | Mesadenia sulcata (Fern.) Harper | MESU9 |
| arnoseris | Arnoseris Gaertn. | ARNOS |
| Arnoseris minima | Hyoseris minima L. | HYMI6 |
| aromatic aster | Symphyotrichum oblongifolium (Nutt.) Nesom | SYOB |
| arrowleaf balsamroot | Balsamorhiza sagittata (Pursh) Nutt. | BASA3 |
| arrowleaf ragwort | Senecio triangularis Hook. | SETR |
| arrowleaf rattlesnakeroot | Prenanthes sagittata (Gray) A. Nels. | PRSA |
| arrowleaf sweet coltsfoot | Petasites frigidus (L.) Fries var. sagittatus (Banks ex Pursh) Cherniawsky | PEFRS5 |
| arrowweed | Pluchea sericea (Nutt.) Coville | PLSE |
| Artemisia abrotanum | Artemisia procera Willd. | ARPR6 |
| Artemisia absinthium | Artemisia absinthium L. var. insipida Stechmann | ARABI3 |
| Artemisia alaskana | Artemisia tyrellii Rydb. | ARTY |
| Artemisia arbuscula ssp. arbuscula | Artemisia tridentata Nutt. ssp. arbuscula (Nutt.) Hall & Clements | ARTRA |
| Artemisia arbuscula ssp. arbuscula | Seriphidium arbusculum (Nutt.) W.A. Weber | SEAR9 |
| Artemisia arbuscula ssp. longiloba | Artemisia arbuscula Nutt. var. longiloba (Osterhout) Dorn | ARARL2 |
| Artemisia arbuscula ssp. longiloba | Artemisia longiloba (Osterhout) Beetle | ARLO9 |
| Artemisia arbuscula ssp. longiloba | Artemisia spiciformis Osterhout var. longiloba Osterhout | ARSPL |
| Artemisia arbuscula ssp. longiloba | Seriphidium arbusculum (Nutt.) W.A. Weber ssp. longilobum (Osterhout) W.A. Weber | SEARL |
| Artemisia arctica ssp. arctica | Artemisia arctica Less. ssp. saxicola (Rydb.) Hult | ARARS |
| Artemisia arctica ssp. arctica | Artemisia norvegica Fries ssp. saxatilis (Bess.) Hall & Clements | ARNOS4 |
| Artemisia arctica ssp. arctica | Artemisia norvegica Fries var. piceetorum Welsh & Goodrich | ARNOP |
| Artemisia arctica ssp. arctica | Artemisia norvegica Fries var. saxatilis (Bess.) Jepson | ARNOS3 |
| Artemisia arctica ssp. beringensis | Artemisia arctica Less. var. beringensis Hult | ARARB2 |
| Artemisia arctica ssp. comata | Artemisia comata Rydb. | ARCO22 |
| Artemisia arctica ssp. comata | Artemisia norvegica Fries var. comata (Rydb.) Welsh | ARNOC |
| Artemisia australis | Artemisia hillebrandii Skottsberg | ARHI6 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia borealis Pallas | ARBO4 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia borealis Pallas ssp. purshii (Hook.) Hult | ARBOP |
| Artemisia campestris ssp. borealis var. borealis | Artemisia borealis Pallas var. latisecta Fern. | ARBOL |
| Artemisia campestris ssp. borealis var. borealis | Artemisia borealis Pallas var. purshii Hook. | ARBOP2 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia campestris L. ssp. canadensis (Michx.) Scoggan | ARCAC9 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia campestris L. var. canadensis (Michx.) Welsh | ARCAC10 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia campestris L. var. purshii (Hook.) Cronq. | ARCAP5 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia canadensis Michx. | ARCA23 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia richardsoniana Bess. | ARRI6 |
| Artemisia campestris ssp. borealis var. borealis | Artemisia spithamea Pursh | ARSP7 |
| Artemisia campestris ssp. borealis var. borealis | Oligosporus groenlandicus (Hornem.) A.& D. L?ve | OLGR2 |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia campestris L. ssp. pacifica (Nutt.) Hall & Clements | ARCAP2 |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia campestris L. var. douglasiana (Bess.) Boivin | ARCAD |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia campestris L. var. pacifica (Nutt.) M.E. Peck | ARCAP3 |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia campestris L. var. strutziae Welsh | ARCAS4 |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia camporum Rydb. | ARCA30 |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia pacifica Nutt. | ARPA28 |
| Artemisia campestris ssp. borealis var. scouleriana | Artemisia ripicola Rydb. | ARRI7 |
| Artemisia campestris ssp. borealis var. scouleriana | Oligosporus campestris (L.) Cass. ssp. pacificus (Nutt.) W.A. Weber | OLCAP |
| Artemisia campestris ssp. borealis var. scouleriana | Oligosporus pacificus (Nutt.) Poljakov | OLPA3 |
| Artemisia campestris ssp. campestris | Oligosporus campestris (L.) Cass. [excluded] | OLCA6 |
| Artemisia campestris ssp. caudata | Artemisia campestris L. var. caudata (Michx.) Palmer & Steyermark | ARCAC11 |
| Artemisia campestris ssp. caudata | Artemisia caudata Michx. | ARCA24 |
| Artemisia campestris ssp. caudata | Artemisia caudata Michx. var. calvens Lunell | ARCAC3 |
| Artemisia campestris ssp. caudata | Artemisia forwoodii S. Wats. | ARFO3 |
| Artemisia campestris ssp. caudata | Oligosporus campestris (L.) Cass. ssp. caudatus (Michx.) W.A. Weber | OLCAC |
| Artemisia campestris ssp. caudata | Oligosporus caudatus Poljakov | OLCA5 |
| Artemisia cana ssp. bolanderi | Artemisia bolanderi Gray | ARBO5 |
| Artemisia cana ssp. bolanderi | Artemisia tridentata Nutt. ssp. bolanderi (Gray) Hall & Clements | ARTRB |
| Artemisia cana ssp. bolanderi | Artemisia tridentata Nutt. var. bolanderi (Gray) McMinn | ARTRB2 |
| Artemisia cana ssp. bolanderi | Seriphidium canum (Pursh) W.A. Weber ssp. bolanderi (Gray) W.A. Weber | SECAB |
| Artemisia cana ssp. cana | Artemisia cana Pursh var. cana | ARCAC12 |
| Artemisia cana ssp. cana | Seriphidium canum (Pursh) W.A. Weber | SECA9 |
| Artemisia cana ssp. viscidula | Artemisia argilosa Beetle | ARAR10 |
| Artemisia cana ssp. viscidula | Artemisia cana Pursh var. viscidula Osterhout | ARCAV |
| Artemisia cana ssp. viscidula | Seriphidium canum (Pursh) W.A. Weber ssp. viscidulum (Osterhout) W.A. Weber | SECAV |
| Artemisia carruthii | Artemisia carruthii Wood ex Carruth. var. wrightii (Gray) Blake | ARCAW2 |
| Artemisia carruthii | Artemisia kansana Britt. | ARKA4 |
| Artemisia douglasiana | Artemisia vulgaris L. ssp. heterophylla (Nutt.) Hall & Clements | ARVUH |
| Artemisia douglasiana | Artemisia vulgaris L. var. douglasiana (Bess. ex Hook.) St. John | ARVUD |
| Artemisia dracunculus | Artemisia dracunculoides Pursh | ARDR5 |
| Artemisia dracunculus | Artemisia dracunculoides Pursh var. dracunculina (S. Wats.) Blake | ARDRD |
| Artemisia dracunculus | Artemisia dracunculus L. ssp. glauca (Pallas ex Willd.) Hall & Clements | ARDRG |
| Artemisia dracunculus | Artemisia dracunculus L. var. glauca (Pallas ex Willd.) Bess. | ARDRG2 |
| Artemisia dracunculus | Artemisia glauca Pallas ex Willd. | ARGL12 |
| Artemisia dracunculus | Artemisia glauca Pallas ex Willd. var. dracunculina (S. Wats.) Fern. | ARGLD2 |
| Artemisia dracunculus | Oligosporus dracunculus (L.) Poljakov | OLDR |
| Artemisia dracunculus | Oligosporus dracunculus (L.) Poljakov ssp. dracunculinus (S. Wats.) W.A. Weber | OLDRD |
| Artemisia dracunculus | Oligosporus dracunculus (L.) Poljakov ssp. glaucus (Pallas ex Willd.) A.& D. L?ve | OLDRG |
| Artemisia filifolia | Oligosporus filifolius (Torr.) W.A. Weber | OLFI |
| Artemisia furcata var. furcata | Artemisia hyperborea Rydb. | ARHY2 |
| Artemisia furcata var. furcata | Artemisia tacomensis Rydb. | ARTA4 |
| Artemisia furcata var. furcata | Artemisia trifurcata Steph. ex Spreng. | ARTR3 |
| Artemisia furcata var. heterophylla | Artemisia heterophylla Bess. | ARHE5 |
| Artemisia globularia | Artemisia flava Jurtzev | ARFL4 |
| Artemisia globularia | Artemisia globularia Cham. ex Bess. var. lutea Hult | ARGLL |
| Artemisia gmelinii | Artemisia sacrorum Ledeb. | ARSA19 |
| Artemisia kauaiensis | Artemisia hillebrandii Skottsberg var. kauaiensis Skottsberg | ARHIK |
| Artemisia laciniata | Artemisia laciniatiformis Komarov | ARLA17 |
| Artemisia lindleyana | Artemisia prescottiana Bess. | ARPR7 |
| Artemisia ludoviciana ssp. albula | Artemisia albula Woot. | ARAL14 |
| Artemisia ludoviciana ssp. albula | Artemisia ludoviciana Nutt. var. albula (Woot.) Shinners | ARLUA2 |
| Artemisia ludoviciana ssp. candicans | Artemisia candicans Rydb. | ARCA28 |
| Artemisia ludoviciana ssp. candicans | Artemisia ludoviciana Nutt. var. latiloba Nutt. | ARLUL |
| Artemisia ludoviciana ssp. incompta | Artemisia incompta Nutt. | ARIN6 |
| Artemisia ludoviciana ssp. incompta | Artemisia ludoviciana Nutt. var. incompta (Nutt.) Cronq. | ARLUI |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia diversifolia Rydb. | ARDI15 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia gnaphalodes Nutt. | ARGN |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia herriotii Rydb. | ARHE6 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia ludoviciana Nutt. ssp. typica Keck | ARLUT |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia ludoviciana Nutt. var. americana (Bess.) Fern. | ARLUA3 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia ludoviciana Nutt. var. brittonii (Rydb.) Fern. | ARLUB |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia ludoviciana Nutt. var. gnaphalodes (Nutt.) Torr. & Gray | ARLUG |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia ludoviciana Nutt. var. latifolia (Bess.) Torr. & Gray | ARLUL3 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia ludoviciana Nutt. var. pabularis (A. Nels.) Fern. | ARLUP |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia pabularis (A. Nels.) Rydb. | ARPA23 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia purshiana Bess. | ARPU12 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia vulgaris L. ssp. ludoviciana (Nutt.) Hall & Clements | ARVUL2 |
| Artemisia ludoviciana ssp. ludoviciana | Artemisia vulgaris L. var. ludoviciana (Nutt.) Kuntze | ARVUL3 |
| Artemisia ludoviciana ssp. mexicana | Artemisia ludoviciana Nutt. var. mexicana (Willd. ex Spreng.) Gray | ARLUM |
| Artemisia ludoviciana ssp. mexicana | Artemisia mexicana Willd. ex Spreng. | ARME9 |
| Artemisia ludoviciana ssp. mexicana | Artemisia neomexicana Greene ex Rydb. | ARNE11 |
| Artemisia ludoviciana ssp. mexicana | Artemisia vulgaris L. var. mexicana (Willd. ex Spreng.) Torr. & Gray | ARVUM |
| Artemisia ludoviciana ssp. redolens | Artemisia ludoviciana Nutt. var. redolens (Gray) Shinners | ARLUR2 |
| Artemisia ludoviciana ssp. redolens | Artemisia redolens Gray | ARRE10 |
| Artemisia ludoviciana ssp. sulcata | Artemisia sulcata Rydb. | ARSU10 |
| Artemisia mauiensis | Artemisia mauiensis (Gray) Skottsberg var. diffusa Skottsberg | ARMAD |
| Artemisia michauxiana | Artemisia vulgaris L. ssp. michauxiana (Bess.) St. John | ARVUM2 |
| Artemisia nesiotica | Artemisia californica Less. var. insularis (Rydb.) Munz | ARCAI |
| Artemisia nova | Artemisia arbuscula Nutt. ssp. nova (A. Nels.) G.H. Ward | ARARN2 |
| Artemisia nova | Artemisia arbuscula Nutt. var. nova (A. Nels.) Cronq. | ARARN |
| Artemisia nova | Artemisia nova A. Nels. var. duchesnicola Welsh & Goodrich | ARNOD |
| Artemisia nova | Artemisia tridentata Nutt. ssp. nova (A. Nels.) Hall & Clements | ARTRN |
| Artemisia nova | Seriphidium novum (A. Nels.) W.A. Weber | SENO |
| Artemisia parryi | Artemisia laciniata Willd. ssp. parryi (Gray) W.A. Weber | ARLAP |
| Artemisia pedatifida | Oligosporus pedatifidus (Nutt.) Poljakov | OLPE |
| Artemisia pygmaea | Seriphidium pygmaeum (Gray) W.A. Weber | SEPY |
| Artemisia rigida | Artemisia trifida Nutt. var. rigida Nutt. | ARTRR6 |
| Artemisia rigida | Seriphidium rigidum (Nutt.) W.A. Weber | SERI6 |
| Artemisia rothrockii | Artemisia tridentata Nutt. ssp. rothrockii (Gray) Hall & Clements | ARTRR3 |
| Artemisia rothrockii | Artemisia tridentata Nutt. var. rothrockii (Gray) McMinn | ARTRR5 |
| Artemisia rothrockii | Seriphidium rothrockii (Gray) W.A. Weber | SERO4 |
| Artemisia thuscula | Artemisia canariensis (Besser) Less. | ARCA43 |
| Artemisia tilesii ssp. elatior | Artemisia elatior (Torr. & Gray) Rydb. | AREL7 |
| Artemisia tilesii ssp. elatior | Artemisia tilesii Ledeb. var. elatior Torr. & Gray | ARTIE2 |
| Artemisia tilesii ssp. gormanii | Artemisia gormanii Rydb. | ARGO |
| Artemisia tilesii ssp. unalaschcensis | Artemisia hookeriana Bess. | ARHO11 |
| Artemisia tilesii ssp. unalaschcensis | Artemisia tilesii auct. non Ledeb. [misapplied] | ARTI4 |
| Artemisia tilesii ssp. unalaschcensis | Artemisia tilesii Ledeb. var. unalaschcensis Bess. | ARTIU |
| Artemisia tridentata ssp. parishii | Artemisia tridentata Nutt. var. parishii (Gray) Jepson | ARTRP3 |
| Artemisia tridentata ssp. parishii | Seriphidium tridentatum (Nutt.) W.A. Weber ssp. parishii (Gray) W.A. Weber | SETRP |
| Artemisia tridentata ssp. spiciformis | Artemisia spiciformis Osterhout | ARSP8 |
| Artemisia tridentata ssp. spiciformis | Artemisia tridentata Nutt. var. spiciformis (Osterhout) Dorn | ARTRS3 |
| Artemisia tridentata ssp. tridentata | Artemisia angusta Rydb. | ARAN20 |
| Artemisia tridentata ssp. tridentata | Artemisia tridentata Nutt. var. angustifolia Gray | ARTRA2 |
| Artemisia tridentata ssp. tridentata | Seriphidium tridentatum (Nutt.) W.A. Weber | SETR4 |
| Artemisia tridentata ssp. vaseyana | Artemisia tridentata Nutt. var. pauciflora Winward & Goodrich | ARTRP4 |
| Artemisia tridentata ssp. vaseyana | Artemisia tridentata Nutt. var. vaseyana (Rydb.) Boivin | ARTRV2 |
| Artemisia tridentata ssp. vaseyana | Artemisia vaseyana Rydb. | ARVA2 |
| Artemisia tridentata ssp. vaseyana | Seriphidium tridentatum (Nutt.) W.A. Weber ssp. vaseyanum (Rydb.) W.A. Weber | SETRV |
| Artemisia tridentata ssp. vaseyana | Seriphidium vaseyanum (Rydb.) W.A. Weber | SEVA |
| Artemisia tridentata ssp. wyomingensis | Artemisia tridentata Nutt. var. wyomingensis (Beetle & Young) Welsh | ARTRW |
| Artemisia tridentata ssp. wyomingensis | Seriphidium tridentatum (Nutt.) W.A. Weber ssp. wyomingense (Beetle & Young) W.A. Weber | SETRW |
| Artemisia tripartita ssp. rupicola | Artemisia tripartita Rydb. var. rupicola (Beetle) Dorn | ARTRR4 |
| Artemisia tripartita ssp. tripartita | Artemisia tridentata Nutt. ssp. trifida (Nutt.) Hall & Clements | ARTRT4 |
| Artemisia tripartita ssp. tripartita | Artemisia trifida Nutt. | ARTR8 |
| Artemisia tripartita ssp. tripartita | Seriphidium tripartitum (Rydb.) W.A. Weber | SETR6 |
| Artemisia umbelliformis | Artemisia laxa (Lam.) Fritsch | ARLA18 |
| Artemisia vulgaris | Artemisia vulgaris L. var. coarctata Forselles ex Besser | ARVUC2 |
| Artemisia vulgaris var. kamtschatica | Artemisia tilesii Ledeb. var. aleutica (Hult?n) Welsh | ARTIA |
| Artemisia vulgaris var. kamtschatica | Artemisia unalaskensis Rydb. | ARUN2 |
| Artemisia vulgaris var. kamtschatica | Artemisia unalaskensis Rydb. var. aleutica Hult | ARUNA |
| Artemisia vulgaris var. vulgaris | Artemisia selengensis Turcz. ex Bess. | ARSE18 |
| Artemisia vulgaris var. vulgaris | Artemisia vulgaris L. var. glabra Ledeb. | ARVUG |
| Artemisia vulgaris var. vulgaris | Artemisia vulgaris L. var. latiloba Ledeb. | ARVUL |
| Artemisia vulgaris var. vulgaris | Artemisia vulgaris L. var. selengensis (Turcz. ex Bess.) Maxim. | ARVUS |
| Asanthus squamulosus | Brickellia squamulosa Gray | BRSQ |
| Ash Meadows gumweed | Grindelia fraxinopratensis Reveal & Beatley | GRFR |
| ashdaisy | Piptocarpha R. Br. | PIPTO2 |
| Ashland thistle | Cirsium ciliolatum (Henderson) J.T. Howell | CICI |
| ashy pricklyleaf | Thymophylla tephroleuca (Blake) Strother | THTE8 |
| ashy sunflower | Helianthus mollis Lam. | HEMO2 |
| aspen fleabane | Erigeron speciosus (Lindl.) DC. | ERSP4 |
| aspen fleabane | Erigeron speciosus (Lindl.) DC. var. macranthus (Nutt.) Cronq. | ERSPM |
| aspen fleabane | Erigeron speciosus (Lindl.) DC. var. speciosus | ERSPS |
| aster | Aster L. | ASTER |
| aster | Eucephalus Nutt. | EUCEP2 |
| aster | Eurybia (Cass.) S.F. Gray | EURYB |
| aster | Ionactis Greene | IONAC |
| aster | Kalimeris (Cass.) Cass. | KALIM |
| aster | Oclemena Greene | OCLEM |
| aster | Oreostemma Greene | OREOS |
| aster | Symphyotrichum Nees | SYMPH4 |
| Aster alpinus var. alpinus | Aster garibaldii Brugger | ASGA9 |
| Aster alpinus var. serpentimontanus | Aster serpentimontanus Tamamsch. | ASSE17 |
| Aster alpinus var. vierhapperi | Aster alpinus L. ssp. vierhapperi Onno | ASALV2 |
| Aster alpinus var. vierhapperi | Diplactis alpina (L.) Semple p.p. | DIAL12 |
| Aster alpinus var. vierhapperi | Diplactis alpina (L.) Semple ssp. vierhapperi (Onno) Semple | DIALV |
| Aster amellus | Aster amelloides Besser | ASAM11 |
| Aster amellus ssp. ibericus | Aster ibericus Steven | ASIB2 |
| Aster flaccidus var. flaccidus | Aster tibeticus Hook. f. | ASTI6 |
| Aster sedifolius ssp. dracunculoides | Aster dracunculoides Lam. | ASDR5 |
| asthmaweed | Conyza bonariensis (L.) Cronq. | COBO |
| asthmaweed | Conyza floribunda Kunth | COFL |
| Astranthium integrifolium ssp. ciliatum | Astranthium integrifolium (Michx.) Nutt. var. ciliatum (Raf.) Larsen | ASINC2 |
| Astranthium integrifolium ssp. ciliatum | Astranthium integrifolium (Michx.) Nutt. var. triflorum (Raf.) Shinners | ASINT2 |
| Astranthium integrifolium ssp. integrifolium | Bellis integrifolia Michx. | BEIN4 |
| Astranthium robustum | Astranthium integrifolium (Michx.) Nutt. var. robustum Shinners | ASINR |
| Atkinson's tickseed | Coreopsis tinctoria Nutt. var. atkinsoniana (Dougl. ex Lindl.) H.M. Parker ex E.B. Sm. | COTIA |
| Atlantic goldenrod | Solidago arguta Ait. | SOAR |
| Atlantic goldenrod | Solidago arguta Ait. var. arguta | SOARA |
| Atlantic goldenrod | Solidago arguta Ait. var. caroliniana Gray | SOARC |
| Atlantic goldenrod | Solidago arguta Ait. var. neurolepis (Fern.) Steyermark | SOARN |
| atrichoseris | Atrichoseris Gray | ATRIC |
| Atrichoseris platyphylla | Malacothrix platyphylla Gray | MAPL3 |
| Australian waterbuttons | Cotula australis (Sieber ex Spreng.) Hook. f. | COAU3 |
| Austrian chamomile | Anthemis austriaca Jacq. | ANAU3 |
| autumn goldenrod | Solidago sphacelata Raf. | SOSP4 |
| Awalua Ridge tetramolopium | Tetramolopium remyi (Gray) Hbd. | TERE3 |
| Awapa fleabane | Erigeron awapensis Welsh | ERAW |
| awnless bushsunflower | Simsia calva (Engelm. & Gray) Gray | SICA7 |
| awnless leastdaisy | Chaetopappa imberbis (Gray) Nesom | CHIM |
| Aztec goldenbush | Isocoma azteca Nesom | ISAZ |
| Aztec marigold | Tagetes erecta L. | TAER |
| baby goldenrod | Solidago nana Nutt. | SONA |
| baccharis | Baccharis L. | BACCH |
| Baccharis halimifolia | Baccharis halimifolia L. var. angustior DC. | BAHAA |
| Baccharis pilularis | Baccharis pilularis DC. ssp. consanguinea (DC.) C.B. Wolf | BAPIC |
| Baccharis pilularis | Baccharis pilularis DC. var. consanguinea (DC.) Kuntze | BAPIC2 |
| Baccharis salicifolia | Baccharis glutinosa Pers. | BAGL2 |
| Baccharis salicifolia | Baccharis viminea DC. | BAVI |
| Baccharis salicifolia | Molina salicifolia Ruiz & Pav?n | MOSA5 |
| Baccharis texana | Linosyris texana Torr. & Gray | LITE9 |
| badland-mule's-ears | Scabrethia scabra (Hook.) W.A. Weber | SCSC15 |
| badlands mule-ears | Scabrethia scabra (Hook.) W.A. Weber ssp. attenuata (W.A. Weber) W.A. Weber | SCSCA2 |
| badlands mule-ears | Scabrethia scabra (Hook.) W.A. Weber ssp. canescens (W.A. Weber) W.A. Weber | SCSCC |
| badlands mule-ears | Scabrethia scabra (Hook.) W.A. Weber ssp. scabra | SCSCS5 |
| Bahama sachsia | Sachsia polycephala Griseb. | SAPO3 |
| Bahaman aster | Symphyotrichum bahamense (Britt.) Nesom | SYBA5 |
| bahia | Bahia Lag. | BAHIA |
| bahia | Picradeniopsis Rydb. ex Britt. | PICRA3 |
| Bahia dissecta | Amauria dissecta Gray | AMDI3 |
| Bahia dissecta | Amauriopsis dissecta (Gray) Rydb. | AMDI5 |
| Bailey's rabbitbrush | Chrysothamnus baileyi Woot. & Standl. | CHBA11 |
| Baileya multiradiata | Baileya multiradiata Harvey & Gray ex Gray var. thurberi (Rydb.) Kittell | BAMUT |
| Baileya pleniradiata | Baileya multiradiata Harvey & Gray ex Gray var. pleniradiata (Harvey & Gray ex Gray) Coville | BAMUP |
| Baileya pleniradiata | Baileya perennis (A. Nels.) Rydb. | BAPE2 |
| Baker's goldfields | Lasthenia californica DC. ex Lindl. ssp. bakeri (J.T. Howell) R. Chan | LACAB |
| Baker's hawksbeard | Crepis bakeri Greene | CRBA2 |
| Baker's hawksbeard | Crepis bakeri Greene ssp. bakeri | CRBAB |
| Baker's paperflower | Psilostrophe bakeri Greene | PSBA2 |
| Baker's stickyseed | Blennosperma bakeri Heiser | BLBA |
| bald fleabane | Erigeron calvus Coville | ERCA3 |
| Balduina angustifolia | Actinospermum angustifolium (Pursh) Torr. & Gray | ACAN5 |
| Balduina atropurpurea | Endorima atropurpurea (Harper) Small | ENAT |
| Balduina uniflora | Endorima uniflora (Nutt.) Raf. | ENUN |
| Baldwin's ironweed | Vernonia baldwinii Torr. | VEBA |
| Baldwin's ironweed | Vernonia baldwinii Torr. ssp. baldwinii | VEBAB |
| ballhead ragwort | Senecio sphaerocephalus Greene | SESP4 |
| balsam groundsel | Packera paupercula (Michx.) A.& D. L?ve | PAPA20 |
| Balsamorhiza hookeri var. hirsuta | Balsamorhiza hirsuta Nutt. | BAHI |
| Balsamorhiza hookeri var. hispidula | Balsamorhiza hispidula Sharp | BAHI2 |
| Balsamorhiza hookeri var. idahoensis | Balsamorhiza macrophylla Nutt. var. idahoensis Sharp | BAMAI |
| Balsamorhiza hookeri var. lagocephala | Balsamorhiza hirsuta Nutt. var. lagocephala Sharp | BAHIL |
| Balsamorhiza hookeri var. neglecta | Balsamorhiza hirsuta Nutt. var. neglecta Sharp | BAHIN |
| Balsamorhiza lanata | Balsamorhiza hookeri (Hook.) Nutt. var. lanata Sharp | BAHOL2 |
| Balsamorhiza macrolepis var. platylepis | Balsamorhiza hookeri (Hook.) Nutt. var. platylepis (Sharp) Cronq. | BAHOP |
| Balsamorhiza macrolepis var. platylepis | Balsamorhiza platylepis Sharp | BAPL5 |
| balsamroot | Balsamorhiza Nutt. | BALSA |
| baltimora | Baltimora L. | BALTI |
| bandanna daisy | Gaillardia coahuilensis B.L. Turner | GACO7 |
| Barbara's buttons | Marshallia Schreb. | MARSH |
| barbed rattlesnakeroot | Prenanthes barbata (Torr. & Gray) Milstead | PRBA |
| Barber's hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. barberi (Greenm.) Babcock & Stebbins | CRRUB |
| Barberton daisy | Gerbera jamesonii Bolus ex Hooker f. | GEJA |
| baretwig neststraw | Stylocline psilocarphoides M.E. Peck | STPS |
| Barkleyanthus salicifolius | Cineraria salicifolia Kunth | CISA3 |
| Barkleyanthus salicifolius | Senecio salignus DC. | SESA4 |
| Barneby's serpentweed | Tonestus kingii (D.C. Eat.) Nesom var. barnebyana (Welsh & Goodrich) Nesom | TOKIB |
| Barneby's thistle | Cirsium barnebyi Welsh & Neese | CIBA |
| barrens silky aster | Symphyotrichum pratense (Raf.) Nesom | SYPR7 |
| Bartlett daisy | Bartlettia scaposa Gray | BASC |
| bartlettia | Bartlettia Gray | BARTL |
| bartlettina | Bartlettina R.M. King & H. Robinson | BARTL2 |
| basalt fleabane | Erigeron basalticus Hoover | ERBA4 |
| bashful ragwort | Senecio pudicus Greene | SEPU3 |
| basin big sagebrush | Artemisia tridentata Nutt. ssp. tridentata | ARTRT |
| basin fleabane | Erigeron pulcherrimus Heller | ERPU9 |
| basindaisy | Platyschkuhria integrifolia (Gray) Rydb. | PLIN7 |
| basindaisy | Platyschkuhria integrifolia (Gray) Rydb. var. integrifolia | PLINI |
| basindaisy | Platyschkuhria integrifolia (Gray) Rydb. var. ourolepis (Blake) W. Ellison | PLINO2 |
| basindaisy | Platyschkuhria Rydb. | PLATY5 |
| Bay Biscayne creeping-oxeye | Sphagneticola trilobata (L.) Pruski | SPTR6 |
| Bay County Indian plaintain | Arnoglossum album L.C. Anders. | ARAL30 |
| beach creeping oxeye | Pascalia glauca Ortega | PAGL9 |
| beach tidytips | Layia carnosa (Nutt.) Torr. & Gray | LACA4 |
| beach wormwood | Artemisia pycnocephala (Less.) DC. | ARPY3 |
| beaked hawksbeard | Crepis vesicaria L. | CRVE3 |
| beaked hawksbeard | Crepis vesicaria L. ssp. taraxacifolia (Thuill.) Thellung | CRVET |
| beaked skeletonweed | Shinnersoseris rostrata (Gray) S. Tomb | SHRO2 |
| beaked skeletonweed | Shinnersoseris S. Tomb | SHINN2 |
| Bear River fleabane | Erigeron ursinus D.C. Eat. | ERUR2 |
| bearded beggarticks | Bidens aristosa (Michx.) Britt. | BIAR |
| beardless cinchweed | Pectis imberbis Gray | PEIM |
| beautiful aster | Eurybia pulchra (Blake) Nesom | EUPU16 |
| beautiful fleabane | Erigeron formosissimus Greene | ERFO3 |
| beautiful woolly sunflower | Eriophyllum ambiguum (Gray) Gray | ERAM3 |
| beautiful woolly sunflower | Eriophyllum ambiguum (Gray) Gray var. ambiguum | ERAMA |
| beautiful woolly sunflower | Eriophyllum ambiguum (Gray) Gray var. paleaceum (Brandeg.) Ferris | ERAMP |
| beautyhead | Baltimora recta L. | BARE2 |
| Beaver Mountain ragwort | Packera castoreus (Welsh) Kartesz | PACA35 |
| Beck's watermarigold | Bidens beckii Torr. ex Spreng. | BIBE2 |
| beggarticks | Bidens L. | BIDEN |
| bejuco de miel | Salmea DC. | SALME |
| bejuco de miel | Salmea scandens (L.) DC. | SASC3 |
| bellis | Bellis L. | BELLI |
| bellorita | Erigeron bellioides DC. | ERBE6 |
| benitoa | Benitoa Keck | BENIT |
| benitoa | Benitoa occidentalis (Hall) Keck | BEOC |
| Benitoa occidentalis | Lessingia occidentalis (Hall) M.A. Lane | LEOC8 |
| berkheya | Berkheya Ehrh. | BERKH |
| Berlandiera betonicifolia | Berlandiera ?betonicifolia (Hook.) Small (pro sp.) [not hybrid] | BEBE |
| Berlandiera betonicifolia | Berlandiera texana DC. | BETE2 |
| Berlandiera betonicifolia | Berlandiera texana DC. var. betonicifolia (Hook.) Torr. & Gray | BETEB |
| Berlandiera lyrata | Berlandiera incisa T. & G. | BEIN6 |
| Berlandiera lyrata | Berlandiera lyrata Benth. var. macrophylla Gray | BELYM |
| Berlandiera pumila var. pumila | Berlandiera dealbata (Torr. & Gray) Small | BEDE3 |
| Berlandiera pumila var. pumila | Berlandiera tomentosa (Pursh) Nutt. | BETO |
| Berlandiera pumila var. pumila | Berlandiera tomentosa (Pursh) Nutt. var. dealbata Torr. & Gray | BETOD |
| betonyleaf brickellbush | Brickellia betonicifolia Gray | BRBE |
| betonyleaf thoroughwort | Conoclinium betonicifolium (P. Mill.) King & H.E. Robins. | COBE4 |
| Beyrich's fleabane | Erigeron strigosus Muhl. ex Willd. var. beyrichii (Fisch. & C.A. Mey.) Torr. & Gray ex Gray | ERSTB |
| biannual lettuce | Lactuca ludoviciana (Nutt.) Riddell | LALU |
| Bidens alba var. radiata | Bidens pilosa L. var. radiata Schultz-Bip. | BIPIR |
| Bidens amplectens | Bidens gracilis Nutt. | BIGR2 |
| Bidens amplectens | Bidens halawana O. Deg. & Sherff | BIHA2 |
| Bidens aristosa | Bidens aristosa (Michx.) Britt. var. fritcheyi Fern. | BIARF |
| Bidens aristosa | Bidens aristosa (Michx.) Britt. var. mutica (Gray) Gattinger | BIARM |
| Bidens aristosa | Bidens aristosa (Michx.) Britt. var. retrorsa (Sherff) Wunderlin | BIARR |
| Bidens aristosa | Bidens involucrata (Nutt.) Britt. | BIIN2 |
| Bidens aristosa | Bidens polylepis Blake | BIPO |
| Bidens aristosa | Bidens polylepis Blake var. retrorsa Sherff | BIPOR |
| Bidens aurea | Bidens aurea (Ait.) Sherff var. wrightii (Gray) Sherff | BIAUW |
| Bidens aurea | Bidens heterophylla Ortega | BIHE3 |
| Bidens aurea | Coreopsis aurea Ait. | COAU6 |
| Bidens beckii | Megalodonta beckii (Torr. ex Spreng.) Greene | MEBE2 |
| Bidens beckii | Megalodonta beckii (Torr. ex Spreng.) Greene var. beckii (Torr. ex Spreng.) Greene [superfluous autonym] | MEBEB |
| Bidens beckii | Megalodonta beckii (Torr. ex Spreng.) Greene var. hendersonii Sherff | MEBEH |
| Bidens beckii | Megalodonta beckii (Torr. ex Spreng.) Greene var. oregonensis Sherff | MEBEO |
| Bidens bidentoides | Bidens bidentoides (Nutt.) Britt. var. mariana (Blake) Sherff | BIBIM |
| Bidens bidentoides | Bidens mariana Blake | BIMA3 |
| Bidens bipinnata | Bidens bipinnata L. var. biternatoides Sherff | BIBIB |
| Bidens campylotheca ssp. campylotheca | Bidens ?magnidisca O. Deg. & Sherff | BIMA2 |
| Bidens campylotheca ssp. pentamera | Bidens campylotheca Schultz-Bip. var. pentamera Sherff | BICAP2 |
| Bidens campylotheca ssp. pentamera | Bidens pentamera (Sherff) O. Deg. & Sherff | BIPE |
| Bidens cernua | Bidens cernua L. var. cernua L. [superfluous autonym] | BICEC |
| Bidens cernua | Bidens cernua L. var. dentata (Nutt.) Boivin | BICED |
| Bidens cernua | Bidens cernua L. var. elliptica Wieg. | BICEE |
| Bidens cernua | Bidens cernua L. var. integra Wieg. | BICEI |
| Bidens cernua | Bidens cernua L. var. minima (Huds.) Pursh | BICEM |
| Bidens cernua | Bidens cernua L. var. oligodonta Fern. & St. John | BICEO |
| Bidens cernua | Bidens cernua L. var. radiata DC. | BICER |
| Bidens cernua | Bidens glaucescens Greene | BIGL |
| Bidens cervicata | Bidens asplenioides Sherff | BIAS |
| Bidens cervicata | Bidens fecunda O. Deg. & Sherff ex Sherff | BIFE |
| Bidens cervicata | Bidens ferax O. Deg. & Sherff | BIFE3 |
| Bidens cervicata | Bidens stokesii Sherff | BIST |
| Bidens connata | Bidens connata Muhl. ex Willd. var. ambiversa Fassett | BICOA |
| Bidens connata | Bidens connata Muhl. ex Willd. var. anomala Farw. | BICOA2 |
| Bidens connata | Bidens connata Muhl. ex Willd. var. fallax (Warnst.) Sherff | BICOF |
| Bidens connata | Bidens connata Muhl. ex Willd. var. gracilipes Fern. | BICOG |
| Bidens connata | Bidens connata Muhl. ex Willd. var. inundata Fern. | BICOI |
| Bidens connata | Bidens connata Muhl. ex Willd. var. petiolata (Nutt.) Farw. | BICOP |
| Bidens connata | Bidens connata Muhl. ex Willd. var. pinnata S. Wats. | BICOP2 |
| Bidens connata | Bidens connata Muhl. ex Willd. var. submutica Fassett | BICOS |
| Bidens coronata | Bidens coronata (L.) Britt. var. brachyodonta Fern. | BICOB |
| Bidens coronata | Bidens coronata (L.) Britt. var. tenuiloba (Gray) Sherff | BICOT |
| Bidens coronata | Bidens coronata (L.) Britt. var. trichosperma (Michx.) Fern. | BICOT2 |
| Bidens coronata | Bidens trichosperma (Michx.) Britt. | BITR2 |
| Bidens cosmoides | Bidens ?dimidiata O. Deg. & Sherff ex Sherff | BIDI2 |
| Bidens cosmoides | Bidens cosmoides (Gray) Sherff var. refracta Hochr. | BICOR |
| Bidens cynapiifolia | Bidens bipinnata L. var. cynapiifolia (Kunth) G. Maza | BIBIC |
| Bidens cynapiifolia | Bidens cynapiifolia Kunth var. portoricensis (Spreng.) O.E. Schulz | BICYP |
| Bidens cynapiifolia | Bidens cynapiifolia Kunth var. tenuis O.E. Schulz | BICYT |
| Bidens eatonii | Bidens eatonii Fern. var. fallax Fern. | BIEAF |
| Bidens eatonii | Bidens eatonii Fern. var. illicita Blake | BIEAI |
| Bidens eatonii | Bidens eatonii Fern. var. interstes Fassett | BIEAI2 |
| Bidens eatonii | Bidens eatonii Fern. var. kennebecensis Fern. | BIEAK |
| Bidens eatonii | Bidens eatonii Fern. var. major Fassett | BIEAM |
| Bidens eatonii | Bidens eatonii Fern. var. mutabilis Fassett | BIEAM2 |
| Bidens eatonii | Bidens eatonii Fern. var. simulans Fassett | BIEAS |
| Bidens ferulifolia | Coreopsis ferulifolia Jacq. | COFE3 |
| Bidens forbesii ssp. forbesii | Bidens asymmetrica (Levl.) Sherff var. subocculata O. Deg. & Sherff ex Sherff | BIASS2 |
| Bidens forbesii ssp. forbesii | Bidens napaliensis Sherff | BINA |
| Bidens frondosa | Bidens frondosa L. var. anomala Porter ex Fern. | BIFRA |
| Bidens frondosa | Bidens frondosa L. var. caudata Sherff | BIFRC |
| Bidens frondosa | Bidens frondosa L. var. pallida Wieg. | BIFRP |
| Bidens frondosa | Bidens frondosa L. var. stenodonta Fern. & St. John | BIFRS |
| Bidens hawaiensis | Bidens skottsbergii Sherff | BISK |
| Bidens hawaiensis | Bidens skottsbergii Sherff var. conglutinata (O. Deg. & Sherff) Sherff | BISKC |
| Bidens hawaiensis | Bidens skottsbergii Sherff var. pololuensis O. Deg. & Sherff ex Sherff | BISKP |
| Bidens heterodoxa | Bidens heterodoxa (Fern.) Fern. & St. John var. agnostica Fern. | BIHEA |
| Bidens heterodoxa | Bidens heterodoxa (Fern.) Fern. & St. John var. atheistica Fern. | BIHEA2 |
| Bidens heterodoxa | Bidens heterodoxa (Fern.) Fern. & St. John var. monardifolia Fern. | BIHEM |
| Bidens heterodoxa | Bidens heterodoxa (Fern.) Fern. & St. John var. orthodoxa Fern. & St. John | BIHEO |
| Bidens heterodoxa | Bidens infirma Fern. | BIIN |
| Bidens heterodoxa | Bidens tripartita L. var. heterodoxa Fern. | BITRH |
| Bidens hyperborea var. hyperborea | Bidens hyperborea Greene var. colpophila (Fern. & St. John) Fern. | BIHYC2 |
| Bidens hyperborea var. hyperborea | Bidens hyperborea Greene var. laurentiana Fassett | BIHYL |
| Bidens hyperborea var. svensonii | Bidens hyperborea Greene var. cathancensis Fern. | BIHYC |
| Bidens laevis | Bidens elegans Greene | BIEL |
| Bidens laevis | Bidens nashii Small | BINA2 |
| Bidens laevis | Helianthus laevis L. | HELA19 |
| Bidens macrocarpa | Bidens macrocarpa (Gray) Sherff var. ovatifolia (Gray) Sherff | BIMAO |
| Bidens mauiensis | Bidens awaluana O.& I. Deg. & Sherff | BIAW |
| Bidens mauiensis | Bidens mauiensis (Gray) Sherff var. ciliata St. John | BIMAC |
| Bidens mauiensis | Bidens mauiensis (Gray) Sherff var. cuneatoides Sherff | BIMAC2 |
| Bidens mauiensis | Bidens mauiensis (Gray) Sherff var. forbesiana Sherff | BIMAF |
| Bidens mauiensis | Bidens mauiensis (Gray) Sherff var. lanaiensis Sherff | BIMAL |
| Bidens mauiensis | Bidens mauiensis (Gray) Sherff var. media Sherff | BIMAM |
| Bidens menziesii ssp. filiformis | Bidens menziesii (Gray) Sherff var. filiformis Sherff | BIMEF |
| Bidens menziesii ssp. filiformis | Bidens menziesii (Gray) Sherff var. leptondontia Sherff | BIMEL2 |
| Bidens menziesii ssp. menziesii | Bidens menziesii (Gray) Sherff var. lepida O. Deg. & Sherff | BIMEL |
| Bidens menziesii ssp. menziesii | Bidens salicoides Sherff | BISA |
| Bidens micrantha ssp. ctenophylla | Bidens ctenophylla Sherff | BICT |
| Bidens micrantha ssp. kalealaha | Bidens distans Sherff | BIDI3 |
| Bidens micrantha ssp. kalealaha | Bidens micrantha Gaud. var. rudimentifera Sherff | BIMIR |
| Bidens micrantha ssp. micrantha | Bidens degeneri Sherff | BIDE2 |
| Bidens micrantha ssp. micrantha | Bidens degeneri Sherff var. apioides Sherff | BIDEA |
| Bidens micrantha ssp. micrantha | Bidens micrantha Gaud. var. caduca (Sherff) Sherff | BIMIC |
| Bidens micrantha ssp. micrantha | Bidens micrantha Gaud. var. laciniata (Hbd.) Sherff | BIMIL |
| Bidens micrantha ssp. micrantha | Bidens perversa O. Deg. & Sherff | BIPE2 |
| Bidens micrantha ssp. micrantha | Bidens perversa O. Deg. & Sherff var. aquilonalis O. Deg. & Sherff | BIPEA |
| Bidens micrantha ssp. micrantha | Bidens sandvicensis Less. var. caduca Sherff | BISAC2 |
| Bidens micrantha ssp. micrantha | Bidens sandvicensis Less. var. leiocarpa O. Deg. & Sherff | BISAL |
| Bidens mitis | Bidens mitis (Michx.) Sherff var. leptophylla (Nutt.) Small | BIMIL2 |
| Bidens pilosa | Bidens odorata Cav. | BIOD |
| Bidens pilosa | Bidens pilosa L. var. bimucronata (Turcz.) Schultz-Bip. | BIPIB |
| Bidens pilosa | Bidens pilosa L. var. minor (Blume) Sherff | BIPIM |
| Bidens pilosa | Bidens pilosa L. var. pilosa L. [superfluous autonym] | BIPIP2 |
| Bidens reptans var. reptans | Coreopsis reptans L. | CORE9 |
| Bidens reptans var. urbanii | Bidens urbanii Greenm. | BIUR |
| Bidens sandvicensis ssp. sandvicensis | Bidens ?micranthoides Sherff | BIMI3 |
| Bidens sandvicensis ssp. sandvicensis | Bidens coartata Sherff | BICO2 |
| Bidens sandvicensis ssp. sandvicensis | Bidens graciloides Sherff | BIGR |
| Bidens sandvicensis ssp. sandvicensis | Bidens obtusiloba Sherff | BIOB |
| Bidens sandvicensis ssp. sandvicensis | Bidens pulchella (Less.) Schultz-Bip. | BIPU |
| Bidens sandvicensis ssp. sandvicensis | Bidens sandvicensis Less. var. antrorsa O. Deg. & Sherff | BISAA |
| Bidens sandvicensis ssp. sandvicensis | Bidens sandvicensis Less. var. imminuta O. Deg. & Sherff | BISAI |
| Bidens sandvicensis ssp. sandvicensis | Bidens sandvicensis Less. var. setosa (Sherff) Sherff | BISAS |
| Bidens sandvicensis ssp. sandvicensis | Bidens waimeana Sherff | BIWA2 |
| Bidens torta | Bidens fulvescens Sherff | BIFU |
| Bidens torta | Bidens micrantha Gaud. var. kaalana Sherff | BIMIK |
| Bidens torta | Bidens waianensis Sherff | BIWA |
| Bidens tripartita | Bidens acuta (Wieg.) Britt. | BIAC |
| Bidens tripartita | Bidens comosa (Gray) Wieg. | BICO3 |
| Bidens vulgata | Bidens frondosa L. var. puberula Wieg. | BIFRP2 |
| Bidens vulgata | Bidens puberula Wieg. | BIPU2 |
| Bidens vulgata | Bidens vulgata Greene var. puberula (Wieg.) Greene | BIVUP |
| Bidens vulgata | Bidens vulgata Greene var. schizantha Lunell | BIVUS |
| Bidens wiebkei | Bidens nematocera (Sherff) Sherff | BINE |
| biennial woollywhite | Hymenopappus biennis B.L. Turner | HYBI |
| biennial wormwood | Artemisia biennis Willd. | ARBI2 |
| biennial wormwood | Artemisia biennis Willd. var. biennis | ARBIB |
| biennial wormwood | Artemisia biennis Willd. var. diffusa Dorn | ARBID |
| Big Bend woodyaster | Xylorhiza wrightii (Gray) Greene | XYWR |
| big devils beggartick | Bidens vulgata Greene | BIVU |
| Big Horn fleabane | Erigeron allocotus Blake | ERAL13 |
| big sagebrush | Artemisia tridentata Nutt. | ARTR2 |
| big sagebrush | Artemisia tridentata Nutt. ssp. parishii (Gray) Hall & Clements | ARTRP2 |
| big sagebrush | Artemisia tridentata Nutt. ssp. spiciformis (Osterhout) Kartesz & Gandhi | ARTRS2 |
| big sagebrush | Artemisia tridentata Nutt. ssp. xericensis Winward ex R. Rosentreter & R. Kelsey | ARTRX |
| big tarweed | Blepharizonia plumosa (Kellogg) Greene | BLPL |
| big tarweed | Blepharizonia plumosa (Kellogg) Greene ssp. plumosa | BLPLP |
| big tarweed | Blepharizonia plumosa (Kellogg) Greene ssp. viscida Keck | BLPLV |
| Bigelow sage | Artemisia bigelovii Gray | ARBI3 |
| Bigelow's bahia | Bahia bigelovii Gray | BABI2 |
| Bigelow's beggarticks | Bidens bigelovii Gray | BIBI |
| Bigelow's beggarticks | Bidens bigelovii Gray var. bigelovii | BIBIB2 |
| Bigelow's bristlehead | Carphochaete bigelovii Gray | CABI6 |
| Bigelow's false willow | Baccharis bigelovii Gray | BABI |
| Bigelow's fleabane | Erigeron bigelovii Gray | ERBI3 |
| Bigelow's rubberweed | Hymenoxys bigelovii (Gray) Parker | HYBI2 |
| Bigelow's sneezeweed | Helenium bigelovii Gray | HEBI |
| Bigelow's tansyaster | Machaeranthera bigelovii (Gray) Greene | MABI |
| Bigelow's tansyaster | Machaeranthera bigelovii (Gray) Greene var. bigelovii | MABIB |
| Bigelow's tansyaster | Machaeranthera bigelovii (Gray) Greene var. commixta (Greene) B.L. Turner | MABIC |
| Bigelow's tansyaster | Machaeranthera bigelovii (Gray) Greene var. mucronata (Greene) B.L. Turner | MABIM |
| Bigelow's thoroughwort | Chromolaena bigelovii (Gray) King & H.E. Robins. | CHBI3 |
| Bigelow's tickseed | Coreopsis bigelovii (Gray) Hall | COBI |
| Bigelowia nudata ssp. australis | Bigelowia nudata (Michx.) DC. var. australis (L.C. Anders.) Shinners | BINUA2 |
| Bigelowia nudata ssp. nudata | Bigelowia virgata (Nutt.) DC. | BIVI3 |
| Bigelowia nudata ssp. nudata | Chondrophora nudata (Michx.) Britt. | CHNU6 |
| Bigelowia nudata ssp. nudata | Chondrophora virgata (Nutt.) Greene | CHVI18 |
| Bigelowia nudata ssp. nudata | Chrysocoma nudata Michx. | CHNU7 |
| bigflower agoseris | Agoseris grandiflora (Nutt.) Greene | AGGR |
| bighead dustymaiden | Chaenactis macrantha D.C. Eat. | CHMA |
| bighead knapweed | Centaurea macrocephala Puschk. ex Willd. | CEMA9 |
| bighead pygmycudweed | Evax prolifera Nutt. ex DC. | EVPR |
| bigleaf aster | Eurybia macrophylla (L.) Cass. | EUMA27 |
| bigleaf crownbeard | Verbesina dissita Gray | VEDI |
| Biolett's erigeron | Erigeron biolettii Greene | ERBI7 |
| birdfoot sagebrush | Artemisia pedatifida Nutt. | ARPE6 |
| bitter fleabane | Erigeron acris L. | ERAC2 |
| bitter fleabane | Erigeron acris L. ssp. debilis (Gray) Piper | ERACD2 |
| bitter fleabane | Erigeron acris L. ssp. kamtschaticus (DC.) Hara | ERACK3 |
| bitter fleabane | Erigeron acris L. ssp. politus (Fries) Schinz & R. Keller | ERACP2 |
| bitter lettuce | Lactuca virosa L. | LAVI8 |
| bitter rubberweed | Hymenoxys odorata DC. | HYOD |
| bittercress ragwort | Packera cardamine (Greene) W.A. Weber & A. L?ve | PACA34 |
| bittervine | Mikania micrantha Kunth | MIMI5 |
| bitterweed | Picris sprengeriana (L.) Poir. | PISP |
| Black Rock Townsend daisy | Townsendia smithii L. Shultz & A. Holmgren | TOSM |
| black sagebrush | Artemisia nova A. Nels. | ARNO4 |
| black salsify | Scorzonera hispanica L. | SCHI2 |
| blackeyed Susan | Rudbeckia hirta L. | RUHI2 |
| blackeyed Susan | Rudbeckia hirta L. var. angustifolia (T.V. Moore) Perdue | RUHIA |
| blackeyed Susan | Rudbeckia hirta L. var. floridana (T.V. Moore) Perdue | RUHIF |
| blackeyed Susan | Rudbeckia hirta L. var. hirta | RUHIH |
| blackeyed Susan | Rudbeckia hirta L. var. pulcherrima Farw. | RUHIP |
| blackfoot | Melampodium L. | MELAM |
| blackhead fleabane | Erigeron melanocephalus (A. Nels.) A. Nels. | ERME2 |
| blackroot | Pterocaulon Ell. | PTERO2 |
| blacksamson echinacea | Echinacea angustifolia DC. | ECAN2 |
| blacksamson echinacea | Echinacea angustifolia DC. var. angustifolia | ECANA |
| Blair's wirelettuce | Stephanomeria blairii Munz & Johnston | STBL2 |
| blanketflower | Gaillardia Foug. | GAILL |
| blazing star | Liatris Gaertn. ex Schreb. | LIATR |
| blepharipappus | Blepharipappus Hook. | BLEPH2 |
| blepharizonia | Blepharizonia Greene | BLEPH3 |
| blessed milkthistle | Silybum marianum (L.) Gaertn. | SIMA3 |
| blessed thistle | Cnicus benedictus L. | CNBE |
| Blochman's erigeron | Erigeron blochmaniae Greene | ERBL4 |
| Bloomer's aster | Symphyotrichum campestre (Nutt.) Nesom var. bloomeri (Nutt.) Nesom | SYCAB |
| blow wives | Achyrachaena mollis Schauer | ACMO2 |
| blow wives | Achyrachaena Schauer | ACHYR |
| blue and white daisybush | Osteospermum ecklonis (DC.) Norl. | OSEC |
| blue boneset | Tamaulipa azurea (DC.) King & H.E. Robins. | TAAZ |
| blue daisy | Felicia amelloides (L.) Voss | FEAM6 |
| blue dwarf fleabane | Erigeron elegantulus Greene | EREL4 |
| blue finger | Senecio mandraliscae (Tineo) Jacobsen | SEMA20 |
| blue lettuce | Lactuca tatarica (L.) C.A. Mey. | LATA |
| blue lettuce | Lactuca tatarica (L.) C.A. Mey. var. pulchella (Pursh) Breitung | LATAP |
| blue mistflower | Conoclinium coelestinum (L.) DC. | COCO13 |
| Blue Ridge goldenrod | Solidago spithamaea M.A. Curtis | SOSP6 |
| bluemink | Ageratum houstonianum P. Mill. | AGHO3 |
| bluewater fleabane | Erigeron acomanus Spellenberg & P. Knight | ERAC7 |
| bluff rockdaisy | Perityle aglossa Gray | PEAG |
| blumea | Blumea lacera (Burman f.) DC. | BLLA3 |
| Blumea viscosa | Conyza lyrata Kunth | COLY |
| Blumea viscosa | Conyza viscosa P. Mill. | COVI13 |
| Blumea viscosa | Eschenbachia lyrata (Kunth) Britt. & Millsp. | ESLY |
| bluntscale bahia | Bahia pedata Gray | BAPE |
| bog aster | Oclemena nemoralis (Ait.) Greene | OCNE2 |
| bog beggarticks | Bidens conjuncta Sherff | BICO4 |
| bog dubautia | Dubautia imbricata St. John & G.D. Carr | DUIM |
| bog dubautia | Dubautia imbricata St. John & G.D. Carr ssp. acronaea G.D. Carr | DUIMA |
| bog dubautia | Dubautia imbricata St. John & G.D. Carr ssp. imbricata | DUIMI |
| bog goldenrod | Solidago uliginosa Nutt. | SOUL |
| bog goldenrod | Solidago uliginosa Nutt. var. levipes (Fern.) Fern. | SOULL |
| bog goldenrod | Solidago uliginosa Nutt. var. linoides (Torr. & Gray) Fern. | SOULL2 |
| bog goldenrod | Solidago uliginosa Nutt. var. terrae-novae (Torr. & Gray) Fern. | SOULT |
| bog goldenrod | Solidago uliginosa Nutt. var. uliginosa | SOULU |
| bogbutton | Sclerolepis Cass. | SCLER5 |
| Bolander's hawkweed | Hieracium bolanderi Gray | HIBO |
| Bolander's madia | Kyhosia bolanderi (Gray) B.G. Baldwin | KYBO |
| Bolander's mock dandelion | Phalacroseris bolanderi Gray | PHBO2 |
| Bolander's mock dandelion | Phalacroseris bolanderi Gray var. bolanderi | PHBOB |
| Bolander's mock dandelion | Phalacroseris bolanderi Gray var. coronata Hall | PHBOC3 |
| Bolander's mule-ears | Agnorhiza bolanderi (Gray) W.A. Weber | AGBO4 |
| Bolander's ragwort | Packera bolanderi (Gray) W.A. Weber & A. L?ve | PABO6 |
| Bolander's ragwort | Packera bolanderi (Gray) W.A. Weber & A. L?ve var. bolanderi | PABOB |
| Boltonia asteroides var. asteroides | Boltonia asteroides (L.) L'H?r. var. glastifolia (Hill) Fern. | BOASG |
| Boltonia asteroides var. latisquama | Boltonia latisquama Gray | BOLA3 |
| Boltonia asteroides var. recognita | Boltonia latisquama Gray var. microcephala Fern. & Grisc. | BOLAM |
| Boltonia asteroides var. recognita | Boltonia latisquama Gray var. occidentalis Gray | BOLAO |
| Boltonia asteroides var. recognita | Boltonia latisquama Gray var. recognita Fern. & Grisc. | BOLAR |
| Boltonia asteroides var. recognita | Boltonia recognita (Fern. & Grisc.) G.N. Jones | BORE8 |
| Boltonia caroliniana | Boltonia ravenelii Fern. & Grisc. | BORA3 |
| Boltonia decurrens | Boltonia asteroides (L.) L'H?r. var. decurrens (Torr. & Gray) Fern. | BOASD |
| Boltonia decurrens | Boltonia latisquama Gray var. decurrens (Torr. & Gray) Fern. & Grisc. | BOLAD |
| Boltonia diffusa var. interior | Boltonia interior (Fern. & Grisc.) G.N. Jones | BOIN5 |
| Bombycilaena californica var. californica | Micropus californicus Fisch. & C.A. Mey. | MICA |
| Bombycilaena californica var. californica | Micropus californicus Fisch. & C.A. Mey. var. californicus Fisch. & C.A. Mey. [superfluous autonym] | MICAC2 |
| Bombycilaena californica var. subvestita | Micropus californicus Fisch. & C.A. Mey. var. subvestitus Gray | MICAS |
| bonebract | Sclerocarpus Jacq. | SCLER3 |
| boneset | Tamaulipa King & H.E. Robins. | TAMAU2 |
| Boott's goldenrod | Solidago arguta Ait. var. boottii (Hook.) Palmer & Steyermark | SOARB |
| boreal sagebrush | Artemisia arctica Less. | ARAR9 |
| boreal sagebrush | Artemisia arctica Less. ssp. arctica | ARARA2 |
| boreal sagebrush | Artemisia arctica Less. ssp. beringensis (Hult?n) Hult | ARARB |
| boreal sagebrush | Artemisia arctica Less. ssp. comata (Rydb.) Hult | ARARC |
| boreal yarrow | Achillea millefolium L. var. borealis (Bong.) Farw. | ACMIB |
| Borrichia arborescens | Buphthalmum arborescens L. | BUAR2 |
| boton de oro | Melampodium divaricatum (L.C. Rich.) DC. | MEDI4 |
| bottomland aster | Symphyotrichum ontarionis (Wieg.) Nesom | SYON2 |
| bouquet aster | Eurybia mirabilis (Torr. & Gray) Nesom | EUMI17 |
| box pussytoes | Antennaria arcuata Cronq. | ANAR4 |
| Brace's aster | Symphyotrichum bracei (Britt. ex Small) Nesom | SYBR |
| bract gumweed | Grindelia camporum Greene var. bracteosa (J.T. Howell) M.A. Lane | GRCAB |
| Bracteantha bracteata | Helichrysum bracteatum (Vent.) Andr. | HEBR6 |
| Bracteantha bracteata | Xeranthemum bracteatum Vent. | XEBR |
| bracted blazing star | Liatris bracteata Gaiser | LIBR |
| bracted strawflower | Bracteantha bracteata (Vent.) A. Anderb. & Heagi | BRBR15 |
| branched blazing star | Liatris cymosa (H. Ness) K. Schum. | LICY2 |
| branched false goldenweed | Oonopsis multicaulis (Nutt.) Greene | OOMU |
| branched lagophylla | Lagophylla ramosissima Nutt. | LARA |
| branched lagophylla | Lagophylla ramosissima Nutt. ssp. congesta (Greene) Keck | LARAC |
| branched lagophylla | Lagophylla ramosissima Nutt. ssp. ramosissima | LARAR |
| Brandegee's four-nerve daisy | Tetraneuris brandegeei (Porter ex Gray) Parker | TEBR |
| Brandegee's tansyaster | Machaeranthera coloradoensis (Gray) Osterhout var. brandegeei (Rydb.) T.J. Wats. ex R.L. Hartman | MACOB |
| Braun's erigeron | Erigeron pulchellus Michx. var. brauniae Fern. | ERPUB |
| Brazilian catsear | Hypochaeris brasiliensis (Less.) Benth. & Hook. ex Griseb. | HYBR5 |
| Brewer's aster | Eucephalus breweri (Gray) Nesom | EUBR12 |
| Brewer's erigeron | Erigeron breweri Gray var. bisanctus Nesom | ERBRB5 |
| Brewer's fleabane | Erigeron breweri Gray | ERBR4 |
| Brewer's fleabane | Erigeron breweri Gray var. breweri | ERBRB |
| Brewer's fleabane | Erigeron breweri Gray var. jacinteus (Hall) Cronq. | ERBRJ |
| Brewer's fleabane | Erigeron breweri Gray var. porphyreticus (M.E. Jones) Cronq. | ERBRP |
| Brewer's ragwort | Packera breweri (Burtt-Davy) W.A. Weber & A. L?ve | PABR11 |
| brickellbush | Asanthus King & H.E. Robins. | ASANT2 |
| brickellbush | Brickellia Ell. | BRICK |
| brickellbush | Brickelliastrum King & H.E. Robins. | BRICK3 |
| brickellbush | Flyriella King & H.E. Robins. | FLYRI |
| brickellbush aster | Eucephalus brickellioides (Greene) Nesom | EUBR13 |
| brickellbush goldenweed | Hazardia brickellioides (Blake) W.D. Clark | HABR3 |
| Brickellia arguta var. arguta | Brickellia atractyloides Gray var. arguta (B.L. Robins.) Jepson | BRATA |
| Brickellia brachyphylla | Brickellia brachyphylla (Gray) Gray var. brachyphylla (Gray) Gray [superfluous autonym] | BRBRB |
| Brickellia californica var. californica | Bulbostylis californica Torr. & Gray | BUCA6 |
| Brickellia cordifolia | Coleosanthus cordifolius (Ell.) Kuntze | COCO21 |
| Brickellia desertorum | Brickellia californica (Torr. & Gray) Gray var. desertorum (Coville) Parish ex Hall | BRCAD |
| Brickellia desertorum | Coleosanthus desertorum (Coville) Coville | CODE5 |
| Brickellia eupatorioides var. chlorolepis | Brickellia chlorolepis (Woot. & Standl.) Shinners | BRCH2 |
| Brickellia eupatorioides var. chlorolepis | Brickellia leptophylla (Scheele) Shinners var. mexicana (Shinners) Shinners | BRLEM |
| Brickellia eupatorioides var. chlorolepis | Brickellia rosemarinifolia (Vent.) W.A. Weber var. chlorolepis (Woot. & Standl.) W.A. Weber | BRROC |
| Brickellia eupatorioides var. chlorolepis | Brickellia rosmarinifolia (Vent.) W.A. Weber ssp. chlorolepis (Woot. & Standl.) W.A. Weber | BRROC2 |
| Brickellia eupatorioides var. chlorolepis | Brickellia shaffneri (Gray) Shinners | BRSH2 |
| Brickellia eupatorioides var. chlorolepis | Kuhnia chlorolepis Woot. & Standl. | KUCH2 |
| Brickellia eupatorioides var. chlorolepis | Kuhnia eupatorioides L. var. chlorolepis (Woot. & Standl.) Cronq. | KUEUC2 |
| Brickellia eupatorioides var. chlorolepis | Kuhnia leptophylla Scheele var. mexicana Shinners | KULEM |
| Brickellia eupatorioides var. chlorolepis | Kuhnia microphylla Shinners | KUMI |
| Brickellia eupatorioides var. chlorolepis | Kuhnia rosemarinifolia Vent. var. chlorolepis (Woot. & Standl.) Blake [orthographic error] | KUROC |
| Brickellia eupatorioides var. chlorolepis | Kuhnia rosmarinifolia Vent. var. chlorolepis (Woot. & Standl.) Blake | KUROC2 |
| Brickellia eupatorioides var. chlorolepis | Kuhnia shaffneri Gray | KUSH |
| Brickellia eupatorioides var. corymbulosa | Kuhnia eupatorioides L. var. corymbulosa Torr. & Gray | KUEUC |
| Brickellia eupatorioides var. corymbulosa | Kuhnia hitchcockii A. Nels. | KUHI |
| Brickellia eupatorioides var. eupatorioides | Brickellia rosemarinifolia (Vent.) W.A. Weber [orthographic error] | BRRO3 |
| Brickellia eupatorioides var. eupatorioides | Brickellia rosmarinifolia (Vent.) W.A. Weber | BRRO9 |
| Brickellia eupatorioides var. eupatorioides | Kuhnia eupatorioides L. | KUEU |
| Brickellia eupatorioides var. eupatorioides | Kuhnia eupatorioides L. var. angustifolia Raf. | KUEUA |
| Brickellia eupatorioides var. eupatorioides | Kuhnia eupatorioides L. var. gracilis Torr. & Gray | KUEUG2 |
| Brickellia eupatorioides var. eupatorioides | Kuhnia eupatorioides L. var. pyramidalis Raf. | KUEUP |
| Brickellia eupatorioides var. eupatorioides | Kuhnia glutinosa Ell. | KUGL |
| Brickellia eupatorioides var. eupatorioides | Kuhnia rosemarinifolia Vent. [orthographic error] | KURO |
| Brickellia eupatorioides var. eupatorioides | Kuhnia rosmarinifolia Vent. | KURO2 |
| Brickellia eupatorioides var. floridana | Brickellia mosieri (Small) Shinners | BRMO3 |
| Brickellia eupatorioides var. floridana | Kuhnia eupatorioides L. var. floridana R.W. Long | KUEUF |
| Brickellia eupatorioides var. floridana | Kuhnia mosieri Small | KUMO |
| Brickellia eupatorioides var. gracillima | Brickellia leptophylla (Scheele) Shinners | BRLE4 |
| Brickellia eupatorioides var. gracillima | Kuhnia eupatorioides L. var. gracillima Gray | KUEUG |
| Brickellia eupatorioides var. gracillima | Kuhnia leptophylla Scheele | KULE |
| Brickellia eupatorioides var. texana | Brickellia eupatorioides (L.) Shinners var. ozarkana (Shinners) Shinners | BREUO |
| Brickellia eupatorioides var. texana | Kuhnia eupatorioides L. var. ozarkana Shinners | KUEUO |
| Brickellia eupatorioides var. texana | Kuhnia eupatorioides L. var. texana Shinners | KUEUT |
| Brickellia grandiflora | Brickellia grandiflora (Hook.) Nutt. var. petiolaris Gray | BRGRP |
| Brickellia grandiflora | Coleosanthus grandiflorus (Hook.) Kuntze | COGR14 |
| Brickellia hinckleyi var. hinckleyi | Brickellia brachyphylla (Gray) Gray var. hinckleyi (Standl.) Flyr | BRBRH |
| Brickellia hinckleyi var. terlinguensis | Brickellia brachyphylla (Gray) Gray var. terlinguensis Flyr | BRBRT |
| Brickellia lemmonii var. lemmonii | Brickellia viejensis Flyr | BRVI2 |
| Brickellia lemmonii var. wootonii | Brickellia lemmonii Gray var. nelsonii (B.L. Robins.) B.L. Turner | BRLEN |
| Brickellia longifolia var. multiflora | Brickellia multiflora Kellogg | BRMU2 |
| Brickellia microphylla var. scabra | Brickellia microphylla (Nutt.) Gray ssp. scabra (Gray) W.A. Weber | BRMIS2 |
| Brickellia microphylla var. scabra | Brickellia scabra (Gray) A. Nels. ex B.L. Robins. | BRSC5 |
| Brickellia microphylla var. watsonii | Brickellia watsonii B.L. Robins. | BRWA |
| Brickellia oblongifolia var. linifolia | Brickellia linifolia D.C. Eat. | BRLI2 |
| Brickellia oblongifolia var. oblongifolia | Brickellia oblongifolia Nutt. var. typica B.L. Robins. | BROBT |
| Brickellia venosa | Coleosanthus venosus Woot. & Standl. | COVE8 |
| Brickellia veronicifolia var. veronicifolia | Eupatorium veronicifolium Kunth | EUVE3 |
| Brickelliastrum fendleri | Brickellia fendleri Gray | BRFE |
| Brickelliastrum fendleri | Eupatorium fendleri (Gray) Gray | EUFE4 |
| brighteyes | Reichardia Roth | REICH |
| brightwhite | Prenanthella exigua (Gray) Rydb. | PREX |
| bristlehead | Carphochaete Gray | CARPH2 |
| bristleleaf chaffhead | Carphephorus pseudoliatris Cass. | CAPS5 |
| bristleleaf pricklyleaf | Thymophylla tenuiloba (DC.) Small | THTE7 |
| bristleleaf pricklyleaf | Thymophylla tenuiloba (DC.) Small var. tenuiloba | THTET |
| bristleweed | Hazardia Greene | HAZAR |
| bristly hawkbit | Leontodon hispidus L. | LEHI |
| bristly hawkbit | Leontodon hispidus L. ssp. danubialis (Jacq.) Simonkai | LEHID |
| bristly hawkbit | Leontodon hispidus L. ssp. hispidus | LEHIH |
| bristly hawksbeard | Crepis setosa Haller f. | CRSE2 |
| bristly oxtongue | Picris echioides L. | PIEC |
| British yellowhead | Inula britannica L. | INBR |
| brittlebush | Encelia Adans. | ENCEL |
| brittlebush | Encelia farinosa Gray ex Torr. | ENFA |
| broad fleabane | Erigeron latus (A. Nels. & J.F. Macbr.) Cronq. | ERLA14 |
| broadleaf arnica | Arnica latifolia Bong. | ARLA8 |
| broadleaf Barbara's buttons | Marshallia trinervia (Walt.) Trel. | MATR2 |
| broadleaf cottonrose | Filago pyramidata L. | FIPY2 |
| broadleaf ironweed | Vernonia glauca (L.) Willd. | VEGL |
| broadleaf tickseed | Coreopsis latifolia Michx. | COLA7 |
| broom snakeweed | Gutierrezia sarothrae (Pursh) Britt. & Rusby | GUSA2 |
| broombush false willow | Baccharis dioica Vahl | BADI3 |
| broomlike ragwort | Senecio spartioides Torr. & Gray | SESP3 |
| broomlike ragwort | Senecio spartioides Torr. & Gray var. multicapitatus (Greenm. ex Rydb.) Welsh | SESPM |
| broomlike ragwort | Senecio spartioides Torr. & Gray var. spartioides | SESPS2 |
| broomsage | Lepidospartum (Gray) Gray | LEPID2 |
| broomweed | Amphiachyris (A. DC.) Nutt. | AMPHI8 |
| Brown's yellowtops | Flaveria brownii A. Powell | FLBR2 |
| browneyed Susan | Rudbeckia triloba L. | RUTR2 |
| browneyed Susan | Rudbeckia triloba L. var. pinnatiloba Torr. & Gray | RUTRP |
| browneyed Susan | Rudbeckia triloba L. var. rupestris (Chickering) Gray | RUTRR |
| browneyed Susan | Rudbeckia triloba L. var. triloba | RUTRT |
| brownfoot | Acourtia wrightii (Gray) Reveal & King | ACWR5 |
| brownplume wirelettuce | Stephanomeria pauciflora (Torr.) A. Nels. | STPA4 |
| brownray knapweed | Centaurea jacea L. | CEJA |
| brownturbans | Malperia tenuis S. Wats. | MATE3 |
| Buckley's goldenrod | Solidago buckleyi Torr. & Gray | SOBU |
| bud sagebrush | Picrothamnus desertorum Nutt. | PIDE4 |
| bud sagebrush | Picrothamnus Nutt. | PICRO |
| Buek's groundsel | Packera subnuda (DC.) D.K. Trock & T.M. Barkl. | PASU40 |
| buff fleabane | Erigeron ochroleucus Nutt. | EROC |
| buff fleabane | Erigeron ochroleucus Nutt. var. ochroleucus | EROCO |
| buff fleabane | Erigeron ochroleucus Nutt. var. scribneri (Canby ex Rydb.) Cronq. | EROCS2 |
| bugheal | Trichocoronis Gray | TRICH4 |
| bull cottonthistle | Onopordum tauricum Willd. | ONTA |
| bull thistle | Cirsium vulgare (Savi) Ten. | CIVU |
| bull's eye | Euryops chrysanthemoides (DC.) B. Nordenstam | EUCH4 |
| burdock | Arctium L. | ARCTI |
| Burgess's broomsage | Lepidospartum burgessii B.L. Turner | LEBU2 |
| Burke's baeria | Lasthenia burkei (Greene) Greene | LABU |
| burnet ragwort | Packera sanguisorboides (Rydb.) W.A. Weber & A. L?ve | PASA12 |
| burnweed | Erechtites Raf. | ERECH |
| burrdaisytree | Fitchia speciosa Cheeseman | FISP3 |
| Burridge's greenthread | Thelesperma burridgeanum (Regel, Korn. & Rach.) Blake | THBU |
| burrobrush | Hymenoclea salsola Torr. & Gray ex Gray | HYSA |
| burrobrush | Hymenoclea salsola Torr. & Gray ex Gray var. fasciculata (A. Nels.) K.M. Peterson & Payne | HYSAF |
| burrobrush | Hymenoclea salsola Torr. & Gray ex Gray var. pentalepis (Rydb.) L. Benson | HYSAP |
| burrobrush | Hymenoclea salsola Torr. & Gray ex Gray var. salsola | HYSAS |
| burrobrush | Hymenoclea Torr. & Gray ex Gray | HYMEN3 |
| burrobush | Ambrosia dumosa (Gray) Payne | AMDU2 |
| burroweed | Isocoma tenuisecta Greene | ISTE2 |
| burrweed | Gymnostyles Juss. | GYMNO7 |
| burrweed | Soliva Ruiz & Pav?n | SOLIV |
| bush arrowleaf | Pleurocoronis pluriseta (Gray) King & H.E. Robins. | PLPL |
| Bush's purple coneflower | Echinacea paradoxa (J.B.S. Norton) Britt. | ECPA2 |
| Bush's purple coneflower | Echinacea paradoxa (J.B.S. Norton) Britt. var. neglecta R.L. McGregor | ECPAN |
| Bush's purple coneflower | Echinacea paradoxa (J.B.S. Norton) Britt. var. paradoxa | ECPAP |
| bushsunflower | Simsia Pers. | SIMSI |
| bushy goldentop | Euthamia leptocephala (Torr. & Gray) Greene ex Porter & Britt. | EULE4 |
| bushy seaside tansy | Borrichia frutescens (L.) DC. | BOFR |
| Butte County western rosinweed | Calycadenia oppositifolia (Greene) Greene | CAOP |
| butterbur | Petasites P. Mill. | PETAS |
| butterweed | Packera glabella (Poir.) C. Jeffrey | PAGL17 |
| button brittlebush | Encelia frutescens (Gray) Gray | ENFR |
| button brittlebush | Encelia resinifera C. Clark ssp. resinifera | ENRER |
| button burrweed | Gymnostyles anthemifolia Juss. | GYAN |
| cacaliopsis | Cacaliopsis Gray | CACAL4 |
| Cacaliopsis nardosmia | Cacalia nardosmia Gray | CANA7 |
| Cacaliopsis nardosmia | Cacalia nardosmia Gray var. glabrata (Piper) Boivin | CANAG |
| Cacaliopsis nardosmia | Cacaliopsis nardosmia (Gray) Gray var. glabrata Piper | CANAG2 |
| Cacaliopsis nardosmia | Luina nardosmia (Gray) Cronq. | LUNA5 |
| Cacaliopsis nardosmia | Luina nardosmia (Gray) Cronq. var. glabrata (Piper) Cronq. | LUNAG |
| caespitose four-nerve daisy | Tetraneuris acaulis (Pursh) Greene var. caespitosa A. Nels. | TEACC |
| Cahaba torch | Liatris oligocephala J. Allison | LIOL2 |
| Cainville thistle | Cirsium calcareum (M.E. Jones) Woot. & Standl. | CICA10 |
| Calendula officinalis | Calendula officinalis L. var. prolifera hort. | CAOFP |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve | SYLA4 |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. angustifolium (Wieg.) Nesom | SYLAA |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. flagellare (Shinners) Nesom | SYLAF |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. horizontale (Desf.) Nesom | SYLAH5 |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. lateriflorum | SYLAL7 |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. spatelliforme (Burgess) Nesom | SYLAS |
| calico aster | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. tenuipes (Wieg.) Nesom | SYLAT |
| California balsamroot | Balsamorhiza macrolepis Sharp | BAMA3 |
| California balsamroot | Balsamorhiza macrolepis Sharp var. macrolepis | BAMAM |
| California balsamroot | Balsamorhiza macrolepis Sharp var. platylepis (Sharp) Ferris | BAMAP |
| California brickellbush | Brickellia californica (Torr. & Gray) Gray | BRCA3 |
| California brickellbush | Brickellia californica (Torr. & Gray) Gray var. californica | BRCAC |
| California brittlebush | Encelia californica Nutt. | ENCA |
| California broomsage | Lepidospartum squamatum (Gray) Gray | LESQ |
| California compassplant | Wyethia angustifolia (DC.) Nutt. | WYAN |
| California coneflower | Rudbeckia californica Gray | RUCA3 |
| California cottonrose | Logfia californica (Nutt.) Holub | LOCA19 |
| California dandelion | Taraxacum californicum Munz & Johnston | TACA5 |
| California desertdandelion | Malacothrix californica DC. | MACA6 |
| California goldenbush | Ericameria ericoides (Less.) Jepson | ERER11 |
| California goldenrod | Solidago californica Nutt. | SOCA5 |
| California goldfields | Lasthenia californica DC. ex Lindl. | LACA7 |
| California goldfields | Lasthenia californica DC. ex Lindl. ssp. californica | LACAC2 |
| California helianthella | Helianthella californica Gray | HECA |
| California helianthella | Helianthella californica Gray ssp. californica | HECAC3 |
| California mountainpincushion | Orochaenactis thysanocarpha (Gray) Coville | ORTH |
| California plumeseed | Rafinesquia californica Nutt. | RACA |
| California ragwort | Senecio californicus DC. | SECA |
| California rayless fleabane | Erigeron inornatus (Gray) Gray | ERIN2 |
| California rayless fleabane | Erigeron inornatus (Gray) Gray var. calidipetris Nesom | ERINC3 |
| California rayless fleabane | Erigeron inornatus (Gray) Gray var. inornatus | ERINI |
| California sandaster | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. californica (DC.) J.P. Saroyan | COFIC |
| California sunflower | Helianthus californicus DC. | HECA5 |
| California tickseed | Coreopsis californica (Nutt.) H.K. Sharsmith | COCA8 |
| California tickseed | Coreopsis californica (Nutt.) H.K. Sharsmith var. californica | COCAC4 |
| California yarrow | Achillea millefolium L. var. californica (Pollard) Jepson | ACMIC |
| callistephus | Callistephus Cass. | CALLI8 |
| Callistephus chinensis | Aster chinensis L. | ASCH12 |
| calotis | Calotis R. Br. | CALOT2 |
| Calycadenia fremontii | Calycadenia ciliosa Greene | CACI4 |
| Calycadenia fremontii | Hemizonia fremontii (Gray) Gray | HEFR4 |
| Calycadenia fremontii | Hemizonia multiglandulosa (DC.) Gray var. sparsa Gray | HEMUS |
| Calycadenia mollis | Hemizonia mollis (Gray) Gray | HEMO7 |
| Calycadenia multiglandulosa | Calycadenia campestris Greene | CACA56 |
| Calycadenia multiglandulosa | Calycadenia hispida (Greene) Greene | CAHI2 |
| Calycadenia multiglandulosa | Calycadenia hispida (Greene) Greene ssp. reducta Keck | CAHIR |
| Calycadenia multiglandulosa | Calycadenia multiglandulosa DC. ssp. bicolor (Greene) Keck | CAMUB |
| Calycadenia multiglandulosa | Calycadenia multiglandulosa DC. ssp. cephalotes (DC.) Keck | CAMUC |
| Calycadenia multiglandulosa | Calycadenia multiglandulosa DC. ssp. robusta Keck | CAMUR |
| Calycadenia multiglandulosa | Hemizonia hispida Greene | HEHI9 |
| Calycadenia oppositifolia | Hemizonia oppositifolia Greene | HEOP |
| Calycadenia pauciflora | Calycadenia elegans Greene | CAEL15 |
| Calycadenia pauciflora | Calycadenia pauciflora Gray var. elegans (Greene) Jepson | CAPAE3 |
| Calycadenia pauciflora | Calycadenia ramulosa Greene | CARA12 |
| Calycadenia pauciflora | Hemizonia pauciflora (Gray) Gray | HEPA17 |
| Calycadenia spicata | Hemizonia spicata Greene | HESP7 |
| Calycadenia truncata ssp. scabrella | Calycadenia scabrella (E. Drew) Greene | CASC22 |
| Calycadenia truncata ssp. scabrella | Calycadenia truncata DC. var. scabrella (E. Drew) Jepson | CATRS3 |
| Calycadenia truncata ssp. scabrella | Hemizonia scabrella E. Drew | HESC10 |
| Calycadenia truncata ssp. scabrella | Lagophylla scabrella (E. Drew) M.E. Jones | LASC4 |
| Calycadenia truncata ssp. truncata | Hemizonia truncata (DC.) Gray | HETR7 |
| Calycadenia villosa | Hemizonia douglasii Gray | HEDO3 |
| calyptocarpus | Calyptocarpus Less. | CALYP2 |
| Calyptocarpus vialis | Synedrella vialis (Less.) Gray | SYVI |
| Calyptocarpus vialis | Synedrellopsis grisebachii auct. non Hieron. & Kuntze [misapplied] | SYGR3 |
| camphor daisy | Rayjacksonia phyllocephala R.L. Hartman & M.A. Lane | RAPH2 |
| camphor pluchea | Pluchea camphorata (L.) DC. | PLCA7 |
| camphor tansy | Tanacetum camphoratum Less. | TACA2 |
| camphorweed | Heterotheca subaxillaris (Lam.) Britt. & Rusby | HESU3 |
| camphorweed | Pluchea Cass. | PLUCH |
| Canada cockleburr | Xanthium strumarium L. var. canadense (P. Mill.) Torr. & Gray | XASTC |
| Canada goldenrod | Solidago canadensis L. | SOCA6 |
| Canada goldenrod | Solidago canadensis L. var. canadensis | SOCAC3 |
| Canada goldenrod | Solidago canadensis L. var. lepida (DC.) Cronq. | SOCAL |
| Canada lettuce | Lactuca canadensis L. | LACA |
| Canada thistle | Cirsium arvense (L.) Scop. | CIAR4 |
| Canadanthus modestus | Aster major (Hook.) Porter | ASMA15 |
| Canadanthus modestus | Aster modestus Lindl. | ASMO3 |
| Canadanthus modestus | Aster unalaschkensis Less. var. major Hook. | ASUNM |
| Canadanthus modestus | Weberaster modestus (Lindl.) A.& D. L?ve | WEMO |
| Canadian hawkweed | Hieracium canadense Michx. | HICA3 |
| Canadian hawkweed | Hieracium canadense Michx. var. canadense | HICAC |
| Canadian hawkweed | Hieracium kalmii L. var. fasciculatum (Pursh) Lepage | HIKAF |
| Canadian horseweed | Conyza canadensis (L.) Cronq. | COCA5 |
| Canadian horseweed | Conyza canadensis (L.) Cronq. var. canadensis | COCAC3 |
| Canadian horseweed | Conyza canadensis (L.) Cronq. var. glabrata (Gray) Cronq. | COCAG |
| Canadian horseweed | Conyza canadensis (L.) Cronq. var. pusilla (Nutt.) Cronq. | COCAP3 |
| Canadian pussytoes | Antennaria howellii Greene ssp. canadensis (Greene) Bayer | ANHOC |
| Canby's aster | Symphyotrichum foliaceum (Lindl. ex DC.) Nesom var. canbyi (Gray) Nesom | SYFOC |
| candyleaf | Stevia Cav. | STEVI |
| candyleaf | Stevia rebaudiana (Bertoni) Bertoni | STRE2 |
| cankerweed | Prenanthes serpentaria Pursh | PRSE |
| canyon sunflower | Venegasia carpesioides DC. | VECA |
| Cape marigold | Castalis tragus (Ait.) Norl. | CATR18 |
| Cape marigold | Dimorphotheca Moench | DIMOR3 |
| Cape Sable thoroughwort | Chromolaena frustrata (B.L. Robins.) King & H.E. Robins. | CHFR4 |
| Cape Sable whiteweed | Ageratum littorale Gray | AGLI3 |
| Cape-ivy | Delairea Lem. | DELAI2 |
| Cape-ivy | Delairea odorata Lem. | DEOD |
| Capeweed | Arctotheca calendula (L.) Levyns | ARCA45 |
| Capeweed | Arctotheca J.C. Wendl. | ARCTO11 |
| capitaneja | Verbesina alata L. | VEAL4 |
| cardoon | Cynara cardunculus L. | CYCA |
| Carduus nutans | Carduus macrocephalus Desf. | CAMA29 |
| Carduus nutans | Carduus macrolepis Peterm. | CAMA30 |
| Carduus nutans | Carduus nutans L. ssp. leiophyllus (Petrovic) Stojanov & Stef. | CANUL |
| Carduus nutans | Carduus nutans L. ssp. macrocephalus (Desf.) Nyman | CANUM |
| Carduus nutans | Carduus nutans L. ssp. macrolepis (Peterm.) Kazmi | CANUM2 |
| Carduus nutans | Carduus nutans L. ssp. nutans L. [superfluous autonym] | CANUN |
| Carduus nutans | Carduus nutans L. var. leiophyllus (Petrovic) Ar?nes | CANUL2 |
| Carduus nutans | Carduus nutans L. var. macrocephalus (Desf.) Boivin | CANUM3 |
| Carduus nutans | Carduus nutans L. var. vestitus (Hallier) Boivin | CANUV |
| Carey's balsamroot | Balsamorhiza careyana Gray | BACA3 |
| Carey's balsamroot | Balsamorhiza careyana Gray var. careyana | BACAC |
| Caribbean cinchweed | Pectis carthusianorum Less. | PECA18 |
| Caribbean thoroughwort | Chromolaena corymbosa (Aubl.) King & H.E. Robins. | CHCO9 |
| carline thistle | Carlina L. | CARLI |
| carline thistle | Carlina vulgaris L. | CAVU3 |
| carline thistle | Carlina vulgaris L. ssp. longifolia Nyman | CAVUL |
| Carlquistia muirii | Raillardella muirii Gray | RAMU |
| Carlquistia muirii | Raillardiopsis muirii (Gray) Rydb. | RAMU3 |
| carminatia | Carminatia Moc. ex DC. | CARMI |
| Carolina crownbeard | Verbesina walteri Shinners | VEWA |
| Carolina desert-chicory | Pyrrhopappus carolinianus (Walt.) DC. | PYCA2 |
| Carolina doll's daisy | Boltonia caroliniana (Walt.) Fern. | BOCA2 |
| Carolina elephantsfoot | Elephantopus carolinianus Raeusch. | ELCA3 |
| Carolina goldenrod | Solidago pulchra Small | SOPU3 |
| Carolina silkgrass | Pityopsis aspera (Shuttlw. ex Small) Small var. adenolepis (Fern.) Semple & Bowers | PIASA |
| Carolina woollywhite | Hymenopappus scabiosaeus L'H?r. | HYSC |
| Carolina woollywhite | Hymenopappus scabiosaeus L'H?r. var. corymbosus (Torr. & Gray) B.L. Turner | HYSCC |
| Carolina woollywhite | Hymenopappus scabiosaeus L'H?r. var. scabiosaeus | HYSCS |
| carpet burrweed | Gymnostyles stolonifera (Brot.) Tutin | GYST |
| Carphephorus carnosus | Litrisa carnosa Small | LICA19 |
| Carphephorus odoratissimus | Trilisa odoratissima (J.F. Gmel.) Cass. | TROD |
| Carphephorus paniculatus | Trilisa paniculata (J.F. Gmel.) Cass. | TRPA7 |
| Carphephorus tomentosus | Carphephorus tomentosus (Michx.) Torr. & Gray var. walteri (Ell.) Fern. | CATOW |
| Carquinez goldenbush | Isocoma arguta Greene | ISAR2 |
| Carrizo Creek ragwort | Packera spellenbergii (T.M. Barkl.) C. Jeffrey | PASP18 |
| Carrizo Sands woollywhite | Hymenopappus carrizoanus B.L. Turner | HYCA18 |
| Carruth's sagewort | Artemisia carruthii Wood ex Carruth. | ARCA14 |
| Carthamus lanatus ssp. creticus | Carthamus baeticus (Boiss. & Reut.) Nyman | CABA5 |
| Carthamus lanatus ssp. creticus | Carthamus lanatus L. ssp. baeticus (Boiss. & Reut.) Maire | CALAB2 |
| Carthamus oxyacanthus | Carthamus oxyacantha Bieb. [orthographic variant] | CAOX2 |
| carveseed | Glyptopleura marginata D.C. Eat. | GLMA2 |
| Cascade aster | Eucephalus ledophyllus (Gray) Greene | EULE14 |
| Cascade aster | Eucephalus ledophyllus (Gray) Greene var. covillei (Greene) Nesom | EULEC |
| Cascade aster | Eucephalus ledophyllus (Gray) Greene var. ledophyllus | EULEL2 |
| Cascade fleabane | Erigeron cascadensis Heller | ERCA5 |
| castalis | Castalis Cass. | CASTA4 |
| Castalis tragus | Dimorphotheca aurantiaca DC., non Horton | DIAU3 |
| Catalina tarweed | Deinandra clementina (Brandeg.) B.G. Baldwin | DECL |
| catsear | Hypochaeris L. | HYPOC |
| catsear | Hypochoeris L. | HYPOC4 |
| celmisia | Celmisia Cass. | CELMI |
| Centaurea cyanus | Leucacantha cyanus (L.) Nieuwl. & Lunell | LECY |
| Centaurea diffusa | Acosta diffusa (Lam.) Soj | ACDI3 |
| Centaurea eriophora | Jacea pratensis Lam. | JAPR3 |
| Centaurea montana | Centaurea montana L. var. alba hort. | CEMOA2 |
| Centaurea nigra | Centaurea nigra L. var. radiata DC. | CENIR |
| Centaurea nigrescens | Centaurea debeauxii Gren. & Godr. ssp. thuillieri Dost | CEDET |
| Centaurea nigrescens | Centaurea dubia Suter ssp. vochinensis (Bernh. ex Reichenb.) Hayek | CEDUV |
| Centaurea nigrescens | Centaurea pratensis Thuill. nom. illeg., non Salisb. | CEPR2 |
| Centaurea nigrescens | Centaurea vochinensis Bernh. ex Reichenb. | CEVO2 |
| Centaurea ovina ssp. besseriana | Centaurea besseriana DC. [excluded] | CEBE6 |
| Centaurea phrygia | Centaurea austriaca Willd. | CEAU3 |
| Centaurea scabiosa | Centaurea scabiosa L. var. vertesensis (Boros) Soo | CESCV2 |
| Centaurea solstitialis | Leucantha solstitialis (L.) A.& D. L?ve | LESO10 |
| Centaurea stoebe ssp. micranthos | Acosta maculosa auct. non Holub [misapplied] | ACMA9 |
| Centaurea stoebe ssp. micranthos | Centaurea biebersteinii DC. | CEBI2 |
| Centaurea stoebe ssp. micranthos | Centaurea maculosa auct. non Lam. [misapplied] | CEMA4 |
| Centaurea transalpina | Centaurea dubia Suter | CEDU3 |
| Centaurea uniflora ssp. nervosa | Centaurea nervosa Willd. | CENE2 |
| Centaurea virgata ssp. squarrosa | Centaurea squarrosa Willd. | CESQ |
| Centaurea virgata ssp. squarrosa | Centaurea triumfettii auct. non All. [misapplied] | CETR8 |
| Centaurea virgata ssp. squarrosa | Centaurea variegata Lam. nom. illeg. | CEVA4 |
| Centaurea virgata ssp. squarrosa | Centaurea virgata Lam. var. squarrosa (Willd.) Boiss. | CEVIS |
| centipeda | Centipeda Lour. | CENTI |
| Centipeda minima | Artemisia minima L. | ARMI9 |
| centratherum | Centratherum Cass. | CENTR6 |
| Centromadia parryi ssp. australis | Hemizonia australis (Keck) Keck | HEAU2 |
| Centromadia parryi ssp. australis | Hemizonia parryi Greene ssp. australis Keck | HEPAA2 |
| Centromadia parryi ssp. congdonii | Hemizonia parryi Greene ssp. congdonii (Robins. & Greenm.) Keck | HEPAC |
| Centromadia parryi ssp. parryi | Hemizonia parryi Greene | HEPA7 |
| Centromadia parryi ssp. parryi | Hemizonia parryi Greene ssp. parryi Greene [superfluous autonym] | HEPAP3 |
| Centromadia parryi ssp. rudis | Hemizonia parryi Greene ssp. rudis (Greene) Keck | HEPAR2 |
| Centromadia pungens ssp. laevis | Hemizonia laevis (Keck) Keck | HELA3 |
| Centromadia pungens ssp. laevis | Hemizonia pungens (Hook. & Arn.) Torr. & Gray ssp. laevis Keck | HEPUL |
| Centromadia pungens ssp. maritima | Hemizonia pungens (Hook. & Arn.) Torr. & Gray ssp. maritima (Greene) Keck | HEPUM |
| Centromadia pungens ssp. pungens | Hemizonia pungens (Hook. & Arn.) Torr. & Gray | HEPU5 |
| Centromadia pungens ssp. pungens | Hemizonia pungens (Hook. & Arn.) Torr. & Gray ssp. pungens (Hook. & Arn.) Torr. & Gray [superfluous autonym] | HEPUP |
| Centromadia pungens ssp. septentrionalis | Hemizonia pungens (Hook. & Arn.) Torr. & Gray ssp. septentrionalis Keck | HEPUS2 |
| Centromadia pungens ssp. septentrionalis | Hemizonia pungens (Hook. & Arn.) Torr. & Gray var. septentrionalis (Keck) Cronq. | HEPUS |
| Chaenactis carphoclinia var. carphoclinia | Chaenactis carphoclinia Gray var. attenuata (Gray) M.E. Jones | CHCAA |
| Chaenactis douglasii var. alpina | Chaenactis alpina (Gray) M.E. Jones | CHAL2 |
| Chaenactis douglasii var. alpina | Chaenactis alpina (Gray) M.E. Jones var. leucopsis (Greene) Cockerell ex Stockwell | CHALL2 |
| Chaenactis douglasii var. alpina | Chaenactis alpina (Gray) M.E. Jones var. rubella (Greene) Stockwell | CHALR2 |
| Chaenactis douglasii var. alpina | Chaenactis leucopsis Greene | CHLE10 |
| Chaenactis douglasii var. alpina | Chaenactis minuscula Greene | CHMI10 |
| Chaenactis douglasii var. douglasii | Chaenactis angustifolia Greene | CHAN11 |
| Chaenactis douglasii var. douglasii | Chaenactis brachiata Greene | CHBR4 |
| Chaenactis douglasii var. douglasii | Chaenactis brachiata Greene var. stansburiana Stockwell | CHBRS2 |
| Chaenactis douglasii var. douglasii | Chaenactis cineria Stockwell | CHCI3 |
| Chaenactis douglasii var. douglasii | Chaenactis douglasii (Hook.) Hook. & Arn. var. achilleifolia (Hook. & Arn.) Gray | CHDOA |
| Chaenactis douglasii var. douglasii | Chaenactis douglasii (Hook.) Hook. & Arn. var. glandulosa Cronq. | CHDOG |
| Chaenactis douglasii var. douglasii | Chaenactis douglasii (Hook.) Hook. & Arn. var. montana M.E. Jones | CHDOM |
| Chaenactis douglasii var. douglasii | Chaenactis douglasii (Hook.) Hook. & Arn. var. nana Stockwell | CHDON |
| Chaenactis douglasii var. douglasii | Chaenactis douglasii (Hook.) Hook. & Arn. var. rubricaulis Rydb. | CHDOR |
| Chaenactis douglasii var. douglasii | Chaenactis douglasii (Hook.) Hook. & Arn. var. typicus Cronq. | CHDOT |
| Chaenactis douglasii var. douglasii | Chaenactis humilis Rydb. | CHHU4 |
| Chaenactis douglasii var. douglasii | Chaenactis panamintensis Stockwell | CHPA35 |
| Chaenactis douglasii var. douglasii | Chaenactis ramosa Stockwell | CHRA2 |
| Chaenactis douglasii var. douglasii | Chaenactis rubricaulis Rydb. | CHRU4 |
| Chaenactis douglasii var. douglasii | Chaenactis suksdorfii Stockwell | CHSU10 |
| Chaenactis evermannii | Chaenactis nevadensis (Kellogg) Gray var. mainsiana (A. Nels. & J.F. Macbr.) Stockwell | CHNEM |
| Chaenactis glabriuscula var. glabriuscula | Chaenactis furcata Stockwell | CHFU5 |
| Chaenactis glabriuscula var. glabriuscula | Chaenactis glabriuscula DC. var. aurea (Greene) Stockwell | CHGLA |
| Chaenactis glabriuscula var. glabriuscula | Chaenactis glabriuscula DC. var. curta (Gray) Jepson | CHGLC |
| Chaenactis glabriuscula var. glabriuscula | Chaenactis glabriuscula DC. var. tenuifolia (Nutt.) Hall | CHGLT |
| Chaenactis glabriuscula var. glabriuscula | Chaenactis tenuifolia Nutt. | CHTE8 |
| Chaenactis glabriuscula var. heterocarpha | Chaenactis glabriuscula DC. var. gracilenta (Greene) Keck | CHGLG |
| Chaenactis glabriuscula var. heterocarpha | Chaenactis heterocarpha Torr. & Gray ex Gray | CHHE5 |
| Chaenactis glabriuscula var. heterocarpha | Chaenactis tanacetifolia Gray | CHTA2 |
| Chaenactis glabriuscula var. heterocarpha | Chaenactis tanacetifolia Gray var. gracilenta (Greene) Stockwell | CHTAG |
| Chaenactis glabriuscula var. lanosa | Chaenactis glabriuscula DC. var. denudata (Nutt.) Munz | CHGLD2 |
| Chaenactis glabriuscula var. lanosa | Chaenactis lanosa DC. | CHLA15 |
| Chaenactis glabriuscula var. orcuttiana | Chaenactis orcuttiana (Greene) Parish | CHOR5 |
| Chaenactis glabriuscula var. orcuttiana | Chaenactis tenuifolia Nutt. var. orcuttiana Greene | CHTEO |
| Chaenactis santolinoides | Chaenactis santolinoides Greene var. indurata Stockwell | CHSAI |
| Chaenactis stevioides | Chaenactis gillespiei Stockwell | CHGI3 |
| Chaenactis stevioides | Chaenactis latifolia Stockwell | CHLA16 |
| Chaenactis stevioides | Chaenactis mexicana Stockwell | CHME8 |
| Chaenactis stevioides | Chaenactis stevioides Hook. & Arn. var. brachypappa (Gray) Hall | CHSTB2 |
| Chaenactis stevioides | Chaenactis stevioides Hook. & Arn. var. thornberi Stockwell | CHSTT |
| Chaenactis suffrutescens | Chaenactis suffrutescens Gray var. incana Stockwell | CHSUI |
| Chaetopappa bellidifolia | Keerlia bellidifolia Gray & Engelm. | KEBE |
| Chaetopappa bellioides | Chaetopappa bellioides (Gray) Shinners var. hirticaulis Shinners | CHBEH |
| Chaetopappa bellioides | Diplostelma bellioides Gray | DIBE2 |
| Chaetopappa effusa | Keerlia effusa Gray | KEEF |
| Chaetopappa ericoides | Aster arenosus (Heller) Blake | ASAR13 |
| Chaetopappa ericoides | Aster ericaefolius Roth. | ASER8 |
| Chaetopappa ericoides | Aster hirtifolius Blake | ASHI2 |
| Chaetopappa ericoides | Aster leucelene Blake | ASLE18 |
| Chaetopappa ericoides | Inula ericoides Torr. | INER |
| Chaetopappa ericoides | Leucelene ericoides (Torr.) Greene | LEER |
| Chaetopappa imberbis | Chaetopappa asteroides Nutt. ex DC. var. imberbis Gray | CHASI |
| chaffbush | Amphipappus Torr. & Gray | AMPHI3 |
| chaffhead | Carphephorus Cass. | CARPH |
| Chalk Hill hymenopappus | Hymenopappus tenuifolius Pursh | HYTE2 |
| chamaechaenactis | Chamaechaenactis Rydb. | CHAMA3 |
| Chamaechaenactis scaposa var. scaposa | Chaenactis scaposa Eastw. | CHSC4 |
| Chamaemelum fuscatum | Anthemis fuscata Brot. | ANFU4 |
| Chamaemelum mixtum | Anthemis mixta L. | ANMI6 |
| Chamaemelum mixtum | Ormenis mixta (L.) Dumort. | ORMI4 |
| Chamaemelum nobile | Anthemis nobilis L. | ANNO2 |
| Chamisso arnica | Arnica chamissonis Less. | ARCH3 |
| Chamisso arnica | Arnica chamissonis Less. ssp. chamissonis | ARCHC |
| Chamisso arnica | Arnica chamissonis Less. ssp. chamissonis var. chamissonis | ARCHC2 |
| Chamisso arnica | Arnica chamissonis Less. ssp. chamissonis var. interior Maguire | ARCHI3 |
| Chamisso arnica | Arnica chamissonis Less. ssp. foliosa (Nutt.) Maguire | ARCHF |
| Chamisso arnica | Arnica chamissonis Less. ssp. foliosa (Nutt.) Maguire var. andina (Nutt.) Ediger & T.M. Barkl. | ARCHA2 |
| Chamisso arnica | Arnica chamissonis Less. ssp. foliosa (Nutt.) Maguire var. bernardina (Greene) Maguire | ARCHB2 |
| Chamisso arnica | Arnica chamissonis Less. ssp. foliosa (Nutt.) Maguire var. incana (Gray) Hult | ARCHI4 |
| Chamisso arnica | Arnica chamissonis Less. ssp. foliosa (Nutt.) Maguire var. maguirei (A. Nels.) Maguire | ARCHM2 |
| chamomile | Anthemis L. | ANTHE |
| changing fleabane | Erigeron versicolor (Greenm.) Nesom | ERVE13 |
| chaparral fleabane | Erigeron oreophilus Greenm. | EROR5 |
| chaparral goldenbush | Ericameria brachylepis (Gray) Hall | ERBR13 |
| chaparral ragwort | Senecio aphanactis Greene | SEAP2 |
| Chapman's blazing star | Liatris chapmanii Torr. & Gray | LICH2 |
| Chapman's crownbeard | Verbesina chapmanii J.R. Coleman | VECH2 |
| Chapman's goldenrod | Solidago odora Ait. var. chapmanii (Gray) Cronq. | SOODC |
| Chapman's thoroughwort | Eupatorium chapmanii Small | EUCH9 |
| Chaptalia nutans | Tussilago nutans L. | TUNU |
| Chaptalia texana | Chaptalia nutans (L.) Polak. var. texana (Greene) Burkart | CHNUT |
| Charleston Mountain goldenbush | Ericameria compacta (Hall) Nesom | ERCO40 |
| Charleston Mountain pussytoes | Antennaria soliceps Blake | ANSO2 |
| charming woodyaster | Xylorhiza venusta (M.E. Jones) Heller | XYVE |
| cheerful sunflower | Helianthus ?laetiflorus Pers. (pro sp.) [pauciflorus ? tuberosus] | HELA |
| chenopod brickellbush | Brickellia chenopodina (Greene) B.L. Robins. | BRCH |
| chickensage | Sphaeromeria Nutt. | SPHAE3 |
| chicory | Cichorium intybus L. | CIIN |
| chicory | Cichorium L. | CICHO |
| chicoryleaf wirelettuce | Stephanomeria cichoriacea Gray | STCI |
| Chihuahua resinbush | Viguiera stenoloba Blake var. chihuahuensis Butterwick, var. nov. ined. | VISTC |
| Chihuahua tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. pinnatifida var. chihuahuana B.L. Turner & R.L. Hartman | MAPIC |
| Chihuahuan brickellbush | Brickellia floribunda Gray | BRFL |
| Chihuahuan fleabane | Erigeron velutipes Hook. & Arn. | ERVE11 |
| China aster | Callistephus chinensis (L.) Nees | CACH25 |
| Chinese yarrow | Achillea alpina L. | ACAL17 |
| Chiricahua fleabane | Erigeron kuschei Eastw. | ERKU |
| Chiricahua Mountain tansyaster | Machaeranthera riparia (Kunth) A.G. Jones | MARI |
| Chisos Mountain brickellbush | Flyriella parryi (Gray) King & H.E. Robins. | FLPA |
| chloracantha | Chloracantha Nesom | CHLOR6 |
| Chloracantha spinosa | Aster spinosus Benth. | ASSP3 |
| Chloracantha spinosa | Chloracantha spinosa (Benth.) G. L. Nesom var. spinosa (Benth.) G. L. Nesom [superfluous autonym] | CHSPS2 |
| Chloracantha spinosa | Erigeron ortegae Blake | EROR6 |
| Chloracantha spinosa | Leucosyris spinosa (Benth.) Greene | LESP3 |
| chondrilla | Chondrilla L. | CHOND |
| Chorisiva nevadensis | Iva nevadensis M.E. Jones | IVNE |
| Chorro Creek Bog thistle | Cirsium fontinale (Greene) Jepson var. obispoense J.T. Howell | CIFOO |
| Chromolaena bigelovii | Eupatorium bigelovii Gray | EUBI7 |
| Chromolaena borinquensis | Eupatorium borinquense (Britt.) B.L. Robins. | EUBO6 |
| Chromolaena borinquensis | Osmia borinquensis Britt. | OSBO |
| Chromolaena corymbosa | Eupatorium corymbosum Aubl. | EUCO23 |
| Chromolaena corymbosa | Osmia corymbosa (Aubl.) Britt. & P. Wilson | OSCO |
| Chromolaena frustrata | Eupatorium frustratum B.L. Robins. | EUFR2 |
| Chromolaena frustrata | Osmia frustrata (B.L. Robins.) Small | OSFR |
| Chromolaena geraniifolia | Eupatorium geraniifolium Urban | EUGE2 |
| Chromolaena geraniifolia | Osmia geraniifolia (Urban) Britt. & P. Wilson | OSGE |
| Chromolaena ivifolia | Eupatorium ivifolium L. | EUIV |
| Chromolaena ivifolia | Osmia ivifolia (L.) Schultz-Bip. | OSIV |
| Chromolaena odorata | Eupatorium odoratum L. | EUOD |
| Chromolaena odorata | Osmia odorata (L.) Schultz-Bip. | OSOD |
| Chromolaena oteroi | Eupatorium oteroi Monachino | EUOT |
| Chromolaena sinuata | Eupatorium sinuatum Lam. | EUSI8 |
| Chromolaena sinuata | Osmia sinuata (Lam.) Britt. & P. Wilson | OSSI |
| chrysactinia | Chrysactinia Gray | CHRYS |
| Chrysanthemum ?morifolium | Chrysanthemum morifolium Ramat. [hybrid] | CHMO6 |
| Chrysanthemum ?morifolium | Dendranthema grandiflorum Kitam. | DEGR11 |
| Chrysanthemum ?morifolium | Dendranthema morifolium (Ramat.) Tzvelev | DEMO |
| Chrysanthemum arcticum ssp. arcticum | Arctanthemum arcticum (L.) Tzvelev | ARAR31 |
| Chrysanthemum arcticum ssp. arcticum | Dendranthema arcticum (L.) Tzvelev | DEAR4 |
| Chrysanthemum arcticum ssp. arcticum | Dendranthema arcticum (L.) Tzvelev ssp. arcticum (L.) Tzvelev [superfluous autonym] | DEARA |
| Chrysanthemum arcticum ssp. arcticum | Leucanthemum arcticum (L.) DC. | LEAR29 |
| Chrysanthemum arcticum ssp. polare | Arctanthemum arcticum (L.) Tzvelev ssp. polare (Hult?n) Tzvelev | ARARP4 |
| Chrysanthemum arcticum ssp. polare | Chrysanthemum arcticum L. var. polare (Hult?n) Boivin | CHARP2 |
| Chrysanthemum arcticum ssp. polare | Dendranthema arcticum (L.) Tzvelev ssp. polare (Hult?n) Heywood | DEARP |
| Chrysanthemum arcticum ssp. polare | Dendranthema hultenii (A.& D. L?ve) Tzvelev | DEHU2 |
| Chrysanthemum cinerariifolium | Pyrethrum cinerariifolium Trevir. | PYCI3 |
| Chrysanthemum cinerariifolium | Tanacetum cinerariifolium (Trevir.) Schultz-Bip. | TACI2 |
| chrysogonum | Chrysogonum L. | CHRYS4 |
| Chrysogonum virginianum var. australe | Chrysogonum australe Alexander ex Small | CHAU4 |
| Chrysogonum virginianum var. virginianum | Chrysogonum virginianum L. var. dentatum Gray | CHVID |
| chrysoma | Chrysoma Nutt. | CHRYS11 |
| Chrysoma pauciflosculosa | Chrysoma solidaginoides Nutt. | CHSO2 |
| Chrysoma pauciflosculosa | Solidago pauciflosculosa Michx. | SOPA5 |
| Chrysopsis floridana | Chrysopsis mariana (L.) Ell. var. floridana (Small) Fern. | CHMAF2 |
| Chrysopsis floridana | Heterotheca floridana (Small) R.W. Long | HEFL8 |
| Chrysopsis floridana | Heterotheca mariana (L.) Shinners ssp. floridana (Small) Harms | HEMAF2 |
| Chrysopsis gossypina ssp. cruiseana | Chrysopsis cruiseana Dress | CHCR4 |
| Chrysopsis gossypina ssp. gossypina | Chrysopsis arenicola Alexander ex Small | CHAR11 |
| Chrysopsis gossypina ssp. gossypina | Chrysopsis decumbens Chapman | CHDE12 |
| Chrysopsis gossypina ssp. gossypina | Chrysopsis longii Fern. | CHLO |
| Chrysopsis gossypina ssp. gossypina | Chrysopsis pilosa (Walt.) Britt., non Nutt. | CHPI6 |
| Chrysopsis gossypina ssp. gossypina | Chrysopsis trichophylla (Nutt.) Ell. | CHTR6 |
| Chrysopsis gossypina ssp. gossypina | Heterotheca gossypina (Michx.) Shinners | HEGO |
| Chrysopsis gossypina ssp. gossypina | Heterotheca trichophylla (Nutt.) Shinners | HETR4 |
| Chrysopsis gossypina ssp. gossypina | Inula gossypina Michx. | INGO |
| Chrysopsis gossypina ssp. hyssopifolia | Chrysopsis gigantea Small | CHGI4 |
| Chrysopsis gossypina ssp. hyssopifolia | Chrysopsis hyssopifolia Nutt. | CHHY4 |
| Chrysopsis gossypina ssp. hyssopifolia | Chrysopsis mixta Dress | CHMI11 |
| Chrysopsis gossypina ssp. hyssopifolia | Heterotheca hyssopifolia (Nutt.) R.W. Long | HEHY2 |
| Chrysopsis gossypina ssp. hyssopifolia | Heterotheca hyssopifolia (Nutt.) R.W. Long var. gigantea (Small) Harms | HEHYG |
| Chrysopsis latisquamea | Heterotheca latisquamea (Pollard) Harms | HELA9 |
| Chrysopsis mariana | Chrysopsis mariana (L.) Ell. var. macradenia Fern. | CHMAM3 |
| Chrysopsis mariana | Heterotheca mariana (L.) Shinners | HEMA10 |
| Chrysopsis mariana | Heterotheca mariana (L.) Shinners var. macradenia (Fern.) Harms | HEMAM2 |
| Chrysopsis mariana | Inula mariana L. | INMA |
| Chrysopsis pilosa | Bradburia pilosa (Nutt.) Semple | BRPI10 |
| Chrysopsis pilosa | Chrysopsis nuttallii Britt. | CHNU5 |
| Chrysopsis pilosa | Heterotheca pilosa (Nutt.) Shinners | HEPI5 |
| Chrysopsis scabrella | Heterotheca scabrella (Torr. & Gray) Harms | HESC7 |
| Chrysopsis subulata | Heterotheca hyssopifolia (Nutt.) R.W. Long var. subulata (Small) R.W. Long | HEHYS |
| Chrysopsis texana | Bradburia hirtella Torr. & Gray | BRHI |
| Chrysothamnus albidus | Ericameria albida (M.E. Jones ex Gray) L.C. Anders. | ERAL23 |
| Chrysothamnus baileyi | Chrysothamnus pulchellus (Gray) Greene ssp. baileyi (Woot. & Standl.) Hall & Clements | CHPUB |
| Chrysothamnus baileyi | Chrysothamnus pulchellus (Gray) Greene var. baileyi (Woot. & Standl.) Blake | CHPUB2 |
| Chrysothamnus baileyi | Ericameria pulchella (Gray) L.C. Anders. ssp. baileyi (Woot. & Standl.) L.C. Anders. | ERPUB2 |
| Chrysothamnus depressus | Ericameria depressa (Nutt.) L.C. Anders. | ERDE15 |
| Chrysothamnus eremobius | Ericameria eremobia (L.C. Anders.) L.C. Anders | ERER13 |
| Chrysothamnus gramineus | Ericameria graminea (Hall) L.C. Anders. | ERGR19 |
| Chrysothamnus gramineus | Petradoria discoidea L.C. Anders. | PEDI3 |
| Chrysothamnus greenei | Chrysothamnus greenei (Gray) Greene ssp. filifolius (Rydb.) Hall & Clements | CHGRF3 |
| Chrysothamnus greenei | Chrysothamnus greenei (Gray) Greene var. filifolius (Rydb.) Blake | CHGRF2 |
| Chrysothamnus greenei | Ericameria filifolia (Rydb.) L.C. Anders. | ERFI5 |
| Chrysothamnus humilis | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. humilis (Greene) Hall & Clements | CHVIH4 |
| Chrysothamnus humilis | Chrysothamnus viscidiflorus (Hook.) Nutt. var. humilis (Greene) Jepson | CHVIH3 |
| Chrysothamnus humilis | Ericameria humilis (Greene) L.C. Anders. | ERHU5 |
| Chrysothamnus linifolius | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. linifolius (Greene) Hall & Clements | CHVIL8 |
| Chrysothamnus linifolius | Chrysothamnus viscidiflorus (Hook.) Nutt. var. linifolius (Greene) Kittell | CHVIL7 |
| Chrysothamnus linifolius | Ericameria linifolia (Greene) L.C. Anders. | ERLI9 |
| Chrysothamnus molestus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. molestus Blake | CHVIM2 |
| Chrysothamnus molestus | Ericameria molesta (Blake) L.C. Anders. | ERMO14 |
| Chrysothamnus pulchellus | Chrysothamnus pulchellus (Gray) Greene ssp. elatior (Standl.) Hall & Clements | CHPUE |
| Chrysothamnus pulchellus | Ericameria pulchella (Gray) L.C. Anders. | ERPU19 |
| Chrysothamnus pulchellus | Ericameria pulchella (Gray) L.C. Anders. var. elatior (Standl.) L.C. Anders. | ERPUE3 |
| Chrysothamnus spathulatus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. ludens Shinners | CHVIL9 |
| Chrysothamnus spathulatus | Ericameria spathulata (L.C. Anders.) L.C. Anders. | ERSP18 |
| Chrysothamnus vaseyi | Bigelovia vaseyi Gray | BIVA2 |
| Chrysothamnus vaseyi | Ericameria vaseyi (Gray) L.C. Anders. | ERVA9 |
| Chrysothamnus viscidiflorus ssp. axillaris | Chrysothamnus axillaris Keck | CHAX |
| Chrysothamnus viscidiflorus ssp. axillaris | Ericameria viscidiflora (Hook.) L.C. Anders. ssp. axillaris (Keck) L.C. Anders. | ERVIA |
| Chrysothamnus viscidiflorus ssp. lanceolatus | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. elegans (Greene) Hall & Clements | CHVIE4 |
| Chrysothamnus viscidiflorus ssp. lanceolatus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. elegans (Greene) Blake | CHVIE3 |
| Chrysothamnus viscidiflorus ssp. lanceolatus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. lanceolatus (Nutt.) Greene | CHVIL6 |
| Chrysothamnus viscidiflorus ssp. lanceolatus | Ericameria viscidiflora (Hook.) L.C. Anders. ssp. lanceolata (Nutt.) L.C. Anders. | ERVIL |
| Chrysothamnus viscidiflorus ssp. planifolius | Ericameria viscidiflora (Hook.) L.C. Anders. ssp. planifolia (L.C. Anders.) L.C. Anders. | ERVIP |
| Chrysothamnus viscidiflorus ssp. puberulus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. puberulus (D.C. Eat.) Jepson | CHVIP6 |
| Chrysothamnus viscidiflorus ssp. puberulus | Ericameria viscidiflora (Hook.) L.C. Anders. ssp. puberula (D.C. Eat.) L.C. Anders. | ERVIP2 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. latifolius | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. latifolius (D.C. Eat.) Hall & Clements | CHVIL5 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. latifolius | Ericameria viscidiflora (Hook.) L.C. Anders. var. latifolia (D.C. Eat.) L.C. Anders. | ERVIL2 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. stenophyllus | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. stenophyllus (Gray) Hall & Clements | CHVIS2 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. stenophyllus | Ericameria viscidiflora (Hook.) L.C. Anders. var. stenophylla (Gray) L.C. Anders. | ERVIS2 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. pumilus (Nutt.) Hall & Clements | CHVIP5 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. typicus Hall & Clements | CHVIT |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. pumilus (Nutt.) Jepson | CHVIP7 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus | Chrysothamnus viscidiflorus (Hook.) Nutt. var. typicus (Hall & Clements) Cronq. | CHVIT2 |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus | Ericameria viscidiflora (Hook.) L.C. Anders. | ERVI22 |
| Cichorium intybus | Cichorium intybus L. var. foliosum Hegi | CIINF |
| Cichorium intybus | Cichorium intybus L. var. sativum (Bisch.) Janch. | CIINS2 |
| cinchweed | Pectis L. | PECTI |
| cinderslope dubautia | Dubautia platyphylla (Gray) Keck | DUPL2 |
| cineraria | Cineraria L. | CINER |
| Cirsium altissimum | Carduus altissimus L. | CAAL22 |
| Cirsium altissimum | Cirsium altissimum (L.) Hill var. biltmoreanum Petrak | CIALB |
| Cirsium andrewsii | Cnicus amplifolius Greene | CNAM |
| Cirsium araneans | Carduus araneosus Osterhout | CAAR22 |
| Cirsium arizonicum | Cirsium arizonicum (Gray) Petrak var. arizonicum (Gray) Petrak [superfluous autonym] | CIARA |
| Cirsium arizonicum | Cirsium arizonicum (Gray) Petrak var. nidulum (M.E. Jones) Welsh | CIARN |
| Cirsium arizonicum | Cirsium nidulum (M.E. Jones) Petrak | CINI |
| Cirsium arizonicum | Cnicus arizonicus Gray | CNAR |
| Cirsium arvense | Breea arvensis Less. | BRAR20 |
| Cirsium arvense | Breea incana (Gmel.) W.A. Weber | BRIN18 |
| Cirsium arvense | Carduus arvensis (L.) Robson | CAAR29 |
| Cirsium arvense | Cirsium arvense (L.) Scop. var. argenteum (Vest) Fiori | CIARA3 |
| Cirsium arvense | Cirsium arvense (L.) Scop. var. horridum Wimmer & Grab. | CIARH |
| Cirsium arvense | Cirsium arvense (L.) Scop. var. integrifolium Wimmer & Grab. | CIARI2 |
| Cirsium arvense | Cirsium arvense (L.) Scop. var. mite Wimmer & Grab. | CIARM |
| Cirsium arvense | Cirsium arvense (L.) Scop. var. vestitum Wimmer & Grab. | CIARV |
| Cirsium arvense | Cirsium incanum (Gmel.) Fisch. | CIIN7 |
| Cirsium arvense | Cirsium setosum (Willd.) Bess. ex Bieb. | CISE |
| Cirsium arvense | Serratula arvensis L. | SEAR12 |
| Cirsium brevifolium | Cirsium palousense Piper | CIPA9 |
| Cirsium calcareum | Carduus pulchellus Greene | CAPU31 |
| Cirsium calcareum | Carduus truncatus Greene | CATR19 |
| Cirsium calcareum | Cirsium bipinnatum (Eastw.) Rydb. | CIBI |
| Cirsium calcareum | Cirsium calcareum (M.E. Jones) Woot. & Standl. var. bipinnatum (Eastw.) Welsh | CICAB2 |
| Cirsium calcareum | Cirsium calcareum (M.E. Jones) Woot. & Standl. var. pulchellum (Greene) Welsh | CICAP2 |
| Cirsium calcareum | Cirsium pulchellum (Greene) Woot. & Standl. | CIPU2 |
| Cirsium calcareum | Cirsium pulchellum (Greene) Woot. & Standl. ssp. bipinnatum (Eastw.) Petrak | CIPUB |
| Cirsium calcareum | Cirsium pulchellum (Greene) Woot. & Standl. var. glabrescens Petrak | CIPUG |
| Cirsium calcareum | Cnicus calcareus M.E. Jones | CNCA |
| Cirsium canescens | Carduus undulatus Nutt. var. canescens (Nutt.) Porter | CAUNC |
| Cirsium canescens | Cirsium nebraskense (Britt.) Lunell | CINE3 |
| Cirsium canescens | Cirsium nelsonii (Pammel) Petrak | CINE4 |
| Cirsium canescens | Cirsium plattense (Rydb.) Cockerell ex Daniels | CIPL2 |
| Cirsium carolinianum | Carduus carolinianus Walt. | CACA47 |
| Cirsium carolinianum | Cirsium flaccidum Small | CIFL2 |
| Cirsium ciliolatum | Cirsium botrys Petrak | CIBO3 |
| Cirsium ciliolatum | Cirsium howellii Petrak | CIHO4 |
| Cirsium cymosum | Cirsium triacanthum Petrak | CITR6 |
| Cirsium discolor | Carduus discolor (Muhl. ex Willd.) Nutt. | CADI25 |
| Cirsium douglasii var. breweri | Cirsium breweri (Gray) Jepson | CIBR4 |
| Cirsium douglasii var. breweri | Cirsium breweri (Gray) Jepson var. lanosissimum Petrak p.p. | CIBRL |
| Cirsium douglasii var. breweri | Cirsium douglasii DC. var. canescens (Petrak) J.T. Howell | CIDOC |
| Cirsium douglasii var. douglasii | Cirsium breweri (Gray) Jepson var. wrangelii Petrak | CIBRW |
| Cirsium drummondii | Cirsium coccinatum Osterhout | CICO5 |
| Cirsium eatonii | Cirsium eatonii (Gray) B.L. Robins. var. harrisonii Welsh | CIEAH |
| Cirsium eatonii | Cirsium eriocephalum Gray var. leiocephalum D.C. Eat. | CIERL |
| Cirsium eatonii | Cirsium hookerianum Nutt. var. eriocephalum (Gray) A. Nels. | CIHOE2 |
| Cirsium eatonii | Cirsium olivescens (Rydb.) Petrak | CIOL |
| Cirsium eatonii | Cirsium polyphyllum (Rydb.) Petrak | CIPO |
| Cirsium eatonii | Cirsium tweedyi (Rydb.) Petrak | CITW |
| Cirsium edule | Carduus macounii Greene | CAMA31 |
| Cirsium edule | Cirsium hallii (Gray) M.E. Jones | CIHA |
| Cirsium edule | Cirsium macounii (Greene) Rydb. | CIMA7 |
| Cirsium engelmannii | Cirsium altissimum (L.) Hill var. filipendulum (Engelm.) Gray | CIALF |
| Cirsium engelmannii | Cirsium filipendulum Engelm. | CIFI |
| Cirsium engelmannii | Cirsium terraenigrae Shinners | CITE |
| Cirsium flodmanii | Cirsium nebraskense (Britt.) Lunell var. discissum Lunell | CINED |
| Cirsium flodmanii | Cirsium oblanceolatum (Rydb.) K. Schum. | CIOB2 |
| Cirsium foliosum | Cirsium foliosum (Hook.) DC. var. minganense (Victorin) Boivin | CIFOM |
| Cirsium fontinale var. campylon | Cirsium campylon H.K. Sharsmith | CICA5 |
| Cirsium hillii | Cirsium pumilum Spreng. ssp. hillii (Canby) Moore & Frankton | CIPUH |
| Cirsium hillii | Cirsium pumilum Spreng. var. hillii (Canby) Boivin | CIPUH2 |
| Cirsium horridulum var. horridulum | Carduus pinetorum Small | CAPI13 |
| Cirsium horridulum var. horridulum | Carduus smallii (Britt.) Ahles | CASM |
| Cirsium horridulum var. horridulum | Carduus spinosissimus Walt. | CASP16 |
| Cirsium horridulum var. horridulum | Cirsium horridulum Michx. var. elliottii Torr. & Gray | CIHOE |
| Cirsium horridulum var. horridulum | Cirsium smallii Britt. | CISM |
| Cirsium horridulum var. horridulum | Cirsium spinosissimum auct. non (L.) Scop. [misapplied] | CISP4 |
| Cirsium horridulum var. vittatum | Cirsium vittatum Small | CIVI7 |
| Cirsium hydrophilum var. hydrophilum | Cirsium vaseyi (Gray) Jepson var. hydrophilum (Greene) Petrak | CIVAH |
| Cirsium hydrophilum var. vaseyi | Cirsium montigenum Petrak | CIMO6 |
| Cirsium hydrophilum var. vaseyi | Cirsium vaseyi (Gray) Jepson | CIVA4 |
| Cirsium hydrophilum var. vaseyi | Cnicus breweri Gray var. vaseyi Gray | CNBRV |
| Cirsium lecontei | Carduus lecontei (Torr. & Gray) Pollard | CALE29 |
| Cirsium murdockii | Cirsium eatonii (Gray) B.L. Robins. var. murdockii Welsh | CIEAM |
| Cirsium murdockii | Cirsium tweedyi auct. non (Rydb.) Petrak [misapplied] | CITW3 |
| Cirsium muticum | Carduus muticus (Michx.) Pers. | CAMU16 |
| Cirsium muticum | Cirsium bigelovii DC. | CIBI2 |
| Cirsium muticum | Cirsium muticum Michx. var. monticola Fern. | CIMUM |
| Cirsium muticum | Cirsium muticum Michx. var. subpinnatifidum (Britt.) Fern. | CIMUS |
| Cirsium neomexicanum | Carduus inamoenus Greene | CAIN27 |
| Cirsium neomexicanum | Cirsium arcuum A. Nels. | CIAR7 |
| Cirsium neomexicanum | Cirsium neomexicanum Gray var. neomexicanum Gray [superfluous autonym] | CINEN |
| Cirsium neomexicanum | Cirsium neomexicanum Gray var. utahense (Petrak) Welsh | CINEU |
| Cirsium neomexicanum | Cirsium utahense Petrak | CIUT |
| Cirsium neomexicanum | Cirsium wallowense M.E. Peck | CIWA2 |
| Cirsium nuttallii | Carduus nuttallii (DC.) Pollard | CANU16 |
| Cirsium occidentale var. californicum | Cirsium californicum Gray | CICA3 |
| Cirsium occidentale var. californicum | Cirsium californicum Gray ssp. pseudoreglense Petrak | CICAP3 |
| Cirsium occidentale var. californicum | Cirsium californicum Gray var. bernardinum (Greene) Petrak | CICAB |
| Cirsium occidentale var. candidissimum | Cirsium candidissimum (Greene) A. Davids. & Moxley | CICA12 |
| Cirsium occidentale var. candidissimum | Cirsium pastoris J.T. Howell | CIPA2 |
| Cirsium occidentale var. occidentale | Cirsium coulteri Harvey & Gray | CICO6 |
| Cirsium occidentale var. venustum | Cirsium proteanum J.T. Howell | CIPR |
| Cirsium ochrocentrum ssp. ochrocentrum | Cnicus ochrocentrus (Gray) Gray | CNOC |
| Cirsium parryi ssp. parryi | Cnicus parryi Gray | CNPA |
| Cirsium pumilum | Carduus pumilus Nutt. nom. illeg. | CAPU30 |
| Cirsium pumilum | Cirsium odoratum (Muhl. ex W. Bart.) Petrak | CIOD |
| Cirsium quercetorum | Cirsium quercetorum (Gray) Jepson var. mendocinum Petrak | CIQUM |
| Cirsium quercetorum | Cirsium quercetorum (Gray) Jepson var. quercetorum (Gray) Jepson [superfluous autonym] | CIQUQ |
| Cirsium quercetorum | Cirsium quercetorum (Gray) Jepson var. walkerianum (Petrak) Jepson | CIQUW |
| Cirsium quercetorum | Cirsium quercetorum (Gray) Jepson var. xerolepis Petrak | CIQUX |
| Cirsium quercetorum | Cirsium walkerianum Petrak | CIWA3 |
| Cirsium remotifolium | Cirsium acanthodontum Blake | CIAC |
| Cirsium remotifolium | Cirsium amblylepis Petrak | CIAM2 |
| Cirsium remotifolium | Cirsium callilepis (Greene) Jepson | CICA4 |
| Cirsium remotifolium | Cirsium callilepis (Greene) Jepson var. oregonense (Petrak) J.T. Howell | CICAO |
| Cirsium remotifolium | Cirsium callilepis (Greene) Jepson var. pseudocarlinoides (Petrak) J.T. Howell | CICAP |
| Cirsium remotifolium | Cirsium mendocinum Petrak | CIME5 |
| Cirsium remotifolium | Cirsium oreganum Piper | CIOR2 |
| Cirsium remotifolium | Cirsium remotifolium (Hook.) DC. ssp. oregonense Petrak | CIREO2 |
| Cirsium remotifolium | Cirsium remotifolium (Hook.) DC. ssp. pseudocarlinoides Petrak | CIREP |
| Cirsium remotifolium | Cirsium remotifolium (Hook.) DC. ssp. remotifolium (Hook.) DC. [superfluous autonym] | CIRER3 |
| Cirsium remotifolium | Cirsium remotifolium (Hook.) DC. var. odontolepis Petrak | CIREO |
| Cirsium remotifolium | Cirsium remotifolium (Hook.) DC. var. rivulare Jepson | CIRER2 |
| Cirsium remotifolium | Cirsium stenolepidum Nutt. | CIST2 |
| Cirsium repandum | Carduus repandus (Michx.) Pers. | CARE13 |
| Cirsium rhothophilum | Cirsium maritimum (Elmer) Petrak | CIMA8 |
| Cirsium rothrockii | Cirsium diffusum (Eastw.) Rydb. | CIDI2 |
| Cirsium rothrockii | Cirsium pulchellum (Greene) Woot. & Standl. ssp. diffusum (Eastw.) Petrak | CIPUD |
| Cirsium rydbergii | Cirsium lactucinum Rydb. | CILA7 |
| Cirsium scapanolepis | Carduus spathulatus Osterhout | CASP17 |
| Cirsium scapanolepis | Cirsium griseum (Rydb.) K. Schum. | CIGR3 |
| Cirsium scapanolepis | Cirsium spathulifolium Rydb. | CISP5 |
| Cirsium scariosum | Carduus americanus (Gray) Rydb. | CAAM19 |
| Cirsium scariosum | Carduus coloradensis Rydb. | CACO52 |
| Cirsium scariosum | Cirsium ?erosum (Rydb.) K. Schum. (pro sp.) [not hybrid] | CIER2 |
| Cirsium scariosum | Cirsium acaule All. var. americanum Gray | CIACA |
| Cirsium scariosum | Cirsium acaulescens (Rydb.) K. Schum. | CIAC3 |
| Cirsium scariosum | Cirsium americanum (Gray) K. Schum. | CIAM4 |
| Cirsium scariosum | Cirsium butleri (Rydb.) Petrak | CIBU3 |
| Cirsium scariosum | Cirsium coloradense (Rydb.) Cockerell | CICO2 |
| Cirsium scariosum | Cirsium coloradense (Rydb.) Cockerell ssp. acaulescens (Rydb.) Petrak | CICOA |
| Cirsium scariosum | Cirsium coloradense (Rydb.) Cockerell ssp. longissimum (Heller) Petrak | CICOL |
| Cirsium scariosum | Cirsium congdonii Moore & Frankton | CICO3 |
| Cirsium scariosum | Cirsium drummondii Torr. & Gray ssp. lanatum Petrak | CIDRL |
| Cirsium scariosum | Cirsium drummondii Torr. & Gray ssp. latisquamum Petrak | CIDRL2 |
| Cirsium scariosum | Cirsium drummondii Torr. & Gray ssp. vexans Petrak | CIDRV |
| Cirsium scariosum | Cirsium drummondii Torr. & Gray var. acaulescens (Rydb.) J.F. Macbr. | CIDRA |
| Cirsium scariosum | Cirsium drummondii Torr. & Gray var. oregonense Petrak | CIDRO |
| Cirsium scariosum | Cirsium kelseyi (Rydb.) Petrak | CIKE |
| Cirsium scariosum | Cirsium lacerum (Rydb.) Petrak | CILA4 |
| Cirsium scariosum | Cirsium magnificum (A. Nels.) Petrak | CIMA3 |
| Cirsium scariosum | Cirsium minganense Victorin | CIMI |
| Cirsium scariosum | Cirsium oreophilum (Rydb.) K. Schum. | CIOR |
| Cirsium scariosum | Cirsium quercetorum (Gray) Jepson var. citrinum Petrak | CIQUC4 |
| Cirsium scariosum | Cirsium scariosum Nutt. var. scariosum Nutt. [superfluous autonym] | CISCS |
| Cirsium scariosum | Cirsium scariosum Nutt. var. thorneae Welsh | CISCT |
| Cirsium scariosum | Cirsium tioganum (Congd.) Petrak | CITI |
| Cirsium scariosum | Cirsium tioganum (Congd.) Petrak var. coloradense (Rydb.) Dorn | CITIC |
| Cirsium scariosum | Cirsium tioganum (Congd.) Petrak var. tioganum (Congd.) Petrak [superfluous autonym] | CITIT |
| Cirsium scariosum | Cnicus drummondii (Torr. & Gray) Gray var. acaulescens Rydb. | CNDRA |
| Cirsium scariosum | Cnicus tioganus Congd. | CNTI |
| Cirsium scopulorum | Cirsium eriocephalum Gray | CIER3 |
| Cirsium scopulorum | Cirsium hesperium (Eastw.) Petrak | CIHE4 |
| Cirsium subniveum | Carduus nevadensis Greene | CANE21 |
| Cirsium subniveum | Cirsium davisii Cronq. | CIDA |
| Cirsium subniveum | Cirsium humboldtense Rydb. | CIHU |
| Cirsium texanum | Carduus austrinus Small | CAAU14 |
| Cirsium texanum | Cirsium texanum Buckl. var. stenolepis Shinners | CITES |
| Cirsium undulatum var. tracyi | Carduus tracyi Rydb. | CATR14 |
| Cirsium undulatum var. tracyi | Cirsium acuatum (Osterhout) Petrak | CIAC4 |
| Cirsium undulatum var. tracyi | Cirsium floccosum (Rydb.) Petrak | CIFL3 |
| Cirsium undulatum var. tracyi | Cirsium tracyi (Rydb.) Petrak | CITR4 |
| Cirsium undulatum var. undulatum | Carduus helleri Small | CAHE13 |
| Cirsium undulatum var. undulatum | Carduus undulatus Nutt. | CAUN9 |
| Cirsium undulatum var. undulatum | Cirsium helleri (Small) Cory | CIHE5 |
| Cirsium undulatum var. undulatum | Cirsium megacephalum (Gray) Cockerell | CIME7 |
| Cirsium undulatum var. undulatum | Cirsium ochrocentrum Gray var. helleri (Small) Petrak | CIOCH |
| Cirsium undulatum var. undulatum | Cirsium undulatum (Nutt.) Spreng. var. megacephalum (Gray) Fern. | CIUNM |
| Cirsium undulatum var. undulatum | Cnicus undulatus Gray var. megacephalus Gray | CNUNM |
| Cirsium virginianum | Carduus virginianus L. | CAVI10 |
| Cirsium virginianum | Cirsium revolutum (Small) Petrak | CIRE4 |
| Cirsium vulgare | Carduus lanceolatus L. | CALA58 |
| Cirsium vulgare | Carduus vulgaris Savi | CAVU4 |
| Cirsium vulgare | Cirsium lanceolatum (L.) Scop. var. hypoleucum DC. | CILAH |
| Cirsium vulgare | Cirsium lanceolatum (L.) Scop., non Hill | CILA8 |
| Cirsium wheeleri | Cirsium blumeri Petrak | CIBL |
| Cirsium wheeleri | Cirsium perennans (Greene) Woot. & Standl. | CIPE |
| Cirsium wheeleri | Cnicus wheeleri Gray | CNWH |
| clammy false oxtongue | Blumea viscosa (P. Mill.) Badillo | BLVI |
| clapdaisy | Clappia Gray | CLAPP |
| Clark's ragwort | Senecio clarkianus Gray | SECL |
| clasping arnica | Arnica amplexicaulis Nutt. | ARAM2 |
| clasping coneflower | Dracopis amplexicaulis (Vahl) Cass. | DRAM |
| clasping yellowtops | Flaveria chlorifolia Gray | FLCH |
| claspingleaf doll's daisy | Boltonia decurrens (Torr. & Gray) Wood | BODE2 |
| clavel de muerto | Tithonia rotundifolia (P. Mill.) Blake | TIRO |
| Clear Creek fleabane | Erigeron religiosus Cronq. | ERRE7 |
| cleftleaf ragwort | Packera moresbiensis (Calder & Taylor) J.F. Bain | PAMO18 |
| Cleveland's desertdandelion | Malacothrix clevelandii Gray | MACL2 |
| Cleveland's ragwort | Packera clevelandii (Greene) W.A. Weber & A. L?ve | PACL10 |
| clibadium | Clibadium L. | CLIBA |
| cliff desertdandelion | Malacothrix saxatilis (Nutt.) Torr. & Gray | MASA2 |
| cliff desertdandelion | Malacothrix saxatilis (Nutt.) Torr. & Gray var. arachnoidea (McGregor) E. Williams | MASAA |
| cliff desertdandelion | Malacothrix saxatilis (Nutt.) Torr. & Gray var. commutata (Torr. & Gray) Ferris | MASAC |
| cliff desertdandelion | Malacothrix saxatilis (Nutt.) Torr. & Gray var. implicata (Eastw.) Hall | MASAI |
| cliff desertdandelion | Malacothrix saxatilis (Nutt.) Torr. & Gray var. saxatilis | MASAS |
| cliff desertdandelion | Malacothrix saxatilis (Nutt.) Torr. & Gray var. tenuifolia (Nutt.) Gray | MASAT |
| cliff false goldenaster | Heterotheca viscida (Gray) Harms | HEVI5 |
| cliff goldenbush | Ericameria cuneata (Gray) McClatchie | ERCU7 |
| cliff goldenbush | Ericameria cuneata (Gray) McClatchie var. cuneata | ERCUC |
| cliff goldenbush | Ericameria cuneata (Gray) McClatchie var. macrocephala Urbatsch | ERCUM |
| cliff goldenbush | Ericameria cuneata (Gray) McClatchie var. spathulata (Gray) Hall | ERCUS |
| cliff thistle | Cirsium turneri Warnock | CITU |
| climbing aster | Ampelaster carolinianus (Walt.) Nesom | AMCA14 |
| climbing aster | Ampelaster Nesom | AMPEL4 |
| climbing hempvine | Mikania scandens (L.) Willd. | MISC |
| Clokey's fleabane | Erigeron clokeyi Cronq. | ERCL |
| cloudcroft thistle | Cirsium inornatum Woot. & Standl. | CIIN5 |
| clustered goldenrod | Solidago glomerata Michx. | SOGL2 |
| clustered goldenweed | Pyrrocoma racemosa (Nutt.) Torr. & Gray | PYRA |
| clustered goldenweed | Pyrrocoma racemosa (Nutt.) Torr. & Gray var. congesta (Greene) Mayes ex G. Brown & Keil | PYRAC2 |
| clustered goldenweed | Pyrrocoma racemosa (Nutt.) Torr. & Gray var. paniculata (Nutt.) Kartesz & Gandhi | PYRAP2 |
| clustered goldenweed | Pyrrocoma racemosa (Nutt.) Torr. & Gray var. pinetorum (Keck) Kartesz & Gandhi | PYRAP |
| clustered goldenweed | Pyrrocoma racemosa (Nutt.) Torr. & Gray var. racemosa | PYRAR |
| clustered goldenweed | Pyrrocoma racemosa (Nutt.) Torr. & Gray var. sessiliflora (Greene) Mayes ex G. Brown and Keil | PYRAS |
| clustered sawwort | Saussurea densa (Hook.) Rydb. | SADE3 |
| clustered tarweed | Hemizonia fasciculata (DC.) Torr. & Gray | HEFA |
| clustered thistle | Cirsium brevistylum Cronq. | CIBR2 |
| clustered yellowtops | Flaveria trinervia (Spreng.) C. Mohr | FLTR |
| cnicus | Cnicus L. | CNICU |
| Cnicus benedictus | Centaurea benedicta (L.) L. | CEBE5 |
| Cnicus benedictus | Cirsium pugnax Sommier & Levier | CIPU6 |
| Coast Range mule-ears | Wyethia glabra Gray | WYGL |
| coast tarweed | Madia sativa Molina | MASA |
| coast yarrow | Achillea millefolium L. var. litoralis Ehrend. ex Nobs | ACMIL2 |
| coastal bluff beggarticks | Bidens forbesii Sherff | BIFO |
| coastal bluff beggarticks | Bidens forbesii Sherff ssp. forbesii | BIFOF |
| coastal burnweed | Erechtites minima (Poir.) DC. | ERMI6 |
| coastal goldfields | Lasthenia minor (DC.) Ornduff | LAMI5 |
| coastal gumweed | Grindelia hirsutula Hook. & Arn. var. maritima (Greene) M.A. Lane | GRHIM |
| coastal moonshine | Deinandra corymbosa (DC.) B.G. Baldwin | DECO14 |
| coastal nehe | Lipochaeta lavarum (Gaud.) DC. | LILA6 |
| coastal plain chaffhead | Carphephorus corymbosus (Nutt.) Torr. & Gray | CACO37 |
| coastal plain creepingoxeye | Wedelia fruticosa Jacq. | WEFR |
| coastal plain crownbeard | Verbesina aristata (Ell.) Heller | VEAR2 |
| coastal plain goldenaster | Chrysopsis scabrella Torr. & Gray | CHSC2 |
| coastal plain hawkweed | Hieracium megacephalon Nash | HIME |
| coastal plain honeycombhead | Balduina angustifolia (Pursh) B.L. Robins. | BAAN3 |
| coastal plain joepyeweed | Eupatoriadelphus dubius (Willd. ex Poir.) King & H.E. Robins. | EUDU2 |
| coastal plain palafox | Palafoxia integrifolia (Nutt.) Torr. & Gray | PAIN8 |
| coastal plain tickseed | Coreopsis gladiata Walt. | COGL2 |
| coastal plain yellowtops | Flaveria bidentis (L.) Kuntze | FLBI |
| coastal ragweed | Ambrosia hispida Pursh | AMHI3 |
| coastal sagebrush | Artemisia californica Less. | ARCA11 |
| coastal silverpuffs | Microseris bigelovii (Gray) Schultz-Bip. | MIBI |
| coastal sneezeweed | Helenium bolanderi Gray | HEBO2 |
| coastal tarweed | Deinandra corymbosa (DC.) B.G. Baldwin ssp. corymbosa | DECOC2 |
| coastal tarweed | Deinandra corymbosa (DC.) B.G. Baldwin ssp. macrocephala (Nutt.) B.G. Baldwin | DECOM |
| coastal tidytips | Layia platyglossa (Fisch. & C.A. Mey.) Gray | LAPL |
| coastal wormwood | Artemisia suksdorfii Piper | ARSU4 |
| coatbuttons | Tridax procumbens L. | TRPR5 |
| cobwebby thistle | Cirsium occidentale (Nutt.) Jepson | CIOC |
| cobwebby thistle | Cirsium occidentale (Nutt.) Jepson var. californicum (Gray) Keil & C. Turner | CIOCC4 |
| cobwebby thistle | Cirsium occidentale (Nutt.) Jepson var. occidentale | CIOCO |
| cobwebby thistle | Cirsium occidentale (Nutt.) Jepson var. venustum (Greene) Jepson | CIOCV |
| Cochise marshtail | Laennecia eriophylla (Gray) Nesom | LAER |
| Cochise rockdaisy | Perityle cochisensis (Niles) A. Powell | PECO17 |
| cocklebur | Xanthium L. | XANTH2 |
| cocoonhead | Lasiospermum bipinnatum (Thunb.) Druce | LABI5 |
| cocoonhead | Lasiospermum M. Lagasca | LASIO |
| collegeflower | Hymenopappus flavescens Gray | HYFL |
| collegeflower | Hymenopappus flavescens Gray var. canotomentosus Gray | HYFLC |
| collegeflower | Hymenopappus flavescens Gray var. flavescens | HYFLF |
| Colorado feverfew | Parthenium ligulatum (M.E. Jones) Barneby | PALI6 |
| Colorado greenthread | Thelesperma ambiguum Gray | THAM4 |
| Colorado gumweed | Grindelia inornata Greene | GRIN2 |
| Colorado gumweed | Grindelia inornata Greene var. angusta Steyermark | GRINA |
| Colorado gumweed | Grindelia inornata Greene var. inornata | GRINI |
| Colorado ragwort | Senecio soldanella Gray | SESO |
| Colorado rubberweed | Hymenoxys richardsonii (Hook.) Cockerell var. floribunda (Gray) Parker | HYRIF |
| Colorado tansyaster | Machaeranthera coloradoensis (Gray) Osterhout | MACO13 |
| Colorado tansyaster | Machaeranthera coloradoensis (Gray) Osterhout var. coloradoensis | MACOC |
| coltsfoot | Tussilago farfara L. | TUFA |
| coltsfoot | Tussilago L. | TUSSI |
| Columbia ragwort | Senecio integerrimus Nutt. var. exaltatus (Nutt.) Cronq. | SEINE |
| Columbia River gumweed | Grindelia columbiana (Piper) Rydb. | GRCO |
| Columbia River wormwood | Artemisia lindleyana Bess. | ARLI2 |
| columbiadoria | Columbiadoria Nesom | COLUM2 |
| Columbiadoria hallii | Haplopappus hallii Gray | HAHA |
| Columbiadoria hallii | Hesperodoria hallii (Gray) Greene | HEHA3 |
| Columbian goldenbush | Ericameria resinosa Nutt. | ERRE8 |
| Columbian whitetop aster | Sericocarpus rigidus Lindl. | SERI4 |
| Colusa tidytips | Layia septentrionalis Keck | LASE2 |
| Comanche Point tidytips | Layia leucopappa Keck | LALE3 |
| common blue wood aster | Symphyotrichum cordifolium (L.) Nesom | SYCO4 |
| common boneset | Eupatorium perfoliatum L. | EUPE3 |
| common boneset | Eupatorium perfoliatum L. var. colpophilum Fern. & Grisc. | EUPEC |
| common boneset | Eupatorium perfoliatum L. var. perfoliatum | EUPEP |
| common brassbuttons | Cotula coronopifolia L. | COCO7 |
| common brighteyes | Reichardia picroides (L.) Roth | REPI |
| common cottonrose | Filago vulgaris Lam. | FIVU2 |
| common crupina | Crupina vulgaris Cass. | CRVU2 |
| common crupina | Crupina vulgaris Cass. var. vulgaris | CRVUV |
| common dandelion | Taraxacum officinale G.H. Weber ex Wiggers | TAOF |
| common dandelion | Taraxacum officinale G.H. Weber ex Wiggers ssp. ceratophorum (Ledeb.) Schinz ex Thellung | TAOFC |
| common dandelion | Taraxacum officinale G.H. Weber ex Wiggers ssp. officinale | TAOFO |
| common gaillardia | Gaillardia aristata Pursh | GAAR |
| common goldenbush | Isocoma coronopifolia (Gray) Greene | ISCO |
| common goldenthistle | Scolymus hispanicus L. | SCHI |
| common hawkweed | Hieracium lachenalii K.C. Gmel. | HILA8 |
| common leopardbane | Arnica acaulis (Walt.) B.S.P. | ARAC3 |
| common madia | Madia elegans D. Don ex Lindl. | MAEL |
| common madia | Madia elegans D. Don ex Lindl. ssp. elegans | MAELE |
| common medicineplant | Adenostemma lavenia (L.) Kuntze | ADLA2 |
| common monolopia | Monolopia lanceolata Nutt. | MOLA3 |
| common nipplewort | Lapsana communis L. | LACO3 |
| common ragwort | Pericallis hybrida B. Nordenstam | PEHY13 |
| common sandaster | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. | COFI2 |
| common sandaster | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. filaginifolia | COFIF |
| common sneezeweed | Helenium autumnale L. | HEAU |
| common sneezeweed | Helenium autumnale L. var. autumnale | HEAUA |
| common sowthistle | Sonchus oleraceus L. | SOOL |
| common spring-gold | Crocidium multicaule Hook. | CRMU |
| common St. Paul's wort | Sigesbeckia orientalis L. | SIOR2 |
| common stickyseed | Blennosperma nanum (Hook.) Blake | BLNA |
| common stickyseed | Blennosperma nanum (Hook.) Blake var. nanum | BLNAN |
| common stickyseed | Blennosperma nanum (Hook.) Blake var. robustum J.T. Howell | BLNAR |
| common sunflower | Helianthus annuus L. | HEAN3 |
| common tansy | Tanacetum vulgare L. | TAVU |
| common tarweed | Centromadia pungens (Hook. & Arn.) Greene ssp. laevis (Keck) B.G. Baldwin | CEPUL |
| common tarweed | Centromadia pungens (Hook. & Arn.) Greene ssp. maritima (Greene) B.G. Baldwin | CEPUM |
| common tarweed | Centromadia pungens (Hook. & Arn.) Greene ssp. pungens | CEPUP6 |
| common tarweed | Centromadia pungens (Hook. & Arn.) Greene ssp. septentrionalis (Keck) B.G. Baldwin | CEPUS2 |
| common Townsend daisy | Townsendia leptotes (Gray) Osterhout | TOLE |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes | ERLA6 |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. achillaeoides (DC.) Jepson | ERLAA |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. aphanactis J.T. Howell | ERLAA2 |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. arachnoideum (Fisch. & Av?-Lall.) Jepson | ERLAA3 |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. croceum (Greene) Jepson | ERLAC |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. cuneatum (Kellogg) Jepson | ERLAC2 |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. grandiflorum (Gray) Jepson | ERLAG |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. integrifolium (Hook.) Smiley | ERLAI |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. lanatum | ERLAL3 |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. lanceolatum (T.J. Howell) Jepson | ERLAL |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. leucophyllum (DC.) W.R. Carter | ERLAL2 |
| common woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. obovatum (Greene) Hall | ERLAO |
| common wormwood | Artemisia vulgaris L. | ARVU |
| common wormwood | Artemisia vulgaris L. var. kamtschatica Bess. | ARVUK |
| common wormwood | Artemisia vulgaris L. var. vulgaris | ARVUV |
| common yarrow | Achillea millefolium L. | ACMI2 |
| common yarrow | Achillea millefolium L. var. alpicola (Rydb.) Garrett | ACMIA |
| common yarrow | Achillea millefolium L. var. arenicola (Heller) Nobs | ACMIA2 |
| common yarrow | Achillea millefolium L. var. millefolium | ACMIM2 |
| common yarrow | Achillea millefolium L. var. nigrescens E. Mey. | ACMIN |
| common yarrow | Achillea millefolium L. var. puberula (Rydb.) Nobs | ACMIP2 |
| compact chickensage | Sphaeromeria compacta (Hall) A. Holmgren, L. Shultz & Lowrey | SPCO8 |
| compact cobwebby thistle | Cirsium occidentale (Nutt.) Jepson var. compactum Hoover | CIOCC2 |
| compassplant | Silphium laciniatum L. | SILA3 |
| compassplant | Silphium laciniatum L. var. laciniatum | SILAL2 |
| Condylidium iresinoides | Eupatorium iresinoides Kunth | EUIR |
| coneflower | Dracopis Cass. | DRACO3 |
| coneflower | Rudbeckia L. | RUDBE |
| Congdon's tarweed | Centromadia parryi (Greene) Greene ssp. congdonii (Robins. & Greenm.) B.G. Baldwin | CEPAC |
| Congdon's woolly sunflower | Eriophyllum congdonii Brandeg. | ERCO16 |
| Connecticut beggarticks | Bidens heterodoxa (Fern.) Fern. & St. John | BIHE2 |
| Conoclinium betonicifolium | Eupatorium betonicifolium P. Mill. | EUBE2 |
| Conoclinium coelestinum | Eupatorium coelestinum L. | EUCO6 |
| Conoclinium greggii | Eupatorium greggii Gray | EUGR2 |
| Constancea nevinii | Eriophyllum nevinii Gray | ERNE7 |
| Contra Costa goldfields | Lasthenia conjugens Greene | LACO6 |
| conyza | Laennecia coulteri (Gray) Nesom | LACO13 |
| Conyza bonariensis | Erigeron bonariensis L. | ERBO4 |
| Conyza bonariensis | Erigeron crispus Pourr. | ERCR11 |
| Conyza bonariensis | Erigeron linifolius Willd. | ERLI2 |
| Conyza bonariensis | Leptilon bonariense (L.) Small | LEBO3 |
| Conyza bonariensis | Leptilon linifolium (Willd.) Small | LELI3 |
| Conyza canadensis var. canadensis | Erigeron canadensis L. | ERCA20 |
| Conyza canadensis var. canadensis | Leptilon canadense (L.) Britt. | LECA16 |
| Conyza canadensis var. glabrata | Erigeron canadensis L. var. glabratus Gray | ERCAG |
| Conyza canadensis var. pusilla | Conyza parva Cronq. | COPA17 |
| Conyza canadensis var. pusilla | Erigeron canadensis L. var. pusillus (Nutt.) Boivin, non Ahles | ERCAP2 |
| Conyza canadensis var. pusilla | Erigeron pusillus Nutt. | ERPU12 |
| Conyza canadensis var. pusilla | Leptilon pusillum (Nutt.) Britt. | LEPU9 |
| Conyza floribunda | Conyza bilboana Remy | COBI3 |
| Conyza floribunda | Conyza bonariensis (L.) Cronq. var. leiotheca (Blake) Cuatrec. | COBOL |
| Conyza floribunda | Erigeron bilboanus (Remy) Cabrera | ERBI5 |
| Conyza floribunda | Erigeron floribundus (Kunth) Schultz-Bip. | ERFL15 |
| Conyza laevigata | Conyza apurensis Kunth | COAP |
| Conyza laevigata | Conyza subspathulata Cronq. | COSU8 |
| Conyza laevigata | Erigeron apurensis (Kunth) Griseb. | ERAP5 |
| Conyza laevigata | Erigeron chinensis Jacq. | ERCH14 |
| Conyza laevigata | Erigeron spathulatus Vahl | ERSP13 |
| Conyza laevigata | Leptilon chinense (Jacq.) Britt. | LECH3 |
| Conyza primulifolia | Conyza chilensis Spreng. | COCH3 |
| Conyza ramosissima | Erigeron divaricatus Michx. | ERDI12 |
| Conyza ramosissima | Leptilon divaricatum (Michx.) Raf. | LEDI8 |
| Cooper's dogweed | Adenophyllum cooperi (Gray) Strother | ADCO2 |
| Cooper's goldenbush | Ericameria cooperi (Gray) Hall | ERCO23 |
| Cooper's rubberweed | Hymenoxys cooperi (Gray) Cockerell | HYCO2 |
| Cooper's rubberweed | Hymenoxys cooperi (Gray) Cockerell var. canescens (D.C. Eat.) Parker | HYCOC |
| Cooper's rubberweed | Hymenoxys cooperi (Gray) Cockerell var. cooperi | HYCOC2 |
| copperweed | Oxytenia acerosa Nutt. | OXAC4 |
| coreocarpus | Coreocarpus Benth. | COREO |
| Coreopsis basalis | Calliopsis basalis A. Dietr. | CABA14 |
| Coreopsis basalis | Coreopsis drummondii (D. Don) Torr. & Gray | CODR3 |
| Coreopsis bigelovii | Leptosyne bigelovii (Gray) Gray | LEBI4 |
| Coreopsis bigelovii | Pugiopappus bigelovii Gray | PUBI |
| Coreopsis californica var. californica | Leptosyne californica Nutt. | LECA17 |
| Coreopsis californica var. newberryi | Coreopsis newberryi Gray | CONE6 |
| Coreopsis calliopsidea | Agarista calliopsidea DC. | AGCA10 |
| Coreopsis delphiniifolia | Coreopsis delphiniifolia Lam. var. chlooidea Sherff | CODEC2 |
| Coreopsis delphiniifolia | Coreopsis major Walt. var. linearis Small | COMAL |
| Coreopsis douglasii | Coreopsis stillmanii (Gray) Blake var. jonesii Sherff | COSTJ |
| Coreopsis douglasii | Leptosyne douglasii DC. | LEDO5 |
| Coreopsis gigantea | Leptosyne gigantea Kellogg | LEGI2 |
| Coreopsis gigantea | Tuckermannia gigantea (Kellogg) M.E. Jones | TUGI |
| Coreopsis gladiata | Coreopsis angustifolia Ait., non L. | COAN9 |
| Coreopsis gladiata | Coreopsis helianthoides Beadle | COHE11 |
| Coreopsis gladiata | Coreopsis longifolia Small | COLO7 |
| Coreopsis gladiata | Coreopsis longifolia Small var. godfreyi Sherff | COLOG2 |
| Coreopsis grandiflora var. grandiflora | Coreopsis grandiflora Hogg ex Sweet var. pilosa Sherff | COGRP2 |
| Coreopsis grandiflora var. harveyana | Coreopsis heterolepis Sherff | COHE8 |
| Coreopsis grandiflora var. longipes | Coreopsis longipes Hook. | COLO9 |
| Coreopsis grandiflora var. saxicola | Coreopsis saxicola Alexander | COSA5 |
| Coreopsis grandiflora var. saxicola | Coreopsis saxicola Alexander var. duncanii Sherff | COSAD |
| Coreopsis hamiltonii | Leptosyne hamiltonii Elmer | LEHA3 |
| Coreopsis lanceolata | Coreopsis crassifolia Ait. | COCR5 |
| Coreopsis lanceolata | Coreopsis heterogyna Fern. | COHE7 |
| Coreopsis lanceolata | Coreopsis lanceolata L. var. villosa Michx. | COLAV |
| Coreopsis latifolia | Leiodon latifolius (Michx.) Shuttlw. | LELA15 |
| Coreopsis leavenworthii | Coreopsis angustata Greene | COAN10 |
| Coreopsis leavenworthii | Coreopsis leavenworthii Torr. & Gray var. curtissii Sherff | COLEC |
| Coreopsis leavenworthii | Coreopsis leavenworthii Torr. & Gray var. garberi Gray | COLEG |
| Coreopsis leavenworthii | Coreopsis leavenworthii Torr. & Gray var. lewtonii (Small) Sherff | COLEL |
| Coreopsis leavenworthii | Coreopsis lewtonii Small | COLE4 |
| Coreopsis linifolia | Coreopsis gladiata Walt. var. linifolia (Nutt.) Cronq. | COGLL |
| Coreopsis linifolia | Coreopsis oniscicarpa Fern. | COON |
| Coreopsis linifolia | Coreopsis oniscicarpa Fern. var. simulans Fern. | COONS |
| Coreopsis linifolia | Coreopsis saxicoloidea Sherff | COSA7 |
| Coreopsis major | Coreopsis major Walt. var. oemleri (Ell.) Britt. ex Small & Vail | COMAO2 |
| Coreopsis major | Coreopsis major Walt. var. rigida (Nutt.) Boynt. | COMAR4 |
| Coreopsis major | Coreopsis major Walt. var. stellata (Nutt.) B.L. Robins. | COMAS |
| Coreopsis maritima | Tuckermannia maritima Nutt. | TUMA2 |
| Coreopsis pubescens var. debilis | Coreopsis corninsularis Sherff | COCO22 |
| Coreopsis pubescens var. debilis | Coreopsis debilis Sherff | CODE6 |
| Coreopsis stillmanii | Leptosyne stillmanii Gray | LEST9 |
| Coreopsis tinctoria var. atkinsoniana | Coreopsis atkinsoniana Dougl. ex Lindl. | COAT3 |
| Coreopsis tinctoria var. similis | Coreopsis similis Boynt. | COSI7 |
| Coreopsis tinctoria var. tinctoria | Coreopsis cardaminefolia (DC.) Torr. & Gray | COCA12 |
| Coreopsis tinctoria var. tinctoria | Coreopsis stenophylla Boynt. | COST11 |
| Coreopsis tinctoria var. tinctoria | Coreopsis tinctoria Nutt. var. imminuta Sherff | COTII |
| Coreopsis tripteris | Coreopsis tripteris L. var. deamii Standl. | COTRD |
| Coreopsis tripteris | Coreopsis tripteris L. var. intercedens Standl. | COTRI |
| Coreopsis tripteris | Coreopsis tripteris L. var. smithii Sherff | COTRS |
| Coreopsis tripteris | Coreopsis tripteris L. var. subrhomboidea Sherff | COTRS2 |
| Coreopsis wrightii | Coreopsis basalis (A. Dietr.) Blake var. wrightii (Gray) Blake | COBAW |
| Coreopsis wrightii | Coreopsis drummondii (D. Don) Torr. & Gray var. wrightii Gray | CODRW |
| Corethrogyne filaginifolia var. californica | Corethrogyne californica DC. | COCA11 |
| Corethrogyne filaginifolia var. californica | Corethrogyne californica DC. var. californica DC. [superfluous autonym] | COCAC5 |
| Corethrogyne filaginifolia var. californica | Corethrogyne californica DC. var. lyonii Blake | COCAL |
| Corethrogyne filaginifolia var. californica | Corethrogyne californica DC. var. obovata (Benth.) Kuntze | COCAO |
| Corethrogyne filaginifolia var. californica | Corethrogyne obovata Benth. | COOB8 |
| Corethrogyne filaginifolia var. californica | Lessingia filaginifolia (Hook. & Arn.) M.A. Lane var. californica (DC.) M.A. Lane | LEFIC2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. bernardina (Abrams) Hall | COFIB |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. brevicula (Greene) Canby | COFIB2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. glomerata Hall | COFIG |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. hamiltonensis Keck | COFIH |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. incana (Nutt.) Canby | COFII |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. latifolia Hall | COFIL |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. linifolia Hall | COFIL2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. peirsonii Canby | COFIP |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. pinetorum I.M. Johnston | COFIP2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. rigida Gray | COFIR2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. robusta Greene | COFIR |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. sessilis (Greene) Canby | COFIS |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. virgata (Benth.) Gray | COFIV |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne filaginifolia (Hook. & Arn.) Nutt. var. viscidula (Greene) Keck | COFIV2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne flagellaris Greene | COFL8 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne floccosa Greene | COFL9 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne incana Nutt. | COIN8 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne leucophylla (Lindl.) Jepson | COLE2 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne linifolia (Hall) Ferris | COLI9 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne scabra Greene | COSC8 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne sessilis Greene | COSE15 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne tomentella (Hook. & Arn.) Torr. & Gray | COTO3 |
| Corethrogyne filaginifolia var. filaginifolia | Corethrogyne viscidula Greene | COVI14 |
| Corethrogyne filaginifolia var. filaginifolia | Lessingia filaginifolia (Hook. & Arn.) M.A. Lane | LEFI11 |
| corkscrew beggarticks | Bidens torta Sherff | BITO |
| corn chamomile | Anthemis arvensis L. | ANAR6 |
| corndaisy | Glebionis segetum (L.) Fourr. | GLSE5 |
| cornel-leaf whitetop | Doellingeria infirma (Michx.) Greene | DOIN2 |
| Corpus Christi fleabane | Erigeron procumbens (Houst. ex P. Mill.) Nesom | ERPR16 |
| corymbflower tansy | Tanacetum corymbosum (L.) Schultz-Bip. | TACO5 |
| cosmos | Cosmos Cav. | COSMO |
| Cosmos caudatus | Bidens caudatus (Kunth) Schultz-Bip. | BICA3 |
| Cosmos parviflorus | Coreopsis parviflora Jacq. | COPA19 |
| cosmosflower beggarticks | Bidens cosmoides (Gray) Sherff | BICO6 |
| Cossatot Mountain leafcup | Polymnia cossatotensis A.B. Pittman & V. Bates | POCO25 |
| costmary | Tanacetum balsamita L. | TABA |
| cottonbatting plant | Pseudognaphalium stramineum (Kunth) A. Anderb. | PSST7 |
| cottonrose | Filago L. | FILAG |
| cottonrose | Logfia Cass. | LOGFI2 |
| cottonseed | Micropus L. | MICRO5 |
| cottonthistle | Onopordum L. | ONOPO |
| cottony goldenaster | Chrysopsis gossypina (Michx.) Ell. | CHGO |
| cottony goldenaster | Chrysopsis gossypina (Michx.) Ell. ssp. cruiseana (Dress) Semple | CHGOC |
| cottony goldenaster | Chrysopsis gossypina (Michx.) Ell. ssp. gossypina | CHGOG |
| cottony goldenaster | Chrysopsis gossypina (Michx.) Ell. ssp. hyssopifolia (Nutt.) Semple | CHGOH |
| Coulter's brickellbush | Brickellia coulteri Gray | BRCO |
| Coulter's goldfields | Lasthenia glabrata Lindl. ssp. coulteri (Gray) Ornduff | LAGLC |
| Coville's erigeron | Erigeron breweri Gray var. covillei (Greene) Nesom | ERBRC3 |
| Coville's mule-ears | Agnorhiza invenusta (Greene) W.A. Weber | AGIN8 |
| coyotebrush | Baccharis pilularis DC. | BAPI |
| creeping aster | Eurybia surculosa (Michx.) Nesom | EUSU7 |
| creeping cudweed | Euchiton gymnocephalus (DC.) A. Anderb. | EUGY2 |
| creeping lettuce | Ixeris stolonifera Gray | IXST |
| creeping silverback | Luina serpentina Cronq. | LUSE |
| creeping spotflower | Acmella decumbens (Sm.) R.K. Jansen | ACDE5 |
| creeping zinnia | Sanvitalia Lam. | SANVI |
| creeping-oxeye | Sphagneticola O. Hoffmann | SPHAG3 |
| creepingoxeye | Wedelia Jacq. | WEDEL |
| Crepis acuminata ssp. acuminata | Crepis acuminata Nutt. ssp. typica Babcock & Stebbins | CRACT |
| Crepis acuminata ssp. acuminata | Psilochenia acuminata (Nutt.) W.A. Weber | PSAC |
| Crepis acuminata ssp. pluriflora | Psilochenia acuminata (Nutt.) W.A. Weber ssp. pluriflora (Babcock & Stebbins) W.A. Weber | PSACP |
| Crepis atribarba ssp. atribarba | Crepis atribarba Heller ssp. cytotaxonomicorum (Boivin) W.A. Weber | CRATC |
| Crepis atribarba ssp. atribarba | Crepis atribarba Heller ssp. typicus Babcock & Stebbins | CRATT |
| Crepis atribarba ssp. atribarba | Crepis atribarba Heller var. cytotaxonomicorum Boivin | CRATC2 |
| Crepis atribarba ssp. atribarba | Psilochenia atribarba (Heller) W.A. Weber | PSAT |
| Crepis atribarba ssp. originalis | Crepis barbigera Leib. ex Coville | CRBA3 |
| Crepis bakeri ssp. bakeri | Psilochenia bakeri (Greene) W.A. Weber | PSBA3 |
| Crepis bakeri ssp. cusickii | Psilochenia bakeri (Greene) W.A. Weber ssp. cusickii (Eastw.) W.A. Weber | PSBAC |
| Crepis bakeri ssp. idahoensis | Psilochenia bakeri (Greene) W.A. Weber ssp. idahoensis (Babcock & Stebbins) W.A. Weber | PSBAI |
| Crepis elegans | Askellia elegans (Hook.) W.A. Weber | ASEL7 |
| Crepis intermedia | Psilochenia intermedia (Gray) W.A. Weber | PSIN4 |
| Crepis modocensis ssp. glareosa | Psilochenia modocensis (Greene) W.A. Weber ssp. glareosa (Piper) W.A. Weber | PSMOG |
| Crepis modocensis ssp. modocensis | Crepis modocensis Greene ssp. typica Babcock & Stebbins | CRMOT |
| Crepis modocensis ssp. modocensis | Psilochenia modocensis (Greene) W.A. Weber | PSMO4 |
| Crepis modocensis ssp. rostrata | Crepis modocensis Greene var. rostrata (Coville) Boivin | CRMOR2 |
| Crepis modocensis ssp. rostrata | Psilochenia modocensis (Greene) W.A. Weber ssp. rostrata (Coville) W.A. Weber | PSMOR |
| Crepis modocensis ssp. subacaulis | Crepis occidentalis Nutt. var. nevadensis Kellogg p.p. | CROCN |
| Crepis modocensis ssp. subacaulis | Psilochenia modocensis (Greene) W.A. Weber ssp. subacaulis (Kellogg) W.A. Weber | PSMOS |
| Crepis monticola | Psilochenia monticola (Coville) W.A. Weber | PSMO5 |
| Crepis nana ssp. nana | Askellia nana (Richards.) W.A. Weber | ASNA5 |
| Crepis nana ssp. nana | Crepis nana Richards. ssp. typica Babcock | CRNAT2 |
| Crepis nana ssp. nana | Crepis nana Richards. var. lyratifolia (Turcz.) Hult | CRNAL |
| Crepis nana ssp. ramosa | Askellia nana (Richards.) W.A. Weber ssp. ramosa (Babcock) W.A. Weber | ASNAR |
| Crepis nana ssp. ramosa | Crepis nana Richards. var. ramosa (Babcock) Cronq. | CRNAR2 |
| Crepis occidentalis ssp. conjuncta | Crepis occidentalis Nutt. var. nevadensis Kellogg | CROCN2 |
| Crepis occidentalis ssp. conjuncta | Psilochenia occidentalis (Nutt.) Nutt. ssp. conjuncta (Jepson) W.A. Weber | PSOCC |
| Crepis occidentalis ssp. costata | Crepis occidentalis Nutt. var. costata Gray | CROCC3 |
| Crepis occidentalis ssp. costata | Psilochenia occidentalis (Nutt.) Nutt. ssp. costata (Gray) W.A. Weber | PSOCC2 |
| Crepis occidentalis ssp. occidentalis | Crepis occidentalis Nutt. ssp. typica Babcock & Stebbins | CROCT |
| Crepis occidentalis ssp. occidentalis | Psilochenia occidentalis (Nutt.) Nutt. | PSOC |
| Crepis occidentalis ssp. pumila | Crepis occidentalis Nutt. var. pumila (Rydb.) Babcock & Stebbins | CROCP2 |
| Crepis pannonica | Crepis rigida Waldst. & Kit. | CRRI7 |
| Crepis pleurocarpa | Psilochenia pleurocarpa (Gray) W.A. Weber | PSPL |
| Crepis runcinata ssp. andersonii | Crepis runcinata (James) Torr. & Gray var. andersonii (Gray) Cronq. | CRRUA2 |
| Crepis runcinata ssp. andersonii | Psilochenia runcinata (James) A.& D. L?ve ssp. andersonii (Gray) W.A. Weber | PSRUA |
| Crepis runcinata ssp. barberi | Crepis barberi Greenm. | CRBA11 |
| Crepis runcinata ssp. barberi | Crepis glauca (Nutt.) Torr. & Gray ssp. barberi (Greenm.) Babcock & Stebbins | CRGLB |
| Crepis runcinata ssp. barberi | Crepis runcinata (James) Torr. & Gray var. barberi (Greenm.) B.L. Turner | CRRUB2 |
| Crepis runcinata ssp. barberi | Psilochenia runcinata (James) A.& D. L?ve ssp. barberi (Greenm.) W.A. Weber | PSRUB |
| Crepis runcinata ssp. glauca | Crepis glauca (Nutt.) Torr. & Gray | CRGL5 |
| Crepis runcinata ssp. glauca | Crepis runcinata (James) Torr. & Gray var. glauca (Nutt.) Boivin | CRRUG2 |
| Crepis runcinata ssp. glauca | Psilochenia runcinata (James) A.& D. L?ve ssp. glauca (Nutt.) W.A. Weber | PSRUG |
| Crepis runcinata ssp. hallii | Psilochenia runcinata (James) A.& D. L?ve ssp. hallii (Babcock & Stebbins) W.A. Weber | PSRUH |
| Crepis runcinata ssp. hispidulosa | Crepis platyphylla Greene | CRPL3 |
| Crepis runcinata ssp. hispidulosa | Crepis riparia A. Nels. | CRRI6 |
| Crepis runcinata ssp. hispidulosa | Crepis runcinata (James) Torr. & Gray var. hispidulosa T.J. Howell ex Rydb. | CRRUH3 |
| Crepis runcinata ssp. hispidulosa | Psilochenia runcinata (James) A.& D. L?ve ssp. hispidulosa (T.J. Howell ex Rydb.) W.A. Weber | PSRUH2 |
| Crepis runcinata ssp. imbricata | Crepis runcinata (James) Torr. & Gray var. imbricata (Babcock & Stebbins) M.E. Peck | CRRUI2 |
| Crepis runcinata ssp. imbricata | Psilochenia runcinata (James) A.& D. L?ve ssp. imbricata (Babcock & Stebbins) W.A. Weber | PSRUI |
| Crepis runcinata ssp. runcinata | Crepis alpicola (Rydb.) A. Nels. | CRAL5 |
| Crepis runcinata ssp. runcinata | Crepis glaucella Rydb. | CRGL6 |
| Crepis runcinata ssp. runcinata | Crepis neomexicana Woot. & Standl. | CRNE3 |
| Crepis runcinata ssp. runcinata | Crepis perplexans Rydb. | CRPE12 |
| Crepis runcinata ssp. runcinata | Crepis runcinata (James) Torr. & Gray ssp. typica Babcock & Stebbins | CRRUT |
| Crepis runcinata ssp. runcinata | Psilochenia runcinata (James) A.& D. L?ve | PSRU2 |
| Crepis vesicaria ssp. taraxacifolia | Crepis vesicaria L. ssp. haenseleri (Boiss. ex DC.) P.D. Sell | CRVEH |
| Crepis vesicaria ssp. taraxacifolia | Crepis vesicaria L. var. taraxacifolia (Thuill.) Boivin | CRVET3 |
| Cretanweed | Hedypnois cretica (L.) Dum.-Cours. | HECR2 |
| crisped goldenbush | Ericameria crispa (L.C. Anders.) Nesom | ERCR7 |
| Critonia portoricensis | Eupatorium portoricense Urban | EUPO7 |
| Cronquist's fleabane | Erigeron cronquistii Maguire | ERCR |
| Cronquist's woodyaster | Xylorhiza cronquistii Welsh & Atwood | XYCR2 |
| crookedstem aster | Symphyotrichum prenanthoides (Muhl. ex Willd.) Nesom | SYPR6 |
| Croptilon divaricatum | Haplopappus divaricatus (Nutt.) Gray | HADI5 |
| Croptilon divaricatum | Inula divaricata Nutt. | INDI |
| Croptilon divaricatum | Isopappus divaricatus (Nutt.) Torr. & Gray | ISDI4 |
| Croptilon hookerianum var. graniticum | Croptilon divaricatum (Nutt.) Raf. var. graniticum (E.B. Sm.) Shinners | CRDIG |
| Croptilon hookerianum var. graniticum | Haplopappus validus (Rydb.) Cory ssp. graniticus E.B. Sm. | HAVAG |
| Croptilon hookerianum var. hookerianum | Croptilon divaricatum (Nutt.) Raf. var. hookerianum (Torr. & Gray) Shinners | CRDIH |
| Croptilon hookerianum var. hookerianum | Haplopappus divaricatus (Nutt.) Gray var. hookerianus (Torr. & Gray) Waterfall | HADIH |
| Croptilon hookerianum var. hookerianum | Haplopappus validus (Rydb.) Cory ssp. torreyi E.B. Sm. | HAVAT |
| Croptilon hookerianum var. hookerianum | Isopappus hookerianus Torr. & Gray | ISHO3 |
| Croptilon hookerianum var. validum | Haplopappus validus (Rydb.) Cory | HAVA |
| Croptilon hookerianum var. validum | Isopappus validus Rydb. | ISVA |
| Croptilon rigidifolium | Croptilon divaricatum (Nutt.) Raf. var. hirtellum (Shinners) Shinners | CRDIH2 |
| Croptilon rigidifolium | Haplopappus rigidifolius E.B. Sm. | HARI |
| crowfoot rockdaisy | Perityle coronopifolia Gray | PECO19 |
| crown mayweed | Matricaria courrantiana DC. | MACO7 |
| crown tickseed | Coreopsis nuecensis Heller | CONU3 |
| crownbeard | Verbesina L. | VERBE2 |
| crowndaisy | Glebionis coronarium (L.) Tzvelev | GLCO6 |
| crowned beggarticks | Bidens coronata (L.) Britt. | BICO |
| Crum's monolopia | Monolopia stricta Crum | MOST |
| crupina | Crupina (Pers.) DC. | CRUPI |
| Crystal Springs lessingia | Lessingia arachnoidea Greene | LEAR33 |
| cucumberleaf sunflower | Helianthus debilis Nutt. | HEDE4 |
| cucumberleaf sunflower | Helianthus debilis Nutt. ssp. cucumerifolius (Torr. & Gray) Heiser | HEDEC2 |
| cucumberleaf sunflower | Helianthus debilis Nutt. ssp. debilis | HEDED |
| cucumberleaf sunflower | Helianthus debilis Nutt. ssp. silvestris Heiser | HEDES |
| cucumberleaf sunflower | Helianthus debilis Nutt. ssp. tardiflorus Heiser | HEDET |
| cucumberleaf sunflower | Helianthus debilis Nutt. ssp. vestitus (E.E. Wats.) Heiser | HEDEV |
| cudweed | Gnaphalium L. | GNAPH |
| cudweed | Pseudognaphalium Kirp. | PSEUD43 |
| cultivated endive | Cichorium endivia L. | CIEN |
| Cuman ragweed | Ambrosia psilostachya DC. | AMPS |
| Cumberland rosinweed | Silphium brachiatum Gattinger | SIBR2 |
| cup plant | Silphium perfoliatum L. | SIPE2 |
| cup plant | Silphium perfoliatum L. var. connatum (L.) Cronq. | SIPEC2 |
| cup plant | Silphium perfoliatum L. var. perfoliatum | SIPEP |
| cupped monolopia | Monolopia major DC. | MOMA2 |
| cure for all | Pluchea carolinensis (Jacq.) G. Don | PLCA10 |
| curly plumeless thistle | Carduus crispus L. | CACR2 |
| curlycup gumweed | Grindelia squarrosa (Pursh) Dunal | GRSQ |
| curlycup gumweed | Grindelia squarrosa (Pursh) Dunal var. quasiperennis Lunell | GRSQQ |
| curlycup gumweed | Grindelia squarrosa (Pursh) Dunal var. serrulata (Rydb.) Steyermark | GRSQS |
| curlycup gumweed | Grindelia squarrosa (Pursh) Dunal var. squarrosa | GRSQS2 |
| curlyhead goldenweed | Pyrrocoma crocea (Gray) Greene | PYCR2 |
| curlyhead goldenweed | Pyrrocoma crocea (Gray) Greene var. crocea | PYCRC |
| curlyhead goldenweed | Pyrrocoma crocea (Gray) Greene var. genuflexa (Greene) Mayes ex G. Brown & Keil | PYCRG |
| curlytop gumweed | Grindelia nuda Wood | GRNU |
| curlytop gumweed | Grindelia nuda Wood var. aphanactis (Rydb.) Nesom | GRNUA |
| curlytop gumweed | Grindelia nuda Wood var. nuda | GRNUN |
| cushion daisy | Erigeron compactus Blake | ERCO3 |
| cushion Townsend daisy | Townsendia condensata Parry ex Gray | TOCO2 |
| cushion Townsend daisy | Townsendia condensata Parry ex Gray var. anomala (Heiser) Dorn | TOCOA |
| cushion Townsend daisy | Townsendia condensata Parry ex Gray var. condensata | TOCOC |
| Cusick's aster | Symphyotrichum cusickii (Gray) Nesom | SYCU2 |
| Cusick's hawksbeard | Crepis bakeri Greene ssp. cusickii (Eastw.) Babcock & Stebbins | CRBAC |
| Cusick's pincushion | Chaenactis cusickii Gray | CHCU |
| Cusick's sunflower | Helianthus cusickii Gray | HECU2 |
| cusp blazing star | Liatris mucronata DC. | LIMU |
| cutleaf balsamroot | Balsamorhiza macrophylla Nutt. | BAMA4 |
| cutleaf burnweed | Erechtites glomerata (Desf. ex Poir.) DC. | ERGL8 |
| cutleaf coneflower | Rudbeckia laciniata L. | RULA3 |
| cutleaf coneflower | Rudbeckia laciniata L. var. ampla (A. Nels.) Cronq. | RULAA |
| cutleaf coneflower | Rudbeckia laciniata L. var. bipinnata Perdue | RULAB |
| cutleaf coneflower | Rudbeckia laciniata L. var. digitata (P. Mill.) Fiori | RULAD |
| cutleaf coneflower | Rudbeckia laciniata L. var. laciniata | RULAL |
| cutleaf daisy | Erigeron compositus Pursh | ERCO4 |
| cutleaf false oxtongue | Blumea laciniata (Roxb.) DC. | BLLA |
| cutleaf gumweed | Grindelia laciniata Rydb. | GRLA |
| cutleaf silverpuffs | Microseris laciniata (Hook.) Schultz-Bip. | MILA |
| cutleaf silverpuffs | Microseris laciniata (Hook.) Schultz-Bip. ssp. laciniata | MILAL |
| cutleaf silverpuffs | Microseris laciniata (Hook.) Schultz-Bip. ssp. leptosepala (Nutt.) Chambers | MILAL2 |
| cutleaf silverpuffs | Microseris laciniata (Hook.) Schultz-Bip. var. siskiyouensis Chambers | MILAS |
| cutleaf vipergrass | Scorzonera laciniata L. | SCLA6 |
| Cutler's alpine goldenrod | Solidago cutleri Fern. | SOCU2 |
| Cyanopsis muricata | Centaurea muricata L. | CEMU |
| Cyanthillium cinereum | Conyza cinerea L. | COCI3 |
| Cyanthillium cinereum | Senecioides cinerea (L.) Kuntze ex Britt. & P. Wilson | SECI3 |
| Cyanthillium cinereum | Vernonia cinerea (L.) Less. | VECI2 |
| Cyanthillium cinereum | Vernonia cinerea (L.) Less. var. parviflora (Reinw.) DC. | VECIP2 |
| Cyclachaena xanthifolia | Iva xanthifolia Nutt. | IVXA |
| cymophora | Cymophora accedens (S.F. Blake) B.L. Turner & A. Powell | CYAC7 |
| cymophora | Cymophora B.L. Robins. | CYMOP3 |
| Cymophora accedens | Tridax accedens S.F. Blake | TRAC2 |
| cynara | Cynara L. | CYNAR |
| dagger flower | Mantisalca salmantica (L.) Briq. & Cavillier | MASA5 |
| dahlia | Dahlia Cav. | DAHLI |
| Dahlia pinnata | Dahlia rosea Cav. | DARO |
| daisy | Chrysanthemum L. | CHRYS2 |
| daisy | Chrysanthemum majus (Desf.) Asch. | CHMA17 |
| daisy | Leucanthemum P. Mill. | LEUCA4 |
| daisy bush | Olearia allomii T. Kirk | OLAL3 |
| daisy bush | Olearia cheesmanii Cockayne & Allan | OLCH2 |
| daisy bush | Olearia Moench | OLEAR |
| daisy desertstar | Monoptilon bellidiforme Torr. & Gray ex Gray | MOBE |
| daisybush | Osteospermum L. | OSTEO2 |
| damianita | Chrysactinia mexicana Gray | CHME3 |
| dandelion | Taraxacum G.H. Weber ex Wiggers | TARAX |
| dandelion ragwort | Senecio taraxacoides (Gray) Greene | SETA |
| Davis's desertdandelion | Malacothrix phaeocarpa W.S. Davis | MAPH3 |
| Davis's fleabane | Erigeron engelmannii A. Nels. var. davisii (Cronq.) Cronq. | EREND |
| Dealbata's bahia | Bahia absinthifolia Benth. var. dealbata (Gray) Gray | BAABD |
| Deam's coneflower | Rudbeckia fulgida Ait. var. deamii (Blake) Perdue | RUFUD |
| Deam's goldenrod | Solidago deamii Fern. | SODE5 |
| Deam's rosinweed | Silphium integrifolium Michx. var. deamii Perry | SIIND |
| Deane's wirelettuce | Stephanomeria exigua Nutt. ssp. deanei (J.F. Macbr.) Gottlieb | STEXD2 |
| deer goldenbush | Ericameria cervina (S. Wats.) Rydb. | ERCE3 |
| Degener's argyrautia | ?Argyrautia degeneri Sherff [Arygroxiphium grayanum ? Dubautia laxa] | ARDE4 |
| Deinandra arida | Hemizonia arida Keck | HEAR4 |
| Deinandra clementina | Hemizonia clementina Brandeg. | HECL |
| Deinandra conjugens | Hemizonia conjugens Keck | HECO8 |
| Deinandra corymbosa ssp. corymbosa | Hemizonia corymbosa (DC.) Torr. & Gray | HECO9 |
| Deinandra corymbosa ssp. corymbosa | Hemizonia corymbosa (DC.) Torr. & Gray ssp. corymbosa (DC.) Torr. & Gray [superfluous autonym] | HECOC3 |
| Deinandra corymbosa ssp. macrocephala | Hemizonia corymbosa (DC.) Torr. & Gray ssp. macrocephala (Nutt.) Keck | HECOM |
| Deinandra halliana | Hemizonia halliana Keck | HEHA |
| Deinandra increscens ssp. foliosa | Hemizonia increscens (Hall ex Keck) Tanowitz ssp. foliosa (Hoover) Tanowitz | HEINF |
| Deinandra increscens ssp. increscens | Hemizonia increscens (Hall ex Keck) Tanowitz | HEIN5 |
| Deinandra increscens ssp. increscens | Hemizonia increscens (Hall ex Keck) Tanowitz ssp. increscens (Hall ex Keck) Tanowitz [superfluous autonym] | HEINI |
| Deinandra increscens ssp. increscens | Hemizonia paniculata Gray ssp. increscens Hall ex Keck | HEPAI |
| Deinandra increscens ssp. villosa | Hemizonia increscens (Hall ex Keck) Tanowitz ssp. villosa Tanowitz | HEINV |
| Deinandra minthornii | Hemizonia minthornii Jepson | HEMI6 |
| Deinandra mohavensis | Hemizonia mohavensis Keck | HEMO5 |
| Deinandra pallida | Hemizonia pallida Keck | HEPA5 |
| Deinandra pentactis | Hemizonia pentactis (Keck) Keck | HEPE2 |
| Delairea odorata | Senecio mikanioides Otto ex Walp. | SEMI |
| Delmarva beggarticks | Bidens bidentoides (Nutt.) Britt. | BIBI3 |
| deltoid balsamroot | Balsamorhiza deltoidea Nutt. | BADE2 |
| Dendranthema indicum | Chrysanthemum indicum L. [excluded] | CHIN23 |
| dense blazing star | Liatris spicata (L.) Willd. | LISP |
| dense blazing star | Liatris spicata (L.) Willd. var. resinosa (Nutt.) Gaiser | LISPR |
| dense blazing star | Liatris spicata (L.) Willd. var. spicata | LISPS |
| dense-spike blackroot | Pterocaulon pycnostachyum (Michx.) Ell. | PTPY2 |
| denseleaf pussytoes | Antennaria densifolia Porsild | ANDE9 |
| densespike blazing star | Liatris densispicata (Bush) Gaiser | LIDE4 |
| densespike blazing star | Liatris densispicata (Bush) Gaiser var. densispicata | LIDED |
| densespike blazing star | Liatris densispicata (Bush) Gaiser var. interrupta Gaiser | LIDEI |
| depauperate fleabane | Erigeron mancus Rydb. | ERMA9 |
| desert baccharis | Baccharis sergiloides Gray | BASE |
| desert basindaisy | Platyschkuhria integrifolia (Gray) Rydb. var. desertorum (M.E. Jones) W. Ellison | PLIND |
| desert brickellbush | Brickellia desertorum Coville | BRDE3 |
| desert goldenrod | Xylothamia Nesom, Suh, D. Morgan & Simpson | XYLOT |
| desert Indianbush | Psacalium decompositum (Gray) H.E. Robins. & Brett. | PSDE2 |
| desert marigold | Baileya Harvey & Gray ex Gray | BAILE |
| desert marigold | Baileya multiradiata Harvey & Gray ex Gray | BAMU |
| desert palafox | Palafoxia arida B.L. Turner & Morris | PAAR8 |
| desert palafox | Palafoxia arida B.L. Turner & Morris var. arida | PAARA2 |
| desert ragwort | Senecio eremophilus Richards. | SEER2 |
| desert ragwort | Senecio eremophilus Richards. var. eremophilus | SEERE |
| desert thistle | Cirsium aridum Dorn | CIAR9 |
| desert twinbugs | Dicoria canescens Gray | DICA4 |
| desert twinbugs | Dicoria canescens Gray ssp. brandegeei (Gray) Kartesz | DICAB |
| desert twinbugs | Dicoria canescens Gray ssp. canescens | DICAC2 |
| desert twinbugs | Dicoria canescens Gray ssp. clarkiae (Kennedy) Keck | DICAC |
| desert twinbugs | Dicoria canescens Gray ssp. hispidula (Rydb.) Keck | DICAH |
| desert twinbugs | Dicoria canescens Gray ssp. wetherillii (Eastw.) Kartesz | DICAW |
| desert wirelettuce | Stephanomeria runcinata Nutt. | STRU3 |
| desert yellow fleabane | Erigeron linearis (Hook.) Piper | ERLI |
| desert yellowhead | Yermo Dorn | YERMO |
| desert yellowhead | Yermo xanthocephalus Dorn | YEXA |
| desert zinnia | Zinnia acerosa (DC.) Gray | ZIAC |
| desert-chicory | Pyrrhopappus DC. | PYRRH |
| desertbroom | Baccharis sarothroides Gray | BASA2 |
| desertdandelion | Malacothrix DC. | MALAC3 |
| desertpeony | Acourtia D. Don | ACOUR |
| desertstar | Monoptilon Torr. & Gray | MONOP |
| desertsunflower | Geraea Torr. & Gray | GERAE |
| Detling's silverpuffs | Microseris laciniata (Hook.) Schultz-Bip. ssp. detlingii Chambers | MILAD |
| devil's beggartick | Bidens frondosa L. | BIFR |
| devil's bite | Liatris scariosa (L.) Willd. | LISC2 |
| devil's bite | Liatris scariosa (L.) Willd. var. scariosa | LISCS3 |
| devil's grandmother | Elephantopus tomentosus L. | ELTO2 |
| dichaetophora | Dichaetophora Gray | DICHA |
| Dicoria canescens ssp. brandegeei | Dicoria brandegeei Gray | DIBR3 |
| Dicoria canescens ssp. brandegeei | Dicoria canescens Gray var. brandegeei (Gray) Cronq. | DICAB2 |
| Dicoria canescens ssp. brandegeei | Dicoria paniculata Eastw. | DIPA2 |
| Dicoria canescens ssp. canescens | Dicoria oblongifolia Rydb. | DIOB |
| Dicoria canescens ssp. clarkiae | Dicoria clarkiae Kennedy | DICL3 |
| Dicoria canescens ssp. hispidula | Dicoria canescens Gray var. hispidula (Rydb.) Cronq. | DICAH2 |
| Dicoria canescens ssp. wetherillii | Dicoria canescens Gray var. wetherillii (Eastw.) Cronq. | DICAW2 |
| Dicoria canescens ssp. wetherillii | Dicoria wetherillii Eastw. | DIWE |
| dicranocarpus | Dicranocarpus Gray | DICRA |
| Dieter's erigeron | Erigeron wilkenii O'Kane | ERWI2 |
| diffuse knapweed | Centaurea diffusa Lam. | CEDI3 |
| dill daisy | Argyranthemum foeniculum (Willd.) Schultz-Bip. | ARFO7 |
| dill daisy | Argyranthemum Webb | ARGYR3 |
| dimeresia | Dimeresia Gray | DIMER |
| Dimorphotheca pluvialis | Dimorphotheca annua Less. | DIAN9 |
| disc mayweed | Matricaria discoidea DC. | MADI6 |
| dissected rockdaisy | Perityle dissecta (Torr.) Gray | PEDI2 |
| distaff thistle | Carthamus L. | CARTH |
| dittrichia | Dittrichia W. Greuter | DITTR |
| Dittrichia graveolens | Inula graveolens (L.) Desf. | INGR |
| Dittrichia viscosa | Cupularia viscosa (L.) Gren. & Godr. | CUVI3 |
| Dittrichia viscosa | Inula viscosa (L.) Ait. | INVI |
| diverseleaf crownbeard | Verbesina heterophylla (Chapman) Gray | VEHE3 |
| Dixie goldenrod | Solidago brachyphylla Chapman | SOBR |
| Dixie whitetop aster | Sericocarpus tortifolius (Michx.) Nees | SETO7 |
| Doellingeria infirma | Aster humilis Willd. | ASHU5 |
| Doellingeria infirma | Aster infirmus Michx. | ASIN2 |
| Doellingeria infirma | Aster umbellatus P. Mill. var. brevisquamis Fern. | ASUMB |
| Doellingeria infirma | Doellingeria humilis (Willd.) Britt. | DOHU2 |
| Doellingeria scabra | Aster scaber Thunb. | ASSC14 |
| Doellingeria sericocarpoides | Aster sericocarpoides (Small) K. Schum. | ASSE10 |
| Doellingeria sericocarpoides | Aster umbellatus P. Mill. var. latifolius Gray | ASUML |
| Doellingeria sericocarpoides | Doellingeria umbellata (P. Mill.) Nees var. latifolia (Gray) House | DOUML |
| Doellingeria umbellata var. pubens | Aster pubentior Cronq. | ASPU4 |
| Doellingeria umbellata var. pubens | Aster umbellatus P. Mill. var. pubens Gray | ASUMP |
| Doellingeria umbellata var. pubens | Doellingeria umbellata (P. Mill.) Nees ssp. pubens (Gray) A.& D. L?ve | DOUMP |
| Doellingeria umbellata var. umbellata | Aster umbellatus P. Mill. | ASUM |
| dog's-tongue | Pseudelephantopus Rohr | PSEUD17 |
| dog's-tongue | Pseudelephantopus spicatus (Juss. ex Aubl.) C.F. Baker | PSSP4 |
| dogfennel | Chamaemelum P. Mill. | CHAMA11 |
| dogfennel | Dysodiopsis (Gray) Rydb. | DYSOD |
| dogfennel | Eupatorium capillifolium (Lam.) Small | EUCA5 |
| dogweed | Adenophyllum Pers. | ADENO5 |
| dogwoodleaf | Spiracantha cornifolia Kunth | SPCO9 |
| dogwoodleaf | Spiracantha Kunth | SPIRA3 |
| doll's daisy | Boltonia L'H?r. | BOLTO |
| doll's head | Lagascea decipiens Hemsl. | LADE7 |
| Dolores River skeletonplant | Lygodesmia doloresensis S. Tomb | LYDO |
| Dominican cudweed | Pseudognaphalium domingense (Lam.) A. Anderb. | PSDO4 |
| donkeyweed | Pectis ciliaris L. | PECI7 |
| dotted blazing star | Liatris punctata Hook. | LIPU |
| dotted blazing star | Liatris punctata Hook. var. punctata | LIPUP |
| doublet | Dimeresia howellii Gray | DIHO2 |
| Douglas aster | Symphyotrichum subspicatum (Nees) Nesom | SYSU4 |
| Douglas aster | Symphyotrichum subspicatum (Nees) Nesom var. subspicatum | SYSUS |
| Douglas's dustymaiden | Chaenactis douglasii (Hook.) Hook. & Arn. | CHDO |
| Douglas's dustymaiden | Chaenactis douglasii (Hook.) Hook. & Arn. var. douglasii | CHDOD |
| Douglas's helianthella | Helianthella uniflora (Nutt.) Torr. & Gray var. douglasii (Torr. & Gray) W.A. Weber | HEUND |
| Douglas's ragwort | Senecio flaccidus Less. var. douglasii (DC.) B.L. Turner & T.M. Barkl. | SEFLD |
| Douglas's sagewort | Artemisia douglasiana Bess. ex Hook. | ARDO3 |
| Douglas's silverpuffs | Microseris douglasii (DC.) Schultz-Bip. | MIDO |
| Douglas's silverpuffs | Microseris douglasii (DC.) Schultz-Bip. ssp. douglasii | MIDOD |
| Douglas's silverpuffs | Microseris douglasii (DC.) Schultz-Bip. ssp. platycarpha (Gray) Chambers | MIDOP |
| Douglas's silverpuffs | Microseris douglasii (DC.) Schultz-Bip. ssp. tenella (Gray) Chambers | MIDOT |
| Douglas's thistle | Cirsium douglasii DC. | CIDO2 |
| Douglas's thistle | Cirsium douglasii DC. var. breweri (Petrak) Keil & C. Turner | CIDOB2 |
| Douglas's thistle | Cirsium douglasii DC. var. douglasii | CIDOD |
| Douglas's tickseed | Coreopsis douglasii (DC.) Hall | CODO2 |
| downy goldenrod | Solidago puberula Nutt. | SOPU |
| downy goldenrod | Solidago puberula Nutt. var. puberula | SOPUP2 |
| downy goldenrod | Solidago puberula Nutt. var. pulverulenta (Nutt.) Chapman | SOPUP |
| downy ragged goldenrod | Solidago petiolaris Ait. | SOPE |
| downy ragged goldenrod | Solidago petiolaris Ait. var. angusta (Torr. & Gray) Gray | SOPEA |
| downy ragged goldenrod | Solidago petiolaris Ait. var. petiolaris | SOPEP |
| dozedaisy | Aphanostephus DC. | APHAN3 |
| Dracopis amplexicaulis | Rudbeckia amplexicaulis Vahl | RUAM7 |
| Dress's goldenaster | Chrysopsis linearifolia Semple ssp. dressii Semple | CHLID |
| Drummond's aster | Symphyotrichum drummondii (Lindl.) Nesom | SYDR |
| Drummond's aster | Symphyotrichum drummondii (Lindl.) Nesom var. drummondii | SYDRD |
| Drummond's aster | Symphyotrichum drummondii (Lindl.) Nesom var. texanum (Burgess) Nesom | SYDRT |
| Drummond's goldenbush | Isocoma drummondii (Torr. & Gray) Greene | ISDR |
| Drummond's sleepydaisy | Xanthisma texanum DC. ssp. drummondii (Torr. & Gray) Semple | XATED2 |
| dubautia | Dubautia Gaud. | DUBAU |
| Dubautia ?demissifolia | Dubautia montana (Mann) Keck var. robustior (Sherff) Keck | DUMOR |
| Dubautia ?demissifolia | Railliardia demissifolia Sherff | RADE3 |
| Dubautia ?demissifolia | Railliardia montana Mann var. robustior Sherff | RAMOR |
| Dubautia ?fallax | Dubautia ?fucosa Sherff | DUFU |
| Dubautia ?fallax | Dubautia kohalae (Skottsberg) St. John | DUKO |
| Dubautia ?fallax | Dubautia lonchophylla (Sherff) Keck | DULO |
| Dubautia ?fallax | Railliardia kohalae Skottsberg | RAKO |
| Dubautia ?fallax | Railliautia ?fallax (Sherff) Sherff | RAFA2 |
| Dubautia ?fallax | Railliautia ?fucosa (Sherff) Sherff | RAFU |
| Dubautia ?media | Dubautia ?mendacoides O. Deg. & Sherff | DUME2 |
| Dubautia ?media | Dubautia ?mendax Sherff | DUME3 |
| Dubautia ?molokaiensis | Dubautia molokaiensis (Hbd.) Keck var. oppositifolia (Sherff) Keck | DUMOO |
| Dubautia ?molokaiensis | Railliardia molokaiensis Hbd. | RAMO3 |
| Dubautia ?molokaiensis | Railliardia molokaiensis Hbd. var. oppositifolia Sherff | RAMOO |
| Dubautia ?montana | Railliardia montana Mann | RAMO4 |
| Dubautia ?thyrsiflora | Dubautia coriacea (Sherff) Keck | DUCO2 |
| Dubautia ?thyrsiflora | Dubautia ternifolia (Sherff) Keck | DUTE |
| Dubautia ?thyrsiflora | Dubautia thyrsiflora (Sherff) Keck var. cernua (Sherff) Keck | DUTHC |
| Dubautia ?thyrsiflora | Railliardia demissifolia Sherff var. dolichophylla St. John | RADED |
| Dubautia ?thyrsiflora | Railliardia ternifolia Sherff | RATE4 |
| Dubautia ?thyrsiflora | Railliardia thyrsiflora Sherff | RATH |
| Dubautia ?thyrsiflora | Railliardia thyrsiflora Sherff var. cernua Sherff | RATHC |
| Dubautia arborea | Railliardia arborea Gray | RAAR4 |
| Dubautia ciliolata ssp. ciliolata | Dubautia ciliolata (DC.) Keck var. juniperoides (Gray) Keck | DUCIJ |
| Dubautia ciliolata ssp. ciliolata | Railliardia ciliolata DC. | RACI3 |
| Dubautia ciliolata ssp. ciliolata | Railliardia ciliolata DC. var. juniperoides Gray | RACIJ |
| Dubautia dolosa | Dubautia waianapanapaenis G.D. Carr | DUWA2 |
| Dubautia dolosa | Railliardia ?dolosa O. Deg. & Sherff | RADO |
| Dubautia dolosa | Railliardia waianapanapaenis (G.D. Carr) St. John | RAWA |
| Dubautia herbstobatae | Railliardia herbstobatae (G.D. Carr) St. John | RAHE5 |
| Dubautia knudsenii ssp. nagatae | Dubautia nagatae St. John | DUNA |
| Dubautia laevigata | Dubautia laevigata Gray var. parvifolia Sherff | DULAP |
| Dubautia latifolia | Railliardia latifolia Gray | RALA4 |
| Dubautia latifolia | Railliardia latifolia Gray var. helleri Sherff | RALAH |
| Dubautia laxa ssp. bryanii | Dubautia laxa Hook. & Arn. var. bryanii O. Deg. & Sherff | DULAB2 |
| Dubautia laxa ssp. hirsuta | Dubautia laxa Hook. & Arn. var. hirsuta Hbd. | DULAH |
| Dubautia laxa ssp. hirsuta | Dubautia laxa Hook. & Arn. var. intercedens O.& I. Deg. & Sherff | DULAI |
| Dubautia laxa ssp. hirsuta | Dubautia laxa Hook. & Arn. var. pedicellata Rock | DULAP2 |
| Dubautia laxa ssp. hirsuta | Dubautia laxa Hook. & Arn. var. skottsbergii Sherff | DULAS |
| Dubautia laxa ssp. hirsuta | Dubautia laxa Hook. & Arn. var. waianensis O. Deg. & Sherff | DULAW |
| Dubautia laxa ssp. laxa | Dubautia knudsenii Hbd. var. degeneri Sherff | DUKND |
| Dubautia laxa ssp. laxa | Dubautia laxa Hook. & Arn. var. greenwelliae O. Deg. & Sherff | DULAG |
| Dubautia laxa ssp. laxa | Dubautia laxa Hook. & Arn. var. hispida Sherff | DULAH2 |
| Dubautia laxa ssp. laxa | Dubautia laxa Hook. & Arn. var. obovata Sherff | DULAO |
| Dubautia laxa ssp. pseudoplantaginea | Dubautia laxa Hook. & Arn. var. pseudoplantaginea Skottsberg | DULAP3 |
| Dubautia linearis ssp. hillebrandii | Dubautia hillebrandii (Mann) Keck | DUHI |
| Dubautia linearis ssp. hillebrandii | Railliardia ?vafra O. Deg. & Sherff | RAVA |
| Dubautia linearis ssp. hillebrandii | Railliardia ciliolata DC. var. leptocephala O. Deg. & Sherff | RACIL |
| Dubautia linearis ssp. hillebrandii | Railliardia hillebrandii Mann | RAHI2 |
| Dubautia linearis ssp. linearis | Railliardia linearis Gaud. | RALI4 |
| Dubautia linearis ssp. opposita | Dubautia linearis (Gaud.) Keck var. opposita (Sherff) Keck | DULIO2 |
| Dubautia linearis ssp. opposita | Railliardia linearis Gaud. var. opposita Sherff | RALIO |
| Dubautia menziesii | Dubautia ciliolata (DC.) Keck var. trinervia Hbd. p.p. | DUCIT |
| Dubautia menziesii | Dubautia menziesii (Gray) Keck var. angustifolia (Sherff) Keck | DUMEA |
| Dubautia menziesii | Dubautia rockii (Sherff) Keck | DURO |
| Dubautia menziesii | Dubautia struthioloides (Gray) Keck | DUST2 |
| Dubautia menziesii | Railliardia ciliolata DC. var. trinervia (Hbd.) Keck p.p. | RACIT |
| Dubautia menziesii | Railliardia menziesii Gray | RAME |
| Dubautia menziesii | Railliardia menziesii Gray var. angustifolia Sherff | RAMEA |
| Dubautia menziesii | Railliardia rockii Sherff | RARO |
| Dubautia menziesii | Railliardia struthioloides Gray | RAST2 |
| Dubautia paleata | Dubautia ?paludicola Sherff | DUPA4 |
| Dubautia plantaginea ssp. magnifolia | Dubautia magnifolia Sherff | DUMA |
| Dubautia plantaginea ssp. plantaginea | Dubautia plantaginea Gaud. var. acridentata Sherff | DUPLA |
| Dubautia plantaginea ssp. plantaginea | Dubautia plantaginea Gaud. var. glandulosa St. John | DUPLG |
| Dubautia plantaginea ssp. plantaginea | Dubautia plantaginea Gaud. var. pauoaensis St. John | DUPLP |
| Dubautia plantaginea ssp. plantaginea | Dubautia plantaginea Gaud. var. platyphylla Hbd. | DUPLP2 |
| Dubautia plantaginea ssp. plantaginea | Dubautia plantaginea Gaud. var. strigosa Skottsberg | DUPLS |
| Dubautia platyphylla | Dubautia platyphylla (Gray) Keck var. leptophylla (Sherff) Keck | DUPLL |
| Dubautia platyphylla | Railliardia platyphylla Gray | RAPL3 |
| Dubautia platyphylla | Railliardia platyphylla Gray var. leptophylla Sherff | RAPLL |
| Dubautia platyphylla | Railliardia platyphylla Gray var. trillioidea O. Deg. & Sherff | RAPLT |
| Dubautia reticulata | Dubautia montana (Mann) Keck var. longifolia (Sherff) Keck | DUMOL |
| Dubautia reticulata | Railliardia montana Mann var. longifolia Sherff | RAMOL |
| Dubautia reticulata | Railliardia reticulata Sherff | RARE6 |
| Dubautia scabra ssp. leiophylla | Dubautia molokaiensis (Hbd.) Keck var. stipitata (Sherff) Keck | DUMOS |
| Dubautia scabra ssp. leiophylla | Dubautia scabra (DC.) Keck var. leiophylla (Gray) Keck | DUSCL |
| Dubautia scabra ssp. leiophylla | Dubautia scabra (DC.) Keck var. munroi (Sherff) Keck | DUSCM |
| Dubautia scabra ssp. leiophylla | Railliardia lonchophylla Sherff var. stipitata (Sherff) Sherff | RALOS |
| Dubautia scabra ssp. leiophylla | Railliardia molokaiensis Hbd. var. stipitata Sherff | RAMOS |
| Dubautia scabra ssp. leiophylla | Railliardia scabra DC. var. leiophylla Gray | RASCL |
| Dubautia scabra ssp. leiophylla | Railliardia scabra DC. var. munroi Sherff | RASCM2 |
| Dubautia sherffiana | Dubautia sherffiana Fosberg var. paucinervia (O. Deg. & Sherff) Herbst | DUSHP |
| Dubautia sherffiana | Railliardia sherffiana (Fosberg) Sherff | RASH |
| Dubautia sherffiana | Railliardia sherffiana (Fosberg) Sherff var. paucinervia O. Deg. & Sherff | RASHP |
| dudweed | Psilostrophe gnaphalioides DC. | PSGN |
| dune ragwort | Senecio blochmaniae Greene | SEBL |
| dune tetramolopium | Tetramolopium rockii Sherff | TERO |
| dune tetramolopium | Tetramolopium rockii Sherff var. calcisabulorum (St. John) Lowrey | TEROC |
| dune tetramolopium | Tetramolopium rockii Sherff var. rockii | TEROR |
| dunedelion | Malacothrix incana (Nutt.) Torr. & Gray | MAIN |
| dusky dogfennel | Chamaemelum fuscatum (Brot.) Vasc. | CHFU2 |
| dusty miller | Centaurea cineraria L. | CECI2 |
| dwarf alpine hawksbeard | Crepis nana Richards. | CRNA |
| dwarf alpine hawksbeard | Crepis nana Richards. ssp. clivicola Leggett | CRNAC |
| dwarf alpine hawksbeard | Crepis nana Richards. ssp. nana | CRNAN |
| dwarf alpine hawksbeard | Crepis nana Richards. ssp. ramosa Babcock | CRNAR |
| dwarf alpinegold | Hulsea nana Gray | HUNA |
| dwarf arctic ragwort | Packera cymbalaria (Pursh) W.A. Weber & A. L?ve | PACY8 |
| dwarf burr ragweed | Ambrosia pumila (Nutt.) Gray | AMPU4 |
| dwarf coastweed | Amblyopappus pusillus Hook. & Arn. | AMPU3 |
| dwarf cottonrose | Logfia depressa (Gray) Holub | LODE9 |
| dwarf crownbeard | Verbesina nana (Gray) Robins. & Greenm. | VENA |
| dwarf desertpeony | Acourtia nana (Gray) Reveal & King | ACNA2 |
| dwarf dwarf-cudweed | Hesperevax caulescens (Benth.) Gray | HECA30 |
| dwarf fleabane | Erigeron nanus Nutt. | ERNA5 |
| dwarf goldenbush | Ericameria nana Nutt. | ERNA7 |
| dwarf goldenrod | Solidago simplex Kunth ssp. simplex var. nana (Gray) Ringius | SOSIN |
| dwarf horseweed | Conyza ramosissima Cronq. | CORA4 |
| dwarf iliau | Wilkesia hobdyi St. John | WIHO3 |
| dwarf lessingia | Lessingia nana Gray | LENA |
| dwarf mountain ragwort | Senecio fremontii Torr. & Gray | SEFR3 |
| dwarf mountain ragwort | Senecio fremontii Torr. & Gray var. blitoides (Greene) Cronq. | SEFRB |
| dwarf mountain ragwort | Senecio fremontii Torr. & Gray var. fremontii | SEFRF |
| dwarf mountain ragwort | Senecio fremontii Torr. & Gray var. inexpectatus Cronq. | SEFRI |
| dwarf mountain ragwort | Senecio fremontii Torr. & Gray var. occidentalis Gray | SEFRO |
| dwarf poreleaf | Porophyllum pygmaeum Keil & J. Morefield | POPY |
| dwarf rattlesnakeroot | Prenanthes nana (Bigelow) Torr. | PRNA |
| dwarf spotflower | Acmella pusilla (Hook. & Arn.) R.K. Jansen | ACPU |
| dwarf thistle | Cirsium drummondii Torr. & Gray | CIDR2 |
| dwarf western rosinweed | Calycadenia villosa DC. | CAVI |
| dwarf woollyheads | Psilocarphus brevissimus Nutt. var. multiflorus Cronq. | PSBRM |
| dwarf yellow fleabane | Erigeron chrysopsidis Gray | ERCH4 |
| dwarf-cudweed | Hesperevax (Gray) Gray | HESPE10 |
| dwarfdandelion | Krigia Schreb. | KRIGI |
| Dyer's plumeless saw-wort | Serratula tinctoria L. | SETI2 |
| Dysodiopsis tagetoides | Dyssodia tagetoides Torr. & Gray | DYTA |
| Dysodiopsis tagetoides | Hymenatherum tagetoides (Torr. & Gray) Gray | HYTA |
| dyssodia | Dyssodia Cav. | DYSSO |
| Dyssodia papposa | Boebera papposa (Vent.) Rydb. ex Britt. | BOPA8 |
| Dyssodia papposa | Tagetes papposa Vent. | TAPA8 |
| eared coneflower | Rudbeckia auriculata (Perdue) Kral | RUAU2 |
| eared goldenrod | Solidago auriculata Shuttlw. ex Blake | SOAU2 |
| eared Indian plantain | Parasenecio auriculata (A. DC.) J.R. Grant | PAAU14 |
| earleaf brickellbush | Brickellia amplexicaulis B.L. Robins. | BRAM3 |
| earleaf brickellbush | Brickellia amplexicaulis B.L. Robins. var. amplexicaulis | BRAMA |
| earleaf brickellbush | Brickellia amplexicaulis B.L. Robins. var. lanceolata (Gray) B.L. Robins. | BRAML |
| early bluetop fleabane | Erigeron vetensis Rydb. | ERVE2 |
| early goldenrod | Solidago juncea Ait. | SOJU |
| early whitetop fleabane | Erigeron vernus (L.) Torr. & Gray | ERVE |
| East Texas greenthread | Thelesperma flavodiscum (Shinners) B.L. Turner | THFL |
| East View rubberweed | Hymenoxys brachyactis Woot. & Standl. | HYBR7 |
| easterbonnets | Antheropeas Rydb. | ANTHE4 |
| eastern annual saltmarsh aster | Symphyotrichum subulatum (Michx.) Nesom | SYSU5 |
| eastern baccharis | Baccharis halimifolia L. | BAHA |
| eastern daisy fleabane | Erigeron annuus (L.) Pers. | ERAN |
| eastern fournerved daisy | Tetraneuris herbacea Greene | TEHE4 |
| eastern purple coneflower | Echinacea purpurea (L.) Moench | ECPU |
| eastern showy aster | Eurybia spectabilis (Ait.) Nesom | EUSP3 |
| eastern silver aster | Symphyotrichum concolor (L.) Nesom | SYCO3 |
| Eastwood's goldenbush | Ericameria fasciculata (Eastw.) J.F. Macbr. | ERFA5 |
| eastwoodia | Eastwoodia Brandeg. | EASTW |
| Eaton's aster | Symphyotrichum eatonii (Gray) Nesom | SYEA2 |
| Eaton's beggarticks | Bidens eatonii Fern. | BIEA |
| Eaton's fleabane | Erigeron eatonii Gray | EREA |
| Eaton's fleabane | Erigeron eatonii Gray var. eatonii | EREAE |
| Eaton's fleabane | Erigeron eatonii Gray var. lavandulus Strother & Ferlatte | EREAL |
| Eaton's fleabane | Erigeron eatonii Gray var. nevadincola (S.F. Blake) Nesom | EREAN |
| Eaton's fleabane | Erigeron eatonii Gray var. plantagineus (Greene) Cronq. | EREAP2 |
| Eaton's fleabane | Erigeron eatonii Gray var. sonnei (Greene) Nesom | EREAS |
| Eaton's fleabane | Erigeron eatonii Gray var. villosus (Cronq.) Cronq. | EREAV2 |
| Eaton's thistle | Cirsium eatonii (Gray) B.L. Robins. | CIEA |
| eatonella | Eatonella Gray | EATON |
| Echinacea angustifolia var. angustifolia | Brauneria angustifolia (DC.) Heller | BRAN5 |
| Echinacea angustifolia var. angustifolia | Echinacea pallida (Nutt.) Nutt. var. angustifolia (DC.) Cronq. | ECPAA |
| Echinacea angustifolia var. strigosa | Echinacea pallida (Nutt.) Nutt. var. strigosa (R.L. McGregor) Gandhi | ECPAS |
| Echinacea laevigata | Echinacea purpurea (L.) Moench var. laevigata (C.L. Boynt. & Beadle) Cronq. | ECPUL2 |
| Echinacea pallida | Brauneria pallida (Nutt.) Britt. | BRPA11 |
| Echinacea pallida | Rudbeckia pallida Nutt. | RUPA23 |
| Echinacea paradoxa var. paradoxa | Echinacea atrorubens Nutt. var. paradoxa (J.B.S. Norton) Cronq. | ECATP |
| Echinacea purpurea | Brauneria purpurea (L.) Britt. | BRPU15 |
| Echinacea purpurea | Echinacea purpurea (L.) Moench var. arkansana Steyermark | ECPUA |
| Echinacea purpurea | Rudbeckia purpurea L. | RUPU9 |
| Echinacea sanguinea | Echinacea pallida (Nutt.) Nutt. var. sanguinea (Nutt.) Gandhi & Thomas | ECPAS2 |
| Echinacea tennesseensis | Echinacea angustifolia DC. var. tennesseensis (Beadle) Blake | ECANT |
| Echinops exaltatus | Echinops commutatus Juratzka | ECCO9 |
| Echinops rito ssp. ruthenicus | Echinops ruthenicus Bieb. | ECRU3 |
| eclipta | Eclipta L. | ECLIP |
| Eclipta prostrata | Eclipta alba (L.) Hassk. | ECAL |
| Eclipta prostrata | Eclipta erecta L. | ECER3 |
| Eclipta prostrata | Verbesina alba L. | VEAL6 |
| Eclipta prostrata | Verbesina prostrata L. | VEPR2 |
| edible thistle | Cirsium edule Nutt. | CIED |
| Edwards Plateau greenthread | Thelesperma curvicarpum T.E. Melchert | THCU2 |
| Edwards's hole-in-the-sand plant | Nicolletia edwardsii Gray | NIED |
| Eggert's sunflower | Helianthus eggertii Small | HEEG |
| Egletes prostrata | Matricaria prostrata Sw. | MAPR5 |
| Egletes viscosa | Cotula viscosa L. | COVI15 |
| eke silversword | Argyroxiphium caliginis Forbes | ARCA22 |
| El Dorado mule-ears | Agnorhiza reticulata (Greene) W.A. Weber | AGRE8 |
| elecampane inula | Inula helenium L. | INHE |
| elegant aster | Eucephalus elegans Nutt. | EUEL2 |
| elegant groundsel | Packera indecora (Greene) A.& D. L?ve | PAIN11 |
| elegant hawksbeard | Crepis elegans Hook. | CREL |
| elegant silverpuffs | Microseris elegans Greene ex Gray | MIEL |
| elegant zinnia | Zinnia violacea Cav. | ZIVI2 |
| Elephantopus angustifolius | Orthopappus angustifolius (Sw.) Gleason [excluded] | ORAN2 |
| Elephantopus carolinianus | Elephantopus flexuosus Raf. | ELFL4 |
| Elephantopus carolinianus | Elephantopus violaceus Schultz-Bip. | ELVI9 |
| Elephantopus elatus | Elephantopus elatus Bertol. var. intermedius Gleason | ELELI |
| Elephantopus mollis | Elephantopus hypomalacus Blake | ELHY2 |
| Elephantopus mollis | Elephantopus martii Graham | ELMA11 |
| Elephantopus mollis | Elephantopus pilosus Philipson | ELPI5 |
| Elephantopus tomentosus | Elephantopus carolinianus Raeusch. var. simplex Nutt. | ELCAS |
| Elephantopus tomentosus | Elephantopus nudicaulis Poir. | ELNU3 |
| elephantsfoot | Elephantopus L. | ELEPH |
| eleutheranthera | Eleutheranthera Poit. ex Bosc | ELEUT2 |
| Eleutheranthera ruderalis | Melampodium ruderale Sw. | MERU4 |
| elk thistle | Cirsium foliosum (Hook.) DC. | CIFO |
| Elliott's aster | Symphyotrichum elliotii (Torr. & Gray) Nesom | SYEL |
| Elliott's goldenrod | Solidago latissimifolia P. Mill. | SOLA4 |
| Elmer's erigeron | Erigeron elmeri (Greene) Greene | EREL15 |
| Elmer's ragwort | Senecio elmeri Piper | SEEL2 |
| elmleaf goldenrod | Solidago ulmifolia Muhl. ex Willd. | SOUL2 |
| elmleaf goldenrod | Solidago ulmifolia Muhl. ex Willd. var. microphylla Gray | SOULM |
| elmleaf goldenrod | Solidago ulmifolia Muhl. ex Willd. var. ulmifolia | SOULU2 |
| Emilia coccinea | Cacalia coccinea Sims | CACO50 |
| Emilia sonchifolia var. javanica | Emilia javanica (Burm. f.) C.B. Robins. | EMJA |
| Emilia sonchifolia var. sonchifolia | Cacalia sonchifolia L. | CASO4 |
| Emory's baccharis | Baccharis emoryi Gray | BAEM |
| Emory's rockdaisy | Perityle emoryi Torr. | PEEM |
| Encelia actonii | Encelia frutescens (Gray) Gray var. actonii (Elmer) Blake | ENFRA |
| Encelia actonii | Encelia virginensis A. Nels. ssp. actonii (Elmer) Keck | ENVIA2 |
| Encelia actonii | Encelia virginensis A. Nels. var. actonii (Elmer) B.L. Turner | ENVIA |
| Encelia farinosa | Encelia farinosa Gray ex Torr. var. farinosa Gray ex Torr. [superfluous autonym] | ENFAF |
| Encelia farinosa | Encelia farinosa Gray ex Torr. var. phenicodonta (Blake) I.M. Johnston | ENFAP |
| Encelia farinosa | Encelia farinosa Gray ex Torr. var. radians Brandeg. ex Blake | ENFAR |
| Encelia frutescens | Encelia frutescens (Gray) Gray var. frutescens (Gray) Gray [superfluous autonym] | ENFRF |
| Encelia frutescens | Simsia frutescens Gray | SIFR |
| Encelia nutans | Enceliopsis nutans (Eastw.) A. Nels. | ENNU2 |
| Encelia resinifera ssp. resinifera | Encelia frutescens (Gray) Gray var. resinosa M.E. Jones ex Blake | ENFRR |
| Encelia scaposa | Encelia scaposa (Gray) Gray var. stenophylla Shinners | ENSCS |
| Encelia scaposa | Simsia scaposa Gray | SISC2 |
| Encelia virginensis | Encelia frutescens (Gray) Gray var. virginensis (A. Nels.) Blake | ENFRV |
| Encelia virginensis | Encelia virginensis A. Nels. var. virginensis A. Nels. [superfluous autonym] | ENVIV |
| Enceliopsis argophylla | Tithonia argophylla D.C. Eat. | TIAR4 |
| Enceliopsis covillei | Enceliopsis argophylla (D.C. Eat.) A. Nels. var. grandiflora Jepson | ENARG |
| Enceliopsis covillei | Helianthella covillei A. Nels. | HECO17 |
| Enceliopsis nudicaulis var. nudicaulis | Encelia nudicaulis Gray | ENNU3 |
| Encinitis false willow | Baccharis vanessae Beauchamp | BAVA3 |
| endive daisy | Rhagadiolus stellatus (L.) Gaertn. | RHST3 |
| Engelmann's aster | Eucephalus engelmannii (D.C. Eat.) Greene | EUEN |
| Engelmann's daisy | Engelmannia Gray ex Nutt. | ENGEL |
| Engelmann's daisy | Engelmannia peristenia (Raf.) Goodman & Lawson | ENPE4 |
| Engelmann's false goldenweed | Oonopsis engelmannii (Gray) Greene | OOEN |
| Engelmann's fleabane | Erigeron engelmannii A. Nels. | EREN |
| Engelmann's fleabane | Erigeron engelmannii A. Nels. var. engelmannii | ERENE |
| Engelmann's thistle | Cirsium engelmannii Rydb. | CIEN2 |
| Engelmannia peristenia | Engelmannia pinnatifida Gray ex Nutt. | ENPI |
| entireleaf daisy | Hulteniella integrifolia (Richards.) Tzvelev | HUIN3 |
| entireleaf western daisy | Astranthium integrifolium (Michx.) Nutt. | ASIN9 |
| entireleaf western daisy | Astranthium integrifolium (Michx.) Nutt. ssp. ciliatum (Raf.) DeJong | ASINC |
| entireleaf western daisy | Astranthium integrifolium (Michx.) Nutt. ssp. integrifolium | ASINI2 |
| Erechtites glomerata | Erechtites arguta (A. Rich.) DC. | ERAR2 |
| Erechtites glomerata | Senecio argutus A. Rich. | SEAR11 |
| Erechtites glomerata | Senecio glomeratus Desf. ex Poir. | SEGL4 |
| Erechtites hieraciifolia | Erechtites hieracifolia (L.) Raf. ex DC. [orthographic variant] | ERHI9 |
| Erechtites hieraciifolia var. cacalioides | Senecio cacalioides Fisch. ex Spreng. | SECA11 |
| Erechtites hieraciifolia var. hieraciifolia | Erechtites hieraciifolia (L.) Raf. ex DC. var. intermedia Fern. | ERHII |
| Erechtites hieraciifolia var. hieraciifolia | Erechtites hieraciifolia (L.) Raf. ex DC. var. praealta (Raf.) Fern. | ERHIP |
| Erechtites hieraciifolia var. hieraciifolia | Senecio hieraciifolius L. | SEHI3 |
| Erechtites hieraciifolia var. megalocarpa | Erechtites megalocarpa Fern. | ERME12 |
| Erechtites minima | Erechtites prenanthoides (A. Rich.) DC. | ERPR17 |
| Erechtites minima | Senecio minimus Poir. | SEMI4 |
| Erechtites valerianifolia | Senecio valerianifolius Link ex Spreng. | SEVA3 |
| erect dwarf-cudweed | Hesperevax sparsiflora (Gray) Greene | HESP9 |
| erect dwarf-cudweed | Hesperevax sparsiflora (Gray) Greene var. sparsiflora | HESPS2 |
| erect tropical daisy | Egletes viscosa (L.) Less. | EGVI |
| Ericameria ?bolanderi | Chrysothamnus bolanderi (Gray) Greene | CHBO12 |
| Ericameria ?bolanderi | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. bolanderi (Gray) Hall & Clements | CHNAB6 |
| Ericameria ?uintahensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. uintahensis L.C. Anders. | CHNAU |
| Ericameria ?uintahensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. uintahensis (L.C. Anders.) Welsh | CHNAU2 |
| Ericameria ?viscosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. viscosus Keck | CHNAV2 |
| Ericameria arborescens | Haplopappus arborescens (Gray) Hall | HAAR |
| Ericameria arborescens | Linosyris arborescens Gray | LIAR8 |
| Ericameria bloomeri | Haplopappus bloomeri Gray | HABL3 |
| Ericameria bloomeri | Haplopappus bloomeri Gray ssp. sonnei (Gray) Hall | HABLS |
| Ericameria bloomeri | Haplopappus bloomeri Gray var. angustatus Gray | HABLA |
| Ericameria bloomeri | Haplopappus bloomeri Gray var. sonnei (Gray) Greene | HABLS2 |
| Ericameria brachylepis | Bigelovia brachylepis Gray | BIBR |
| Ericameria brachylepis | Haplopappus propinquus Blake | HAPR |
| Ericameria cervina | Haplopappus cervinus S. Wats. | HACE |
| Ericameria compacta | Haplopappus bloomeri Gray ssp. compactus Hall | HABLC2 |
| Ericameria compacta | Haplopappus compactus (Hall) L.C. Anders. | HACO3 |
| Ericameria cooperi | Ericameria cooperi (Gray) H. M. Hall var. cooperi (Gray) H. M. Hall [superfluous autonym] | ERCOC14 |
| Ericameria cooperi | Haplopappus cooperi (Gray) Hall | HACO4 |
| Ericameria crispa | Haplopappus crispus L.C. Anders. | HACR6 |
| Ericameria cuneata var. cuneata | Haplopappus cuneatus Gray | HACU2 |
| Ericameria cuneata var. spathulata | Haplopappus cuneatus Gray var. spathulatus (Gray) Blake ex Munz | HACUS |
| Ericameria discoidea var. discoidea | Haplopappus macronema (Nutt.) Gray | HAMA2 |
| Ericameria discoidea var. discoidea | Haplopappus macronema (Nutt.) Gray var. typicus Hall | HAMAT |
| Ericameria discoidea var. discoidea | Macronema discoidea Nutt. | MADI9 |
| Ericameria discoidea var. linearis | Haplopappus macronema (Nutt.) Gray var. canescens (A. Nels.) Cronq. | HAMAC |
| Ericameria discoidea var. linearis | Haplopappus macronema (Nutt.) Gray var. linearis (Rydb.) Dorn | HAMAL |
| Ericameria discoidea var. linearis | Macronema lineare Rydb. | MALI3 |
| Ericameria discoidea var. linearis | Macronema lineare Rydb. var. canescens A. Nels. | MALIC |
| Ericameria ericoides | Diplopappus ericoides Less. | DIER6 |
| Ericameria ericoides | Haplopappus ericoides (Less.) Hook. & Arn. | HAER |
| Ericameria ericoides | Haplopappus ericoides (Less.) Hook. & Arn. ssp. blakei C.B. Wolf | HAERB |
| Ericameria fasciculata | Chrysoma fasciculata Eastw. | CHFA3 |
| Ericameria fasciculata | Haplopappus eastwoodiae Hall | HAEA |
| Ericameria gilmanii | Haplopappus gilmanii Blake | HAGI |
| Ericameria greenei | Haplopappus bloomeri Gray var. greenei (Gray) Cronq. | HABLG |
| Ericameria greenei | Haplopappus greenei Gray | HAGR6 |
| Ericameria greenei | Haplopappus greenei Gray var. mollis Gray | HAGRM |
| Ericameria greenei | Macronema greenei (Gray) Greene | MAGR12 |
| Ericameria laricifolia | Haplopappus laricifolius Gray | HALA5 |
| Ericameria lignumviridis | Haplopappus lignumviridis Welsh | HALI8 |
| Ericameria linearifolia | Haplopappus linearifolius DC. | HALI5 |
| Ericameria linearifolia | Haplopappus linearifolius DC. ssp. interior (Coville) Hall | HALII |
| Ericameria linearifolia | Haplopappus linearifolius DC. var. interior (Coville) M.E. Jones | HALII2 |
| Ericameria linearifolia | Stenotopsis interior (Coville) Rydb. | STIN7 |
| Ericameria linearifolia | Stenotopsis linearifolia (DC.) Rydb. | STLI6 |
| Ericameria linearifolia | Stenotopsis linearifolia (DC.) Rydb. var. interior (Coville) Hall | STLII |
| Ericameria nana | Haplopappus nanus (Nutt.) D.C. Eat. | HANA |
| Ericameria nauseosa ssp. consimilis var. arenaria | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. arenarius L.C. Anders. | CHNAA4 |
| Ericameria nauseosa ssp. consimilis var. arenaria | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. arenarius (L.C. Anders.) Welsh | CHNAA5 |
| Ericameria nauseosa ssp. consimilis var. ceruminosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. ceruminosus (Dur. & Hilg.) Hall & Clements | CHNAC |
| Ericameria nauseosa ssp. consimilis var. juncea | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. junceus (Greene) Hall & Clements | CHNAJ |
| Ericameria nauseosa ssp. consimilis var. juncea | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. junceus (Greene) Hall | CHNAJ2 |
| Ericameria nauseosa ssp. consimilis var. leiosperma | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. leiospermus (Gray) Hall & Clements | CHNAL3 |
| Ericameria nauseosa ssp. consimilis var. leiosperma | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. abbreviatus (M.E. Jones) Blake | CHNAA6 |
| Ericameria nauseosa ssp. consimilis var. leiosperma | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. leiospermus (Gray) Hall | CHNAL4 |
| Ericameria nauseosa ssp. consimilis var. mohavensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. mohavensis (Greene) Hall & Clements | CHNAM |
| Ericameria nauseosa ssp. consimilis var. mohavensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. mohavensis (Greene) Hall | CHNAM3 |
| Ericameria nauseosa ssp. consimilis var. nitida | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. nitidus L.C. Anders. | CHNAN |
| Ericameria nauseosa ssp. consimilis var. nitida | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. nitidus (L.C. Anders.) Welsh | CHNAN5 |
| Ericameria nauseosa ssp. consimilis var. oreophila | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. consimilis (Greene) Hall & Clements | CHNAC2 |
| Ericameria nauseosa ssp. consimilis var. oreophila | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. pinifolius (Greene) Hall & Clements | CHNAP2 |
| Ericameria nauseosa ssp. consimilis var. oreophila | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. artus (A. Nels.) Cronq. | CHNAA8 |
| Ericameria nauseosa ssp. consimilis var. oreophila | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. consimilis (Greene) Hall | CHNAC3 |
| Ericameria nauseosa ssp. consimilis var. oreophila | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. oreophilus (A. Nels.) Hall | CHNAO |
| Ericameria nauseosa ssp. consimilis var. oreophila | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird var. arta (A. Nels.) Nesom & Baird | ERNAA4 |
| Ericameria nauseosa ssp. consimilis var. turbinata | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. turbinatus (M.E. Jones) Hall & Clements | CHNAT |
| Ericameria nauseosa ssp. consimilis var. turbinata | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. turbinatus (M.E. Jones) Blake | CHNAT4 |
| Ericameria nauseosa ssp. nauseosa var. bernardina | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. bernardinus (Hall) Hall & Clements | CHNAB |
| Ericameria nauseosa ssp. nauseosa var. bigelovii | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. bigelovii (Gray) Hall & Clements | CHNAB2 |
| Ericameria nauseosa ssp. nauseosa var. bigelovii | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. bigelovii (Gray) Hall | CHNAB3 |
| Ericameria nauseosa ssp. nauseosa var. glabrata | Chrysothamnus graveolens (Nutt.) Greene | CHGR12 |
| Ericameria nauseosa ssp. nauseosa var. glabrata | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. graveolens (Nutt.) Piper | CHNAG2 |
| Ericameria nauseosa ssp. nauseosa var. glabrata | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. glabratus (Gray) Cronq. | CHNAG5 |
| Ericameria nauseosa ssp. nauseosa var. glabrata | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. graveolens (Nutt.) Piper ex Hall | CHNAG6 |
| Ericameria nauseosa ssp. nauseosa var. glabrata | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. petrophilus Cronq. | CHNAP4 |
| Ericameria nauseosa ssp. nauseosa var. glareosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. glareosus (M.E. Jones) Hall | CHNAG7 |
| Ericameria nauseosa ssp. nauseosa var. hololeuca | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. gnaphalodes (Greene) Hall & Clements | CHNAG4 |
| Ericameria nauseosa ssp. nauseosa var. hololeuca | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. hololeucus (Gray) Hall & Clements | CHNAH |
| Ericameria nauseosa ssp. nauseosa var. hololeuca | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. gnaphalodes (Greene) Hall | CHNAG3 |
| Ericameria nauseosa ssp. nauseosa var. hololeuca | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. hololeucus (Gray) Hall | CHNAH2 |
| Ericameria nauseosa ssp. nauseosa var. iridis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. iridis L.C. Anders. | CHNAI |
| Ericameria nauseosa ssp. nauseosa var. iridis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. iridis (L.C. Anders.) Welsh | CHNAI2 |
| Ericameria nauseosa ssp. nauseosa var. latisquamea | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. latisquameus (Gray) Hall & Clements | CHNAL2 |
| Ericameria nauseosa ssp. nauseosa var. latisquamea | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. latisquameus (Gray) Hall | CHNAL5 |
| Ericameria nauseosa ssp. nauseosa var. nana | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. nanus (Cronq.) Keck | CHNAN2 |
| Ericameria nauseosa ssp. nauseosa var. nana | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. nanus Cronq. | CHNAN4 |
| Ericameria nauseosa ssp. nauseosa var. nauseosa | Chrysothamnus frigidus Greene | CHFR7 |
| Ericameria nauseosa ssp. nauseosa var. nauseosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt | CHNA2 |
| Ericameria nauseosa ssp. nauseosa var. nauseosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. typicus (Hall) Cronq. | CHNAT3 |
| Ericameria nauseosa ssp. nauseosa var. nauseosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt. var. nauseosus (Pallas ex Pursh) Britt. [superfluous autonym] | CHNAN8 |
| Ericameria nauseosa ssp. nauseosa var. psilocarpa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. psilocarpus (Blake) L.C. Anders. | CHNAP |
| Ericameria nauseosa ssp. nauseosa var. psilocarpa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. psilocarpus Blake | CHNAP3 |
| Ericameria nauseosa ssp. nauseosa var. salicifolia | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. salicifolius (Rydb.) Hall & Clements | CHNAS |
| Ericameria nauseosa ssp. nauseosa var. salicifolia | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. salicifolius (Rydb.) Hall | CHNAS4 |
| Ericameria nauseosa ssp. nauseosa var. speciosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. albicaulis (Nutt.) Hall & Clements | CHNAA3 |
| Ericameria nauseosa ssp. nauseosa var. speciosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. speciosus (Nutt.) Hall & Clements | CHNAS2 |
| Ericameria nauseosa ssp. nauseosa var. speciosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. albicaulis (Nutt.) Rydb. | CHNAA7 |
| Ericameria nauseosa ssp. nauseosa var. speciosa | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. speciosus (Nutt.) Hall | CHNAS3 |
| Ericameria nauseosa ssp. nauseosa var. texensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. texensis L.C. Anders. | CHNAT2 |
| Ericameria nauseosa ssp. nauseosa var. washoensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt ssp. washoensis L.C. Anders. | CHNAW |
| Ericameria nauseosa ssp. nauseosa var. washoensis | Chrysothamnus nauseosus (Pallas ex Pursh) Britt var. washoensis (L.C. Anders.) Cronq. | CHNAW3 |
| Ericameria obovata | Haplopappus rydbergii Blake | HARY |
| Ericameria obovata | Haplopappus watsonii Gray var. rydbergii (Blake) Welsh | HAWAR |
| Ericameria obovata | Macronema obovatum Rydb., non Haplopappus obovatus Phil. | MAOB4 |
| Ericameria ophitidis | Haplopappus bloomeri Gray var. ophitidis J.T. Howell | HABLO |
| Ericameria ophitidis | Haplopappus ophitidis (J.T. Howell) Keck | HAOP |
| Ericameria palmeri var. pachylepis | Haplopappus palmeri Gray ssp. pachylepis Hall | HAPAP3 |
| Ericameria palmeri var. pachylepis | Xylothamia palmeri (Gray) Nesom var. pachylepis (Hall) Nesom ex M. Lane & R.L. Hartman | XYPAP |
| Ericameria palmeri var. palmeri | Haplopappus palmeri Gray | HAPA8 |
| Ericameria paniculata | Chrysothamnus paniculatus (Gray) Hall | CHPA12 |
| Ericameria parishii | Ericameria parishii (Greene) H. M. Hall var. parishii (Greene) H. M. Hall [superfluous autonym] | ERPAP13 |
| Ericameria parishii | Haplopappus parishii (Greene) Blake | HAPA5 |
| Ericameria parryi var. affinis | Chrysothamnus parryi (Gray) Greene ssp. affinis (A. Nels.) L.C. Anders. | CHPAA2 |
| Ericameria parryi var. affinis | Chrysothamnus parryi (Gray) Greene var. affinis (A. Nels.) Cronq. | CHPAA10 |
| Ericameria parryi var. aspra | Chrysothamnus parryi (Gray) Greene ssp. asper (Greene) Hall & Clements | CHPAA3 |
| Ericameria parryi var. aspra | Chrysothamnus parryi (Gray) Greene var. asper (Greene) Munz | CHPAA6 |
| Ericameria parryi var. attenuata | Chrysothamnus parryi (Gray) Greene ssp. attenuatus (M.E. Jones) Hall & Clements | CHPAA4 |
| Ericameria parryi var. attenuata | Chrysothamnus parryi (Gray) Greene var. attenuatus (M.E. Jones) Kittell | CHPAA5 |
| Ericameria parryi var. howardii | Chrysothamnus howardii (Parry ex Gray) Greene | CHHO6 |
| Ericameria parryi var. howardii | Chrysothamnus parryi (Gray) Greene ssp. howardii (Parry ex Gray) Hall & Clements | CHPAH |
| Ericameria parryi var. howardii | Chrysothamnus parryi (Gray) Greene var. howardii (Parry ex Gray) Kittell | CHPAH2 |
| Ericameria parryi var. imula | Chrysothamnus parryi (Gray) Greene ssp. imulus Hall & Clements | CHPAI |
| Ericameria parryi var. latior | Chrysothamnus parryi (Gray) Greene ssp. latior Hall & Clements | CHPAL |
| Ericameria parryi var. monocephala | Chrysothamnus parryi (Gray) Greene ssp. monocephalus (A. Nels. & Kennedy) Hall & Clements | CHPAM |
| Ericameria parryi var. monocephala | Chrysothamnus parryi (Gray) Greene var. monocephalus (A. Nels. & Kennedy) Jepson | CHPAM3 |
| Ericameria parryi var. montana | Chrysothamnus parryi (Gray) Greene ssp. montanus L.C. Anders. | CHPAM2 |
| Ericameria parryi var. nevadensis | Chrysothamnus parryi (Gray) Greene ssp. nevadensis (Gray) Hall & Clements | CHPAN |
| Ericameria parryi var. nevadensis | Chrysothamnus parryi (Gray) Greene var. nevadensis (Gray) Kittell | CHPAN2 |
| Ericameria parryi var. parryi | Chrysothamnus parryi (Gray) Greene | CHPA13 |
| Ericameria parryi var. parryi | Chrysothamnus parryi (Gray) Greene ssp. typicus Hall & Clements | CHPAT |
| Ericameria parryi var. salmonensis | Chrysothamnus parryi (Gray) Greene ssp. salmonensis L.C. Anders. | CHPAS |
| Ericameria parryi var. vulcanica | Chrysothamnus parryi (Gray) Greene ssp. vulcanicus (Greene) Hall & Clements | CHPAV |
| Ericameria parryi var. vulcanica | Chrysothamnus parryi (Gray) Greene var. vulcanicus (Greene) Jepson | CHPAV2 |
| Ericameria pinifolia | Haplopappus pinifolius Gray | HAPI |
| Ericameria resinosa | Haplopappus resinosus (Nutt.) Gray | HARE3 |
| Ericameria suffruticosa | Haplopappus suffruticosus (Nutt.) Gray | HASU |
| Ericameria suffruticosa | Macronema suffruticosum Nutt. | MASU7 |
| Ericameria teretifolia | Chrysothamnus teretifolius (Dur. & Hilg.) Hall | CHTE4 |
| Ericameria watsonii | Haplopappus watsonii Gray | HAWA |
| Ericameria watsonii | Macronema watsonii (Gray) Greene | MAWA3 |
| Ericameria zionis | Haplopappus zionis L.C. Anders. | HAZI |
| Erigeron acris ssp. debilis | Erigeron acris auct. non L. p.p. [misapplied] | ERAC9 |
| Erigeron acris ssp. debilis | Erigeron acris L. var. debilis Gray | ERACD6 |
| Erigeron acris ssp. debilis | Erigeron angulosus Gaudin ssp. debilis (Gray) Piper | ERAND2 |
| Erigeron acris ssp. debilis | Erigeron debilis (Gray) Rydb. | ERDE12 |
| Erigeron acris ssp. debilis | Erigeron jucundus Greene | ERJU |
| Erigeron acris ssp. debilis | Erigeron nivalis Nutt. | ERNI6 |
| Erigeron acris ssp. debilis | Trimorpha acris (L.) S.F. Gray var. debilis (Gray) Nesom | TRACD |
| Erigeron acris ssp. debilis | Trimorpha acris auct. non (L.) S.F. Gray p.p. [misapplied] | TRAC3 |
| Erigeron acris ssp. kamtschaticus | Erigeron acris L. var. kamtschaticus (DC.) Herder | ERACK2 |
| Erigeron acris ssp. kamtschaticus | Erigeron kamtschaticus DC. | ERKA3 |
| Erigeron acris ssp. kamtschaticus | Trimorpha acris (L.) S.F. Gray var. kamtschatica (DC.) Nesom | TRACK |
| Erigeron acris ssp. politus | Erigeron acris auct. non L. p.p. [misapplied] | ERAC9 |
| Erigeron acris ssp. politus | Erigeron acris L. var. asteroides (Andrz. ex Bess.) DC. | ERACA2 |
| Erigeron acris ssp. politus | Erigeron droebachianus O.F. Muell. ex Retz. | ERDR |
| Erigeron acris ssp. politus | Erigeron elongatus Ledeb. | EREL14 |
| Erigeron acris ssp. politus | Erigeron politus Fries | ERPO82 |
| Erigeron acris ssp. politus | Trimorpha acris (L.) S.F. Gray var. asteroides (Andrz. ex Bess.) Nesom | TRACA |
| Erigeron acris ssp. politus | Trimorpha acris auct. non (L.) S.F. Gray p.p. [misapplied] | TRAC3 |
| Erigeron acris ssp. politus | Trimorpha elongata (Ledeb.) Vierh. | TREL15 |
| Erigeron algidus | Erigeron petiolaris Greene | ERPE4 |
| Erigeron annuus | Erigeron annuus (L.) Pers. var. discoideus (Victorin & Rouss.) Cronq. | ERAND |
| Erigeron annuus | Stenactis annua (L.) Nees | STAN10 |
| Erigeron aphanactis var. aphanactis | Erigeron concinnus (Hook. & Arn.) Torr. & Gray var. aphanactis Gray | ERCOA3 |
| Erigeron arizonicus | Erigeron rusbyi Gray | ERRU5 |
| Erigeron asper | Erigeron glabellus Nutt. var. pubescens Hook. p.p. | ERGLP2 |
| Erigeron atticus | Erigeron villarsii Bellardi | ERVI19 |
| Erigeron aureus var. aureus | Haplopappus brandegeei Gray | HABR6 |
| Erigeron austiniae | Erigeron chrysopsidis Gray var. austiniae (Greene) Cronq. | ERCHA6 |
| Erigeron bellidiastrum var. arenarius | Erigeron arenarius Greene | ERAR29 |
| Erigeron biolettii | Erigeron inornatus (Gray) Gray var. biolettii (Greene) Jepson | ERINB |
| Erigeron blochmaniae | Erigeron foliosus Nutt. var. blochmaniae (Greene) Hall | ERFOB |
| Erigeron bloomeri var. bloomeri | Erigeron bloomeri Gray var. typicus Cronq. | ERBLT |
| Erigeron breweri var. covillei | Erigeron foliosus Nutt. var. covillei (Greene) Compton | ERFOC2 |
| Erigeron caespitosus | Erigeron caespitosus Nutt. var. laccoliticus M.E. Jones | ERCAL |
| Erigeron caucasicus ssp. venustus | Erigeron venustus Botsch. | ERVE12 |
| Erigeron cervinus | Erigeron delicatus Cronq. | ERDE4 |
| Erigeron chrysopsidis | Erigeron chrysopsidis Gray var. brevifolius Piper | ERCHB |
| Erigeron colomexicanus | Erigeron divergens Torr. & Gray var. cinereus Gray | ERDIC |
| Erigeron compositus | Erigeron compositus Pursh var. discoideus Gray | ERCOD |
| Erigeron compositus | Erigeron compositus Pursh var. glabratus Macoun | ERCOG |
| Erigeron compositus | Erigeron compositus Pursh var. multifidus (Rydb.) J.F. Macbr. & Payson | ERCOM2 |
| Erigeron compositus | Erigeron compositus Pursh var. typicus Hook. | ERCOT2 |
| Erigeron compositus | Erigeron trifidus Hook. | ERTR20 |
| Erigeron concinnus var. concinnus | Distasis concinna Hook. & Arn. | DICO9 |
| Erigeron concinnus var. concinnus | Erigeron brandegeei Gray | ERBR12 |
| Erigeron concinnus var. concinnus | Erigeron pumilus Nutt. ssp. concinnoides Cronq. | ERPUC |
| Erigeron concinnus var. concinnus | Erigeron pumilus Nutt. var. concinnus (Hook. & Arn.) Dorn | ERPUC3 |
| Erigeron concinnus var. concinnus | Erigeron pumilus Nutt. var. euconcinnoides Cronq. | ERPUE |
| Erigeron concinnus var. condensatus | Erigeron condensatus (D.C. Eat.) Greene | ERCO34 |
| Erigeron concinnus var. condensatus | Erigeron pumilus Nutt. var. condensatus (D.C. Eat.) Cronq. | ERPUC4 |
| Erigeron concinnus var. subglaber | Erigeron perglaber Blake | ERPE11 |
| Erigeron concinnus var. subglaber | Erigeron pumilus Nutt. var. subglaber Cronq. | ERPUS2 |
| Erigeron consimilis | Erigeron compactus Blake var. consimilis (Cronq.) Blake | ERCOC |
| Erigeron decumbens var. robustior | Erigeron decumbens Nutt. ssp. robustior Cronq. | ERDER |
| Erigeron divergens | Erigeron divergens Torr. & Gray var. typicus Cronq. | ERDIT |
| Erigeron eatonii var. eatonii | Erigeron canaani Welsh | ERCA10 |
| Erigeron eatonii var. eatonii | Erigeron eatonii Gray ssp. typicus Cronq. | EREAT |
| Erigeron eatonii var. nevadincola | Erigeron nevadincola S.F. Blake | ERNE10 |
| Erigeron eatonii var. plantagineus | Erigeron eatonii Gray ssp. plantagineus (Greene) Cronq. | EREAP |
| Erigeron eatonii var. sonnei | Erigeron nevadensis S.F. Blake var. sonnei (Greene) Smilty | ERNES |
| Erigeron eatonii var. sonnei | Erigeron sonnei Greene | ERSO3 |
| Erigeron eatonii var. villosus | Erigeron eatonii Gray ssp. villosus Cronq. | EREAV |
| Erigeron elatior | Erigeron grandiflorus Hook. var. elatior Gray | ERGRE2 |
| Erigeron elatus | Erigeron acris L. var. elatus (Hook.) Cronq. | ERACE |
| Erigeron elatus | Erigeron alpinus L. var. elatus Hook. | ERALE |
| Erigeron elatus | Erigeron elatus (Hook.) Greene var. oligocephalus (Fern. & Wieg.) Fern. | ERELO |
| Erigeron elatus | Trimorpha elata (Hook.) Nesom | TREL10 |
| Erigeron elegantulus | Erigeron linearis (Hook.) Piper var. elegantulus J.T. Howell | ERLIE |
| Erigeron elmeri | Erigeron breweri Gray var. elmeri Greene | ERBRE |
| Erigeron engelmannii var. davisii | Erigeron engelmannii A. Nels. ssp. davisii Cronq. | EREND2 |
| Erigeron engelmannii var. engelmannii | Erigeron engelmannii A. Nels. ssp. typicus Cronq. | ERENT |
| Erigeron eximius | Erigeron superbus Greene ex Rydb. | ERSU3 |
| Erigeron filifolius var. filifolius | Erigeron filifolius (Hook.) Nutt. var. typicus Cronq. | ERFIT |
| Erigeron flagellaris | Erigeron flagellaris Gray var. typicus Cronq. | ERFLT |
| Erigeron flagellaris | Erigeron nudiflorus Buckl. | ERNU7 |
| Erigeron foliosus var. foliosus | Erigeron foliosus Nutt. var. stenophyllus (Nutt.) Gray | ERFOS |
| Erigeron foliosus var. mendocinus | Erigeron mendocinus Greene | ERME16 |
| Erigeron formosissimus | Erigeron formosissimus Greene var. formosissimus Greene [superfluous autonym] | ERFOF2 |
| Erigeron formosissimus | Erigeron formosissimus Greene var. typicus Cronq. | ERFOT |
| Erigeron formosissimus | Erigeron formosissimus Greene var. viscidus (Rydb.) Cronq. | ERFOV |
| Erigeron formosissimus | Erigeron glabellus Nutt. var. viscidus (Rydb.) Boivin | ERGLV |
| Erigeron formosissimus | Erigeron viscidus Rydb. | ERVI15 |
| Erigeron garrettii | Erigeron controversus Greene | ERCO32 |
| Erigeron glabellus var. glabellus | Erigeron asperum Nutt. p.p. | ERAS4 |
| Erigeron glabellus var. glabellus | Erigeron glabellus Nutt. ssp. typicus Cronq. | ERGLT |
| Erigeron glabellus var. glabellus | Erigeron oblanceolatus Rydb. | EROB4 |
| Erigeron glabellus var. pubescens | Erigeron anodonta Lunell | ERAN12 |
| Erigeron glabellus var. pubescens | Erigeron asperum Nutt. var. pubescens (Hook.) Breitung | ERASP4 |
| Erigeron glabellus var. pubescens | Erigeron glabellus Nutt. ssp. pubescens (Hook.) Cronq. | ERGLP3 |
| Erigeron glabellus var. pubescens | Erigeron oligodontus Lunell | EROL |
| Erigeron humilis | Erigeron unalaschkensis (DC.) Vierh. | ERUN80 |
| Erigeron humilis | Erigeron uniflorus L. var. unalaschkensis (DC.) Ostenf. | ERUNU2 |
| Erigeron hyperboreus | Erigeron alaskanus Cronq. | ERAL19 |
| Erigeron jonesii | Erigeron wahwahensis Welsh | ERWA6 |
| Erigeron lassenianus var. lassenianus | Erigeron flexuosus Cronq. | ERFL3 |
| Erigeron linearis | Erigeron peucephyllus Gray | ERPE12 |
| Erigeron lonchophyllus | Erigeron lonchophyllus Hook. var. laurentianus Victorin | ERLOL |
| Erigeron lonchophyllus | Erigeron minor (Hook.) Rydb. | ERMI10 |
| Erigeron lonchophyllus | Trimorpha lonchophylla (Hook.) Nesom | TRLO3 |
| Erigeron maguirei | Erigeron maguirei Cronq. var. harrisonii Welsh | ERMAH |
| Erigeron melanocephalus | Erigeron uniflorus L. var. melanocephalus A. Nels. | ERUNM |
| Erigeron modestus | Erigeron lobatus A. Nels. var. warnockii Shinners | ERLOW |
| Erigeron modestus | Erigeron plateauensis Cronq. | ERPL6 |
| Erigeron modestus | Erigeron warnockii (Shinners) Shinners | ERWA |
| Erigeron muirii | Erigeron grandiflorus Hook. ssp. muirii (Gray) Hult | ERGRM2 |
| Erigeron neomexicanus | Erigeron delphiniifolius Willd. ssp. neomexicanus (Gray) Cronq. | ERDEN2 |
| Erigeron neomexicanus | Erigeron delphiniifolius Willd. var. euneomexicanus Cronq. | ERDEE3 |
| Erigeron ochroleucus var. ochroleucus | Erigeron parryi Canby & Rose | ERPA17 |
| Erigeron oreophilus | Erigeron delphiniifolius Willd. var. oreophilus (Greenm.) Cronq. | ERDEO |
| Erigeron peregrinus ssp. callianthemus var. callianthemus | Erigeron callianthemus Greene | ERCA21 |
| Erigeron peregrinus ssp. callianthemus var. callianthemus | Erigeron peregrinus (Banks ex Pursh) Greene var. angustifolius (Gray) Cronq. | ERPEA2 |
| Erigeron peregrinus ssp. callianthemus var. callianthemus | Erigeron peregrinus (Banks ex Pursh) Greene var. eucallianthemus Cronq. | ERPEE |
| Erigeron peregrinus ssp. callianthemus var. callianthemus | Erigeron peregrinus (Banks ex Pursh) Greene var. scaposus (Torr. & Gray) Cronq. | ERPES3 |
| Erigeron peregrinus ssp. peregrinus var. peregrinus | Erigeron unalaschkensis Less. | ERUN6 |
| Erigeron petrophilus var. viscidulus | Erigeron inornatus (Gray) Gray var. viscidulus Gray | ERINV |
| Erigeron philadelphicus var. philadelphicus | Erigeron philadelphicus L. var. glaber Henry | ERPHG2 |
| Erigeron philadelphicus var. philadelphicus | Erigeron philadelphicus L. var. scaturicola (Fern.) Fern. | ERPHS |
| Erigeron philadelphicus var. philadelphicus | Erigeron purpureus Ait. | ERPU13 |
| Erigeron philadelphicus var. provancheri | Erigeron philadelphicus L. ssp. provancheri (Victorin & Rouss.) J.K. Morton | ERPHP4 |
| Erigeron philadelphicus var. provancheri | Erigeron provancheri Victorin & Rouss. | ERPR14 |
| Erigeron pinnatisectus | Erigeron compositus Pursh var. pinnatisectus Gray | ERCOP |
| Erigeron poliospermus var. poliospermus | Erigeron poliospermus Gray var. typicus Cronq. | ERPOT |
| Erigeron procumbens | Aster procumbens Houst. ex P. Mill. | ASPR12 |
| Erigeron procumbens | Erigeron myrionactis Small | ERMY |
| Erigeron procumbens | Erigeron repens Gray | ERRE10 |
| Erigeron proselyticus | Erigeron flagellaris Gray var. trilobatus Maguire ex Cronq. | ERFLT2 |
| Erigeron proselyticus | Erigeron sionis Cronq. var. trilobatus (Maguire ex Cronq.) Welsh | ERSIT |
| Erigeron pulchellus | Erigeron bellidifolius Muhl. ex Willd. | ERBE7 |
| Erigeron pulcherrimus | Erigeron pulcherrimus Heller var. wyomingia (Rydb.) Cronq. | ERPUW |
| Erigeron pulcherrimus | Erigeron wyomingia Rydb. | ERWY |
| Erigeron pumilus ssp. intermedius var. intermedius | Erigeron pumilus Nutt. var. euintermedius Cronq. | ERPUE2 |
| Erigeron pumilus ssp. pumilus | Erigeron pumilus Nutt. ssp. typicus Cronq. | ERPUT2 |
| Erigeron pumilus ssp. pumilus | Erigeron pumilus Nutt. var. pumilus | ERPUP6 |
| Erigeron reductus var. angustatus | Erigeron inornatus (Gray) Gray var. angustatus Gray | ERINA |
| Erigeron reductus var. reductus | Erigeron inornatus (Gray) Gray var. reductus Cronq. | ERINR |
| Erigeron speciosus var. macranthus | Erigeron macranthus Nutt. | ERMA11 |
| Erigeron speciosus var. speciosus | Erigeron speciosus (Lindl.) DC. var. typicus Cronq. | ERSPT |
| Erigeron strigosus var. beyrichii | Erigeron ramosus (Walt.) B.S.P. var. beyrichii (Fisch. & C.A. Mey.) Gray | ERRAB |
| Erigeron strigosus var. septentrionalis | Erigeron strigosus Muhl. ex Willd. ssp. septentrionalis (Fern. & Wieg.) Wagenitz | ERSTS4 |
| Erigeron strigosus var. strigosus | Erigeron annuus (L.) Pers. ssp. strigosus (Muhl. ex Willd.) Wagenitz | ERANS8 |
| Erigeron strigosus var. strigosus | Erigeron ramosus (Walt.) B.S.P. | ERRA8 |
| Erigeron strigosus var. strigosus | Erigeron strigosus Muhl. ex Willd. var. discoideus Robbins ex Gray | ERSTD2 |
| Erigeron strigosus var. strigosus | Erigeron strigosus Muhl. ex Willd. var. eligulatus Cronq. | ERSTE |
| Erigeron strigosus var. strigosus | Erigeron strigosus Muhl. ex Willd. var. typicus Cronq. | ERSTT |
| Erigeron strigosus var. strigosus | Erigeron traversii Shinners | ERTR16 |
| Erigeron strigosus var. strigosus | Stenactis strigosa (Muhl. ex Willd.) DC. | STST14 |
| Erigeron subtrinervis var. conspicuus | Erigeron conspicuus Rydb. | ERCO33 |
| Erigeron subtrinervis var. conspicuus | Erigeron speciosus (Lindl.) DC. var. conspicuus (Rydb.) Breitung | ERSPC |
| Erigeron subtrinervis var. conspicuus | Erigeron subtrinervis Rydb. ex Porter & Britt. ssp. conspicuus (Rydb.) Cronq. | ERSUC2 |
| Erigeron subtrinervis var. subtrinervis | Erigeron glabellus Nutt. var. mollis Gray | ERGLM |
| Erigeron subtrinervis var. subtrinervis | Erigeron speciosus (Lindl.) DC. var. mollis (Gray) Welsh | ERSPM2 |
| Erigeron subtrinervis var. subtrinervis | Erigeron subtrinervis Rydb. ex Porter & Britt. ssp. typicus Cronq. | ERSUT |
| Erigeron thunbergii ssp. glabratus | Erigeron thunbergii Gray var. glabratus Gray | ERTHG2 |
| Erigeron uintahensis | Erigeron speciosus (Lindl.) DC. var. uintahensis (Cronq.) Welsh | ERSPU |
| Erigeron uncialis | Erigeron uncialis S. F. Blake var. uncialis S. F. Blake [superfluous autonym] | ERUNU3 |
| Erigeron uncialis ssp. conjugans | Erigeron uncialis Blake var. conjugans Blake | ERUNC2 |
| Erigeron uncialis ssp. uncialis | Erigeron cavernensis Welsh & Atwood | ERCA24 |
| Erigeron uniflorus ssp. eriocephalus | Erigeron eriocephalus J. Vahl | ERER8 |
| Erigeron uniflorus ssp. eriocephalus | Erigeron uniflorus L. var. eriocephalus (J. Vahl) Boivin | ERUNE2 |
| Erigeron untermannii | Erigeron carringtoniae Welsh | ERCA30 |
| Erigeron utahensis var. utahensis | Erigeron utahensis Gray var. tetrapleuris (Gray) Cronq. | ERUTT |
| Erigeron versicolor | Achaetogeron chihuahuensis Larsen | ACCH3 |
| Erigeron versicolor | Achaetogeron versicolor Greenm. | ACVE7 |
| Erigeron versicolor | Erigeron geiseri Shinners var. calcicola Shinners | ERGEC |
| Erigeron versicolor | Erigeron gilensis Woot. & Standl. | ERGI4 |
| Erigeron versicolor | Erigeron mimegletes Shinners | ERMI |
| Erigeron vreelandii | Erigeron platyphyllus Greene | ERPL7 |
| Erigeron watsonii | Aster watsonii Gray | ASWA8 |
| Erigeron yukonensis | Erigeron glabellus Nutt. var. yukonensis (Rydb.) Hult | ERGLY |
| Eriophyllum confertiflorum var. confertiflorum | Eriophyllum confertiflorum (DC.) Gray var. discoideum (Rydb.) Munz | ERCOD4 |
| Eriophyllum confertiflorum var. confertiflorum | Eriophyllum confertiflorum (DC.) Gray var. latum Hall | ERCOL3 |
| Eriophyllum confertiflorum var. confertiflorum | Eriophyllum confertiflorum (DC.) Gray var. laxiflorum Gray | ERCOL4 |
| Eriophyllum confertiflorum var. confertiflorum | Eriophyllum confertiflorum (DC.) Gray var. tridactylum (Rydb.) Munz | ERCOT3 |
| Eriophyllum confertiflorum var. tanacetiflorum | Eriophyllum tanacetiflorum Greene | ERTA |
| Eriophyllum congdonii | Eriophyllum nubigenum Greene ex Gray var. congdonii (Brandeg.) Constance | ERNUC |
| Eriophyllum lanatum var. integrifolium | Eriophyllum integrifolium (Hook.) Greene | ERIN12 |
| Eriophyllum lanatum var. integrifolium | Eriophyllum lanatum (Pursh) Forbes var. monoense (Rydb.) Jepson | ERLAM |
| Eriophyllum lanatum var. lanatum | Eriophyllum lanatum (Pursh) Forbes var. typicum Constance | ERLAT |
| Eriophyllum stoechadifolium | Eriophyllum stoechadifolium Lag. var. artemisiifolium (Less.) J.F. Macbr. | ERSTA2 |
| Eriophyllum stoechadifolium | Eriophyllum stoechadifolium Lag. var. depressum Greene | ERSTD |
| erlangea | Erlangea Sch. Bip. | ERLAN2 |
| Ertter's ragwort | Senecio ertterae T.M. Barkl. | SEER4 |
| estuary beggarticks | Bidens hyperborea Greene | BIHY |
| estuary beggarticks | Bidens hyperborea Greene var. hyperborea | BIHYH |
| Eucephalus breweri | Aster breweri (Gray) Semple | ASBR12 |
| Eucephalus breweri | Chrysopsis breweri Gray | CHBR8 |
| Eucephalus breweri | Chrysopsis breweri Gray var. multibracteata Jepson | CHBRM |
| Eucephalus breweri | Chrysopsis gracilis Eastw. | CHGR10 |
| Eucephalus breweri | Chrysopsis wrightii Gray | CHWR3 |
| Eucephalus breweri | Heterotheca breweri (Gray) Shinners | HEBR7 |
| Eucephalus brickellioides | Aster brickellioides Greene | ASBR4 |
| Eucephalus elegans | Aster elegans (Nutt.) Torr. & Gray, non Willd. | ASEL6 |
| Eucephalus elegans | Aster perelegans A. Nels. & J.F. Macbr. | ASPE3 |
| Eucephalus elegans | Eucephalus perelegans (A. Nels. & J.F. Macbr.) W.A. Weber | EUPE17 |
| Eucephalus engelmannii | Aster elegans (Nutt.) Torr. & Gray var. engelmannii D.C. Eat. | ASELE |
| Eucephalus engelmannii | Aster engelmannii (D.C. Eat.) Gray | ASEN2 |
| Eucephalus glabratus | Aster brickellioides Greene var. glabratus Greene | ASBRG |
| Eucephalus glabratus | Aster siskiyouensis A. Nels. & J.F. Macbr. | ASSI8 |
| Eucephalus glaucescens | Aster engelmannii (D.C. Eat.) Gray var. glaucescens Gray | ASENG2 |
| Eucephalus glaucescens | Aster glaucescens (Gray) Blake | ASGL2 |
| Eucephalus gormanii | Aster gormanii (Piper) Blake | ASGO |
| Eucephalus ledophyllus var. covillei | Aster covillei (Greene) Blake ex Peck | ASCO40 |
| Eucephalus ledophyllus var. covillei | Aster ledophyllus (Gray) Gray var. covillei (Greene) Cronq. | ASLEC3 |
| Eucephalus ledophyllus var. covillei | Eucephalus covillei Greene | EUCO18 |
| Eucephalus ledophyllus var. ledophyllus | Aster engelmannii (D.C. Eat.) Gray var. ledophyllus Gray | ASENL |
| Eucephalus ledophyllus var. ledophyllus | Aster ledophyllus (Gray) Gray | ASLE3 |
| Eucephalus paucicapitatus | Aster engelmannii (D.C. Eat.) Gray var. paucicapitatus B.L. Robins. | ASENP |
| Eucephalus paucicapitatus | Aster paucicapitatus (B.L. Robins.) B.L. Robins. | ASPA7 |
| Eucephalus tomentellus | Aster tomentellus (Greene) Frye & Rigg, non Hook. | ASTO4 |
| Eucephalus tomentellus | Sericocarpus tomentellus Greene | SETO5 |
| Eucephalus vialis | Aster vialis (Bradshaw) Blake | ASVI4 |
| euchiton | Euchiton Cass. | EUCHI |
| Euchiton gymnocephalus | Gnaphalium collinum Labill. | GNCO |
| Euchiton gymnocephalus | Gnaphalium gymnocephalus DC. | GNGY |
| Euchiton japonicus | Gnaphalium japonicum Thunb. | GNJA |
| Eupatoriadelphus dubius | Eupatorium dubium Willd. ex Poir. | EUDU |
| Eupatoriadelphus fistulosus | Eupatorium fistulosum Barratt | EUFI |
| Eupatoriadelphus maculatus var. bruneri | Eupatorium bruneri Gray | EUBR4 |
| Eupatoriadelphus maculatus var. bruneri | Eupatorium maculatum L. ssp. bruneri (Gray) G.W. Douglas | EUMAB3 |
| Eupatoriadelphus maculatus var. bruneri | Eupatorium maculatum L. var. bruneri (Gray) Breitung | EUMAB2 |
| Eupatoriadelphus maculatus var. foliosum | Eupatorium maculatum L. var. foliosum (Fern.) Wieg. | EUMAF |
| Eupatoriadelphus maculatus var. foliosum | Eupatorium purpureum L. var. foliosum Fern. | EUPUF |
| Eupatoriadelphus maculatus var. foliosum | Eupatorium trifoliatum L. var. foliosum (Fern.) Farw. | EUTRF |
| Eupatoriadelphus maculatus var. maculatus | Eupatorium maculatum L. | EUMA6 |
| Eupatoriadelphus maculatus var. maculatus | Eupatorium maculatum L. var. maculatum L. [superfluous autonym] | EUMAM |
| Eupatoriadelphus maculatus var. maculatus | Eupatorium purpureum L. var. maculatum (L.) Darl. | EUPUM |
| Eupatorium ?pinnatifidum | Eupatorium eugenei Small | EUEU2 |
| Eupatorium ?pinnatifidum | Eupatorium pectinatum Small | EUPE12 |
| Eupatorium ?pinnatifidum | Eupatorium smithii Greene & C. Mohr | EUSM2 |
| Eupatorium ?truncatum | Eupatorium ?polyneuron (F.J. Herm.) Wunderlin | EUPO11 |
| Eupatorium ?truncatum | Eupatorium cuneatum (Engelm. ex Gray) Engelm. ex Small | EUCU5 |
| Eupatorium ?truncatum | Eupatorium perfoliatum L. var. cuneatum Engelm. ex Gray | EUPEC2 |
| Eupatorium ?truncatum | Eupatorium perfoliatum L. var. truncatum (Muhl. ex Willd.) Gray | EUPET |
| Eupatorium ?truncatum | Eupatorium resinosum Torr. ex DC. var. kentuckiense Fern. | EUREK3 |
| Eupatorium ?truncatum | Eupatorium serotinum Michx. var. polyneuron F.J. Herm. | EUSEP |
| Eupatorium album var. album | Eupatorium album L. var. glandulosum (Michx.) DC. | EUALG |
| Eupatorium album var. album | Eupatorium fernaldii Godfrey | EUFE3 |
| Eupatorium album var. album | Eupatorium glandulosum Michx. | EUGL10 |
| Eupatorium album var. album | Eupatorium petaloideum Britt. ex Small | EUPE13 |
| Eupatorium altissimum | Eupatorium saltuense Fern., non Agertina altissima (L.) King & H.E. Robins. | EUSA5 |
| Eupatorium glaucescens | Eupatorium cuneifolium Willd. | EUCU2 |
| Eupatorium glaucescens | Eupatorium hyssopifolium L. var. linearifolium (Walt.) Fern. | EUHYL2 |
| Eupatorium glaucescens | Eupatorium linearifolium Walt. | EULI2 |
| Eupatorium glaucescens | Eupatorium tortifolium Chapman | EUTO5 |
| Eupatorium hyssopifolium var. hyssopifolium | Eupatorium lecheifolium Greene | EULE2 |
| Eupatorium hyssopifolium var. hyssopifolium | Eupatorium linearifolium sensu Michx., non Walt. | EULI5 |
| Eupatorium hyssopifolium var. hyssopifolium | Eupatorium torreyanum Short & Peter | EUTO6 |
| Eupatorium lancifolium | Eupatorium semiserratum DC. var. lancifolium Torr. & Gray | EUSEL |
| Eupatorium leptophyllum | Eupatorium capillifolium (Lam.) Small var. leptophyllum (DC.) Ahles | EUCAL2 |
| Eupatorium leucolepis | Pyrenula farrea auct. | PYFA3 |
| Eupatorium mohrii | Eupatorium recurvans Small | EURE3 |
| Eupatorium pilosum | Eupatorium rotundifolium L. var. saundersii (Porter ex Britt.) Cronq. | EUROS2 |
| Eupatorium purpureum var. holzingeri | Eupatorium holzingeri Rydb. | EUHO3 |
| Eupatorium purpureum var. purpureum | Eupatoriadelphus purpureus (L.) King & H.E. Robins. | EUPU8 |
| Eupatorium purpureum var. purpureum | Eupatorium falcatum Michx. | EUFA3 |
| Eupatorium purpureum var. purpureum | Eupatorium purpureum L. var. amoenum (Pursh) Gray | EUPUA |
| Eupatorium purpureum var. purpureum | Eupatorium trifoliatum L. | EUTR7 |
| Eupatorium rotundifolium var. cordigerum | Eupatorium cordigerum (Fern.) Fern. | EUCO19 |
| Eupatorium rotundifolium var. ovatum | Eupatorium pubescens Muhl. ex Willd. | EUPU11 |
| Eupatorium rotundifolium var. ovatum | Eupatorium rotundifolium L. ssp. ovatum (Bigelow) Montgomery & Fairbrothers p.p. | EUROO2 |
| Eupatorium rotundifolium var. rotundifolium | Eupatorium verbenifolium Reichard | EUVE4 |
| Eupatorium rotundifolium var. scabridum | Eupatorium scabridum Ell. | EUSC2 |
| Eupatorium semiserratum | Eupatorium cuneifolium Willd. var. semiserratum (DC.) Fern. & Grisc. | EUCUS |
| Eupatorium sessilifolium var. vaseyi | Eupatorium album L. var. monardifolium Fern. | EUALM |
| Eupatorium sessilifolium var. vaseyi | Eupatorium album L. var. vaseyi (Porter) Cronq. | EUALV |
| Eupatorium sessilifolium var. vaseyi | Eupatorium vaseyi Porter | EUVA2 |
| Eupatorium sordidum | Bartlettina sordida (Less.) King & H.E. Robins. [excluded] | BASO3 |
| Eupatorium triplinerve | Ayapana triplinervis (Vahl) King & H.E. Robins. | AYTR |
| European hawkweed | Hieracium lactucella Wallr. | HILA10 |
| European umbrella milkwort | Tolpis barbata (L.) Gaertn. | TOBA |
| Eurybia ?herveyi | Aster commixtus auct. non (Nees) Kuntze [misapplied] | ASCO21 |
| Eurybia ?herveyi | Aster herveyi Gray | ASHE12 |
| Eurybia ?herveyi | Eurybia commixta auct. non Nees [misapplied] | EUCO17 |
| Eurybia avita | Aster avitus Alexander | ASAV |
| Eurybia chapmanii | Aster chapmanii Torr. & Gray | ASCH8 |
| Eurybia chlorolepis | Aster chlorolepis Burgess | ASCH3 |
| Eurybia chlorolepis | Aster divaricatus (Nutt.) Torr. & Gray var. chlorolepis (Burgess) Ahles | ASDIC |
| Eurybia compacta | Aster gracilis Nutt. | ASGR7 |
| Eurybia conspicua | Aster conspicuus Lindl. | ASCO3 |
| Eurybia divaricata | Aster boykinii Burgess | ASBO5 |
| Eurybia divaricata | Aster carmesinus Burgess | ASCA18 |
| Eurybia divaricata | Aster castaneus Burgess | ASCA30 |
| Eurybia divaricata | Aster claytonii Burgess | ASCL4 |
| Eurybia divaricata | Aster divaricatus L. | ASDI |
| Eurybia divaricata | Aster excavatus Burgess | ASEX4 |
| Eurybia divaricata | Aster flexilis Burgess | ASFL3 |
| Eurybia divaricata | Aster stilettiformis Burgess | ASST16 |
| Eurybia divaricata | Aster tenebrosus Burgess | ASTE17 |
| Eurybia eryngiifolia | Aster eryngiifolius Torr. & Gray | ASER5 |
| Eurybia furcata | Aster furcatus Burgess | ASFU |
| Eurybia glauca | Aster glaucodes Blake | ASGL3 |
| Eurybia glauca | Aster glaucodes Blake var. formosus (Greene) Kittell | ASGLF |
| Eurybia glauca | Aster glaucus Torr. & Gray, non Nees | ASGL10 |
| Eurybia glauca | Eucephalus formosus Greene | EUFO4 |
| Eurybia glauca | Eucephalus glaucus Nutt. | EUGL13 |
| Eurybia hemispherica | Aster gattingeri Alexander, non Kuntze | ASGA3 |
| Eurybia hemispherica | Aster hemisphericus Alexander | ASHE7 |
| Eurybia hemispherica | Aster paludosus Ait. ssp. hemisphericus (Alexander) Cronq. | ASPAH |
| Eurybia hemispherica | Aster pedionomus Alexander | ASPE10 |
| Eurybia hemispherica | Aster verutifolius Alexander | ASVE9 |
| Eurybia hemispherica | Heleastrum hemisphericum (Alexander) Shinners | HEHE9 |
| Eurybia horrida | Aster horridus (Woot. & Standl.) Blake | ASHO6 |
| Eurybia horrida | Herrickia horrida Woot. & Standl. | HEHO7 |
| Eurybia integrifolia | Aster integrifolius Nutt. | ASIN3 |
| Eurybia jonesiae | Aster jonesiae Lamboy | ASJO3 |
| Eurybia macrophylla | Aster ianthinus Burgess | ASIA |
| Eurybia macrophylla | Aster macrophyllus L. | ASMA2 |
| Eurybia macrophylla | Aster macrophyllus L. var. apricensis Burgess | ASMAA |
| Eurybia macrophylla | Aster macrophyllus L. var. excelsior Burgess | ASMAE |
| Eurybia macrophylla | Aster macrophyllus L. var. ianthinus (Burgess) Fern. | ASMAI |
| Eurybia macrophylla | Aster macrophyllus L. var. pinguifolius Burgess | ASMAP2 |
| Eurybia macrophylla | Aster macrophyllus L. var. sejunctus Burgess | ASMAS |
| Eurybia macrophylla | Aster macrophyllus L. var. velutinus Burgess | ASMAV |
| Eurybia macrophylla | Aster multiformis Burgess | ASMU6 |
| Eurybia macrophylla | Aster nobilis Burgess | ASNO5 |
| Eurybia macrophylla | Aster riciniatus Burgess | ASRI5 |
| Eurybia macrophylla | Aster roscidus Burgess | ASRO3 |
| Eurybia macrophylla | Aster violaris Burgess | ASVI14 |
| Eurybia merita | Aster behringensis Gandog. | ASBE7 |
| Eurybia merita | Aster meritus A. Nels. | ASME6 |
| Eurybia merita | Aster richardsonii Spreng. | ASRI6 |
| Eurybia merita | Aster sibiricus L. ssp. richardsonii (Spreng.) A.& D. L?ve | ASSIR2 |
| Eurybia merita | Aster sibiricus L. var. giganteus (Hook.) Gray | ASSIG |
| Eurybia merita | Aster sibiricus L. var. meritus (A. Nels.) Raup | ASSIM |
| Eurybia merita | Eurybia sibirica (L.) Nesom var. gigantea (Hook.) Nesom | EUSIG |
| Eurybia mirabilis | Aster commixtus auct. non (Nees) Kuntze [misapplied] | ASCO21 |
| Eurybia mirabilis | Aster mirabilis Torr. & Gray | ASMI16 |
| Eurybia mirabilis | Eurybia commixta auct. non Nees [misapplied] | EUCO17 |
| Eurybia paludosa | Aster paludosus Ait. | ASPA2 |
| Eurybia pulchra | Aster glaucodes Blake ssp. pulcher Blake | ASGLP |
| Eurybia pulchra | Aster glaucodes Blake var. pulcher (Blake) Kearney & Peebles ex Welsh | ASGLP3 |
| Eurybia radula | Aster radula Ait. | ASRA8 |
| Eurybia radula | Aster radula Ait. var. strictus (Pursh) Gray | ASRAS |
| Eurybia radula | Aster strictus Pursh, non Poir. | ASST17 |
| Eurybia radulina | Aster eliasii A. Nels. | ASEL8 |
| Eurybia radulina | Aster radulinus Gray | ASRA |
| Eurybia radulina | Weberaster radulinus (Gray) A.& D. L?ve | WERA |
| Eurybia saxicastellii | Aster saxicastellii J. Campbell & M. Medley | ASSA9 |
| Eurybia schreberi | Aster chasei G.N. Jones | ASCH11 |
| Eurybia schreberi | Aster curvescens Burgess | ASCU12 |
| Eurybia schreberi | Aster glomeratus (Bernh. ex Nees) Burgess | ASGL11 |
| Eurybia schreberi | Aster schreberi Nees | ASSC2 |
| Eurybia schreberi | Eurybia glomerata Bernh. ex Nees | EUGL9 |
| Eurybia sibirica | Aster sibiricus L. | ASSI |
| Eurybia sibirica | Aster subintegerrimus (Trautv.) Ostenf. & Resvoll | ASSU27 |
| Eurybia spectabilis | Aster commixtus (Nees) Kuntze | ASCO26 |
| Eurybia spectabilis | Aster smallii Alexander | ASSM |
| Eurybia spectabilis | Aster spectabilis Ait. | ASSP11 |
| Eurybia spectabilis | Aster spectabilis Ait. var. cinerascens Blake | ASSPC |
| Eurybia spectabilis | Aster spectabilis Ait. var. suffultus Fern. | ASSPS2 |
| Eurybia spectabilis | Eurybia commixta Nees | EUCO20 |
| Eurybia spinulosa | Aster spinulosus Chapman | ASSP12 |
| Eurybia surculosa | Aster surculosus Michx. | ASSU9 |
| Eurybia wasatchensis | Aster glaucus Torr. & Gray var. wasatchensis M.E. Jones | ASGLW |
| Eurybia wasatchensis | Aster wasatchensis (M.E. Jones) Blake | ASWA |
| euryops | Euryops (Cass.) Cass. | EURYO |
| Euryops multifidus | Euryops subcarnosus DC. ssp. vulgaris B. Nord | EUSUV |
| Euthamia caroliniana | Euthamia microcephala Greene | EUMI11 |
| Euthamia caroliniana | Euthamia microphylla Greene | EUMI12 |
| Euthamia caroliniana | Euthamia minor (Michx.) Greene | EUMI6 |
| Euthamia caroliniana | Euthamia tenuifolia (Pursh) Nutt. | EUTE7 |
| Euthamia caroliniana | Euthamia tenuifolia (Pursh) Nutt. var. tenuifolia (Pursh) Nutt. [superfluous autonym] | EUTET |
| Euthamia caroliniana | Solidago caroliniana (L.) B.S.P. | SOCA13 |
| Euthamia caroliniana | Solidago microcephala (Greene) Bush | SOMI9 |
| Euthamia caroliniana | Solidago microphylla (Greene) Bush | SOMI7 |
| Euthamia caroliniana | Solidago minor (Michx.) Fern. | SOMI6 |
| Euthamia caroliniana | Solidago tenuifolia Pursh | SOTE5 |
| Euthamia galetorum | Euthamia graminifolia (L.) Nutt. var. galetorum (Greene) Friesner | EUGRG2 |
| Euthamia galetorum | Euthamia tenuifolia (Pursh) Nutt. var. pycnocephala (Fern.) C.& J. Taylor | EUTEP |
| Euthamia galetorum | Solidago galetorum (Greene) Friesner | SOGA3 |
| Euthamia galetorum | Solidago graminifolia (L.) Salisb. var. galetorum (Greene) House | SOGRG2 |
| Euthamia galetorum | Solidago tenuifolia Pursh var. pycnocephala Fern. | SOTEP |
| Euthamia graminifolia var. graminifolia | Chrysocoma graminifolia L. | CHGR24 |
| Euthamia graminifolia var. graminifolia | Euthamia floribunda Greene | EUFL5 |
| Euthamia graminifolia var. graminifolia | Euthamia graminifolia (L.) Nutt. var. major (Michx.) Moldenke | EUGRM |
| Euthamia graminifolia var. graminifolia | Euthamia graminifolia (L.) Nutt. var. nuttallii (Greene) W. Stone | EUGRN |
| Euthamia graminifolia var. graminifolia | Euthamia nuttallii Greene | EUNU4 |
| Euthamia graminifolia var. graminifolia | Solidago graminifolia (L.) Salisb. | SOGR8 |
| Euthamia graminifolia var. graminifolia | Solidago graminifolia (L.) Salisb. var. major (Michx.) Fern. | SOGRM3 |
| Euthamia graminifolia var. graminifolia | Solidago graminifolia (L.) Salisb. var. nuttallii (Greene) Fern. | SOGRN |
| Euthamia graminifolia var. graminifolia | Solidago graminifolia (L.) Salisb. var. polycephala (Fern.) Fern. | SOGRP |
| Euthamia graminifolia var. graminifolia | Solidago hirtella (Greene) Bush | SOHI6 |
| Euthamia graminifolia var. graminifolia | Solidago nuttallii (Greene) Bush | SONU3 |
| Euthamia graminifolia var. graminifolia | Solidago polycephala Fern. | SOPO3 |
| Euthamia graminifolia var. hirtipes | Euthamia hirtipes (Fern.) Sieren (pro hybr.) | EUHI4 |
| Euthamia graminifolia var. hirtipes | Solidago ?hirtipes Fern. | SOHI3 |
| Euthamia gymnospermoides | Euthamia camporum Greene | EUCA8 |
| Euthamia gymnospermoides | Euthamia chrysothamnoides Greene | EUCH8 |
| Euthamia gymnospermoides | Euthamia glutinosa Rydb. | EUGL12 |
| Euthamia gymnospermoides | Euthamia media Greene | EUME9 |
| Euthamia gymnospermoides | Euthamia pulverulenta Greene | EUPU5 |
| Euthamia gymnospermoides | Euthamia remota Greene | EURE9 |
| Euthamia gymnospermoides | Solidago camporum (Greene) A. Nels. | SOCA11 |
| Euthamia gymnospermoides | Solidago chrysothamnoides (Greene) Bush | SOCH2 |
| Euthamia gymnospermoides | Solidago graminifolia (L.) Salisb. var. gymnospermoides (Greene) Croat | SOGRG |
| Euthamia gymnospermoides | Solidago graminifolia (L.) Salisb. var. media (Greene) S.K. Harris | SOGRM2 |
| Euthamia gymnospermoides | Solidago gymnospermoides (Greene) Fern. | SOGY2 |
| Euthamia gymnospermoides | Solidago gymnospermoides (Greene) Fern. var. callosa S.K. Harris | SOGYC |
| Euthamia gymnospermoides | Solidago media (Greene) Bush | SOME2 |
| Euthamia gymnospermoides | Solidago moseleyi Fern. | SOMO2 |
| Euthamia gymnospermoides | Solidago perglabra Friesner | SOPE3 |
| Euthamia gymnospermoides | Solidago remota (Greene) Friesner | SORE2 |
| Euthamia gymnospermoides | Solidago texensis Friesner | SOTE7 |
| Euthamia leptocephala | Solidago leptocephala Torr. & Gray | SOLE7 |
| Euthamia occidentalis | Euthamia californica Gandog. | EUCA13 |
| Euthamia occidentalis | Euthamia linearifolia Gandog. | EULI3 |
| Euthamia occidentalis | Solidago occidentalis (Nutt.) Torr. & Gray | SOOC4 |
| Evax candida | Calymmandra candida Torr. & Gray | CACA61 |
| Evax candida | Diaperia candida (Torr. & Gray) Benth. | DICA17 |
| Evax candida | Filago candida (Torr. & Gray) Shinners | FICA5 |
| Evax prolifera | Diaperia prolifera (Nutt. ex DC.) Nutt. | DIPR2 |
| Evax prolifera | Filago nuttallii Shinners | FINU |
| Evax prolifera | Filago prolifera (Nutt. ex DC.) Britt., non Pomel | FIPR |
| Evax verna var. drummondii | Diaperia drummondii (Torr. & Gray) Benth. | DIDR |
| Evax verna var. drummondii | Evax multicaulis DC. var. drummondii (Torr. & Gray) Gray | EVMUD |
| Evax verna var. drummondii | Filaginopsis drummondii Torr. & Gray | FIDR2 |
| Evax verna var. drummondii | Filago verna (Raf.) Shinners var. drummondii (Torr. & Gray) Shinners | FIVED |
| Evax verna var. verna | Diaperia multicaulis (DC.) Nutt. | DIMU6 |
| Evax verna var. verna | Evax multicaulis DC. | EVMU |
| Evax verna var. verna | Filaginopsis multicaulis (DC.) Torr. & Gray | FIMU |
| Evax verna var. verna | Filago nivea Small | FINI |
| Evax verna var. verna | Filago verna (Raf.) Shinners | FIVE |
| Everglades squarestem | Melanthera angustifolia A. Rich. | MEAN2 |
| evergreen everlasting | Antennaria suffrutescens Greene | ANSU3 |
| everlasting | Gamochaeta Weddell | GAMOC |
| everlasting-flower | Helichrysum formosissimum Sch. Bip. | HEFO7 |
| Evermann's fleabane | Erigeron evermannii Rydb. | EREV |
| Evermann's pincushion | Chaenactis evermannii Greene | CHEV |
| Facelis retusa | Facelis apiculata Cass. | FAAP |
| fall dandelion | Leontodon autumnalis L. | LEAU2 |
| fall dandelion | Leontodon autumnalis L. ssp. autumnalis | LEAUA |
| fall dandelion | Leontodon autumnalis L. ssp. pratensis (Link) Arcang. | LEAUP2 |
| fall goldenrod | Solidago simulans Fern. | SOSI4 |
| fall sneezeweed | Helenium autumnale L. var. grandiflorum (Nutt.) Torr. & Gray | HEAUG |
| fall tansyaster | Machaeranthera asteroides (Torr.) Greene | MAAS2 |
| fall tansyaster | Machaeranthera asteroides (Torr.) Greene var. asteroides | MAASA2 |
| false agoseris | Agoseris glauca (Pursh) Raf. var. laciniata (D.C. Eat.) Smiley | AGGLL |
| false boneset | Brickellia eupatorioides (L.) Shinners | BREU |
| false boneset | Brickellia eupatorioides (L.) Shinners var. chlorolepis (Woot. & Standl.) B.L. Turner | BREUC2 |
| false boneset | Brickellia eupatorioides (L.) Shinners var. corymbulosa (Torr. & Gray) Shinners | BREUC |
| false boneset | Brickellia eupatorioides (L.) Shinners var. eupatorioides | BREUE |
| false boneset | Brickellia eupatorioides (L.) Shinners var. floridana (R.W. Long) B.L. Turner | BREUF |
| false boneset | Brickellia eupatorioides (L.) Shinners var. gracillima (Gray) B.L. Turner | BREUG |
| false boneset | Brickellia eupatorioides (L.) Shinners var. texana (Shinners) Shinners | BREUT |
| false broomweed | Haploesthes Gray | HAPLO |
| false broomweed | Haploesthes greggii Gray | HAGR4 |
| false chicken-sage | Vesicarpa potentilloides (Gray) Rydb. | VEPO6 |
| false clapdaisy | Pseudoclappia Rydb. | PSEUD3 |
| false cottonseed | Bombycilaena californica (Fisch. & C.A. Mey.) Holub | BOCA8 |
| false daisy | Eclipta prostrata (L.) L. | ECPR |
| false dogfennel | Dysodiopsis tagetoides (Torr. & Gray) Rydb. | DYTA2 |
| false fennel | Eupatorium leptophyllum DC. | EULE3 |
| false fleabane | Pulicaria Gaertn. | PULIC |
| false goldenaster | Heterotheca Cass. | HETER8 |
| false goldeneye | Heliomeris Nutt. | HELIO4 |
| false goldenweed | Oonopsis (Nutt.) Greene | OONOP |
| false Indian plaintain | Hasteola Raf. | HASTE2 |
| false Indian plaintain | Hasteola suaveolens (L.) Pojark. | HASU3 |
| false leopardbane | Doronicum L. | DORON |
| false mayweed | Tripleurospermum maritima (L.) W.D.J. Koch | TRMA17 |
| false mayweed | Tripleurospermum maritima (L.) W.D.J. Koch ssp. maritima | TRMAM |
| false mayweed | Tripleurospermum maritima (L.) W.D.J. Koch ssp. phaeocephala (Rupr.) Hamet-Ahti | TRMAP |
| false neststraw | Ancistrocarphus filagineus Gray | ANFI3 |
| false oxtongue | Blumea DC. | BLUME |
| false rosinweed | Osmadenia tenella Nutt. | OSTE |
| false silverback | Rainiera stricta (Greene) Greene | RAST |
| false sowthistle | Reichardia tingitana (L.) Roth | RETI |
| false sunflower | Phoebanthus Blake | PHOEB2 |
| false threadleaf | Schkuhria Roth | SCHKU |
| false yellowhead | Dittrichia viscosa (L.) W. Greuter | DIVI6 |
| falsegold groundsel | Packera pseudaurea (Rydb.) W.A. Weber & A. L?ve | PAPS5 |
| falsegold groundsel | Packera pseudaurea (Rydb.) W.A. Weber & A. L?ve var. flavula (Greene) D.K. Trock & T.M. Barkl. | PAPSF |
| falsegold groundsel | Packera pseudaurea (Rydb.) W.A. Weber & A. L?ve var. pseudaurea | PAPSP2 |
| falsegold groundsel | Packera pseudaurea (Rydb.) W.A. Weber & A. L?ve var. semicordata (Mackenzie & Bush) D.K. Trock & T.M. Barkl. | PAPSS |
| fanleaf fleabane | Erigeron flabellifolius Rydb. | ERFL8 |
| father-and-child plant | Euchiton japonicus (Thunb.) A. Anderb. | EUJA6 |
| feather-head knapweed | Centaurea trichocephala Bieb. ex Willd. | CETR12 |
| featherleaf desertpeony | Acourtia runcinata (Lag. ex D. Don) B.L. Turner | ACRU3 |
| featherleaf fleabane | Erigeron pinnatisectus (Gray) A. Nels. | ERPI6 |
| featherweed | Gamochaeta ustulata (Nutt.) Nesom | GAUS |
| Feay's palafox | Palafoxia feayi Gray | PAFE |
| Felicia amelloides | Aster rotundifolius Thunb. | ASRO9 |
| Felicia fruticosa | Aster fruticosus L. | ASFR9 |
| Felicia uliginosa | Aster uliginosus J. M. Wood & M. S. Evans | ASUL2 |
| Fendler's aster | Symphyotrichum fendleri (Gray) Nesom | SYFE |
| Fendler's brickellbush | Brickelliastrum fendleri (Gray) King & H.E. Robins. | BRFE2 |
| Fendler's desertdandelion | Malacothrix fendleri Gray | MAFE |
| Fendler's ragwort | Packera fendleri (Gray) W.A. Weber & A. L?ve | PAFE4 |
| Fendler's Townsend daisy | Townsendia fendleri Gray | TOFE |
| fernleaf yarrow | Achillea filipendulina Lam. | ACFI |
| Ferris's goldfields | Lasthenia ferrisiae Ornduff | LAFE |
| fetid marigold | Dyssodia papposa (Vent.) A.S. Hitchc. | DYPA |
| feverfew | Parthenium L. | PARTH2 |
| feverfew | Tanacetum parthenium (L.) Schultz-Bip. | TAPA6 |
| fewflower beggarticks | Bidens leptocephala Sherff | BILE |
| fewflower blazing star | Liatris pauciflora Pursh | LIPA8 |
| fewleaf sunflower | Helianthus occidentalis Riddell | HEOC2 |
| fewleaf sunflower | Helianthus occidentalis Riddell ssp. occidentalis | HEOCO |
| fewleaf sunflower | Helianthus occidentalis Riddell ssp. plantagineus (Torr. & Gray) Shinners | HEOCP |
| fewleaf thistle | Cirsium remotifolium (Hook.) DC. | CIRE |
| fiddleleaf hawksbeard | Crepis runcinata (James) Torr. & Gray | CRRU3 |
| fiddleleaf hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. glauca (Nutt.) Babcock & Stebbins | CRRUG |
| fiddleleaf hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. hispidulosa (T.J. Howell ex Rydb.) Babcock & Stebbins | CRRUH2 |
| fiddleleaf hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. imbricata Babcock & Stebbins | CRRUI |
| fiddleleaf hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. runcinata | CRRUR |
| field burrweed | Soliva sessilis Ruiz & Pav?n | SOSE2 |
| field cottonrose | Logfia arvensis (L.) Holub | LOAR5 |
| field goldeneye | Viguiera phenax Blake | VIPH |
| field marigold | Calendula arvensis L. | CAAR |
| field pussytoes | Antennaria neglecta Greene | ANNE |
| field sagewort | Artemisia campestris L. | ARCA12 |
| field sagewort | Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements | ARCAB2 |
| field sagewort | Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements var. borealis (Pallas) M.E. Peck | ARCAB4 |
| field sagewort | Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements var. petiolata Welsh | ARCAP4 |
| field sagewort | Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements var. scouleriana (Hook.) Cronq. | ARCAS5 |
| field sagewort | Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements var. wormskioldii (Bess. ex Hook.) Cronq. | ARCAW |
| field sagewort | Artemisia campestris L. ssp. campestris L. [excluded] | ARCAC13 |
| field sagewort | Artemisia campestris L. ssp. caudata (Michx.) Hall & Clements | ARCAC |
| field sowthistle | Sonchus arvensis L. | SOAR2 |
| field sowthistle | Sonchus arvensis L. ssp. arvensis | SOARA2 |
| field thistle | Cirsium discolor (Muhl. ex Willd.) Spreng. | CIDI |
| Filago pyramidata | Filago germanica Huds. | FIGE4 |
| Filago pyramidata | Filago pyramidata L. var. pyramidata L. [superfluous autonym] | FIPYP2 |
| Filago vulgaris | Filago germanica L. 1763, non Huds. 1762 | FIGE2 |
| Filago vulgaris | Gifola germanica Dumort. | GIGE2 |
| Filago vulgaris | Gnaphalium germanicum Scopoli | GNGE |
| Filifolium sibiricum | Artemisia sibirica (L.) Maxim. | ARSI8 |
| finehair hymenopappus | Hymenopappus filifolius Hook. var. tomentosus (Rydb.) B.L. Turner | HYFIT |
| fineleaf fournerved daisy | Tetraneuris linearifolia (Hook.) Greene | TELI3 |
| fineleaf fournerved daisy | Tetraneuris linearifolia (Hook.) Greene var. arenicola Bierner | TELIA |
| fineleaf fournerved daisy | Tetraneuris linearifolia (Hook.) Greene var. linearifolia | TELIL |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. | HYFI |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. cinereus (Rydb.) I.M. Johnston | HYFIC |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. eriopodus (A. Nels.) B.L. Turner | HYFIE |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. filifolius | HYFIF |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. idahoensis B.L. Turner | HYFII |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. luteus (Nutt.) B.L. Turner | HYFIL2 |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. megacephalus B.L. Turner | HYFIM |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. nanus (Rydb.) B.L. Turner | HYFIN |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. parvulus (Greene) B.L. Turner | HYFIP2 |
| fineleaf hymenopappus | Hymenopappus filifolius Hook. var. pauciflorus (I.M. Johnston) B.L. Turner | HYFIP |
| firewheel | Gaillardia pulchella Foug. | GAPU |
| firewheel | Gaillardia pulchella Foug. var. australis Turner & M.A. Whalen | GAPUA |
| firewheel | Gaillardia pulchella Foug. var. picta (Sweet) Gray | GAPUP |
| firewheel | Gaillardia pulchella Foug. var. pulchella | GAPUP2 |
| Fish Creek fleabane | Erigeron piscaticus Nesom | ERPI9 |
| Fish Lake thistle | Cirsium clavatum (M.E. Jones) Petrak | CICL |
| Fitch's tarweed | Hemizonia fitchii Gray | HEFI |
| fitchia | Fitchia Hook. f. | FITCH |
| fivebract cinchweed | Pectis filipes Harvey & Gray | PEFI |
| fivebract cinchweed | Pectis filipes Harvey & Gray var. subnuda Fern. | PEFIS |
| fivefinger chickensage | Vesicarpa potentilloides (Gray) Rydb. var. nitrophilum (Cronq.) Kartesz | VEPON |
| fivefinger chickensage | Vesicarpa potentilloides (Gray) Rydb. var. potentilloides | VEPOP |
| fiveflower rockdaisy | Perityle quinqueflora (Steyermark) Shinners | PEQU |
| fiveneedle pricklyleaf | Thymophylla pentachaeta (DC.) Small | THPE4 |
| fiveneedle pricklyleaf | Thymophylla pentachaeta (DC.) Small var. belenidium (DC.) Strother | THPEB |
| fiveneedle pricklyleaf | Thymophylla pentachaeta (DC.) Small var. pentachaeta | THPEP |
| fiveneedle pricklyleaf | Thymophylla pentachaeta (DC.) Small var. puberula (Rydb.) Strother | THPEP2 |
| fivenerve helianthella | Helianthella quinquenervis (Hook.) Gray | HEQU2 |
| Flagstaff ragwort | Senecio actinella Greene | SEAC2 |
| flame ragwort | Packera greenei (Gray) W.A. Weber & A. L?ve | PAGR9 |
| flat-top goldentop | Euthamia graminifolia (L.) Nutt. | EUGR5 |
| flat-top goldentop | Euthamia graminifolia (L.) Nutt. var. graminifolia | EUGRG |
| flat-top goldentop | Euthamia graminifolia (L.) Nutt. var. hirtipes (Fern.) C.& J. Taylor | EUGRH |
| flat-top pussytoes | Antennaria corymbosa E. Nels. | ANCO |
| flat-top whiteweed | Ageratum corymbosum Zuccagni ex Pers. | AGCO2 |
| flatspine burr ragweed | Ambrosia acanthicarpa Hook. | AMAC2 |
| Flaveria brownii | Flaveria oppositifolia auct. non (DC.) Rydb. [misapplied] | FLOP2 |
| Flaveria linearis | Flaveria ?latifolia (J.R. Johnston) Long & Rhamstine | FLLA |
| Flaveria trinervia | Oedera trinervia Spreng. | OETR3 |
| flaxleaf whitetop aster | Ionactis linariifolius (L.) Greene | IOLI2 |
| fleabane | Erigeron L. | ERIGE2 |
| fleabane | Erigeron oxyodontus Lunell | EROX4 |
| Fleischmannia incarnata | Eupatorium incarnatum Walt. | EUIN |
| Fleischmannia microstemon | Eupatorium microstemon Cass. | EUMI8 |
| Fleischmannia pycnocephala | Eupatorium pycnocephalum Less. | EUPY2 |
| Fleischmannia sonorae | Eupatorium sonorae Gray | EUSO2 |
| fleshcolor pincushion | Chaenactis xantiana Gray | CHXA |
| fleshy clapdaisy | Clappia suaedifolia Gray | CLSU |
| fleshy dandelion | Taraxacum carneocoloratum A. Nels. | TACA6 |
| Flett's fleabane | Erigeron flettii G.N. Jones | ERFL2 |
| Flett's ragwort | Packera flettii (Wieg.) W.A. Weber & A. L?ve | PAFL15 |
| Flodman's thistle | Cirsium flodmanii (Rydb.) Arthur | CIFL |
| florestina | Florestina Cass. | FLORE |
| Florestina tripteris | Palafoxia tripteris (DC.) Shinners | PATR9 |
| Florestina tripteris | Palafoxia tripteris (DC.) Shinners var. brevis Shinners | PATRB |
| Florida blazing star | Liatris ohlingerae (Blake) B.L. Robins. | LIOH |
| Florida cacalia | Arnoglossum floridanum (Gray) H.E. Robins. | ARFL2 |
| Florida cinchweed | Pectis linearifolia Urban | PELI8 |
| Florida false sunflower | Phoebanthus grandiflorus (Torr. & Gray) Blake | PHGR12 |
| Florida goldenaster | Chrysopsis floridana Small | CHFL8 |
| Florida greeneyes | Berlandiera subacaulis (Nutt.) Nutt. | BESU |
| Florida hartwrightia | Hartwrightia floridana Gray ex S. Wats. | HAFL4 |
| Florida ironweed | Vernonia blodgettii Small | VEBL3 |
| Florida Keys hempvine | Mikania cordifolia (L. f.) Willd. | MICO9 |
| Florida Keys thoroughwort | Koanophyllon villosum (Sw.) King & H.E. Robins. | KOVI2 |
| Florida sunflower | Helianthus floridanus Gray ex Chapman | HEFL2 |
| Florida tasselflower | Emilia fosbergii D.H. Nicols. | EMFO |
| Florida thoroughwort | Eupatorium anomalum Nash | EUAN4 |
| Florida tickseed | Coreopsis floridana E.B. Sm. | COFL6 |
| Florida water aster | Symphyotrichum fontinale (Alexander) Nesom | SYFO3 |
| Florida yellowtops | Flaveria floridana J.R. Johnston | FLFL |
| florist's daisy | Chrysanthemum ?morifolium Ramat. (pro sp.) | CHMO14 |
| Flourensia pringlei | Helianthella pringlei Gray | HEPR6 |
| fly marshelder | Iva cheiranthifolia Kunth | IVCH |
| Flyr's nemesis | Brickellia cordifolia Ell. | BRCO8 |
| Flyriella parryi | Brickellia shineri M.E. Jones ex Flyr | BRSH |
| Flyriella parryi | Eupatorium parryi Gray | EUPA11 |
| foothill arnica | Arnica fulgens Pursh | ARFU3 |
| foothill fleabane | Erigeron consimilis Cronq. | ERCO15 |
| foothill sunburst | Pseudobahia heermannii (Dur.) Rydb. | PSHE |
| forest dubautia | Dubautia knudsenii Hbd. | DUKN |
| forest dubautia | Dubautia knudsenii Hbd. ssp. filiformis G.D. Carr | DUKNF |
| forest dubautia | Dubautia knudsenii Hbd. ssp. knudsenii | DUKNK |
| forest dubautia | Dubautia knudsenii Hbd. ssp. nagatae (St. John) G.D. Carr | DUKNN |
| forest tetramolopium | Tetramolopium consanguineum (Gray) Hbd. | TECO5 |
| forest tetramolopium | Tetramolopium consanguineum (Gray) Hbd. ssp. consanguineum | TECOC |
| forest tetramolopium | Tetramolopium consanguineum (Gray) Hbd. ssp. leptophyllum (Sherff) Lowrey | TECOL |
| forest tetramolopium | Tetramolopium consanguineum (Gray) Hbd. ssp. leptophyllum (Sherff) Lowrey var. leptophyllum Sherff | TECOL2 |
| forked aster | Eurybia furcata (Burgess) Nesom | EUFU3 |
| forked hareleaf | Lagophylla dichotoma Benth. | LADI |
| forked wormwood | Artemisia furcata Bieb. | ARFU4 |
| forked wormwood | Artemisia furcata Bieb. var. furcata | ARFUF |
| forked wormwood | Artemisia furcata Bieb. var. heterophylla (Bess.) Hult | ARFUH |
| Foster's rockdaisy | Perityle fosteri A. Powell | PEFO6 |
| fountain thistle | Cirsium fontinale (Greene) Jepson | CIFO2 |
| fountain thistle | Cirsium fontinale (Greene) Jepson var. fontinale | CIFOF |
| four-nerve daisy | Tetraneuris Greene | TETRA17 |
| fourpart horsebrush | Tetradymia tetrameres (Blake) Strother | TETE4 |
| fox-tail blackroot | Pterocaulon alopecuroidies (Lam.) DC. | PTAL4 |
| fragile hempvine | Mikania fragilis Urban | MIFR4 |
| fragile pygmydaisy | Pentachaeta fragilis Brandeg. | PEFR6 |
| fragrant hempvine | Mikania odoratissima Urban | MIOD |
| fragrant snakeroot | Ageratina herbacea (Gray) King & H.E. Robins. | AGHE5 |
| Franciscan erigeron | Erigeron foliosus Nutt. var. franciscensis Nesom | ERFOF3 |
| Franciscan thistle | Cirsium andrewsii (Gray) Jepson | CIAN2 |
| Fremont's chaffbush | Amphipappus fremontii Torr. & Gray ex Gray | AMFR2 |
| Fremont's chaffbush | Amphipappus fremontii Torr. & Gray ex Gray ssp. fremontii | AMFRF |
| Fremont's chaffbush | Amphipappus fremontii Torr. & Gray ex Gray ssp. spinosus (A. Nels.) Keck | AMFRS2 |
| Fremont's goldfields | Lasthenia fremontii (Torr. ex Gray) Greene | LAFR4 |
| Fremont's tidytips | Layia fremontii (Torr. & Gray) Gray | LAFR2 |
| Fremont's western rosinweed | Calycadenia fremontii Gray | CAFR |
| Fremont's-gold | Syntrichopappus Gray | SYNTR |
| French marigold | Tagetes patula L. | TAPA |
| Fries's pussytoes | Antennaria friesiana (Trautv.) Ekman | ANFR |
| Fries's pussytoes | Antennaria friesiana (Trautv.) Ekman ssp. alaskana (Malte) Hult | ANFRA |
| Fries's pussytoes | Antennaria friesiana (Trautv.) Ekman ssp. friesiana | ANFRF |
| Fries's pussytoes | Antennaria friesiana (Trautv.) Ekman ssp. neoalaskana (Porsild) Bayer & Stebbins | ANFRN |
| fringed rockdaisy | Perityle ciliata (L.H. Dewey) Rydb. | PECI8 |
| fringed sneezeweed | Helenium drummondii H. Rock | HEDR2 |
| fringed thistle | Cirsium centaureae (Rydb.) K. Schum. | CICE |
| fringeleaf tickseed | Coreopsis integrifolia Poir. | COIN4 |
| fullstem | Chamaechaenactis scaposa (Eastw.) Rydb. | CHSC |
| fullstem | Chamaechaenactis scaposa (Eastw.) Rydb. var. parva Preece & Turner | CHSCP |
| fullstem | Chamaechaenactis scaposa (Eastw.) Rydb. var. scaposa | CHSCS |
| fuscate groundsel | Tephroseris lindstroemii (Ostenf.) A.& D. L?ve | TELI6 |
| Gaillardia aestivalis var. aestivalis | Gaillardia chrysantha Small | GACH2 |
| Gaillardia aestivalis var. aestivalis | Gaillardia fastigiata Greene | GAFA4 |
| Gaillardia aestivalis var. aestivalis | Gaillardia lanceolata Michx. | GALA8 |
| Gaillardia aestivalis var. aestivalis | Gaillardia lanceolata Michx. var. fastigiata (Greene) Waterfall | GALAF |
| Gaillardia aestivalis var. aestivalis | Gaillardia rigida Small ex Rydb. | GARI |
| Gaillardia aestivalis var. aestivalis | Gaillardia serotina (Walt.) H. Rock | GASE4 |
| Gaillardia aestivalis var. flavovirens | Gaillardia lanceolata Michx. var. flavovirens C. Mohr | GALAF2 |
| Gaillardia aestivalis var. flavovirens | Gaillardia lutea Greene | GALU2 |
| Gaillardia aestivalis var. winkleri | Gaillardia lutea Greene var. winkleri Cory | GALUW |
| Gaillardia arizonica | Gaillardia arizonica Gray var. arizonica Gray [superfluous autonym] | GAARA |
| Gaillardia arizonica | Gaillardia arizonica Gray var. pringlei (Rydb.) Blake | GAARP2 |
| Gaillardia arizonica | Gaillardia pringlei Rydb. | GAPR4 |
| Gaillardia coahuilensis | Gaillardia mexicana auct. non Gray [misapplied] | GAME2 |
| Gaillardia pinnatifida var. pinnatifida | Gaillardia gracilis A. Nels. | GAGR6 |
| Gaillardia pinnatifida var. pinnatifida | Gaillardia mearnsii Rydb. | GAME |
| Gaillardia pulchella var. picta | Gaillardia picta Sweet | GAPI4 |
| Gaillardia pulchella var. pulchella | Gaillardia drummondii (Hook.) DC. | GADR2 |
| Gaillardia pulchella var. pulchella | Gaillardia neomexicana A. Nels. | GANE3 |
| Gaillardia pulchella var. pulchella | Gaillardia villosa Rydb. | GAVI4 |
| Gaillardia suavis | Agassizia suavis Gray & Engelm. | AGSU2 |
| Gaillardia suavis | Gaillardia trinervata Small | GATR10 |
| Galatella punctata | Aster punctatus Waldst. & Kit. | ASPU15 |
| Galinsoga parviflora | Galinsoga parviflora Cav. var. parviflora Cav. [superfluous autonym] | GAPAP4 |
| Galinsoga parviflora | Galinsoga parviflora Cav. var. semicalva Gray | GAPAS |
| Galinsoga parviflora | Galinsoga semicalva (Gray) St. John & White | GASE5 |
| Galinsoga parviflora | Galinsoga semicalva (Gray) St. John & White var. percalva Blake | GASEP2 |
| Galinsoga quadriradiata | Galinsoga aristulata Bickn. | GAAR7 |
| Galinsoga quadriradiata | Galinsoga bicolorata St. John & White | GABI4 |
| Galinsoga quadriradiata | Galinsoga caracasana (DC.) Schultz-Bip. | GACA10 |
| Galinsoga quadriradiata | Galinsoga ciliata (Raf.) Blake | GACI4 |
| Galinsoga urticifolia | Galinsoga ciliata auct. non (Raf.) Blake [misapplied] | GACI5 |
| gall of the earth | Prenanthes trifoliolata (Cass.) Fern. | PRTR |
| gallant soldier | Galinsoga parviflora Cav. | GAPA2 |
| gallant soldier | Galinsoga Ruiz & Pav?n | GALIN |
| Gamochaeta americana | Gamochaeta spicata (Lam.) Cabrera | GASP8 |
| Gamochaeta americana | Gnaphalium americanum P. Mill. | GNAM |
| Gamochaeta americana | Gnaphalium purpureum L. var. americanum (P. Mill.) Klatt | GNPUA |
| Gamochaeta americana | Gnaphalium spicatum Lam. | GNSP |
| Gamochaeta falcata | Gamochaeta calviceps (Fern.) Cabrera | GACA6 |
| Gamochaeta falcata | Gnaphalium calviceps Fern. | GNCA3 |
| Gamochaeta falcata | Gnaphalium falcatum Lam. | GNFA2 |
| Gamochaeta falcata | Gnaphalium purpureum L. var. falcatum (Lam.) Torr. & Gray | GNPUF |
| Gamochaeta pensylvanica | Gnaphalium pensylvanicum Willd. | GNPE3 |
| Gamochaeta pensylvanica | Gnaphalium peregrinum Fern. | GNPE2 |
| Gamochaeta pensylvanica | Gnaphalium purpureum L. var. spathulatum (Lam.) Baker | GNPUS |
| Gamochaeta pensylvanica | Gnaphalium spathulatum Lam. | GNSP2 |
| Gamochaeta purpurea | Gnaphalium purpureum L. | GNPU2 |
| Gamochaeta sphacilata | Gnaphalium sphacilatum Kunth | GNSP3 |
| Gamochaeta ustulata | Gnaphalium purpureum L. var. ustulatum (Nutt.) Boivin | GNPUU |
| Gamochaeta ustulata | Gnaphalium ustulatum Nutt. | GNUS |
| Gander's ragwort | Packera ganderi (T.M. Barkl. & Beauchamp) W.A. Weber & A. L?ve | PAGA5 |
| Garber's blazing star | Liatris garberi Gray | LIGA |
| garberia | Garberia Gray | GARBE |
| garberia | Garberia heterophylla (Bartr.) Merr. & F. Harper | GAHE4 |
| Garberia heterophylla | Garberia fruticosa (Nutt.) Gray | GAFR4 |
| garden cornflower | Centaurea cyanus L. | CECY2 |
| garden cosmos | Cosmos bipinnatus Cav. | COBI2 |
| garden lettuce | Lactuca sativa L. | LASA3 |
| Garrett's fleabane | Erigeron garrettii A. Nels. | ERGA3 |
| Gattinger's goldenrod | Solidago gattingeri Chapman | SOGA |
| Gattinger's rosinweed | Silphium integrifolium Michx. var. gattingeri Perry | SIING |
| gazania | Gazania Gaertn. | GAZAN |
| Gazania linearis | Gazania longiscapa DC. | GALO2 |
| Gazania linearis | Gorteria linearis Thunb. | GOLI2 |
| Gazania rigens | Gazania splendens Lem. | GASP14 |
| Geiser's fleabane | Erigeron geiseri Shinners | ERGE |
| Georgia aster | Symphyotrichum georgianum (Alexander) Nesom | SYGE |
| Georgia Indian plaintain | Arnoglossum sulcatum (Fern.) H.E. Robins. | ARSU5 |
| Georgia ironweed | Vernonia pulchella Small | VEPU2 |
| Georgia tickseed | Coreopsis nudata Nutt. | CONU5 |
| Geraea canescens | Geraea canescens Torr. & Gray var. canescens Torr. & Gray [superfluous autonym] | GECAC2 |
| Geraea canescens | Geraea canescens Torr. & Gray var. paniculata (Gray) Blake | GECAP |
| geraniumleaf thoroughwort | Chromolaena geraniifolia (Urban) King & H.E. Robins. | CHGE |
| German chamomile | Matricaria recutita L. | MARE6 |
| Geyer's aster | Symphyotrichum laeve (L.) A.& D. L?ve var. geyeri (Gray) Nesom | SYLAG |
| giant coreopsis | Coreopsis gigantea (Kellogg) Hall | COGI |
| giant goldenrod | Solidago gigantea Ait. | SOGI |
| giant ironweed | Vernonia gigantea (Walt.) Trel. | VEGI |
| giant ironweed | Vernonia gigantea (Walt.) Trel. ssp. gigantea | VEGIG |
| giant ironweed | Vernonia gigantea (Walt.) Trel. ssp. ovalifolia (Torr. & Gray) Urbatsch | VEGIO |
| giant mountain aster | Canadanthus modestus (Lindl.) Nesom | CAMO32 |
| giant rockgoldenrod | Petradoria pumila (Nutt.) Greene ssp. graminea (Woot. & Standl.) L.C. Anders. | PEPUG |
| giant Spanish needle | Palafoxia arida B.L. Turner & Morris var. gigantea (M.E. Jones) B.L. Turner & Morris | PAARG |
| giant sumpweed | Cyclachaena xanthifolia (Nutt.) Fresen. | CYXA |
| giant sunflower | Helianthus giganteus L. | HEGI |
| giant yarrow | Achillea millefolium L. var. gigantea (Pollard) Nobs | ACMIG |
| giantdaisy | Leucanthemella serotina (L.) Tzvelev | LESE6 |
| Gila rockdaisy | Perityle gilensis (M.E. Jones) J.F. Macbr. | PEGI2 |
| Gila rockdaisy | Perityle gilensis (M.E. Jones) J.F. Macbr. var. gilensis | PEGIG |
| Gila thistle | Cirsium gilense Woot. & Standl. | CIGI |
| glandular blazing star | Liatris glandulosa Nesom & R. O'Kennon | LIGL5 |
| glandular Cape marigold | Dimorphotheca sinuata DC. | DISI4 |
| glandular hareleaf | Lagophylla glandulosa Gray | LAGL |
| Glass Mountain rockdaisy | Perityle vitreomontana Warnock | PEVI10 |
| Glebionis carinatum | Chrysanthemum carinatum Schousboe | CHCA9 |
| Glebionis coronarium | Chrysanthemum coronarium L. | CHCO7 |
| Glebionis coronarium | Chrysanthemum coronarium L. var. coronarium L. [superfluous autonym] | CHCOC |
| Glebionis coronarium | Chrysanthemum coronarium L. var. spatiosum L. H. Bailey | CHCOS |
| Glebionis coronarium | Chrysanthemum spatiosum (L. H. Bailey) L. H. Bailey | CHSP9 |
| Glebionis segetum | Chrysanthemum segetum L. | CHSE |
| globe artichoke | Cynara scolymus L. | CYSC2 |
| globethistle | Echinops L. | ECHIN8 |
| glowweed | Hesperodoria Greene | HESPE9 |
| glowwort | Sartwellia Gray | SARTW |
| glyptopleura | Glyptopleura D.C. Eat. | GLYPT |
| Gmelin's wormwood | Artemisia gmelinii Webb ex Stechmann | ARGM |
| Gnaphalium exilifolium | Gnaphalium grayi A. Nels. & J.F. Macbr. | GNGR |
| Gnaphalium exilifolium | Gnaphalium uliginosum auct. non L. [misapplied] | GNUL2 |
| Gnaphalium palustre | Filaginella palustris (Nutt.) Holub | FIPA3 |
| Gnaphalium polycaulon | Gnaphalium indicum auct. non L. [misapplied] | GNIN |
| Gnaphalium uliginosum | Filaginella uliginosa (L.) Opiz | FIUL2 |
| goatsbeard | Tragopogon L. | TRAGO |
| gochnatia | Gochnatia Kunth | GOCHN |
| Godfrey's blazing star | Liatris provincialis Godfrey | LIPR3 |
| Godfrey's goldenaster | Chrysopsis godfreyi Semple | CHGO2 |
| Godfrey's thoroughwort | Eupatorium godfreyanum Cronq. | EUGO4 |
| golden chaetopappa | Pentachaeta aurea Nutt. | PEAU3 |
| golden chamomile | Anthemis tinctoria L. | ANTI |
| golden crownbeard | Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray | VEEN |
| golden crownbeard | Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray ssp. encelioides | VEENE3 |
| golden crownbeard | Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray ssp. exauriculata (Robins. & Greenm.) J.R. Coleman | VEENE2 |
| golden madia | Madia radiata Kellogg | MARA |
| golden ragwort | Packera aurea (L.) A.& D. L?ve | PAAU3 |
| golden tickseed | Coreopsis tinctoria Nutt. | COTI3 |
| golden tickseed | Coreopsis tinctoria Nutt. var. similis (Boynt.) H.M. Parker | COTIS |
| golden tickseed | Coreopsis tinctoria Nutt. var. tinctoria | COTIT |
| golden-yarrow | Eriophyllum confertiflorum (DC.) Gray | ERCO25 |
| golden-yarrow | Eriophyllum confertiflorum (DC.) Gray var. confertiflorum | ERCOC12 |
| golden-yarrow | Eriophyllum confertiflorum (DC.) Gray var. tanacetiflorum (Greene) Jepson | ERCOT |
| goldenaster | Chrysopsis (Nutt.) Ell. | CHRYS7 |
| goldenbush | Ericameria Nutt. | ERICA2 |
| goldenbush | Isocoma Nutt. | ISOCO |
| goldeneye | Viguiera Kunth | VIGUI |
| goldenfleece | Ericameria arborescens (Gray) Greene | ERAR27 |
| goldenhead | Acamptopappus (Gray) Gray | ACAMP |
| goldenmane tickseed | Coreopsis basalis (A. Dietr.) Blake | COBA2 |
| goldenrod | Oligoneuron Small | OLIGO3 |
| goldenrod | Oreochrysum Rydb. | OREOC |
| goldenrod | Solidago L. | SOLID |
| goldenthistle | Scolymus L. | SCOLY |
| goldentop | Euthamia Nutt. ex Cass. | EUTHA |
| goldenwave tickseed | Coreopsis intermedia Sherff | COIN2 |
| goldenweed | Pyrrocoma Hook. | PYRRO |
| goldfields | Lasthenia Cass. | LASTH |
| goldilocks | Aster linosyris (L.) Bernh. | ASLI15 |
| Goodding's tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. gooddingii (A. Nels.) B.L. Turner & R.L. Hartman | MAPIG |
| Goodding's tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. gooddingii (A. Nels.) B.L. Turner & R.L. Hartman var. gooddingii | MAPIG2 |
| Goodding's tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. gooddingii (A. Nels.) B.L. Turner & R.L. Hartman var. paradoxa B.L. Turner & R.L. Hartman | MAPIP3 |
| gorge fleabane | Erigeron oreganus Gray | EROR2 |
| Gorman's aster | Eucephalus gormanii Piper | EUGO5 |
| Graham's thistle | Cirsium grahamii Gray | CIGR2 |
| Grand Canyon glowweed | Hesperodoria scopulorum (M.E. Jones) Greene | HESC15 |
| Grand Canyon rockdaisy | Perityle congesta (M.E. Jones) Shinners | PECO18 |
| granite serpentweed | Tonestus graniticus (Tiehm & L. Shultz) Nesom & D. Morgan | TOGR2 |
| grassland beggarticks | Bidens micrantha Gaud. | BIMI2 |
| grassland beggarticks | Bidens micrantha Gaud. ssp. ctenophylla (Sherff) Nagata & Ganders | BIMIC2 |
| grassland beggarticks | Bidens micrantha Gaud. ssp. micrantha | BIMIM |
| grassland moonshine | Deinandra increscens (Hall ex Keck) B.G. Baldwin | DEIN15 |
| grassland nehe | Lipochaeta subcordata Gray | LISU6 |
| grassland silverpuffs | Microseris heterocarpa (Nutt.) Chambers | MIHE |
| grassland tarweed | Deinandra increscens (Hall ex Keck) B.G. Baldwin ssp. foliosa (Hoover) B.G. Baldwin | DEINF2 |
| grassland tarweed | Deinandra increscens (Hall ex Keck) B.G. Baldwin ssp. increscens | DEINI8 |
| grassland tarweed | Deinandra increscens (Hall ex Keck) B.G. Baldwin ssp. villosa (Tanowitz) B.G. Baldwin | DEINV3 |
| grassleaf Barbara's buttons | Marshallia graminifolia (Walt.) Small | MAGR6 |
| grassleaf Barbara's buttons | Marshallia graminifolia (Walt.) Small var. cynanthera (Ell.) Beadle & F.E. Boynt. | MAGRC2 |
| grassleaf Barbara's buttons | Marshallia graminifolia (Walt.) Small var. graminifolia | MAGRG3 |
| grassleaf coneflower | Rudbeckia graminifolia (Torr. & Gray) C.L. Boynt. & Beadle | RUGR7 |
| grassleaf goldaster | Pityopsis oligantha (Chapman ex Torr. & Gray) Small | PIOL |
| grassleaf lettuce | Lactuca graminifolia Michx. | LAGR |
| grassleaf lettuce | Lactuca graminifolia Michx. var. arizonica McVaugh | LAGRA |
| grassleaf lettuce | Lactuca graminifolia Michx. var. graminifolia | LAGRG |
| grasslike mock goldenweed | Stenotus armerioides Nutt. var. gramineus (Welsh & F.J. Sm.) Kartesz & Gandhi | STARG |
| grassy rockgoldenrod | Petradoria pumila (Nutt.) Greene | PEPU7 |
| grassy rockgoldenrod | Petradoria pumila (Nutt.) Greene ssp. pumila | PEPUP |
| grassy tarweed | Madia gracilis (Sm.) Keck & J. Clausen ex Applegate | MAGR3 |
| gravelbar brickellbush | Brickellia cylindracea Gray & Engelm. | BRCY |
| gravelweed | Verbesina helianthoides Michx. | VEHE |
| gray aster | Eurybia glauca (Nutt.) Nesom | EUGL19 |
| gray chickensage | Sphaeromeria cana (D.C. Eat.) Heller | SPCA7 |
| gray everlasting | Gamochaeta coarctata (Willd.) Kergu?len | GACO11 |
| gray goldenrod | Solidago nemoralis Ait. | SONE |
| gray goldenrod | Solidago nemoralis Ait. var. longipetiolata (Mackenzie & Bush) Palmer & Steyermark | SONEL |
| gray goldenrod | Solidago nemoralis Ait. var. nemoralis | SONEN |
| gray rockdaisy | Perityle cinerea (Gray) A. Powell | PECI9 |
| Gray's aster | Symphyotrichum subspicatum (Nees) Nesom var. grayi (Suksdorf) Nesom | SYSUG |
| Gray's feverfew | Parthenium confertum Gray | PACO11 |
| Gray's feverfew | Parthenium confertum Gray var. confertum | PACOC |
| Gray's feverfew | Parthenium confertum Gray var. divaricatum Rollins | PACOD |
| Gray's feverfew | Parthenium confertum Gray var. intermedium Mears, var. nov. ined. | PACOI |
| Gray's feverfew | Parthenium confertum Gray var. lyratum (Gray) Rollins | PACOL |
| Gray's feverfew | Parthenium confertum Gray var. microcephalum Rollins | PACOM |
| Gray's Townsend daisy | Townsendia glabella Gray | TOGL4 |
| graygreen thistle | Cirsium canovirens (Rydb.) Petrak | CICA6 |
| graylocks four-nerve daisy | Tetraneuris grandiflora (Torr. & Gray ex Gray) Parker | TEGR3 |
| great coneflower | Rudbeckia maxima Nutt. | RUMA3 |
| great false leopardbane | Doronicum pardalianches L. | DOPA2 |
| great globethistle | Echinops sphaerocephalus L. | ECSP |
| great Indian plaintain | Arnoglossum reniforme (Hook.) H.E. Robins. | ARRE6 |
| Great Plains false willow | Baccharis salicina Torr. & Gray | BASA |
| Great Plains ragwort | Packera tampicana (DC.) C. Jeffrey | PATA5 |
| great ragweed | Ambrosia trifida L. | AMTR |
| great ragweed | Ambrosia trifida L. var. trifida | AMTRT2 |
| Great Valley gumweed | Grindelia camporum Greene | GRCA |
| Great Valley gumweed | Grindelia camporum Greene var. camporum | GRCAC |
| Greata's aster | Symphyotrichum greatae (Parish) Nesom | SYGR7 |
| greater burdock | Arctium lappa L. | ARLA3 |
| greater knapweed | Centaurea scabiosa L. | CESC2 |
| greater tickseed | Coreopsis major Walt. | COMA6 |
| green and gold | Chrysogonum virginianum L. | CHVI5 |
| green and gold | Chrysogonum virginianum L. var. australe (Alexander ex Small) Ahles | CHVIA |
| green and gold | Chrysogonum virginianum L. var. virginianum | CHVIV |
| green prairie coneflower | Ratibida tagetes (James) Barnh. | RATA |
| green rabbitbrush | Ericameria teretifolia (Dur. & Hilg.) Jepson | ERTE18 |
| Greene brickellbush | Brickellia greenei Gray | BRGR2 |
| Greene's goldenbush | Ericameria greenei (Gray) Nesom | ERGR16 |
| Greene's goldfields | Lasthenia debilis (Greene ex Gray) Ornduff | LADE8 |
| Greene's hawkweed | Hieracium greenei Gray | HIGR2 |
| Greene's rabbitbrush | Chrysothamnus greenei (Gray) Greene | CHGR6 |
| greeneyes | Berlandiera DC. | BERLA |
| greenstem paperflower | Psilostrophe sparsiflora (Gray) A. Nels. | PSSP |
| greensword | Argyroxiphium virescens Hbd. | ARVI8 |
| greenthread | Thelesperma Less. | THELE |
| Greenwood's goldenbush | Ericameria lignumviridis (Welsh) Nesom | ERLI8 |
| Gregg's poreleaf | Porophyllum greggii Gray | POGR6 |
| Grindelia adenodonta | Grindelia microcephala DC. var. adenodonta Steyermark | GRMIA |
| Grindelia arizonica var. arizonica | Grindelia arizonica Gray var. dentata Steyermark | GRARD |
| Grindelia arizonica var. arizonica | Grindelia arizonica Gray var. microphylla Steyermark | GRARM |
| Grindelia arizonica var. neomexicana | Grindelia neomexicana Woot. & Standl. | GRNE2 |
| Grindelia arizonica var. neomexicana | Grindelia scabra Greene var. neomexicana (Woot. & Standl.) Steyermark | GRSCN |
| Grindelia camporum var. bracteosa | Grindelia robusta Nutt. var. bracteosa (J.T. Howell) Keck | GRROB |
| Grindelia camporum var. camporum | Grindelia camporum Greene var. parviflora Steyermark | GRCAP |
| Grindelia camporum var. camporum | Grindelia paludosa Greene | GRPA |
| Grindelia camporum var. camporum | Grindelia procera Greene | GRPR |
| Grindelia camporum var. camporum | Grindelia robusta Nutt. p.p. | GRRO2 |
| Grindelia columbiana | Grindelia nana Nutt. ssp. columbiana Piper | GRNAC |
| Grindelia columbiana | Grindelia nana Nutt. var. discoidea (Nutt.) Gray | GRNAD |
| Grindelia hirsutula var. hallii | Grindelia hallii Steyermark ex Rothrock | GRHA |
| Grindelia hirsutula var. hirsutula | Grindelia hirsutula Hook. & Arn. ssp. rubricaulis (DC.) Keck | GRHIR |
| Grindelia hirsutula var. hirsutula | Grindelia humilis Hook. & Arn. | GRHU |
| Grindelia hirsutula var. maritima | Grindelia maritima (Greene) Steyermark | GRMA |
| Grindelia lanceolata var. lanceolata | Grindelia littoralis Steyermark | GRLI3 |
| Grindelia lanceolata var. lanceolata | Grindelia texana Scheele var. lanceolata (Nutt.) Shinners | GRTEL |
| Grindelia lanceolata var. texana | Grindelia texana Scheele | GRTE8 |
| Grindelia nana var. nana | Grindelia nana Nutt. var. integrifolia Nutt. | GRNAI2 |
| Grindelia nana var. nana | Grindelia squarrosa (Pursh) Dunal var. integrifolia (Nutt.) Boivin | GRSQI |
| Grindelia nuda var. aphanactis | Grindelia aphanactis Rydb. | GRAP |
| Grindelia nuda var. nuda | Grindelia squarrosa (Pursh) Dunal var. nuda (Wood) Gray | GRSQN |
| Grindelia papposa | Haplopappus ciliatus (Nutt.) DC. | HACI5 |
| Grindelia papposa | Prionopsis ciliata (Nutt.) Nutt. | PRCI |
| Grindelia pusilla | Grindelia microcephala DC. var. pusilla Steyermark | GRMIP |
| Grindelia squarrosa var. quasiperennis | Grindelia perennis A. Nels. | GRPE2 |
| Grindelia squarrosa var. serrulata | Grindelia serrulata Rydb. | GRSE4 |
| Grindelia stricta var. angustifolia | Grindelia robusta Nutt. var. angustifolia Gray | GRROA |
| Grindelia stricta var. platyphylla | Grindelia latifolia Kellogg p.p. | GRLA6 |
| Grindelia stricta var. platyphylla | Grindelia latifolia Kellogg ssp. platyphylla (Greene) Keck | GRLAP |
| Grindelia stricta var. platyphylla | Grindelia latifolia Kellogg var. platyphylla Greene | GRLAP2 |
| Grindelia stricta var. platyphylla | Grindelia stricta DC. ssp. venulosa (Jepson) Keck | GRSTV |
| Grindelia stricta var. stricta | Grindelia arenicola Steyermark | GRAR4 |
| Grindelia stricta var. stricta | Grindelia integrifolia DC. var. macrophylla (Greene) Cronq. | GRINM |
| Grindelia stricta var. stricta | Grindelia stricta DC. ssp. blakei (Steyermark) Keck | GRSTB |
| groovestem Indian plaintain | Arnoglossum plantagineum Raf. | ARPL4 |
| groundsel | Roldana Llave ex Lex. | ROLDA |
| groundsel | Tephroseris (Reichenb.) Reichenb. | TEPHR3 |
| guaco | Mikania congesta DC. | MICO8 |
| Guadalupe leastdaisy | Chaetopappa hersheyi Blake | CHHE |
| Guadalupe rabbitbrush | Chrysothamnus spathulatus L.C. Anders. | CHSP3 |
| guardiola | Guardiola Cerv. ex Humb. & Bonpl. | GUARD |
| guayule | Parthenium argentatum Gray | PAAR5 |
| Guirado goldenrod | Solidago guiradonis Gray | SOGU |
| guizotia | Guizotia Cass. | GUIZO |
| Gulf blazing star | Liatris tenuis Shinners | LITE |
| gumhead | Gymnosperma glutinosum (Spreng.) Less. | GYGL |
| gumweed | Grindelia Willd. | GRIND |
| gundelia | Gundelia L. | GUNDE |
| gundlachia | Gundlachia Gray | GUNDL |
| Gutierrezia arizonica | Greenella arizonica Gray | GRAR3 |
| Gutierrezia arizonica | Xanthocephalum arizonicum (Gray) Shinners | XAAR |
| Gutierrezia californica | Gutierrezia bracteata Abrams | GUBR2 |
| Gutierrezia microcephala | Brachyris microcephala DC. | BRMI6 |
| Gutierrezia microcephala | Gutierrezia glomerella Greene | GUGL5 |
| Gutierrezia microcephala | Gutierrezia lucida (Greene) Greene | GULU |
| Gutierrezia microcephala | Gutierrezia sarothrae (Pursh) Britt. & Rusby var. microcephala (DC.) L. Benson | GUSAM |
| Gutierrezia microcephala | Xanthocephalum lucidum Greene | XALU |
| Gutierrezia microcephala | Xanthocephalum microcephalum (DC.) Shinners | XAMI |
| Gutierrezia petradoria | Xanthocephalum petradoria Welsh & Goodrich | XAPE |
| Gutierrezia sarothrae | Gutierrezia diversifolia Greene | GUDI3 |
| Gutierrezia sarothrae | Gutierrezia lepidota Greene | GULE |
| Gutierrezia sarothrae | Gutierrezia linearifolia Lag. | GULI2 |
| Gutierrezia sarothrae | Gutierrezia linearis Rydb. | GULI3 |
| Gutierrezia sarothrae | Gutierrezia linoides Greene | GULI4 |
| Gutierrezia sarothrae | Gutierrezia longipappa Blake | GULO3 |
| Gutierrezia sarothrae | Gutierrezia pomariensis (Welsh) Welsh | GUPO2 |
| Gutierrezia sarothrae | Gutierrezia sarothrae (Pursh) Britt. & Rusby var. pomariensis Welsh | GUSAP |
| Gutierrezia sarothrae | Gutierrezia tenuis Greene | GUTE3 |
| Gutierrezia sarothrae | Solidago sarothrae Pursh | SOSA5 |
| Gutierrezia sarothrae | Xanthocephalum sarothrae (Pursh) Shinners | XASA4 |
| Gutierrezia sarothrae | Xanthocephalum sarothrae (Pursh) Shinners var. pomariense (Welsh) Welsh | XASAP |
| Gutierrezia sarothrae | Xanthocephalum tenue (Greene) Shinners | XATE2 |
| Gutierrezia serotina | Gutierrezia polyantha A. Nels. | GUPO3 |
| Gutierrezia sphaerocephala | Gutierrezia eriocarpa Gray | GUER2 |
| Gutierrezia sphaerocephala | Xanthocephalum sphaerocephalum (Gray) Shinners | XASP4 |
| Gutierrezia sphaerocephala | Xanthocephalum sphaerocephalum (Gray) Shinners var. eriocarpum (Gray) Shinners | XASPE |
| Gutierrezia texana var. glutinosa | Gutierrezia glutinosa (S. Schauer) Schultz-Bip. | GUGL4 |
| Gutierrezia texana var. glutinosa | Hemiachyris glutinosa S. Schauer | HEGL15 |
| Gutierrezia texana var. texana | Hemiachyris texana DC. | HETE16 |
| Gutierrezia texana var. texana | Xanthocephalum texanum (DC.) Shinners | XATE4 |
| Gutierrezia wrightii | Greenella discoidea Gray | GRDI |
| Gutierrezia wrightii | Xanthocephalum wrightii (Gray) Gray | XAWR3 |
| gymnosperma | Gymnosperma Less. | GYMNO6 |
| Gymnosperma glutinosum | Selloa glutinosa Spreng. | SEGL7 |
| Gymnosperma glutinosum | Xanthocephalum glutinosum (Spreng.) Shinners | XAGL |
| Gymnostyles anthemifolia | Soliva anthemifolia (Juss.) R. Br. ex Less. | SOAN7 |
| Gymnostyles stolonifera | Gymnostyles nasturtiifolia auct. non Juss. [misapplied] | GYNA |
| Gymnostyles stolonifera | Soliva nasturtiifolia auct. non (Juss.) DC. [misapplied] | SONA3 |
| Gymnostyles stolonifera | Soliva stolonifera (Brot.) Loud. | SOST6 |
| gymsum-lovingTownsend daisy | Townsendia gypsophila T.K. Lowrey & P.J. Knight | TOGY |
| gynura | Gynura Cass. | GYNUR |
| gypsum tansyaster | Machaeranthera gypsophila B.L. Turner | MAGY3 |
| hairless fleabane | Erigeron subglaber Cronq. | ERSU9 |
| hairy arnica | Arnica mollis Hook. | ARMO4 |
| hairy balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. hirsuta (Nutt.) A. Nels. | BAHOH |
| hairy balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. hispidula (Sharp) Cronq. | BAHOH2 |
| hairy beggarticks | Bidens pilosa L. | BIPI |
| hairy catsear | Hypochaeris radicata L. | HYRA3 |
| hairy chaffhead | Carphephorus paniculatus (J.F. Gmel.) Herbert | CAPA53 |
| hairy desertsunflower | Geraea canescens Torr. & Gray | GECA2 |
| hairy dozedaisy | Aphanostephus pilosus Buckl. | APPI |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners | HEVI4 |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. ballardii (Rydb.) Semple | HEVIB |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. depressa (Rydb.) Semple | HEVID |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. foliosa (Nutt.) Harms | HEVIF |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. minor (Hook.) Semple | HEVIM3 |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. nana (Gray) Semple | HEVIN |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. pedunculata (Greene) Harms ex Semple | HEVIP |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. scabra (Eastw.) Semple | HEVIS |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. sierrablancensis Semple | HEVIS3 |
| hairy false goldenaster | Heterotheca villosa (Pursh) Shinners var. villosa | HEVIV |
| hairy fleabane | Erigeron pubescens Kunth | ERPU10 |
| hairy goldenrod | Solidago hispida Muhl. ex Willd. | SOHI |
| hairy goldenrod | Solidago hispida Muhl. ex Willd. var. arnoglossa Fern. | SOHIA |
| hairy goldenrod | Solidago hispida Muhl. ex Willd. var. hispida | SOHIH |
| hairy goldenrod | Solidago hispida Muhl. ex Willd. var. lanata (Hook.) Fern. | SOHIL |
| hairy goldenrod | Solidago hispida Muhl. ex Willd. var. tonsa Fern. | SOHIT |
| hairy greenthread | Thelesperma pubescens Dorn | THPU4 |
| hairy gumweed | Grindelia hirsutula Hook. & Arn. | GRHI |
| hairy gumweed | Grindelia hirsutula Hook. & Arn. var. davyi (Jepson) M.A. Lane | GRHID2 |
| hairy gumweed | Grindelia hirsutula Hook. & Arn. var. hirsutula | GRHIH3 |
| hairy hawkweed | Hieracium longipilum Torr. | HILO2 |
| hairy horsebrush | Tetradymia comosa Gray | TECO2 |
| hairy leafcup | Smallanthus uvedalius (L.) Mackenzie ex Small | SMUV |
| hairy lettuce | Lactuca hirsuta Muhl. ex Nutt. | LAHI |
| hairy lettuce | Lactuca hirsuta Muhl. ex Nutt. var. albiflora (Torr. & Gray) Shinners | LAHIA |
| hairy lettuce | Lactuca hirsuta Muhl. ex Nutt. var. hirsuta | LAHIH3 |
| hairy lettuce | Lactuca hirsuta Muhl. ex Nutt. var. sanguinea (Bigelow) Fern. | LAHIS2 |
| hairy New York aster | Symphyotrichum novi-belgii (L.) Nesom var. villicaule (Gray) J. Labrecque & L. Brouillet | SYNOV |
| hairy ragweed | Ambrosia canescens Gray | AMCA7 |
| hairy spotflower | Acmella pilosa R.K. Jansen | ACPI4 |
| hairy sunflower | Helianthus hirsutus Raf. | HEHI2 |
| hairy Townsend daisy | Townsendia strigosa Nutt. | TOST |
| hairy wedelia | Wedelia texana (Gray) B.L. Turner | WETE |
| hairy white oldfield aster | Symphyotrichum pilosum (Willd.) Nesom | SYPI2 |
| hairy white oldfield aster | Symphyotrichum pilosum (Willd.) Nesom var. pilosum | SYPIP3 |
| hairy-seed goldenrod | Solidago villosicarpa LeBlond | SOVI10 |
| hairybeast turtleback | Psathyrotes pilifera Gray | PSPI |
| hairyseed bahia | Bahia absinthifolia Benth. | BAAB |
| hairyseed bahia | Bahia absinthifolia Benth. var. absinthifolia | BAABA |
| Haleakalae tetramolopium | Tetramolopium humile (Gray) Hbd. ssp. haleakalae Lowrey | TEHUH |
| Hall's aster | Symphyotrichum hallii (Gray) Nesom | SYHA |
| Hall's columbiadoria | Columbiadoria hallii (Gray) Nesom | COHA5 |
| Hall's fleabane | Erigeron aequifolius Hall | ERAE |
| Hall's gumweed | Grindelia hirsutula Hook. & Arn. var. hallii (Steyermark ex Rothrock) M.A. Lane | GRHIH2 |
| Hall's hawksbeard | Crepis runcinata (James) Torr. & Gray ssp. hallii Babcock & Stebbins | CRRUH |
| Hall's madia | Harmonia hallii (Keck) B.G. Baldwin | HAHA11 |
| Hall's mule-ears | Agnorhiza elata (Hall) W.A. Weber | AGEL8 |
| Hall's ragwort | Senecio bigelovii Gray var. hallii Gray | SEBIH |
| Hall's tarweed | Deinandra halliana (Keck) B.G. Baldwin | DEHA7 |
| Hall's woolly sunflower | Eriophyllum lanatum (Pursh) Forbes var. hallii Constance | ERLAH |
| hammock snakeroot | Ageratina jucunda (Greene) Clewell & Woot. | AGJU2 |
| hammockherb | Hasteola robertiorum L.C. Anders. | HARO |
| Hana Forest silversword | Argyroxiphium grayanum (Hbd.) O. Deg. | ARGR5 |
| Hanaupah rockdaisy | Perityle villosa (Blake) Shinners | PEVI9 |
| haplopappus | Haplopappus Cass. | HAPLO11 |
| hardheads | Acroptilon Cass. | ACROP |
| hardheads | Acroptilon repens (L.) DC. | ACRE3 |
| hareleaf | Lagophylla Nutt. | LAGOP |
| Harford's ragwort | Packera bolanderi (Gray) W.A. Weber & A. L?ve var. harfordii (Greenm.) D.K. Trock & T.M. Barkl. | PABOH |
| Harger's goldenrod | Solidago canadensis L. var. hargeri Fern. | SOCAH |
| Harmonia doris-nilesiae | Madia doris-nilesiae T.W. & J.P. Nelson | MADO3 |
| Harmonia hallii | Madia hallii Keck | MAHA |
| Harmonia nutans | Madia nutans (Greene) Keck | MANU |
| Harmonia stebbinsii | Madia stebbinsii T.W. & J.P. Nelson | MAST3 |
| harp dandelion | Taraxacum lyratum (Ledeb.) DC. | TALY |
| harp onefruit | Haplocarpha lyrata Harr. | HALY2 |
| Harris's goldenrod | Solidago arguta Ait. var. harrisii (Steele) Cronq. | SOARH |
| Hart's ragwort | Packera hartiana (Heller) W.A. Weber & A. L?ve | PAHA16 |
| Hartweg's fleabane | Erigeron foliosus Nutt. var. hartwegii (Greene) Jepson | ERFOH |
| Hartweg's golden sunburst | Pseudobahia bahiifolia (Benth.) Rydb. | PSBA |
| Hartweg's groundsel | Roldana hartwegii (Benth.) H.E. Robins. & Brett. | ROHA3 |
| Hartweg's pricklyleaf | Thymophylla pentachaeta (DC.) Small var. hartwegii (Gray) Strother | THPEH |
| hartwrightia | Hartwrightia Gray ex S. Wats. | HARTW |
| Hasteola suaveolens | Cacalia suaveolens L. | CASU |
| Hasteola suaveolens | Synosma suaveolens (L.) Raf. ex Britt. | SYSU |
| Havana snakeroot | Ageratina havanensis (Kunth) King & H.E. Robins. | AGHA4 |
| Havard's false willow | Baccharis havardii Gray | BAHA2 |
| Havard's gumweed | Grindelia havardii Steyermark | GRHA2 |
| Hawai'i beggarticks | Bidens hawaiensis Gray | BIHA |
| Hawai'i silversword | Argyroxiphium sandwicense DC. | ARSA5 |
| Hawai'i silversword | Argyroxiphium sandwicense DC. ssp. macrocephalum (Gray) M?rat | ARSAM |
| Hawai'i silversword | Argyroxiphium sandwicense DC. ssp. sandwicense | ARSAS |
| hawk's eye | Euryops multifidus (Thunb.) DC. | EUMU |
| hawkbit | Leontodon L. | LEONT |
| hawksbeard | Crepis L. | CREPI |
| hawkweed | Hieracium L. | HIERA |
| hawkweed oxtongue | Picris hieracioides L. | PIHI |
| hawkweed oxtongue | Picris hieracioides L. ssp. hieracioides | PIHIH |
| hawkweed oxtongue | Picris hieracioides L. ssp. kamtschatica (Ledeb.) Hult | PIHIK |
| hayfield tarweed | Hemizonia congesta DC. | HECO7 |
| hayfield tarweed | Hemizonia congesta DC. ssp. calyculata Babcock & Hall | HECOC5 |
| hayfield tarweed | Hemizonia congesta DC. ssp. clevelandii (Greene) Babcock & Hall | HECOC6 |
| hayfield tarweed | Hemizonia congesta DC. ssp. congesta | HECOC2 |
| hayfield tarweed | Hemizonia congesta DC. ssp. leucocephala (Tanowitz) Keil | HECOL2 |
| hayfield tarweed | Hemizonia congesta DC. ssp. luzulifolia (DC.) Babcock & Hall | HECOL3 |
| hayfield tarweed | Hemizonia congesta DC. ssp. tracyi Babcock & Hall | HECOT |
| hayfield tarweed | Hemizonia congesta DC. ssp. vernalis (Keck) Tanowitz | HECOV |
| Hazardia brickellioides | Haplopappus brickellioides Blake | HABR |
| Hazardia cana | Haplopappus canus (Gray) Blake | HACA4 |
| Hazardia detonsa | Haplopappus detonsus (Greene) Raven | HADE3 |
| Hazardia squarrosa var. grindelioides | Haplopappus squarrosus Hook. & Arn. ssp. grindelioides (DC.) Keck | HASQG |
| Hazardia squarrosa var. obtusa | Haplopappus squarrosus Hook. & Arn. ssp. obtusus (Greene) Hall | HASQO |
| Hazardia squarrosa var. squarrosa | Haplopappus squarrosus Hook. & Arn. | HASQ |
| Hazardia stenolepis | Haplopappus squarrosus Hook. & Arn. ssp. stenolepis Hall | HASQS |
| Hazardia whitneyi var. discoidea | Haplopappus whitneyi Gray ssp. discoideus (J.T. Howell) Keck | HAWHD |
| Hazardia whitneyi var. whitneyi | Haplopappus whitneyi Gray | HAWH2 |
| heal and draw | Chaptalia nutans (L.) Polak. | CHNU2 |
| heartleaf arnica | Arnica cordifolia Hook. | ARCO9 |
| heartleaf goldeneye | Viguiera cordifolia Gray | VICO |
| heartleaf hempvine | Mikania cordata (Burm. f.) B.L. Robins. [excluded] | MICO16 |
| Hebeclinium macrophyllum | Eupatorium macrophyllum L. | EUMA17 |
| hecastocleis | Hecastocleis Gray | HECAS |
| Hedosyne ambrosiifolia | Iva ambrosiifolia (Gray) Gray | IVAM |
| hedypnois | Hedypnois P. Mill. | HEDYP |
| Heermann's tarweed | Holocarpha heermannii (Greene) Keck | HOHE |
| Helenium amarum var. amarum | Helenium tenuifolium Nutt. | HETE14 |
| Helenium amarum var. badium | Helenium badium (Gray ex S. Wats.) Greene | HEBA |
| Helenium amarum var. badium | Helenium tenuifolium Nutt. var. badium Gray | HETEB |
| Helenium autumnale var. autumnale | Helenium autumnale L. var. canaliculatum (Lam.) Torr. & Gray | HEAUC |
| Helenium autumnale var. autumnale | Helenium autumnale L. var. parviflorum (Nutt.) Fern. | HEAUP |
| Helenium autumnale var. autumnale | Helenium canaliculatum Lam. | HECA24 |
| Helenium autumnale var. autumnale | Helenium latifolium P. Mill. | HELA21 |
| Helenium autumnale var. autumnale | Helenium parviflorum Nutt. | HEPA15 |
| Helenium autumnale var. grandiflorum | Helenium macranthum Rydb. | HEMA12 |
| Helenium autumnale var. montanum | Helenium montanum Nutt. | HEMO9 |
| Helenium bigelovii | Helenium rivulare (Greene) Rydb. | HERI4 |
| Helenium bolanderi | Dugaldia grandiflora Rydb. | DUGR2 |
| Helenium bolanderi | Helenium bigelovii Gray var. festivum Jepson | HEBIF |
| Helenium brevifolium | Helenium curtisii Gray | HECU6 |
| Helenium drummondii | Helenium fimbriatum auct. non (Michx.) Gray [misapplied] | HEFI2 |
| Helenium drummondii | Leptopoda fimbriata Torr. & Gray | LEFI4 |
| Helenium elegans var. amphilobum | Helenium amphilobum Gray | HEAM10 |
| Helenium flexuosum | Helenium floridanum Fern. | HEFL9 |
| Helenium flexuosum | Helenium godfreyi Fern. | HEGO2 |
| Helenium flexuosum | Helenium nudiflorum Nutt. | HENU3 |
| Helenium microcephalum var. ooclinium | Helenium ooclinium Gray | HEOO2 |
| Helenium pinnatifidum | Helenium incisum (Torr. & Gray) Wood | HEIN8 |
| Helenium pinnatifidum | Helenium vernale auct. non Walt. [misapplied] | HEVE5 |
| Helenium puberulum | Helenium decurrens (Less.) Vatke, non Moench | HEDE8 |
| Helenium vernale | Helenium helenium (Nutt.) Small | HEHE11 |
| Helenium vernale | Helenium nuttallii Gray | HENU4 |
| helianthella | Helianthella Torr. & Gray | HELIA |
| Helianthella californica ssp. californica | Helianthella californica Gray var. californica | HECAC |
| Helianthella californica ssp. nevadensis | Helianthella californica Gray var. nevadensis (Greene) Jepson | HECAN |
| Helianthella californica ssp. shastensis | Helianthella californica Gray var. shastensis W.A. Weber | HECAS2 |
| Helianthella microcephala | Encelia microcephala Gray | ENMI |
| Helianthella quinquenervis | Helianthus quinquenervis Hook. | HEQU4 |
| Helianthella uniflora var. uniflora | Helianthus uniflorus Nutt. | HEUN6 |
| Helianthus ?cinereus | Helianthus cinereus Torr. & Gray var. sullivantii Torr. & Gray | HECIS2 |
| Helianthus ?doronicoides | Helianthus pilosus Tausch | HEPI7 |
| Helianthus ?laetiflorus | Helianthus scaberrimus Ell. | HESC13 |
| Helianthus angustifolius | Helianthus angustifolius L. var. planifolius Fern. | HEANP |
| Helianthus annuus | Helianthus annuus L. ssp. jaegeri (Heiser) Heiser | HEANJ |
| Helianthus annuus | Helianthus annuus L. ssp. lenticularis (Dougl. ex Lindl.) Cockerell | HEANL |
| Helianthus annuus | Helianthus annuus L. ssp. texanus Heiser | HEANT |
| Helianthus annuus | Helianthus annuus L. var. lenticularis (Dougl. ex Lindl.) Steyermark | HEANL2 |
| Helianthus annuus | Helianthus annuus L. var. macrocarpus (DC.) Cockerell | HEANM |
| Helianthus annuus | Helianthus annuus L. var. texanus (Heiser) Shinners | HEANT2 |
| Helianthus annuus | Helianthus aridus Rydb. | HEAR14 |
| Helianthus annuus | Helianthus lenticularis Dougl. ex Lindl. | HELE5 |
| Helianthus anomalus | Helianthus deserticola Heiser | HEDE5 |
| Helianthus atrorubens | Helianthus atrorubens L. var. alsodes Fern. | HEATA |
| Helianthus bolanderi | Helianthus exilis Gray | HEEX |
| Helianthus debilis ssp. cucumerifolius | Helianthus cucumerifolius Torr. & Gray | HECU7 |
| Helianthus debilis ssp. cucumerifolius | Helianthus debilis Nutt. var. cucumerifolius (Torr. & Gray) Gray | HEDEC3 |
| Helianthus debilis ssp. silvestris | Helianthus debilis Nutt. var. silvestris (Heiser) Cronq. | HEDES2 |
| Helianthus debilis ssp. tardiflorus | Helianthus debilis Nutt. var. tardiflorus (Heiser) Cronq. | HEDET2 |
| Helianthus debilis ssp. vestitus | Helianthus debilis Nutt. var. vestitus (E.E. Wats.) Cronq. | HEDEV2 |
| Helianthus debilis ssp. vestitus | Helianthus vestitus E.E. Wats. | HEVE6 |
| Helianthus decapetalus | Helianthus scrophulariifolius Britt. | HESC12 |
| Helianthus decapetalus | Helianthus tracheliifolius P. Mill. | HETR8 |
| Helianthus divaricatus | Helianthus divaricatus L. var. angustifolius Kuntze | HEDIA |
| Helianthus giganteus | Helianthus alienus E.E. Wats. | HEAL7 |
| Helianthus giganteus | Helianthus borealis E.E. Wats. | HEBO6 |
| Helianthus giganteus | Helianthus giganteus L. ssp. alienus (E.E. Wats.) R.W. Long | HEGIA |
| Helianthus giganteus | Helianthus giganteus L. var. subtuberosus Britt. | HEGIS |
| Helianthus giganteus | Helianthus nuttallii Torr. & Gray var. subtuberosus (Britt.) Boivin | HENUS |
| Helianthus giganteus | Helianthus subtuberosus (Britt.) Britt. | HESU10 |
| Helianthus giganteus | Helianthus validus E.E. Wats. | HEVA |
| Helianthus grosseserratus | Helianthus grosseserratus Martens ssp. maximus R.W. Long | HEGRM |
| Helianthus grosseserratus | Helianthus grosseserratus Martens var. hypoleucus Gray | HEGRH |
| Helianthus grosseserratus | Helianthus instabilis E.E. Wats. | HEIN9 |
| Helianthus hirsutus | Helianthus hirsutus Raf. var. stenophyllus Torr. & Gray | HEHIS |
| Helianthus hirsutus | Helianthus hirsutus Raf. var. trachyphyllus Torr. & Gray | HEHIT |
| Helianthus hirsutus | Helianthus stenophyllus (Torr. & Gray) E.E. Wats. | HEST4 |
| Helianthus laciniatus | Helianthus crenatus R.C. Jackson | HECR6 |
| Helianthus laciniatus | Helianthus heiseri R.C. Jackson | HEHE10 |
| Helianthus laevigatus | Helianthus reindutus (Steele) E.E. Wats. | HERE8 |
| Helianthus maximiliani | Helianthus dalyi Britt. | HEDA2 |
| Helianthus mollis | Helianthus mollis Lam. var. cordatus S. Wats. | HEMOC |
| Helianthus niveus ssp. canescens | Helianthus canescens (Gray) S. Wats. | HECA25 |
| Helianthus niveus ssp. canescens | Helianthus canus (Britt.) Woot. & Standl. | HECA28 |
| Helianthus niveus ssp. canescens | Helianthus petiolaris Nutt. var. canescens Gray | HEPEC |
| Helianthus niveus ssp. tephrodes | Helianthus tephrodes Gray | HETE15 |
| Helianthus nuttallii ssp. nuttallii | Helianthus fascicularis Greene | HEFA6 |
| Helianthus nuttallii ssp. nuttallii | Helianthus nuttallii Torr. & Gray ssp. canadensis R.W. Long | HENUC |
| Helianthus nuttallii ssp. nuttallii | Helianthus nuttallii Torr. & Gray ssp. coloradensis (Cockerell) R.W. Long | HENUC2 |
| Helianthus nuttallii ssp. parishii | Helianthus parishii Gray | HEPA23 |
| Helianthus nuttallii ssp. rydbergii | Helianthus nuttallii Torr. & Gray var. rydbergii (Britt.) Boivin | HENUR2 |
| Helianthus nuttallii ssp. rydbergii | Helianthus rydbergii Britt. | HERY80 |
| Helianthus occidentalis ssp. occidentalis | Helianthus dowellianus M.A. Curtis | HEDO4 |
| Helianthus occidentalis ssp. occidentalis | Helianthus occidentalis Riddell var. dowellianus (M.A. Curtis) Torr. & Gray | HEOCD |
| Helianthus occidentalis ssp. plantagineus | Helianthus occidentalis Riddell var. plantagineus Torr. & Gray | HEOCP2 |
| Helianthus pauciflorus ssp. pauciflorus | Helianthus laetiflorus Pers. var. rigidus (Cass.) Fern. | HELAR |
| Helianthus pauciflorus ssp. pauciflorus | Helianthus rigidus (Cass.) Desf. | HERI2 |
| Helianthus pauciflorus ssp. subrhomboideus | Helianthus laetiflorus Pers. var. subrhomboideus (Rydb.) Fern. | HELAS |
| Helianthus pauciflorus ssp. subrhomboideus | Helianthus pauciflorus Nutt. var. subrhomboideus (Rydb.) Cronq. | HEPAS2 |
| Helianthus pauciflorus ssp. subrhomboideus | Helianthus rigidus (Cass.) Desf. ssp. laetiflorus (Rydb.) Heiser | HERIL |
| Helianthus pauciflorus ssp. subrhomboideus | Helianthus rigidus (Cass.) Desf. ssp. subrhomboideus (Rydb.) Heiser | HERIS2 |
| Helianthus pauciflorus ssp. subrhomboideus | Helianthus rigidus (Cass.) Desf. var. subrhomboideus (Rydb.) Cronq. | HERIS3 |
| Helianthus pauciflorus ssp. subrhomboideus | Helianthus subrhomboideus Rydb. | HESU11 |
| Helianthus petiolaris ssp. fallax | Helianthus petiolaris Nutt. var. fallax (Heiser) B.L. Turner | HEPEF2 |
| Helianthus porteri | Heliomeris porteri (Gray) Cockerell | HEPO6 |
| Helianthus porteri | Viguiera porteri (Gray) Blake | VIPO3 |
| Helianthus praecox ssp. hirtus | Helianthus debilis Nutt. ssp. hirtus Heiser | HEDEH |
| Helianthus praecox ssp. praecox | Helianthus debilis Nutt. ssp. praecox (Engelm. & Gray) Heiser | HEDEP |
| Helianthus praecox ssp. runyonii | Helianthus debilis Nutt. ssp. runyonii Heiser | HEDER2 |
| Helianthus praecox ssp. runyonii | Helianthus praecox Engelm. & Gray var. runyonii (Heiser) B.L. Turner | HEPRR2 |
| Helianthus resinosus | Helianthus tomentosus auct. non Michx. [misapplied] | HETO3 |
| Helianthus salicifolius | Helianthus filiformis Small | HEFI3 |
| Helianthus salicifolius | Helianthus orgyalis DC. | HEOR4 |
| Helianthus silphioides | Helianthus atrorubens L. var. pubescens Kuntze | HEATP |
| Helianthus strumosus | Helianthus montanus E.E. Wats. | HEMO8 |
| Helianthus strumosus | Helianthus saxicola Small | HESA6 |
| Helianthus tuberosus | Helianthus tomentosus Michx. | HETO4 |
| Helianthus tuberosus | Helianthus tuberosus L. var. subcanescens Gray | HETUS2 |
| Helichrysum petiolare | Helichrysum petiolatum (L.) DC. | HEPE9 |
| Heliograph Peak fleabane | Erigeron heliographis Nesom | ERHE5 |
| Heliomeris hispida | Gymnolomia hispida (Gray) Robins. & Greenm. | GYHI2 |
| Heliomeris hispida | Gymnolomia hispida (Gray) Robins. & Greenm. var. ciliata Robins. & Greenm. | GYHIC |
| Heliomeris hispida | Viguiera ciliata (Robins. & Greenm.) Blake | VICI3 |
| Heliomeris longifolia var. annua | Heliomeris annua (M.E. Jones) Cockerell | HEAN11 |
| Heliomeris longifolia var. annua | Viguiera annua (M.E. Jones) Blake | VIAN5 |
| Heliomeris longifolia var. annua | Viguiera longifolia (Robins. & Greenm.) Blake var. annua (M.E. Jones) Welsh | VILOA |
| Heliomeris longifolia var. longifolia | Gymnolomia longifolia Robins. & Greenm. | GYLO |
| Heliomeris longifolia var. longifolia | Viguiera longifolia (Robins. & Greenm.) Blake | VILO7 |
| Heliomeris multiflora var. brevifolia | Viguiera ovalis Blake | VIOV |
| Heliomeris multiflora var. macrocephala | Viguiera multiflora (Nutt.) Blake var. macrocephala (Heiser) B.L. Turner | VIMUM |
| Heliomeris multiflora var. multiflora | Viguiera multiflora (Nutt.) Blake | VIMU |
| Heliomeris multiflora var. nevadensis | Viguiera multiflora (Nutt.) Blake var. nevadensis (A. Nels.) Blake | VIMUN |
| Heliomeris soliceps | Viguiera soliceps Barneby | VISO2 |
| heliopsis | Heliopsis Pers. | HELIO2 |
| Heliopsis helianthoides var. gracilis | Heliopsis gracilis Nutt. | HEGR18 |
| Heliopsis helianthoides var. helianthoides | Heliopsis helianthoides (L.) Sweet var. solidaginoides (L.) Fern. | HEHES2 |
| Heliopsis helianthoides var. occidentalis | Heliopsis helianthoides (L.) Sweet ssp. occidentalis T.R. Fisher | HEHEO2 |
| Heliopsis helianthoides var. scabra | Heliopsis helianthoides (L.) Sweet ssp. scabra (Dunal) T.R. Fisher | HEHES4 |
| Heliopsis helianthoides var. scabra | Heliopsis minor (Hook.) C. Mohr | HEMI11 |
| Heliopsis helianthoides var. scabra | Heliopsis scabra Dunal | HESC14 |
| Heller's blazing star | Liatris helleri Porter | LIHE2 |
| Heller's cudweed | Pseudognaphalium helleri (Britt.) A. Anderb. | PSHE4 |
| Heller's cudweed | Pseudognaphalium helleri (Britt.) A. Anderb. ssp. helleri | PSHEH7 |
| Heller's cudweed | Pseudognaphalium helleri (Britt.) A. Anderb. ssp. micradenium (Weatherby) Kartesz | PSHEM |
| Hemizonella minima | Madia minima (Gray) Keck | MAMI |
| Hemizonia congesta ssp. calyculata | Hemizonia calyculata (Babcock & Hall) Keck | HECA6 |
| Hemizonia congesta ssp. clevelandii | Hemizonia clevelandii Greene | HECL2 |
| Hemizonia congesta ssp. congesta | Hemizonia congesta DC. ssp. lutescens (Greene) Babc. & H. M. Hall | HECOL4 |
| Hemizonia congesta ssp. congesta | Hemizonia lutescens (Greene) Keck | HELU2 |
| Hemizonia congesta ssp. congesta | Hemizonia luzulifolia DC. var. lutescens Greene | HELUL2 |
| Hemizonia congesta ssp. congesta | Hemizonia multicaulis Hook. & Arn. | HEMU |
| Hemizonia congesta ssp. leucocephala | Hemizonia leucocephala Tanowitz | HELE3 |
| Hemizonia congesta ssp. luzulifolia | Hemizonia luzulifolia DC. | HELU3 |
| Hemizonia congesta ssp. luzulifolia | Hemizonia luzulifolia DC. ssp. rudis (Benth.) Keck | HELUR |
| Hemizonia congesta ssp. tracyi | Hemizonia luzulifolia DC. ssp. tracyi Babcock & Hall | HELUT |
| Hemizonia congesta ssp. tracyi | Hemizonia tracyi (Babcock & Hall) Keck | HETR |
| Hemizonia congesta ssp. vernalis | Hemizonia multicaulis Hook. & Arn. ssp. vernalis Keck | HEMUV |
| Hemizonia fasciculata | Hemizonia ramosissima Benth. | HERA2 |
| hemp agrimony | Eupatorium cannabinum L. | EUCA9 |
| hempleaf ragwort | Senecio cannabinifolius Hook. & Arn. | SECA5 |
| hempvine | Mikania Willd. | MIKAN |
| Henrieville woodyaster | Xylorhiza confertifolia (Cronq.) T.J. Wats. | XYCO3 |
| Hesperevax acaulis var. acaulis | Evax acaulis (Kellogg) Greene | EVAC |
| Hesperevax acaulis var. acaulis | Stylocline acaulis Kellogg | STAC3 |
| Hesperevax caulescens | Evax acaulis Greene, non (Kellogg) Greene | EVAC2 |
| Hesperevax caulescens | Evax caulescens (Benth.) Gray var. humilis (Greene) Jepson | EVCAH |
| Hesperevax caulescens | Evax caulescens (Benth.) Gray var. petiolata Gray | EVCAP |
| Hesperevax caulescens | Evax involucrata Greene | EVIN |
| Hesperevax sparsiflora var. brevifolia | Evax sparsiflora (Gray) Jepson var. brevifolia (Gray) Jepson | EVSPB |
| Hesperevax sparsiflora var. sparsiflora | Evax sparsiflora (Gray) Jepson | EVSP |
| Hesperodoria salicina | Haplopappus salicinus Blake | HASA3 |
| Hesperodoria scopulorum | Haplopappus scopulorum (M.E. Jones) Blake | HASC |
| Hesperodoria scopulorum | Haplopappus scopulorum (M.E. Jones) Blake var. hirtellus Blake | HASCH |
| Hesperomannia arborescens | Hesperomannia arborescens Gray var. bushiana (O. Deg.) Carlq. | HEARB |
| Hesperomannia arborescens | Hesperomannia arborescens Gray var. swezeyi (O. Deg.) Carlq. | HEARS |
| Hesperomannia arbuscula | Hesperomannia arbuscula Hbd. ssp. oahuensis (Hbd.) Carlq. | HEARO |
| Hesperomannia arbuscula | Hesperomannia arbuscula Hbd. var. pearsallii St. John | HEARP |
| Hesperomannia arbuscula | Hesperomannia mauiensis St. John | HEMA13 |
| Hess's fleabane | Erigeron hessii Nesom | ERHE9 |
| Heteropappus altaicus | Aster altaicus Willd. | ASAL20 |
| heterosperma | Heterosperma Cav. | HETER7 |
| Heterotheca barbata | Chrysopsis barbata Rydb. | CHBA3 |
| Heterotheca camporum var. camporum | Chrysopsis camporum Greene | CHCA15 |
| Heterotheca camporum var. camporum | Chrysopsis villosa (Pursh) Nutt. ex DC. var. camporum (Greene) Cronq. | CHVIC6 |
| Heterotheca camporum var. camporum | Heterotheca villosa (Pursh) Shinners var. camporum (Greene) Wunderlin | HEVIC |
| Heterotheca camporum var. glandulissimum | Chrysopsis camporum Greene var. glandulissimum (Semple) Cronq. | CHCAG2 |
| Heterotheca canescens | Chrysopsis berlandieri Greene | CHBE7 |
| Heterotheca canescens | Chrysopsis canescens (DC.) Torr. & Gray, non DC. | CHCA16 |
| Heterotheca canescens | Chrysopsis villosa (Pursh) Nutt. ex DC. var. canescens (DC.) Gray | CHVIC3 |
| Heterotheca fulcrata var. amplifolia | Chrysopsis amplifolia Rydb. | CHAM7 |
| Heterotheca fulcrata var. amplifolia | Chrysopsis caudata Rydb. | CHCA18 |
| Heterotheca fulcrata var. amplifolia | Chrysopsis nitidula Woot. & Standl. | CHNI3 |
| Heterotheca fulcrata var. fulcrata | Chrysopsis cryptocephala Woot. & Standl. | CHCR5 |
| Heterotheca fulcrata var. fulcrata | Chrysopsis fulcrata Greene | CHFU4 |
| Heterotheca fulcrata var. fulcrata | Chrysopsis resinolens A. Nels. | CHRE7 |
| Heterotheca fulcrata var. senilis | Chrysopsis senilis Woot. & Standl. | CHSE13 |
| Heterotheca grandiflora | Heterotheca floribunda Benth. | HEFL10 |
| Heterotheca jonesii | Chrysopsis jonesii Blake | CHJO3 |
| Heterotheca oregona var. compacta | Chrysopsis oregona (Nutt.) Gray var. compacta Keck | CHORC |
| Heterotheca oregona var. oregona | Ammodia oregona Nutt. | AMOR |
| Heterotheca oregona var. oregona | Chrysopsis oregona (Nutt.) Gray | CHOR4 |
| Heterotheca oregona var. rudis | Chrysopsis oregona (Nutt.) Gray var. rudis (Greene) Jepson | CHORR |
| Heterotheca oregona var. scaberrima | Chrysopsis oregona (Nutt.) Gray var. scaberrima Gray | CHORS |
| Heterotheca pumila | Chrysopsis alpicola Rydb. | CHAL14 |
| Heterotheca pumila | Chrysopsis alpicola Rydb. var. glomerata A. Nels. | CHALG |
| Heterotheca pumila | Chrysopsis cooperi A. Nels. | CHCO16 |
| Heterotheca pumila | Chrysopsis pumila Greene | CHPU5 |
| Heterotheca pumila | Chrysopsis villosa (Pursh) Nutt. ex DC. var. glomerata (A. Nels.) Harms | CHVIG |
| Heterotheca rutteri | Chrysopsis rutteri (Rothrock) Greene | CHRU2 |
| Heterotheca sessiliflora ssp. bolanderi | Chrysopsis bolanderi Gray | CHBO8 |
| Heterotheca sessiliflora ssp. bolanderi | Chrysopsis villosa (Pursh) Nutt. ex DC. var. bolanderi (Gray) Gray ex Jepson | CHVIB |
| Heterotheca sessiliflora ssp. bolanderi | Heterotheca bolanderi (Gray) Harms | HEBO4 |
| Heterotheca sessiliflora ssp. echioides var. camphorata | Chrysopsis camphorata Eastw. | CHCA14 |
| Heterotheca sessiliflora ssp. echioides var. camphorata | Chrysopsis villosa (Pursh) Nutt. ex DC. var. camphorata (Eastw.) Jepson | CHVIC5 |
| Heterotheca sessiliflora ssp. echioides var. camphorata | Heterotheca camphorata (Eastw.) Semple | HECA15 |
| Heterotheca sessiliflora ssp. echioides var. echioides | Chrysopsis californica Elmer | CHCA17 |
| Heterotheca sessiliflora ssp. echioides var. echioides | Chrysopsis echioides Benth. | CHEC |
| Heterotheca sessiliflora ssp. echioides var. echioides | Chrysopsis villosa (Pursh) Nutt. ex DC. var. echioides (Benth.) Gray | CHVIE2 |
| Heterotheca sessiliflora ssp. echioides var. echioides | Heterotheca echioides (Benth.) Shinners | HEEC |
| Heterotheca sessiliflora ssp. fastigiata var. fastigiata | Chrysopsis fastigiata Greene | CHFA4 |
| Heterotheca sessiliflora ssp. fastigiata var. fastigiata | Chrysopsis villosa (Pursh) Nutt. ex DC. var. fastigiata (Greene) Hall | CHVIF3 |
| Heterotheca sessiliflora ssp. fastigiata var. fastigiata | Heterotheca fastigiata (Greene) Harms | HEFA4 |
| Heterotheca sessiliflora ssp. sessiliflora | Chrysopsis sessiliflora Nutt. | CHSE14 |
| Heterotheca sessiliflora ssp. sessiliflora | Chrysopsis villosa (Pursh) Nutt. ex DC. var. sessiliflora (Nutt.) Gray | CHVIS3 |
| Heterotheca shevockii | Heterotheca villosa (Pursh) Shinners var. shevockii Semple | HEVIS2 |
| Heterotheca stenophylla var. angustifolia | Chrysopsis angustifolia Rydb. | CHAN12 |
| Heterotheca stenophylla var. angustifolia | Chrysopsis villosa (Pursh) Nutt. ex DC. var. angustifolia (Rydb.) Cronq. | CHVIA3 |
| Heterotheca stenophylla var. angustifolia | Heterotheca villosa (Pursh) Shinners var. angustifolia (Rydb.) Semple | HEVIA2 |
| Heterotheca stenophylla var. stenophylla | Chrysopsis hispida (Hook.) DC. var. stenophylla Gray | CHHIS |
| Heterotheca stenophylla var. stenophylla | Chrysopsis scabrifolia A. Nels. | CHSC5 |
| Heterotheca stenophylla var. stenophylla | Chrysopsis stenophylla (Gray) Greene | CHST7 |
| Heterotheca stenophylla var. stenophylla | Chrysopsis villosa (Pursh) Nutt. ex DC. var. stenophylla (Gray) Gray | CHVIS4 |
| Heterotheca subaxillaris | Chrysopsis scabra (Pursh) Ell. | CHSC6 |
| Heterotheca subaxillaris | Heterotheca lamarckii Cass. | HELA20 |
| Heterotheca subaxillaris | Heterotheca latifolia Buckl. | HELA5 |
| Heterotheca subaxillaris | Heterotheca latifolia Buckl. var. arkansana Wagenkn. | HELAA |
| Heterotheca subaxillaris | Heterotheca latifolia Buckl. var. macgregoris Wagenkn. | HELAM |
| Heterotheca subaxillaris | Heterotheca psammophila Wagenkn. | HEPS |
| Heterotheca subaxillaris | Heterotheca scabra (Pursh) DC. | HESC11 |
| Heterotheca subaxillaris | Heterotheca subaxillaris (Lam.) Britt. & Rusby var. latifolia (Buckl.) Gandhi & Thomas | HESUL |
| Heterotheca subaxillaris | Heterotheca subaxillaris (Lam.) Britt. & Rusby var. petiolaris Benke | HESUP |
| Heterotheca subaxillaris | Heterotheca subaxillaris (Lam.) Britt. & Rusby var. procumbens Wagenkn. | HESUP3 |
| Heterotheca subaxillaris | Heterotheca subaxillaris (Lam.) Britt. & Rusby var. psammophila (Wagenkn.) Gandhi | HESUP2 |
| Heterotheca villosa var. ballardii | Chrysopsis ballardii Rydb. | CHBA5 |
| Heterotheca villosa var. depressa | Chrysopsis depressa Rydb. | CHDE13 |
| Heterotheca villosa var. depressa | Heterotheca depressa (Rydb.) Dorn | HEDE7 |
| Heterotheca villosa var. foliosa | Chrysopsis butleri Rydb. | CHBU3 |
| Heterotheca villosa var. foliosa | Chrysopsis foliosa Nutt. | CHFO6 |
| Heterotheca villosa var. foliosa | Chrysopsis hirsutissima Greene | CHHI4 |
| Heterotheca villosa var. foliosa | Chrysopsis imbricata A. Nels. | CHIM3 |
| Heterotheca villosa var. foliosa | Chrysopsis villosa (Pursh) Nutt. ex DC. var. foliosa (Nutt.) D.C. Eat. | CHVIF2 |
| Heterotheca villosa var. foliosa | Heterotheca foliosa (Nutt.) Shinners | HEFO9 |
| Heterotheca villosa var. minor | Chrysopsis arida A. Nels. | CHAR12 |
| Heterotheca villosa var. minor | Chrysopsis bakeri Greene | CHBA4 |
| Heterotheca villosa var. minor | Chrysopsis columbiana Greene | CHCO17 |
| Heterotheca villosa var. minor | Chrysopsis hispida (Hook.) DC. | CHHI5 |
| Heterotheca villosa var. minor | Chrysopsis villosa (Pursh) Nutt. ex DC. var. hispida (Hook.) Gray | CHVIH |
| Heterotheca villosa var. minor | Chrysopsis wisconsinensis Shinners | CHWI |
| Heterotheca villosa var. minor | Heterotheca villosa (Pursh) Shinners var. hispida (Hook.) Harms | HEVIH |
| Heterotheca villosa var. minor | Heterotheca wisconsinensis (Shinners) Shinners | HEWI |
| Heterotheca villosa var. nana | Chrysopsis canescens (DC.) Torr. & Gray var. nana Gray | CHCAN2 |
| Heterotheca villosa var. nana | Chrysopsis horrida Rydb. | CHHO7 |
| Heterotheca villosa var. nana | Heterotheca horrida (Rydb.) Harms | HEHO3 |
| Heterotheca villosa var. nana | Heterotheca villosa (Pursh) Shinners var. horrida (Hook.) Semple | HEVIH2 |
| Heterotheca villosa var. pedunculata | Chrysopsis pedunculata Greene | CHPE6 |
| Heterotheca villosa var. scabra | Chrysopsis viscida (Gray) Greene ssp. cinerascens Blake | CHVIC4 |
| Heterotheca villosa var. scabra | Heterotheca horrida (Rydb.) Harms ssp. cinerascens (Blake) Semple | HEHOC |
| Heterotheca villosa var. villosa | Chrysopsis mollis Nutt. | CHMO7 |
| Heterotheca villosa var. villosa | Chrysopsis villosa (Pursh) Nutt. ex DC. | CHVI10 |
| Heterotheca viscida | Chrysopsis villosa (Pursh) Nutt. ex DC. var. viscida Gray | CHVIV5 |
| Heterotheca viscida | Chrysopsis viscida (Gray) Greene | CHVI11 |
| Hieracium ?fernaldii | Hieracium canadense Michx. var. hirtirameum Fern. | HICAH |
| Hieracium ?flagellare var. cernuiforme | Hieracium ?duplex Peter | HIDU2 |
| Hieracium ?flagellare var. cernuiforme | Hieracium ?macrostolonum Schneid. | HIMA4 |
| Hieracium ?flagellare var. cernuiforme | Hieracium flagellare Willd. ssp. cernuiforme Naegeli & Peter | HIFLC2 |
| Hieracium ?flagellare var. glatzense | Hieracium flagellare Willd. ssp. glatzense Naegeli & Peter [excluded] | HIFLG4 |
| Hieracium ?floribundum | Hieracium ?dorei Lepage | HIDO |
| Hieracium ?floribundum | Hieracium auricula L. p.p. | HIAU2 |
| Hieracium albiflorum | Chlorocrepis albiflora (Hook.) W.A. Weber | CHAL16 |
| Hieracium albiflorum | Hieracium helleri Gandog. | HIHE |
| Hieracium albiflorum | Hieracium siskiyouense M.E. Peck | HISI |
| Hieracium argutum | Hieracium argutum Nutt. var. parishii (Gray) Jepson | HIARP2 |
| Hieracium caespitosum | Hieracium pratense Tausch | HIPR |
| Hieracium canadense var. canadense | Hieracium columbianum auct. non Rydb. [misapplied] | HICO7 |
| Hieracium canadense var. canadense | Hieracium kalmii L. var. canadense (Michx.) Reveal | HIKAC |
| Hieracium canadense var. canadense | Hieracium scabriusculum Schwein. var. columbianum auct. non (Rydb.) Lepage [misapplied] | HISCC2 |
| Hieracium canadense var. canadense | Hieracium umbellatum L. var. canadense (Michx.) Breitung | HIUMC |
| Hieracium canadense var. canadense | Hieracium umbellatum L. var. scabriusculum Farw. | HIUMS |
| Hieracium cynoglossoides | Hieracium scouleri Hook. var. griseum (Rydb.) A. Nels. | HISCG |
| Hieracium fendleri var. fendleri | Chlorocrepis fendleri (Schultz-Bip.) W.A. Weber | CHFE5 |
| Hieracium gracile var. gracile | Chlorocrepis tristis (Willd. ex Spreng.) A.& D. L?ve ssp. gracilis (Hook.) W.A. Weber | CHTRG |
| Hieracium gracile var. gracile | Hieracium gracile Hook. var. densifloccosum (Zahn) Cronq. | HIGRD2 |
| Hieracium gracile var. gracile | Hieracium triste Willd. ex Spreng. ssp. gracile (Hook.) Calder & Taylor | HITRG |
| Hieracium gracile var. gracile | Hieracium triste Willd. ex Spreng. var. gracile (Hook.) Gray | HITRG2 |
| Hieracium greenii | Hieracium traillii Greene | HITR5 |
| Hieracium gronovii | Hieracium gronovii L. var. foliosum Michx. | HIGRF |
| Hieracium kalmii var. fasciculatum | Hieracium canadense Michx. var. fasciculatum (Pursh) Fern. | HICAF |
| Hieracium kalmii var. kalmii | Hieracium canadense Michx. var. kalmii (L.) Scoggan | HICAK |
| Hieracium kalmii var. subintegrum | Hieracium canadense Michx. var. subintegrum Lepage | HICAS2 |
| Hieracium lachenalii | Hieracium acuminatum Jord. | HIAC4 |
| Hieracium lachenalii | Hieracium vulgatum Fries | HIVU |
| Hieracium laevigatum | Hieracium acranthophorum Om. | HIAC5 |
| Hieracium laevigatum | Hieracium acranthophorum Om. var. isortoquense B?cher | HIACI2 |
| Hieracium laevigatum | Hieracium devoldii Om. | HIDE3 |
| Hieracium laevigatum | Hieracium eugenii Om. | HIEU2 |
| Hieracium laevigatum | Hieracium musartutense Om. | HIMU8 |
| Hieracium laevigatum | Hieracium nepiocratum Om. | HINE3 |
| Hieracium laevigatum | Hieracium rigorosum (Laestad.) Almquist | HIRI4 |
| Hieracium laevigatum | Hieracium rigorosum (Laestad.) Almquist var. nanusekense Om. | HIRIN2 |
| Hieracium laevigatum | Hieracium rigorosum (Laestad.) Almquist var. sermilikense Om. | HIRIS2 |
| Hieracium laevigatum | Hieracium rigorosum (Laestad.) Almquist var. unanakense Om. | HIRIU2 |
| Hieracium laevigatum | Hieracium stiptocaule Om. | HIST6 |
| Hieracium lemmonii | Hieracium crepidispermum Fries | HICR2 |
| Hieracium marianum | Hieracium ?marianum Willd. (pro sp.) [not hybrid] | HIMA |
| Hieracium marianum | Hieracium pennsylvanicum Fries | HIPE2 |
| Hieracium megacephalon | Hieracium argyraeum Small | HIAR3 |
| Hieracium piloselloides | Hieracium florentinum All. | HIFL |
| Hieracium robinsonii | Hieracium ungavense Lepage | HIUN2 |
| Hieracium rusbyi | Hieracium abscissum Lessing | HIAB2 |
| Hieracium sabaudum | Hieracium vagum Jord. | HIVA2 |
| Hieracium schultzii | Hieracium wrightii (Gray) Robins. & Greenm. | HIWR |
| Hieracium scouleri var. albertinum | Hieracium albertinum Farr | HIAL |
| Hieracium scouleri var. albertinum | Hieracium cusickii Gandog. | HICU2 |
| Hieracium scouleri var. albertinum | Hieracium flettii St. John & Warren | HIFL5 |
| Hieracium scouleri var. nudicaule | Hieracium cynoglossoides Arv.-Touv. var. nudicaule Gray | HICYN |
| Hieracium scouleri var. nudicaule | Hieracium nudicaule (Gray) A. Heller | HINU |
| Hieracium scouleri var. scouleri | Hieracium chapacanum Zahn | HICH |
| Hieracium scouleri var. scouleri | Hieracium parryi Zahn | HIPA5 |
| Hieracium scribneri | Hieracium ?scribneri Small (pro sp.) [not hybrid] | HISC4 |
| Hieracium triste var. triste | Chlorocrepis tristis (Willd. ex Spreng.) A.& D. L?ve | CHTR7 |
| Hieracium triste var. triste | Hieracium triste Willd. ex Spreng. var. tritiforme Zahn | HITRT |
| Hieracium umbellatum | Hieracium columbianum Rydb. | HICO4 |
| Hieracium umbellatum | Hieracium scabriusculum Schwein. | HISC8 |
| Hieracium umbellatum | Hieracium scabriusculum Schwein. var. columbianum (Rydb.) Lepage | HISCC |
| Hieracium umbellatum | Hieracium scabriusculum Schwein. var. perhirsutum Lepage | HISCP |
| Hieracium umbellatum | Hieracium scabriusculum Schwein. var. saximontanum Lepage | HISCS3 |
| Hieracium umbellatum | Hieracium scabriusculum Schwein. var. scabrum (Schwein.) Lepage | HISCS4 |
| Hieracium venosum | Hieracium venosum L. var. nudicaule (Michx.) Farw. | HIVEN |
| high plains goldenrod | Solidago altiplanities C.& J. Taylor | SOAL5 |
| Hill's thistle | Cirsium hillii (Canby) Fern. | CIHI |
| Hillebrand's dubautia | Dubautia linearis (Gaud.) Keck ssp. hillebrandii (Mann) G.D. Carr | DULIH |
| Himalayan fleabane | Erigeron multiradiatus (Lindl. ex DC.) Benth. ex C. B. Clarke | ERMU10 |
| Hinckley's brickellbush | Brickellia hinckleyi Standl. | BRHI4 |
| Hinckley's brickellbush | Brickellia hinckleyi Standl. var. hinckleyi | BRHIH |
| hispid starburr | Acanthospermum hispidum DC. | ACHI |
| hoary balsamroot | Balsamorhiza incana Nutt. | BAIN |
| hoary blackfoot | Melampodium cinereum DC. | MECI |
| hoary blackfoot | Melampodium cinereum DC. var. cinereum | MECIC |
| hoary blackfoot | Melampodium cinereum DC. var. hirtellum Stuessy | MECIH |
| hoary blackfoot | Melampodium cinereum DC. var. ramosissimum (DC.) Gray | MECIR |
| hoary false goldenaster | Heterotheca canescens (DC.) Shinners | HECA8 |
| hoary fleabane | Erigeron canus Gray | ERCA4 |
| hoary groundsel | Packera werneriifolia (Gray) W.A. Weber & A. L?ve | PAWE4 |
| hoary ragwort | Senecio erucifolius L. | SEER5 |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray | MACA2 |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens | MACAC |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. ambigua B.L. Turner | MACAA |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. canescens | MACAC3 |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. incana (Lindl.) Gray | MACAI2 |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. sessiliflora (Nutt.) B.L. Turner | MACAS2 |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. glabra (Gray) B.L. Turner | MACAG |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. glabra (Gray) B.L. Turner var. aristata (Eastw.) B.L. Turner | MACAA2 |
| hoary tansyaster | Machaeranthera canescens (Pursh) Gray ssp. glabra (Gray) B.L. Turner var. glabra Gray | MACAG2 |
| hoary Townsend daisy | Townsendia incana Nutt. | TOIN |
| hole-in-the-sand plant | Nicolletia Gray | NICOL |
| hollyleaf burr ragweed | Ambrosia ilicifolia (Gray) Payne | AMIL2 |
| Holm's ragwort | Senecio amplectens Gray var. holmii (Greene) Harrington | SEAMH |
| holozonia | Holozonia Greene | HOLOZ |
| holy dandelion | Glyptopleura setulosa Gray | GLSE4 |
| Holzinger's eupatorium | Eupatorium purpureum L. var. holzingeri (Rydb.) E. Lamont | EUPUH |
| honeycombhead | Balduina Nutt. | BALDU |
| Honolulu nehe | Lipochaeta ovata R.C. Gardner | LIOV2 |
| Hooker's balsamroot | Balsamorhiza hookeri (Hook.) Nutt. | BAHO |
| Hooker's balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. hookeri | BAHOH3 |
| Hooker's inula | Inula hookeri C.B. Clarke | INHO3 |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House | CRHO7 |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House var. graniticum (E.B. Sm.) E.B. Sm. | CRHOG |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House var. hookerianum | CRHOH |
| Hooker's scratchdaisy | Croptilon hookerianum (Torr. & Gray) House var. validum (Rydb.) E.B. Sm. | CRHOV |
| Hooker's Townsend daisy | Townsendia hookeri Beaman | TOHO |
| Hoover's western rosinweed | Calycadenia hooveri G.D. Carr | CAHO18 |
| Hopi tea greenthread | Thelesperma megapotamicum (Spreng.) Kuntze | THME |
| horrid herrickia | Eurybia horrida (Woot. & Standl.) Nesom | EUHO4 |
| horsebrush | Tetradymia DC. | TETRA3 |
| horseweed | Conyza Less. | CONYZ |
| Houghton's goldenrod | Oligoneuron houghtonii (Torr. & Gray ex Gray) Nesom | OLHO |
| houndstongue hawkweed | Hieracium cynoglossoides Arv.-Touv. | HICY |
| Houston tansyaster | Rayjacksonia aurea (Gray) R.L. Hartman & M.A. Lane | RAAU4 |
| Howaiaulu island-daisy | Keysseria maviensis (Mann) Cabrera | KEMA |
| Howell's fleabane | Erigeron howellii Gray | ERHO3 |
| Howell's gumweed | Grindelia howellii Steyermark | GRHO |
| Howell's pussytoes | Antennaria howellii Greene | ANHO |
| Howell's pussytoes | Antennaria howellii Greene ssp. howellii | ANHOH |
| Howell's pussytoes | Antennaria howellii Greene ssp. neodioica (Greene) Bayer | ANHON |
| Howell's silverpuffs | Microseris howellii Gray | MIHO2 |
| Huachuca hawkweed | Hieracium carneum Greene | HICA4 |
| Huachuca Mountain ragwort | Senecio multidentatus Schultz-Bip. ex Hemsl. | SEMU9 |
| Huachuca Mountain ragwort | Senecio multidentatus Schultz-Bip. ex Hemsl. var. huachucanus (Gray) T.M. Barkl. | SEMUH |
| Huber's fleabane | Erigeron huberi Welsh & Atwood | ERHU6 |
| Hueco rockdaisy | Perityle huecoensis A. Powell | PEHU5 |
| huisache daisy | Amblyolepis setigera DC. | AMSE |
| Hulsea algida | Hulsea caespitosa A. Nels. & Kennedy | HUCA5 |
| Hulsea algida | Hulsea carnosa Rydb. | HUCA3 |
| Hulsea algida | Hulsea nevadensis Gandog. | HUNE |
| Hulsea nana | Hulsea larsenii (Gray) Rydb. | HULA |
| Hulsea nana | Hulsea nana Gray var. larsenii Gray | HUNAL |
| Hulsea nana | Hulsea volcanica Gandog. | HUVO |
| Hulsea vestita ssp. callicarpha | Hulsea callicarpha (Hall) S. Wats. ex Rydb. | HUCA4 |
| Hulsea vestita ssp. callicarpha | Hulsea vestita Gray var. callicarpha Hall | HUVEC2 |
| Hulsea vestita ssp. inyoensis | Hulsea californica Torr. & Gray ssp. inyoensis Keck | HUCAI2 |
| Hulsea vestita ssp. inyoensis | Hulsea inyoensis (Keck) Munz | HUIN2 |
| Hulsea vestita ssp. parryi | Hulsea parryi Gray | HUPA |
| Hulsea vestita ssp. pygmaea | Hulsea vestita Gray var. pygmaea Gray | HUVEP3 |
| Hulten's fleabane | Erigeron hultenii Spongberg | ERHU3 |
| Hulteniella integrifolia | Arctanthemum integrifolium (Richards.) Tzvelev | ARIN25 |
| Hulteniella integrifolia | Chrysanthemum integrifolium Richards. | CHIN18 |
| Hulteniella integrifolia | Leucanthemum integrifolium (Richards.) DC. | LEIN4 |
| Humboldt mule-ears | Wyethia longicaulis Gray | WYLO |
| Hymenoclea salsola var. fasciculata | Hymenoclea fasciculata A. Nels. | HYFA2 |
| Hymenoclea salsola var. fasciculata | Hymenoclea salsola Torr. & Gray ex Gray var. patula (A. Nels.) K.M. Peterson & Payne | HYSAP2 |
| Hymenoclea salsola var. pentalepis | Hymenoclea pentalepis Rydb. | HYPE4 |
| Hymenoclea sandersonii | Ambrosia sandersonii Welsh | AMSA6 |
| hymenopappus | Hymenopappus L'H?r. | HYMEN4 |
| Hymenopappus artemisiifolius var. artemisiifolius | Hymenopappus scabiosaeus L'H?r. var. artemisiifolius (DC.) Gandhi & Thomas | HYSCA2 |
| Hymenopappus artemisiifolius var. riograndensis | Hymenopappus scabiosaeus L'H?r. var. riograndensis (B.L. Turner) Gandhi | HYSCR |
| Hymenopappus filifolius var. cinereus | Hymenopappus arenosus Heller | HYAR6 |
| Hymenopappus filifolius var. cinereus | Hymenopappus cinereus Rydb. | HYCI4 |
| Hymenopappus filifolius var. eriopodus | Hymenopappus eriopodus A. Nels. | HYER |
| Hymenopappus filifolius var. lugens | Hymenopappus gloriosus Heller | HYGL4 |
| Hymenopappus filifolius var. lugens | Hymenopappus lugens Greene | HYLU3 |
| Hymenopappus filifolius var. luteus | Hymenopappus luteus Nutt. | HYLU2 |
| Hymenopappus filifolius var. nudipes | Hymenopappus filifolius Hook. var. alpestris (Maguire) Shinners | HYFIA |
| Hymenopappus filifolius var. pauciflorus | Hymenopappus pauciflorus I.M. Johnston | HYPA7 |
| Hymenopappus filifolius var. polycephalus | Hymenopappus polycephalus Osterhout | HYPO5 |
| Hymenopappus flavescens var. canotomentosus | Hymenopappus robustus Greene | HYRO5 |
| Hymenopappus newberryi | Leucampyx newberryi Gray | LENE6 |
| Hymenopappus scabiosaeus var. corymbosus | Hymenopappus corymbosus Torr. & Gray | HYCO10 |
| Hymenopappus scabiosaeus var. scabiosaeus | Hymenopappus carolinensis (Lam.) Porter | HYCA14 |
| Hymenoxys ambigens var. ambigens | Plummera ambigens Blake | PLAM |
| Hymenoxys ambigens var. floribunda | Hymenoxys microcephala (Gray) Bierner | HYMI10 |
| Hymenoxys ambigens var. floribunda | Plummera floribunda Gray | PLFL2 |
| Hymenoxys bigelovii | Macdougalia bigelovii (Gray) Heller | MABI7 |
| Hymenoxys cooperi var. canescens | Actinea canescens (D.C. Eat.) Blake | ACCA13 |
| Hymenoxys cooperi var. cooperi | Actinea cooperi (Gray) Kuntze | ACCO9 |
| Hymenoxys helenioides | Picradenia helenioides Rydb. | PIHE7 |
| Hymenoxys hoopesii | Dugaldia hoopesii (Gray) Rydb. | DUHO |
| Hymenoxys hoopesii | Helenium hoopesii Gray | HEHO5 |
| Hymenoxys odorata | Picradenia odorata (DC.) Britt. | PIOD |
| Hymenoxys richardsonii var. floribunda | Actinella richardsonii (Hook.) Nutt. var. floribunda Gray | ACRIF |
| Hymenoxys richardsonii var. floribunda | Hymenoxys olivacea Cockerell | HYOL |
| Hymenoxys richardsonii var. floribunda | Hymenoxys richardsonii (Hook.) Cockerell var. utahensis Cockerell | HYRIU |
| Hymenoxys richardsonii var. floribunda | Picradenia richardsonii Hook. var. floribunda (Gray) W.A. Weber | PIRIF |
| Hymenoxys richardsonii var. richardsonii | Actinea richardsonii (Hook.) Kuntze | ACRI3 |
| Hymenoxys richardsonii var. richardsonii | Picradenia richardsonii Hook. | PIRI6 |
| Hymenoxys vaseyi | Actinea vaseyi (Gray) Kuntze | ACVA2 |
| Hypochaeris brasiliensis var. tweediei | Hypochaeris brasiliensis (Less.) Griseb. var. tweedyi (Hook. & Arn.) Baker [orthographic variant] | HYBRT |
| Hypochaeris brasiliensis var. tweediei | Hypochaeris elata auct. non (Weddell) Griseb. [misapplied] | HYEL5 |
| Hypochaeris brasiliensis var. tweediei | Hypochaeris tweediei Hook. & Arn. | HYTW2 |
| Hypochaeris brasiliensis var. tweediei | Hypochaeris tweedyi Hook. & Arn. [orthographic variant] | HYTW |
| hyssopleaf fleabane | Erigeron hyssopifolius Michx. | ERHY5 |
| hyssopleaf fleabane | Erigeron hyssopifolius Michx. var. hyssopifolius | ERHYH2 |
| hyssopleaf thoroughwort | Eupatorium hyssopifolium L. | EUHY |
| hyssopleaf thoroughwort | Eupatorium hyssopifolium L. var. calcaratum Fern. & Schub. | EUHYC |
| hyssopleaf thoroughwort | Eupatorium hyssopifolium L. var. hyssopifolium | EUHYH |
| hyssopleaf thoroughwort | Eupatorium hyssopifolium L. var. laciniatum Gray | EUHYL |
| Iberian knapweed | Centaurea iberica Trev. ex Spreng. | CEIB |
| Idaho balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. idahoensis (Sharp) Cronq. | BAHOI |
| Idaho fleabane | Erigeron asperugineus (D.C. Eat.) Gray | ERAS |
| Idaho goldenweed | Tonestus aberrans (A. Nels.) Nesom & D. Morgan | TOAB |
| Idaho gumweed | Grindelia nana Nutt. | GRNA |
| Idaho gumweed | Grindelia nana Nutt. var. integerrima (Rydb.) Steyermark | GRNAI |
| Idaho gumweed | Grindelia nana Nutt. var. nana | GRNAN |
| Idaho hawksbeard | Crepis bakeri Greene ssp. idahoensis Babcock & Stebbins | CRBAI |
| Idaho hymenopappus | Hymenopappus filifolius Hook. var. lugens (Greene) Jepson | HYFIL |
| iliau | Wilkesia Gray | WILKE |
| iliau | Wilkesia gymnoxiphium Gray | WIGY |
| Illyrian cottonthistle | Onopordum illyricum L. | ONIL |
| imberis woodyaster | Xylorhiza tortifolia (Torr. & Gray) Greene var. imberbis (Cronq.) T.J. Wats. | XYTOI |
| Indian aster | Kalimeris indica (L.) Schultz-Bip. | KAIN5 |
| Indian camphorweed | Pluchea indica (L.) Less. | PLIN4 |
| Indian Canyon fleabane | Erigeron untermannii Welsh & Goodrich | ERUN5 |
| Indian headdress | Tracyina Blake | TRACY |
| Indian headdress | Tracyina rostrata Blake | TRRO |
| Indian lettuce | Lactuca indica L. | LAIN13 |
| Indian plaintain | Arnoglossum Raf. | ARNOG |
| Indian plantain | Parasenecio W.W. Sm. & Small | PARAS2 |
| Indianbush | Psacalium Cass. | PSACA |
| interior ironweed | Vernonia baldwinii Torr. ssp. interior (Small) Faust | VEBAI2 |
| intermediate balsamroot | Balsamorhiza careyana Gray var. intermedia Cronq. | BACAI |
| Intermountain rubberweed | Hymenoxys helenioides (Rydb.) Cockerell | HYHE |
| Inyo rockdaisy | Perityle inyoensis (Ferris) A. Powell | PEIN8 |
| Ionactis alpina | Aster scopulorum Gray | ASSC3 |
| Ionactis alpina | Chrysopsis alpina Nutt. | CHAL21 |
| Ionactis elegans | Chaetopappa elegans Soreng & Spellenberg | CHEL2 |
| Ionactis linariifolius | Aster linariifolius L. | ASLI2 |
| Ionactis linariifolius | Aster linariifolius L. var. victorinii Fern. | ASLIV |
| Ionactis stenomeres | Aster stenomeres Gray | ASST3 |
| Iranian knapweed | Centaurea depressa Bieb. | CEDE10 |
| ironweed | Cyanthillium Blume | CYANT2 |
| ironweed | Vernonia anthelmintica (L.) Willd. | VEAN5 |
| ironweed | Vernonia galamensis (Cass.) Less. | VEGA |
| ironweed | Vernonia Schreb. | VERNO |
| island bristleweed | Hazardia detonsa (Greene) Greene | HADE4 |
| island cinchweed | Pectis tenuicaulis Urban | PETE10 |
| island hazardia | Hazardia cana (Gray) Greene | HACA6 |
| island sagebrush | Artemisia nesiotica Raven | ARNE6 |
| island senecio | Senecio lyonii Gray | SELY |
| island-aster | Hesperomannia Gray | HESPE8 |
| islandthicket thoroughwort | Koanophyllon polyodon (Urban) King & H.E. Robins. | KOPO |
| Isocarpha oppositifolia | Calea oppositifolia L. | CAOP4 |
| Isocoma acradenia var. acradenia | Haplopappus acradenius (Greene) Blake | HAAC2 |
| Isocoma acradenia var. bracteosa | Haplopappus acradenius (Greene) Blake ssp. bracteosus (Greene) Hall | HAACB |
| Isocoma acradenia var. bracteosa | Isocoma bracteosa Greene | ISBR2 |
| Isocoma acradenia var. eremophila | Haplopappus acradenius (Greene) Blake ssp. eremophilus (Greene) Hall | HAACE |
| Isocoma acradenia var. eremophila | Isocoma acradenia (Greene) Greene ssp. eremophila (Greene) Beauchamp | ISACE |
| Isocoma acradenia var. eremophila | Isocoma eremophila Greene | ISER |
| Isocoma arguta | Haplopappus venetus (Kunth) Blake var. argutus (Greene) Keck | HAVEA |
| Isocoma coronopifolia | Isocoma coronopifolia (Gray) Greene var. pedicellata (Greene) Nesom | ISCOP |
| Isocoma coronopifolia | Isocoma pedicellata Greene | ISPE |
| Isocoma drummondii | Haplopappus drummondii (Torr. & Gray) Blake | HADR2 |
| Isocoma drummondii | Isocoma megalantha Shinners | ISME4 |
| Isocoma humilis | Haplopappus leverichii Cronq. | HALE7 |
| Isocoma menziesii var. decumbens | Haplopappus venetus (Kunth) Blake ssp. furfuraceus (Greene) Hall | HAVEF |
| Isocoma menziesii var. decumbens | Isocoma veneta (Kunth) Greene var. furfuracea (Greene) Beauchamp | ISVEF |
| Isocoma menziesii var. menziesii | Haplopappus venetus (Kunth) Blake ssp. oxyphyllus (Greene) Hall | HAVEO |
| Isocoma menziesii var. menziesii | Isocoma oxyphylla Greene | ISOX |
| Isocoma menziesii var. menziesii | Isocoma veneta (Kunth) Greene var. oxyphylla (Greene) Beauchamp | ISVEO |
| Isocoma menziesii var. sedoides | Haplopappus venetus (Kunth) Blake var. sedoides (Greene) Munz | HAVES2 |
| Isocoma menziesii var. sedoides | Isocoma veneta (Kunth) Greene var. sedoides (Greene) Jepson | ISVES |
| Isocoma menziesii var. vernonioides | Haplopappus venetus (Kunth) Blake ssp. vernonioides (Nutt.) Hall | HAVEV |
| Isocoma menziesii var. vernonioides | Isocoma veneta (Kunth) Greene var. vernonioides (Nutt.) Jepson | ISVEV2 |
| Isocoma menziesii var. vernonioides | Isocoma vernonioides Nutt. | ISVE3 |
| Isocoma pluriflora | Haplopappus heterophyllus (Gray) Blake | HAHE2 |
| Isocoma pluriflora | Haplopappus pluriflorus (Torr. & Gray) Hall | HAPL |
| Isocoma pluriflora | Isocoma wrightii (Gray) Rydb. | ISWR |
| Isocoma rusbyi | Haplopappus rusbyi (Greene) Cronq. | HARU |
| Isocoma tenuisecta | Haplopappus tenuisectus (Greene) Blake | HATE |
| Isocoma veneta | Haplopappus venetus (Kunth) Blake [excluded] | HAVE5 |
| Italian aster | Aster amellus L. | ASAM12 |
| Italian hawksbeard | Crepis bursifolia L. | CRBU3 |
| Italian plumeless thistle | Carduus pycnocephalus L. | CAPY2 |
| Iva annua var. ?macrocarpa | Iva ciliata Willd. var. macrocarpa Blake | IVCIM |
| Iva annua var. annua | Iva ciliata Willd. | IVCI2 |
| Iva annua var. caudata | Iva caudata Small | IVCA3 |
| Iva axillaris | Iva axillaris Pursh ssp. robustior (Hook.) Bassett | IVAXR |
| Iva axillaris | Iva axillaris Pursh var. robustior Hook. | IVAXR2 |
| Iva frutescens ssp. oraria | Iva frutescens L. var. oraria (Bartlett) Fern. & Grisc. | IVFRO |
| Iva texensis | Iva angustifolia Nutt. ex DC. var. latior Shinners | IVANL |
| Ives's fournerved daisy | Tetraneuris ivesiana Greene | TEIV |
| ivyleaf thoroughwort | Chromolaena ivifolia (L.) King & H.E. Robins. | CHIV |
| ixeris | Ixeris (Cass.) Cass. | IXERI |
| Ixeris stolonifera | Lactuca stolonifera (Gray) Maxim. | LAST3 |
| Jack in the bush | Chromolaena odorata (L.) King & H.E. Robins. | CHOD |
| Jack-go-to-bed-at-noon | Tragopogon lamottei Rouy | TRLA30 |
| jackass breadnut | Clibadium erosum (Sw.) DC. | CLER |
| Jackson Hole thistle | Cirsium subniveum Rydb. | CISU |
| Jalisco rabbit-tobacco | Pseudognaphalium jaliscense (Greenm.) A. Anderb. | PSJA4 |
| Jamaican fleabane | Erigeron jamaicensis L. | ERJA2 |
| Jame's rubberweed | Hymenoxys jamesii Bierner | HYJA |
| jamesianthus | Jamesianthus Blake & Sherff | JAMES2 |
| Japanese nipplewort | Lapsanastrum apogonoides (Maxim.) J.H. Pak & K. Bremer | LAAP3 |
| Japanese sweet coltsfoot | Petasites japonicus (Sieb. & Zucc.) Maxim. | PEJA3 |
| Japanese thistle | Cirsium japonicum Fisch. ex DC. | CIJA2 |
| jaumea | Jaumea Pers. | JAUME |
| jefea | Jefea Strother | JEFEA |
| Jefea brevifolia | Zexmenia brevifolia Gray | ZEBR2 |
| Jensia rammii | Madia rammii Greene | MARA2 |
| Jensia yosemitana | Madia yosemitana Parry ex Gray | MAYO |
| Jepson's brickellbush | Brickellia californica (Torr. & Gray) Gray var. jepsonii B.L. Robins. | BRCAJ |
| Jepson's woolly sunflower | Eriophyllum jepsonii Greene | ERJE |
| Jersey cudweed | Pseudognaphalium luteoalbum (L.) Hilliard & Burtt | PSLU6 |
| Jersey knapweed | Centaurea paniculata L. | CEPA14 |
| Jerusalem artichoke | Helianthus tuberosus L. | HETU |
| Jessica's aster | Symphyotrichum jessicae (Piper) Nesom | SYJE |
| Jesuit's bark | Iva frutescens L. | IVFR |
| Jesuit's bark | Iva frutescens L. ssp. frutescens | IVFRF |
| Jesuit's bark | Iva frutescens L. ssp. oraria (Bartlett) R.C. Jackson | IVFRO2 |
| jeweled distaff thistle | Carthamus oxyacanthus Bieb. | CAOX6 |
| jeweled thistle | Cirsium araneans Rydb. | CIAR6 |
| John Day's pincushion | Chaenactis nevii Gray | CHNE6 |
| Jones's aster | Eurybia jonesiae (Lamboy) Nesom | EUJO3 |
| Jones's false goldenaster | Heterotheca jonesii (Blake) Welsh & Atwood | HEJO |
| Jones's fleabane | Erigeron jonesii Cronq. | ERJO2 |
| Jones's tidytips | Layia jonesii Gray | LAJO |
| Jones's Townsend daisy | Townsendia jonesii (Beaman) Reveal | TOJO |
| Jones's Townsend daisy | Townsendia jonesii (Beaman) Reveal var. jonesii | TOJOJ |
| Jones's Townsend daisy | Townsendia jonesii (Beaman) Reveal var. tumulosa Reveal | TOJOT |
| Julia's goldenrod | Solidago juliae Nesom | SOJU2 |
| Junak's desertdandelion | Malacothrix junakii W.S. Davis | MAJU2 |
| justiceweed | Eupatorium leucolepis (DC.) Torr. & Gray | EULE |
| justiceweed | Eupatorium leucolepis (DC.) Torr. & Gray var. leucolepis | EULEL |
| justiceweed | Eupatorium leucolepis (DC.) Torr. & Gray var. novae-angliae Fern. | EULEN |
| kachina fleabane | Erigeron kachinensis Welsh & Moore | ERKA |
| Kahili beggarticks | Bidens forbesii Sherff ssp. kahiliensis Ganders & Nagata | BIFOK |
| Kaibab pussytoes | Antennaria rosulata Rydb. | ANRO3 |
| Kalalau rim dubautia | Dubautia kenwoodii G.D. Carr | DUKE |
| Kalalau Valley remya | Remya montgomeryi W.L. Wagner & Herbst | REMO |
| Kalealaha beggarticks | Bidens micrantha Gaud. ssp. kalealaha Nagata & Ganders | BIMIK2 |
| Kalimeris mongolica | Aster mongolicus Franch. | ASMO17 |
| Kalm's hawkweed | Hieracium kalmii L. | HIKA2 |
| Kalm's hawkweed | Hieracium kalmii L. var. kalmii | HIKAK2 |
| Kamchatka thistle | Cirsium kamtschaticum Ledeb. ex DC. | CIKA |
| kau silversword | Argyroxiphium kauense (Rock & Neal) O.& I. Deg. | ARKA2 |
| Kauai beggarticks | Bidens cervicata Sherff | BICE2 |
| Kauai dubautia | Dubautia microcephala Skottsberg | DUMI |
| Kauai island-aster | Hesperomannia lydgatei Forbes | HELY |
| Kauai nehe | Lipochaeta micrantha (Nutt.) Gray | LIMI8 |
| Kauai nehe | Lipochaeta micrantha (Nutt.) Gray var. exigua (O. Deg. & Sherff) R.C. Gardner | LIMIE |
| Kauai nehe | Lipochaeta micrantha (Nutt.) Gray var. micrantha | LIMIM |
| Kauai remya | Remya kauaiensis Hbd. | REKA |
| Kauai tetramolopium | Tetramolopium consanguineum (Gray) Hbd. ssp. leptophyllum (Sherff) Lowrey var. kauense Lowrey | TECOK |
| Kauai wormwood | Artemisia kauaiensis (Skottsberg) Skottsberg | ARKA3 |
| Keaau Valley dubautia | Dubautia herbstobatae G.D. Carr | DUHE |
| Keil's erigeron | Erigeron inornatus (Gray) Gray var. keilii Nesom | ERINK |
| Kellogg's tarweed | Hemizonia kelloggii Greene | HEKE |
| Kern Canyon false goldenaster | Heterotheca shevockii (Semple) Semple | HESH4 |
| Kern River fleabane | Erigeron multiceps Greene | ERMU2 |
| Kern tarweed | Deinandra pallida (Keck) B.G. Baldwin | DEPA17 |
| Keysseria erici | Lagenifera erici Forbes | LAER2 |
| Keysseria helenae | Lagenifera helenae Forbes & Lydgate | LAHE4 |
| Keysseria maviensis | Keysseria lavandula St. John | KELA |
| Keysseria maviensis | Lagenifera maviensis Mann | LAMA7 |
| Keysseria maviensis | Lagenophora viridis St. John | LAVI6 |
| kidneyleaf rosinweed | Silphium compositum Michx. | SICO5 |
| kidneyleaf rosinweed | Silphium compositum Michx. var. compositum | SICOC |
| kidneyleaf rosinweed | Silphium compositum Michx. var. ovatifolium Torr. & Gray | SICOO2 |
| kidneyleaf rosinweed | Silphium compositum Michx. var. reniforme (Raf. ex Nutt.) Torr. & Gray | SICOR2 |
| kidneyleaf rosinweed | Silphium compositum Michx. var. venosum (Small) Kartesz & Gandhi | SICOV2 |
| King's ragwort | Senecio eremophilus Richards. var. kingii (Rydb.) Greenm. | SEERK |
| King's serpentweed | Tonestus kingii (D.C. Eat.) Nesom | TOKI |
| King's serpentweed | Tonestus kingii (D.C. Eat.) Nesom var. kingii | TOKIK |
| kingdevil | Hieracium praealtum Vill. ex Gochnat | HIPR3 |
| kingdevil | Hieracium praealtum Vill. ex Gochnat var. decipiens W.D.J. Koch | HIPRD |
| kingdevil | Hieracium praealtum Vill. ex Gochnat var. praealtum Vill. ex Gochnat [excluded] | HIPRP2 |
| Kjellman's groundsel | Tephroseris kjellmanii (Porsild) Holub | TEKJ |
| Klamath arnica | Arnica spathulata Greene | ARSP4 |
| Klamath coneflower | Rudbeckia klamathensis P. Cox & Urbatsch | RUKL |
| Klamath erigeron | Erigeron breweri Gray var. klamathensis Nesom | ERBRK |
| Kleinia anteuphorbium | Senecio anteuphorbium (L.) Sch. Bip. | SEAN8 |
| Klickitat aster | Eucephalus glaucescens (Gray) Greene | EUGL11 |
| Knapp brickellbush | Brickellia knappiana E. Drew | BRKN |
| knapweed | Centaurea L. | CENTA |
| knapweed | Cyanopsis Cass. | CYANO |
| ko'oko'olau | Lipochaeta perdita Sherff | LIPE4 |
| Koanophyllon dolicholepis | Eupatorium dolicholepis (Urban) Britt. | EUDO2 |
| Koanophyllon droserolepis | Eupatorium droserolepis B.L. Robins. | EUDR |
| Koanophyllon polyodon | Eupatorium polyodon Urban | EUPO6 |
| Koanophyllon solidaginifolium | Eupatorium solidaginifolium Gray | EUSO |
| Koanophyllon villosum | Eupatorium villosum Sw. | EUVI4 |
| koholapehu | Dubautia latifolia (Gray) Keck | DULA3 |
| kokolau | Bidens amplectens Sherff | BIAM3 |
| Koolau Range beggarticks | Bidens asymmetrica (Levl.) Sherff | BIAS3 |
| Kral's aster | Symphyotrichum kralii Nesom | SYKR |
| Krigia biflora | Krigia amplexicaulis Nutt. | KRAM |
| Krigia biflora var. biflora | Cynthia virginica (L.) D. Don, non Hyoseris virginica L. | CYVI13 |
| Krigia biflora var. biflora | Hyoseris biflora Walt. | HYBI5 |
| Krigia biflora var. biflora | Krigia biflora (Walt.) Blake ssp. glandulifera (Fern.) Iltis | KRBIG |
| Krigia biflora var. viridis | Cynthia viridis Standl. | CYVI14 |
| Krigia caespitosa | Krigia cespitosa (Raf.) Chambers [orthographic variant] | KRCE |
| Krigia caespitosa | Krigia gracilis (DC.) Shinners | KRGR2 |
| Krigia caespitosa | Krigia oppositifolia Raf. | KROP2 |
| Krigia caespitosa | Serinia oppositifolia (Raf.) Kuntze | SEOP |
| Krigia dandelion | Cynthia dandelion (L.) DC. | CYDA5 |
| Krigia montana | Cynthia montana (Michx.) Standl. | CYMO9 |
| Krigia occidentalis | Cymbia occidentalis (Nutt.) Standl. | CYOC3 |
| Krigia virginica | Hyoseris virginica L. | HYVI5 |
| Kure Atoll nehe | Lipochaeta integrifolia (Nutt.) Gray | LIIN4 |
| Kyhosia bolanderi | Madia bolanderi (Gray) Gray | MABO |
| la graciosa thistle | Cirsium loncholepis Petrak | CILO |
| La Playa Springs tansyaster | Machaeranthera gypsitherma Nesom, Vorobik & R.L. Hartman | MAGY2 |
| lace-leaved rockdaisy | Perityle ambrosiifolia Greene ex A. Powell & S.C. Yarborough | PEAM11 |
| Lackschewitz's fleabane | Erigeron lackschewitzii Nesom & W.A. Weber | ERLA17 |
| Lactuca biennis | Lactuca spicata (Lam.) A.S. Hitchc. var. integrifolia (Torr. & Gray) Britt. | LASPI |
| Lactuca biennis | Lactuca spicata auct. non (Lam.) A.S. Hitchc. [misapplied] | LASP4 |
| Lactuca biennis | Mulgedium spicatum (Lam.) Small var. integrifolium (Torr. & Gray) Small | MUSPI |
| Lactuca biennis | Mulgedium spicatum auct. non (Lam.) Small [misapplied] | MUSP2 |
| Lactuca canadensis | Lactuca canadensis L. var. integrifolia (Bigelow) Torr. & Gray | LACAI |
| Lactuca canadensis | Lactuca canadensis L. var. latifolia Kuntze | LACAL |
| Lactuca canadensis | Lactuca canadensis L. var. longifolia (Michx.) Farw. | LACAL2 |
| Lactuca canadensis | Lactuca canadensis L. var. obovata Wieg. | LACAO |
| Lactuca canadensis | Lactuca canadensis L. var. typica Wieg. | LACAT |
| Lactuca canadensis | Lactuca sagittifolia Ell. | LASA4 |
| Lactuca canadensis | Lactuca steelei Britt. | LAST8 |
| Lactuca floridana var. floridana | Mulgedium floridanum (L.) DC. | MUFL |
| Lactuca floridana var. villosa | Lactuca villosa Jacq. | LAVI4 |
| Lactuca floridana var. villosa | Mulgedium villosum (Jacq.) Small | MUVI3 |
| Lactuca ludoviciana | Lactuca campestris Greene | LACA6 |
| Lactuca ludoviciana | Lactuca campestris Greene var. typica Wieg. | LACAT2 |
| Lactuca saligna | Lactuca saligna L. var. runcinata Gren. & Godr. | LASAR |
| Lactuca sativa | Lactuca scariola L. var. integrata Gren. & Godr. | LASCI |
| Lactuca sativa | Lactuca scariola L. var. integrifolia (Bogenh.) G. Beck | LASCI2 |
| Lactuca serriola | Lactuca scariola L. | LASC6 |
| Lactuca tatarica var. pulchella | Lactuca oblongifolia Nutt. | LAOB2 |
| Lactuca tatarica var. pulchella | Lactuca pulchella (Pursh) DC. | LAPU |
| Lactuca tatarica var. pulchella | Lactuca tatarica (L.) C.A. Mey. ssp. pulchella (Pursh) Stebbins | LATAP2 |
| Lactuca tatarica var. pulchella | Lactuca tatarica (L.) C.A. Mey. var. heterophylla (Nutt.) Boivin | LATAH |
| Lactuca tatarica var. pulchella | Sonchus tataricus L. p.p. | SOTA |
| lacy tansyaster | Machaeranthera pinnatifida (Hook.) Shinners | MAPI |
| lacy tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. pinnatifida | MAPIP |
| lacy tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. pinnatifida var. glaberrima (Rydb.) B.L. Turner & R.L. Hartman | MAPIG3 |
| lacy tansyaster | Machaeranthera pinnatifida (Hook.) Shinners ssp. pinnatifida var. pinnatifida | MAPIP4 |
| lacy thistle | Cirsium modestum (Osterhout) Cockerell | CIMO2 |
| ladies's false fleabane | Pulicaria arabica (L.) Cass. | PUAR2 |
| ladies's tobacco | Pseudognaphalium californicum (DC.) A. Anderb. | PSCA13 |
| Laennecia coulteri | Conyza coulteri Gray | COCO4 |
| Laennecia coulteri | Conyza coulteri Gray var. virgata (Benth.) Gray | COCOV2 |
| Laennecia coulteri | Eschenbachia coulteri (Gray) Rydb. | ESCO2 |
| Laennecia eriophylla | Conyza eriophylla (Gray) Cronq. | COER7 |
| Laennecia eriophylla | Erigeron eriophyllus Gray | ERER7 |
| Laennecia filaginoides | Conyza filaginoides (DC.) Hieron. | COFI3 |
| Laennecia schiedeana | Conyza schiedeana (Less.) Cronq. | COSC3 |
| Laennecia schiedeana | Erigeron schiedeanus Less. | ERSC10 |
| Laennecia schiedeana | Leptilon integrifolium Woot. & Standl. | LEIN8 |
| Laennecia sophiifolia | Conyza coulteri Gray var. tenuisecta Gray | COCOT |
| Laennecia sophiifolia | Conyza sophiifolia Kunth | COSO2 |
| Laennecia sophiifolia | Eschenbachia tenuisecta (Gray) Woot. & Standl. | ESTE |
| laennicia | Laennecia Cass. | LAENN |
| lagascea | Lagascea Cav. | LAGAS |
| Lagascea mollis | Nocca mollis (Cav.) Jacq. | NOMO |
| Lagophylla glandulosa | Lagophylla glandulosa Gray ssp. serrata (Greene) Keck | LAGLS |
| Lagophylla ramosissima ssp. congesta | Lagophylla congesta Greene | LACO |
| Lake Huron tansy | Tanacetum bipinnatum (L.) Schultz-Bip. | TABI |
| Lake Huron tansy | Tanacetum bipinnatum (L.) Schultz-Bip. ssp. bipinnatum | TABIB |
| Lake Huron tansy | Tanacetum bipinnatum (L.) Schultz-Bip. ssp. huronense (Nutt.) Breitung | TABIH |
| Lake Powell fleabane | Erigeron zothecinus Welsh | ERZO |
| Lake Tahoe serpentweed | Tonestus eximius (Hall) A. Nels. & J.F. Macbr. | TOEX3 |
| lakeside sunflower | Helianthus carnosus Small | HECA14 |
| lamb succory | Arnoseris minima (L.) Schweig. & Koerte | ARMI3 |
| lambstongue ragwort | Senecio integerrimus Nutt. | SEIN2 |
| lambstongue ragwort | Senecio integerrimus Nutt. var. integerrimus | SEINI |
| lambstongue ragwort | Senecio integerrimus Nutt. var. major (Gray) Cronq. | SEINM |
| Lanai island-aster | Hesperomannia arborescens Gray | HEAR9 |
| lanate balsamroot | Balsamorhiza lanata (Sharp) W.A. Weber | BALA8 |
| lance-leaf goldenrod | Solidago lancifolia Torr. & Gray | SOLA6 |
| lanceleaf arnica | Arnica lanceolata Nutt. | ARLA7 |
| lanceleaf blanketflower | Gaillardia aestivalis (Walt.) H. Rock | GAAE |
| lanceleaf blanketflower | Gaillardia aestivalis (Walt.) H. Rock var. aestivalis | GAAEA |
| lanceleaf blanketflower | Gaillardia aestivalis (Walt.) H. Rock var. flavovirens (C. Mohr) Cronq. | GAAEF |
| lanceleaf blazing star | Liatris lancifolia (Greene) Kittell | LILA |
| lanceleaf goldenweed | Pyrrocoma lanceolata (Hook.) Greene | PYLA |
| lanceleaf goldenweed | Pyrrocoma lanceolata (Hook.) Greene var. lanceolata | PYLAL |
| lanceleaf goldenweed | Pyrrocoma lanceolata (Hook.) Greene var. subviscosa (Greene) Mayes ex G. Brown & Keil | PYLAS |
| lanceleaf ragweed | Ambrosia bidentata Michx. | AMBI2 |
| lanceleaf thoroughwort | Eupatorium lancifolium (Torr. & Gray) Small | EULA7 |
| lanceleaf tickseed | Coreopsis lanceolata L. | COLA5 |
| Lapsanastrum apogonoides | Lapsana apogonoides Maxim. | LAAP |
| Laramie chickensage | Sphaeromeria simplex (A. Nels.) Heller | SPSI3 |
| large mountain fleabane | Erigeron coulteri Porter | ERCO6 |
| largeflower aster | Symphyotrichum grandiflorum (L.) Nesom | SYGR5 |
| largeflower fleabane | Erigeron grandiflorus Hook. | ERGR3 |
| largeflower fleabane | Erigeron grandiflorus Hook. ssp. arcticus Porsild | ERGRA |
| largeflower fleabane | Erigeron grandiflorus Hook. ssp. grandiflorus | ERGRG |
| largeflower goldenweed | Pyrrocoma carthamoides Hook. | PYCA3 |
| largeflower goldenweed | Pyrrocoma carthamoides Hook. var. carthamoides | PYCAC2 |
| largeflower goldenweed | Pyrrocoma carthamoides Hook. var. cusickii (Gray) Kartesz & Gandhi | PYCAC3 |
| largeflower goldenweed | Pyrrocoma carthamoides Hook. var. subsquarrosa (Greene) G. Brown & Keil | PYCAS |
| largeflower hawksbeard | Crepis occidentalis Nutt. | CROC |
| largeflower hawksbeard | Crepis occidentalis Nutt. ssp. conjuncta (Jepson) Babcock & Stebbins | CROCC |
| largeflower hawksbeard | Crepis occidentalis Nutt. ssp. costata (Gray) Babcock & Stebbins | CROCC2 |
| largeflower hawksbeard | Crepis occidentalis Nutt. ssp. occidentalis | CROCO2 |
| largeflower hawksbeard | Crepis occidentalis Nutt. ssp. pumila (Rydb.) Babcock & Stebbins | CROCP |
| largeflower skeletonplant | Lygodesmia grandiflora (Nutt.) Torr. & Gray | LYGR |
| largeflower tickseed | Coreopsis grandiflora Hogg ex Sweet | COGR5 |
| largeflower tickseed | Coreopsis grandiflora Hogg ex Sweet var. grandiflora | COGRG |
| largeflower tickseed | Coreopsis grandiflora Hogg ex Sweet var. harveyana (Gray) Sherff | COGRH |
| largeflower tickseed | Coreopsis grandiflora Hogg ex Sweet var. longipes (Hook.) Torr. & Gray | COGRL |
| largeflower tickseed | Coreopsis grandiflora Hogg ex Sweet var. saxicola (Alexander) E.B. Sm. | COGRS |
| largeflower Townsend daisy | Townsendia grandiflora Nutt. | TOGR |
| largefruit beggarticks | Bidens macrocarpa (Gray) Sherff | BIMA |
| largeleaf goldenrod | Solidago macrophylla Pursh | SOMA4 |
| largeleaf thoroughwort | Hebeclinium macrophyllum (L.) DC. | HEMA9 |
| larger western mountain aster | Symphyotrichum spathulatum (Lindl.) Nesom var. intermedium (Gray) Nesom | SYSPI |
| larkdaisy | Centratherum punctatum Cass. | CEPU6 |
| larkspurleaf tickseed | Coreopsis delphiniifolia Lam. | CODE3 |
| Larsen's ironweed | Vernonia larsenii B.L. King & S.B. Jones | VELA3 |
| lasianthaea | Lasianthaea DC. | LASIA3 |
| Lasianthaea podocephala | Verbesina podocephala Gray | VEPO2 |
| Lasianthaea podocephala | Zexmenia podocephala (Gray) Gray | ZEPO2 |
| Lasiospermum bipinnatum | Lasiospermum radiatum Trev. | LARA3 |
| Lasiospermum bipinnatum | Lidbeckia bipinnata Thunb. | LIBI9 |
| Last Chance Townsend daisy | Townsendia aprica Welsh & Reveal | TOAP |
| Lasthenia californica ssp. bakeri | Baeria bakeri J.T. Howell | BABA2 |
| Lasthenia californica ssp. bakeri | Baeria macrantha (Gray) Gray var. bakeri (J.T. Howell) Keck | BAMAB |
| Lasthenia californica ssp. bakeri | Lasthenia macrantha (Gray) Greene ssp. bakeri (J.T. Howell) Ornduff | LAMAB |
| Lasthenia californica ssp. californica | Baeria chrysostoma Fisch. & C.A. Mey. | BACH |
| Lasthenia californica ssp. californica | Baeria chrysostoma Fisch. & C.A. Mey. ssp. gracilis (DC.) Ferris | BACHG |
| Lasthenia californica ssp. californica | Baeria chrysostoma Fisch. & C.A. Mey. ssp. hirsutula (Greene) Ferris | BACHH |
| Lasthenia californica ssp. californica | Baeria chrysostoma Fisch. & C.A. Mey. var. gracilis (DC.) Hall | BACHG2 |
| Lasthenia californica ssp. californica | Baeria hirsutula (Greene) Greene | BAHI5 |
| Lasthenia californica ssp. californica | Lasthenia chrysostoma (Fisch. & C.A. Mey.) Greene | LACH3 |
| Lasthenia californica ssp. macrantha | Baeria macrantha (Gray) Gray | BAMA9 |
| Lasthenia californica ssp. macrantha | Baeria macrantha (Gray) Gray var. pauciaristata Gray | BAMAP2 |
| Lasthenia californica ssp. macrantha | Baeria macrantha (Gray) Gray var. thalassophila J.T. Howell | BAMAT |
| Lasthenia californica ssp. macrantha | Lasthenia macrantha (Gray) Greene | LAMA6 |
| Lasthenia californica ssp. macrantha | Lasthenia macrantha (Gray) Greene ssp. macrantha (Gray) Greene [superfluous autonym] | LAMAM |
| Lasthenia californica ssp. macrantha | Lasthenia macrantha (Gray) Greene ssp. prisca Ornduff | LAMAP4 |
| Lasthenia chrysantha | Crockeria chrysantha Greene ex Gray | CRCH9 |
| Lasthenia conjugens | Baeria fremontii (Torr. ex Gray) Gray var. conjugens (Greene) Ferris | BAFRC |
| Lasthenia coronaria | Baeria californica (Hook.) Chambers | BACA6 |
| Lasthenia debilis | Baeria debilis Greene ex Gray | BADE4 |
| Lasthenia fremontii | Baeria fremontii (Torr. ex Gray) Gray | BAFR3 |
| Lasthenia fremontii | Baeria fremontii (Torr. ex Gray) Gray var. heterochaeta Hoover | BAFRH |
| Lasthenia glabrata ssp. coulteri | Lasthenia glabrata Lindl. var. coulteri Gray | LAGLC2 |
| Lasthenia leptalea | Baeria leptalea (Gray) Gray | BALE5 |
| Lasthenia maritima | Baeria maritima Gray | BAMA6 |
| Lasthenia maritima | Baeria minor (DC.) Ferris ssp. maritima (Gray) Ferris | BAMIM |
| Lasthenia maritima | Lasthenia minor (DC.) Ornduff ssp. maritima (Gray) Ornduff | LAMIM |
| Lasthenia maritima | Lasthenia minor (DC.) Ornduff var. maritima (Gray) Cronq. | LAMIM2 |
| Lasthenia microglossa | Baeria microglossa (DC.) Greene | BAMI7 |
| Lasthenia minor | Baeria minor (DC.) Ferris | BAMI5 |
| Lasthenia minor | Baeria uliginosa (Nutt.) Gray | BAUL |
| Lasthenia platycarpha | Baeria platycarpha (Gray) Gray | BAPL4 |
| late goldenrod | Solidago altissima L. | SOAL6 |
| late purple aster | Symphyotrichum patens (Ait.) Nesom | SYPA11 |
| late purple aster | Symphyotrichum patens (Ait.) Nesom var. gracile (Hook.) Nesom | SYPAG |
| late purple aster | Symphyotrichum patens (Ait.) Nesom var. patens | SYPAP2 |
| late purple aster | Symphyotrichum patens (Ait.) Nesom var. patentissimum (Lindl. ex DC.) Nesom | SYPAP |
| late snakeweed | Gutierrezia serotina Greene | GUSE |
| lateflowering thoroughwort | Eupatorium serotinum Michx. | EUSE2 |
| Latin American fleabane | Erigeron karvinskianus DC. | ERKA2 |
| launaea | Launaea Cass. | LAUNA |
| Launaea intybacea | Bracyrhamphus intybaceus (Jacq.) DC. | BRIN8 |
| Launaea intybacea | Lactuca intybacea Jacq. | LAIN8 |
| Lava aster | Ionactis alpina (Nutt.) Greene | IOAL |
| lava dubautia | Dubautia ciliolata (DC.) Keck | DUCI |
| lava dubautia | Dubautia ciliolata (DC.) Keck ssp. ciliolata | DUCIC |
| lava dubautia | Dubautia ciliolata (DC.) Keck ssp. glutinosa G.D. Carr | DUCIG |
| lavaflow nehe | Lipochaeta heterophylla Gray | LIHE3 |
| lavender cotton | Santolina chamaecyparissus L. | SACH2 |
| lavender cotton | Santolina L. | SANTO |
| lavender oldfield aster | Symphyotrichum priceae (Britt.) Nesom | SYPR4 |
| lavender thoroughwort | Fleischmannia pycnocephala (Less.) King & H.E. Robins. | FLPY |
| lawndaisy | Bellis perennis L. | BEPE2 |
| laxflower | Baileya pauciradiata Harvey & Gray ex Gray | BAPA |
| Layia chrysanthemoides | Layia chrysanthemoides (DC.) Gray ssp. maritima Keck | LACHM |
| Layia glandulosa | Layia glandulosa (Hook.) Hook. & Arn. ssp. lutea Keck | LAGLL2 |
| Layia hieracioides | Layia paniculata Keck | LAPA6 |
| Layia platyglossa | Layia platyglossa (Fisch. & C.A. Mey.) Gray ssp. campestris Keck | LAPLC |
| Layia platyglossa | Layia platyglossa (Fisch. & C.A. Mey.) Gray var. breviseta Gray | LAPLB |
| Layia platyglossa | Layia ziegleri Munz | LAZI2 |
| Layne's ragwort | Packera layneae (Greene) W.A. Weber & A. L?ve | PALA41 |
| Le Conte's thistle | Cirsium lecontei Torr. & Gray | CILE2 |
| leafstem tickseed | Coreopsis calliopsidea (DC.) Gray | COCA9 |
| leafy brickellbush | Brickellia dentata (DC.) Schultz-Bip. | BRDE2 |
| leafy desertdandelion | Malacothrix foliosa Gray | MAFO |
| leafy desertdandelion | Malacothrix foliosa Gray ssp. foliosa | MAFOF |
| leafy false goldenweed | Oonopsis foliosa (Gray) Greene | OOFO |
| leafy false goldenweed | Oonopsis foliosa (Gray) Greene var. foliosa | OOFOF |
| leafy fleabane | Erigeron foliosus Nutt. | ERFO2 |
| leafy fleabane | Erigeron foliosus Nutt. var. confinis (T.J. Howell) Jepson | ERFOC |
| leafy fleabane | Erigeron foliosus Nutt. var. foliosus | ERFOF |
| leafy marshtail | Laennecia sophiifolia (Kunth) Nesom | LASO2 |
| leafy raillardiopsis | Anisocarpus scabridus (Eastw.) B.G. Baldwin | ANSC14 |
| leafy rockdaisy | Perityle rupestris (Gray) Shinners | PERU3 |
| leafy rockdaisy | Perityle rupestris (Gray) Shinners var. albiflora A. Powell | PERUA |
| leafy rockdaisy | Perityle rupestris (Gray) Shinners var. rupestris | PERUR |
| leastdaisy | Chaetopappa DC. | CHAET2 |
| Leavenworth's goldenrod | Solidago leavenworthii Torr. & Gray | SOLE5 |
| Leavenworth's tickseed | Coreopsis leavenworthii Torr. & Gray | COLE3 |
| Leiberg's fleabane | Erigeron leibergii Piper | ERLE5 |
| Leibnitzia lyrata | Chaptalia alsophila Greene | CHAL4 |
| Leibnitzia lyrata | Chaptalia leucocephala Greene | CHLE8 |
| Leibnitzia lyrata | Chaptalia seemannii (Schultz-Bip.) Hemsl. | CHSE15 |
| Leibnitzia lyrata | Leibnitzia seemannii (Schultz-Bip.) Nesom | LESE5 |
| Lemmon's beggarticks | Bidens lemmonii Gray | BILE2 |
| Lemmon's brickellbush | Brickellia lemmonii Gray | BRLE |
| Lemmon's brickellbush | Brickellia lemmonii Gray var. lemmonii | BRLEL |
| Lemmon's brickellbush | Brickellia lemmonii Gray var. wootonii (Greene) B.L. Robins. | BRLEW |
| Lemmon's candyleaf | Stevia lemmonii (Gray) Gray | STLE |
| Lemmon's fleabane | Erigeron lemmonii Gray | ERLE14 |
| Lemmon's hawkweed | Hieracium lemmonii Gray | HILE2 |
| Lemmon's lessingia | Lessingia lemmonii Gray | LELE13 |
| Lemmon's lessingia | Lessingia lemmonii Gray var. lemmonii | LELEL |
| Lemmon's lessingia | Lessingia lemmonii Gray var. ramulosissima (A. Nels.) Ferris | LELER2 |
| Lemmon's marigold | Tagetes lemmonii Gray | TALE |
| Lemmon's ragwort | Senecio lemmonii Gray | SELE8 |
| Lemmon's rockdaisy | Perityle lemmonii (Gray) J.F. Macbr. | PELE11 |
| Lemmon's rubberweed | Hymenoxys lemmonii (Greene) Cockerell | HYLE |
| Lemmon's snakeroot | Ageratina lemmonii (B.L. Robins.) King & H.E. Robins. | AGLE3 |
| lemonscent | Pectis angustifolia Torr. | PEAN |
| lemonscent | Pectis angustifolia Torr. var. fastigiata (Gray) Keil | PEANF |
| lemonscent | Pectis angustifolia Torr. var. tenella (DC.) Keil | PEANT |
| lemonscented madia | Madia citriodora Greene | MACI2 |
| lemonyellow false goldenaster | Heterotheca camporum (Greene) Shinners | HECA16 |
| lemonyellow false goldenaster | Heterotheca camporum (Greene) Shinners var. camporum | HECAC2 |
| lemonyellow false goldenaster | Heterotheca camporum (Greene) Shinners var. glandulissimum Semple | HECAG |
| Leontodon autumnalis ssp. autumnalis | Apargia autumnalis (L.) Hoffmann | APAU2 |
| Leontodon autumnalis ssp. pratensis | Leontodon autumnalis L. var. pratensis (Link) W.D.J. Koch | LEAUP |
| Leontodon hispidus ssp. danubialis | Leontodon danubialis Jacq. | LEDA4 |
| Leontodon hispidus ssp. danubialis | Leontodon hastilis L. | LEHA2 |
| Leontodon hispidus ssp. danubialis | Leontodon hastilis L. var. glabratus W.D.J. Koch | LEHAG |
| Leontodon hispidus ssp. danubialis | Leontodon hispidus L. var. glabratus (W.D.J. Koch) Bisch. | LEHIG |
| Leontodon hispidus ssp. hispidus | Apargia hispida (L.) Willd. | APHI |
| Leontodon hispidus ssp. hispidus | Leontodon hastilis L. var. vulgaris W.D.J. Koch | LEHAV |
| Leontodon taraxacoides ssp. taraxacoides | Apargia nudicaulis (L.) Britt. | APNU |
| Leontodon taraxacoides ssp. taraxacoides | Leontodon hirtus auct. non L. [misapplied] | LEHI4 |
| Leontodon taraxacoides ssp. taraxacoides | Leontodon leysseri (Wallr.) G. Beck | LELE4 |
| Leontodon taraxacoides ssp. taraxacoides | Leontodon nudicaulis (L.) Banks ex Schinz & R. Keller | LENU2 |
| Leontodon taraxacoides ssp. taraxacoides | Leontodon nudicaulis (L.) Banks ex Schinz & R. Keller ssp. taraxacoides (Vill.) Schinz & Thellung | LENUT |
| Lepidospartum squamatum | Lepidospartum squamatum (Gray) Gray var. palmeri (Gray) L.C. Wheeler | LESQP |
| lesser burdock | Arctium minus Bernh. | ARMI2 |
| lesser California rayless fleabane | Erigeron reductus (Cronq.) Nesom | ERRE12 |
| lesser California rayless fleabane | Erigeron reductus (Cronq.) Nesom var. angustatus (Gray) Nesom | ERREA |
| lesser California rayless fleabane | Erigeron reductus (Cronq.) Nesom var. reductus | ERRER |
| lesser hareleaf | Lagophylla minor (Keck) Keck | LAMI |
| lesser hawkbit | Leontodon taraxacoides (Vill.) M?rat | LETA |
| lesser hawkbit | Leontodon taraxacoides (Vill.) M?rat ssp. longirostris Finch & Sell | LETAL |
| lesser hawkbit | Leontodon taraxacoides (Vill.) M?rat ssp. taraxacoides | LETAT |
| lesser knapweed | Centaurea nigra L. | CENI2 |
| lesser marigold | Tagetes pusilla Kunth | TAPU5 |
| lesser snakeroot | Ageratina aromatica (L.) Spach | AGAR4 |
| lesser snakeroot | Ageratina aromatica (L.) Spach var. aromatica | AGARA |
| lesser snakeroot | Ageratina aromatica (L.) Spach var. incisa (Gray) C.F. Reed | AGARI2 |
| lesser wirelettuce | Stephanomeria minor (Hook.) Nutt. | STMI13 |
| lessingia | Lessingia Cham. | LESSI |
| Lessingia arachnoidea | Lessingia hololeuca Greene var. arachnoidea (Greene) J.T. Howell | LEHOA |
| Lessingia arachnoidea | Lessingia micradenia Greene var. arachnoidea (Greene) Ferris | LEMIA |
| Lessingia glandulifera var. glandulifera | Lessingia germanorum Cham. var. glandulifera (Gray) J.T. Howell | LEGEG |
| Lessingia glandulifera var. pectinata | Lessingia germanorum Cham. var. pectinata (Greene) J.T. Howell | LEGEP2 |
| Lessingia glandulifera var. tomentosa | Lessingia germanorum Cham. var. tomentosa (Greene) J.T. Howell | LEGET2 |
| Lessingia lemmonii var. lemmonii | Lessingia germanorum Cham. var. lemmonii (Gray) J.T. Howell | LEGEL |
| Lessingia lemmonii var. peirsonii | Lessingia germanorum Cham. var. peirsonii J.T. Howell | LEGEP3 |
| Lessingia lemmonii var. ramulosissima | Lessingia germanorum Cham. var. ramulosissima (A. Nels.) J.T. Howell | LEGER |
| Lessingia micradenia var. glabrata | Lessingia ramulosa Gray var. glabrata Keck | LERAG |
| Lessingia micradenia var. micradenia | Lessingia ramulosa Gray var. micradenia (Greene) J.T. Howell | LERAM |
| Lessingia tenuis | Lessingia germanorum Cham. var. parvula (Greene) J.T. Howell | LEGEP |
| Lessingia tenuis | Lessingia germanorum Cham. var. tenuis (Gray) J.T. Howell | LEGET |
| lettuce | Lactuca L. | LACTU |
| lettuce wirelettuce | Stephanomeria lactucina Gray | STLA |
| leucanthemella | Leucanthemella Tzvelev | LEUCA5 |
| Leucanthemella serotina | Chrysanthemum serotinum L. | CHSE16 |
| Leucanthemella serotina | Chrysanthemum uliginosum Pers. (Waldst. & Kit. ex Willd.) | CHUL |
| Leucanthemella serotina | Leucanthemum serotinum (L.) Stankov | LESE8 |
| Leucanthemella serotina | Tanacetum serotinum (L.) Schultz-Bip. | TASE2 |
| Leucanthemum ?superbum | Chrysanthemum ?superbum Bergmans ex J.W. Ingram | CHSU20 |
| Leucanthemum lacustre | Chrysanthemum lacustre Brot. | CHLA14 |
| Leucanthemum maximum | Chrysanthemum maximum Ramond | CHMA12 |
| Leucanthemum vulgare | Chrysanthemum leucanthemum L. | CHLE80 |
| Leucanthemum vulgare | Chrysanthemum leucanthemum L. var. boecheri Boivin | CHLEB |
| Leucanthemum vulgare | Chrysanthemum leucanthemum L. var. pinnatifidum Lecoq & Lamotte | CHLEP |
| Leucanthemum vulgare | Leucanthemum leucanthemum (L.) Rydb. | LELE12 |
| Leucanthemum vulgare | Leucanthemum vulgare Lam. var. pinnatifidum (Lecoq & Lamotte) Moldenke | LEVUP |
| Leuciva dealbata | Iva dealbata Gray | IVDE |
| Lewis's groundsel | Packera eurycephala (Torr. & Gray ex Gray) W.A. Weber & A. L?ve var. lewisrosei (J.T. Howell) J.F. Bain | PAEUL |
| Liatris ?boykinii | Lacinaria boykinii (Torr. & Gray) Kuntze | LABO3 |
| Liatris acidota | Lacinaria acidota (Engelm. & Gray) Kuntze | LAAC2 |
| Liatris aspera var. aspera | Lacinaria aspera (Michx.) Greene | LAAS2 |
| Liatris aspera var. intermedia | Lacinaria squarrosa (L.) Hill var. intermedia (Lunell) DC. | LASQI |
| Liatris chapmanii | Lacinaria chapmanii (Torr. & Gray) Kuntze | LACH4 |
| Liatris cokeri | Liatris regimontis auct. non (Small) K. Schum. [misapplied] | LIRE11 |
| Liatris cylindracea | Lacinaria cylindracea (Michx.) Kuntze | LACY3 |
| Liatris densispicata var. interrupta | Liatris angustifolia (Bush) Gaiser | LIAN4 |
| Liatris elegans var. elegans | Lacinaria elegans (Walt.) Kuntze | LAEL |
| Liatris elegans var. flabellata | Lacinaria flabellata Small | LAFL4 |
| Liatris garberi | Lacinaria chlorolepis Small | LACH5 |
| Liatris garberi | Lacinaria garberi (Gray) Kuntze | LAGA3 |
| Liatris garberi | Lacinaria nashii Small | LANA |
| Liatris gracilis | Lacinaria gracilis (Pursh) Kuntze | LAGR8 |
| Liatris gracilis | Lacinaria laxa Small | LALA9 |
| Liatris helleri | Lacinaria helleri (Porter) Porter ex Heller | LAHE5 |
| Liatris lancifolia | Lacinaria lancifolia Greene | LALA10 |
| Liatris lancifolia | Liatris kansana Britt. | LIKA2 |
| Liatris ligulistylis | Lacinaria ligulistylis A. Nels. | LALI3 |
| Liatris microcephala | Lacinaria microcephala Small | LAMI8 |
| Liatris ohlingerae | Ammopursus ohlingerae (Blake) Small | AMOH |
| Liatris pauciflora | Lacinaria pauciflora (Pursh) Kuntze | LAPA10 |
| Liatris pauciflora | Lacinaria secunda (Ell.) Small | LASE6 |
| Liatris pauciflora | Liatris secunda Ell. | LISE4 |
| Liatris pilosa var. elegantula | Lacinaria elegantula Greene | LAEL2 |
| Liatris pilosa var. elegantula | Liatris graminifolia Willd. var. elegantula (Greene) K. Schum. | LIGRE |
| Liatris pilosa var. lasia | Liatris graminifolia Willd. var. lasia Fern. & Grisc. | LIGRL |
| Liatris pilosa var. pilosa | Lacinaria graminifolia (Willd.) Kuntze | LAGR7 |
| Liatris pilosa var. pilosa | Lacinaria pilosa (Ait.) Heller | LAPI |
| Liatris pilosa var. pilosa | Liatris graminifolia Willd. | LIGR10 |
| Liatris pilosa var. pilosa | Liatris graminifolia Willd. var. dubia (W. Bart.) Gray | LIGRD |
| Liatris pilosa var. pilosa | Liatris graminifolia Willd. var. racemosa (DC.) Venard | LIGRR |
| Liatris pilosa var. pilosa | Liatris spicata (L.) Willd. var. racemosa DC. | LISPR2 |
| Liatris punctata var. punctata | Lacinaria punctata (Hook.) Kuntze | LAPU8 |
| Liatris punctata var. punctata | Liatris punctata Hook. var. typica Gaiser | LIPUT |
| Liatris pycnostachya var. pycnostachya | Lacinaria pycnostachya (Michx.) Kuntze | LAPY |
| Liatris pycnostachya var. pycnostachya | Liatris bebbiana Rydb. | LIBE5 |
| Liatris scariosa var. nieuwlandii | Lacinaria scariosa (L.) Hill var. nieuwlandii Lunell | LASCN |
| Liatris scariosa var. nieuwlandii | Liatris ?nieuwlandii (Lunell) Gaiser | LINI |
| Liatris scariosa var. nieuwlandii | Liatris novae-angliae (Lunell) Shinners var. nieuwlandii (Lunell) Shinners | LINON |
| Liatris scariosa var. novae-angliae | Liatris borealis Nutt. | LIBO6 |
| Liatris scariosa var. novae-angliae | Liatris novae-angliae (Lunell) Shinners | LINO3 |
| Liatris scariosa var. scariosa | Lacinaria scariosa (L.) Hill | LASC5 |
| Liatris scariosa var. scariosa | Liatris scariosa (L.) Willd. var. virginiana (Lunell) Gaiser | LISCV |
| Liatris spheroidea | Lacinaria aspera (Michx.) Greene var. spheroidea (Michx.) Alexander | LAASS |
| Liatris spicata var. spicata | Lacinaria spicata (L.) Kuntze | LASP5 |
| Liatris squarrosa var. alabamensis | Liatris glabrata Rydb. var. alabamensis (Alexander) Shinners | LIGLA |
| Liatris squarrosa var. compacta | Liatris compacta (Torr. & Gray) Rydb. | LICO12 |
| Liatris squarrosa var. glabrata | Liatris glabrata Rydb. | LIGL4 |
| Liatris squarrosa var. hirsuta | Liatris hirsuta Rydb. | LIHI2 |
| Liatris squarrosa var. squarrosa | Lacinaria squarrosa (L.) Hill | LASQ2 |
| Liatris squarrosa var. squarrosa | Liatris squarrosa (L.) Michx. var. gracilenta Gaiser | LISQG2 |
| Liatris squarrulosa | Lacinaria ruthii Alexander | LARU2 |
| Liatris squarrulosa | Lacinaria shortii Alexander | LASH |
| Liatris squarrulosa | Lacinaria tracyi Alexander | LATR7 |
| Liatris squarrulosa | Liatris earlei (Greene) K. Schum. | LIEA |
| Liatris squarrulosa | Liatris scabra (Greene) K. Schum. | LISC |
| Liatris squarrulosa | Liatris scariosa (L.) Willd. var. squarrulosa (Michx.) Gray | LISCS |
| Liatris tenuifolia var. quadriflora | Liatris laevigata (Nutt.) Small | LILA5 |
| Liatris tenuifolia var. quadriflora | Liatris tenuifolia Nutt. var. laevigata (Nutt.) B.L. Robins. | LITEL |
| Liatris tenuifolia var. tenuifolia | Lacinaria tenuifolia (Nutt.) Kuntze | LATE2 |
| Liatris turgida | Lacinaria pilosa auct. non (Ait.) Heller [misapplied] | LAPI2 |
| Liatris virgata | Lacinaria regimontis Small as to type | LARE4 |
| Liatris virgata | Lacinaria smallii Britt. | LASM |
| Liatris virgata | Liatris graminifolia Willd. var. smallii (Britt.) Fern. & Grisc. | LIGRS |
| Liatris virgata | Liatris graminifolia Willd. var. virgata (Nutt.) Fern. | LIGRV |
| Liatris virgata | Liatris regimontis (Small) K. Schum. as to type | LIRE10 |
| licorice marigold | Tagetes micrantha Cav. | TAMI |
| licorice-plant | Helichrysum petiolare Hilliard & Burtt | HEPE8 |
| Ligularia dentata | Senecio clivorum Maxim. | SECL3 |
| Ligurian yarrow | Achillea ligustica All. | ACLI2 |
| lilac tasselflower | Emilia sonchifolia (L.) DC. | EMSO |
| lilac tasselflower | Emilia sonchifolia (L.) DC. var. javanica (Burm. f.) Mattf. | EMSOJ |
| lilac tasselflower | Emilia sonchifolia (L.) DC. var. sonchifolia | EMSOS |
| limestone bugheal | Trichocoronis wrightii (Torr. & Gray) Gray | TRWR2 |
| limestone goldenrod | Solidago calcicola Fern. | SOCA9 |
| limestone hawksbeard | Crepis intermedia Gray | CRIN4 |
| limestone thoroughwort | Chromolaena borinquensis (Britt.) King & H.E. Robins. | CHBO3 |
| Lindheimer's crownbeard | Verbesina lindheimeri Robins. & Greenm. | VELI2 |
| Lindheimer's rockdaisy | Perityle lindheimeri (Gray) Shinners | PELI3 |
| Lindheimer's rockdaisy | Perityle lindheimeri (Gray) Shinners var. halimifolia (Gray) A. Powell | PELIH2 |
| Lindheimer's rockdaisy | Perityle lindheimeri (Gray) Shinners var. lindheimeri | PELIL |
| lindheimera | Lindheimera Gray & Engelm. | LINDH |
| Lindley's aster | Symphyotrichum ciliolatum (Lindl.) A.& D. L?ve | SYCI |
| Lindley's silverpuffs | Microseris lindleyi (DC.) Gray | MILI5 |
| Lipochaeta connata var. acris | Lipochaeta acris Sherff | LIAC4 |
| Lipochaeta connata var. acris | Lipochaeta connata (Gaud.) DC. var. lata St. John | LICOL |
| Lipochaeta connata var. acris | Lipochaeta lobata (Gaud.) DC. var. incisior St. John | LILOI |
| Lipochaeta connata var. connata | Lipochaeta alata Sherff | LIAL4 |
| Lipochaeta connata var. connata | Lipochaeta alata Sherff var. acrior Sherff | LIALA2 |
| Lipochaeta connata var. connata | Lipochaeta alata Sherff var. pulchrior Sherff | LIALP |
| Lipochaeta connata var. connata | Lipochaeta profusa Sherff | LIPR6 |
| Lipochaeta connata var. connata | Lipochaeta profusa Sherff var. robustior O. Deg. & Sherff | LIPRR |
| Lipochaeta fauriei | Lipochaeta deltoidea St. John | LIDE6 |
| Lipochaeta heterophylla | Lipochaeta hastata Hbd. | LIHA5 |
| Lipochaeta heterophylla | Lipochaeta heterophylla Gray var. molokaiensis Sherff | LIHEM |
| Lipochaeta integrifolia | Lipochaeta integrifolia (Nutt.) Gray var. argentea Sherff | LIINA |
| Lipochaeta integrifolia | Lipochaeta integrifolia (Nutt.) Gray var. gracilis Sherff | LIING |
| Lipochaeta integrifolia | Lipochaeta integrifolia (Nutt.) Gray var. major Sherff | LIINM |
| Lipochaeta integrifolia | Lipochaeta integrifolia (Nutt.) Gray var. megacephala O. Deg. & Sherff | LIINM2 |
| Lipochaeta integrifolia | Lipochaeta porophila O.& I. Deg. | LIPO4 |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. conferta Sherff | LILAC |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. hillebrandiana Sherff | LILAH |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. lanaiensis Sherff | LILAL |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. longifolia Sherff | LILAL2 |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. maneleana Sherff | LILAM |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. ovata Sherff | LILAO |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. salicifolia Sherff | LILAS |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. scaposa St. John | LILAS4 |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. skottsbergii Sherff | LILAS2 |
| Lipochaeta lavarum | Lipochaeta lavarum (Gaud.) DC. var. stearnsii O. Deg. & Sherff | LILAS3 |
| Lipochaeta lavarum | Lipochaeta molokiniensis St. John | LIMO9 |
| Lipochaeta lavarum | Lipochaeta warshauerii St. John | LIWA3 |
| Lipochaeta lobata var. lobata | Lipochaeta calycosa Gray | LICA24 |
| Lipochaeta lobata var. lobata | Lipochaeta christophersenii St. John | LICH5 |
| Lipochaeta lobata var. lobata | Lipochaeta garberi St. John | LIGA2 |
| Lipochaeta lobata var. lobata | Lipochaeta kaenaensis St. John | LIKA3 |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. albescens Sherff | LILOA |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. aprevalliana (del Castillo) Sherff | LILOA2 |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. denticulata (Wawra) Sherff | LILOD |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. grossedentata O. Deg. & Sherff | LILOG |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. hastulata (Hook. & Arn.) Sherff | LILOH2 |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. hastulatoides O. Deg. & Sherff | LILOH |
| Lipochaeta lobata var. lobata | Lipochaeta lobata (Gaud.) DC. var. hosakae St. John | LILOH3 |
| Lipochaeta lobata var. lobata | Lipochaeta niihauensis St. John | LINI3 |
| Lipochaeta lobata var. lobata | Lipochaeta trilobata St. John | LITR5 |
| Lipochaeta lobata var. lobata | Lipochaeta vittata St. John | LIVI6 |
| Lipochaeta micrantha var. exigua | Lipochaeta exigua O. Deg. & Sherff | LIEX |
| Lipochaeta perdita | Lipochaeta kawaihoaensis St. John | LIKA5 |
| Lipochaeta rockii | Lipochaeta elliptica St. John | LIEL4 |
| Lipochaeta rockii | Lipochaeta forbesii Sherff | LIFO4 |
| Lipochaeta rockii | Lipochaeta forbesii Sherff var. sherffii O. Deg. & Clay | LIFOS |
| Lipochaeta rockii | Lipochaeta heterophylla Gray var. malvacea O. Deg. & Sherff | LIHEM2 |
| Lipochaeta rockii | Lipochaeta kahoolawensis Sherff | LIKA4 |
| Lipochaeta rockii | Lipochaeta lobata (Gaud.) DC. var. makenensis O. Deg. & Sherff | LILOM |
| Lipochaeta rockii | Lipochaeta lobata (Gaud.) DC. var. maunaloensis Sherff | LILOM2 |
| Lipochaeta rockii | Lipochaeta mauiensis St. John | LIMA13 |
| Lipochaeta rockii | Lipochaeta nesophila St. John | LINE4 |
| Lipochaeta rockii | Lipochaeta rockii Sherff var. dissecta Sherff | LIROD |
| Lipochaeta rockii | Lipochaeta rockii Sherff var. parva St. John | LIROP |
| Lipochaeta rockii | Lipochaeta rockii Sherff var. subovata Sherff | LIROS |
| Lipochaeta rockii | Lipochaeta scabra St. John | LISC8 |
| Lipochaeta rockii | Lipochaeta succulenta (Hook. & Arn.) DC. var. trifida Sherff | LISUT |
| Lipochaeta subcordata | Lipochaeta flexuosa del Castillo | LIFL6 |
| Lipochaeta subcordata | Lipochaeta intermedia O. Deg. & Sherff | LIIN7 |
| Lipochaeta subcordata | Lipochaeta populifolia (Sherff) R.C. Gardner | LIPO3 |
| Lipochaeta subcordata | Lipochaeta subcordata Gray var. membranacea Sherff | LISUM |
| Lipochaeta subcordata | Lipochaeta subcordata Gray var. populifolia Sherff | LISUP |
| Lipochaeta succulenta | Lipochaeta connata (Gaud.) DC. var. decurrens Gray | LICOD |
| Lipochaeta succulenta | Lipochaeta connata (Gaud.) DC. var. littoralis Hbd. | LICOL2 |
| Lipochaeta succulenta | Lipochaeta lanceolata Nutt. | LILA11 |
| Lipochaeta succulenta | Lipochaeta robusta St. John | LIRO3 |
| Lipochaeta succulenta | Lipochaeta succulenta (Hook. & Arn.) DC. var. angustata Sherff | LISUA |
| Lipochaeta succulenta | Lipochaeta succulenta (Hook. & Arn.) DC. var. barclayi Sherff | LISUB |
| Lipochaeta succulenta | Lipochaeta succulenta (Hook. & Arn.) DC. var. decurrens (Gray) Sherff | LISUD |
| Lipochaeta succulenta | Lipochaeta variolosa Levl. | LIVA |
| Lipochaeta tenuis | Lipochaeta dubia O. Deg. & Sherff | LIDU2 |
| Lipochaeta tenuis | Lipochaeta minuscula O. Deg. & Sherff | LIMI11 |
| Lipochaeta tenuis | Lipochaeta tenuis O. Deg. & Sherff var. sellingii O. Deg. & Sherff | LITES |
| Lipochaeta venosa | Lipochaeta pinnatifida St. John | LIPI5 |
| Lipochaeta venosa | Lipochaeta setosa St. John | LISE6 |
| little cottonrose | Logfia minima (Sm.) Dumort. | LOMI4 |
| little gumweed | Grindelia pusilla (Steyermark) Nesom | GRPU2 |
| little ironweed | Cyanthillium cinereum (L.) H.E. Robins. | CYCI4 |
| little lemonhead | Coreocarpus arizonicus (Gray) Blake | COAR5 |
| little sagebrush | Artemisia arbuscula Nutt. | ARAR8 |
| little sagebrush | Artemisia arbuscula Nutt. ssp. arbuscula | ARARA |
| little sagebrush | Artemisia arbuscula Nutt. ssp. longicaulis Winward & McArthur | ARARL3 |
| little sagebrush | Artemisia arbuscula Nutt. ssp. longiloba (Osterhout) L. Shultz | ARARL |
| little sagebrush | Artemisia arbuscula Nutt. ssp. thermopola Beetle | ARART |
| little sunflower | Helianthus pumilus Nutt. | HEPU3 |
| littlehead gumweed | Grindelia microcephala DC. | GRMI |
| littleleaf brickellbush | Brickellia microphylla (Nutt.) Gray | BRMI |
| littleleaf brickellbush | Brickellia microphylla (Nutt.) Gray var. microphylla | BRMIM |
| littleleaf horsebrush | Tetradymia glabrata Torr. & Gray | TEGL |
| littleleaf pussytoes | Antennaria microphylla Rydb. | ANMI3 |
| littleleaf silverback | Luina hypoleuca Benth. | LUHY |
| Livermore moonshine | Deinandra bacigalupii B.G. Baldwin | DEBA10 |
| lobed fleabane | Erigeron lobatus A. Nels. | ERLO6 |
| lobed tickseed | Coreopsis auriculata L. | COAU |
| lobeleaf groundsel | Packera multilobata (Torr. & Gray ex Gray) W.A. Weber & A. L?ve | PAMU11 |
| Logfia arizonica | Filago arizonica Gray | FIAR |
| Logfia arizonica | Oglifa arizonica (Gray) Chrtek & Holub | OGAR |
| Logfia arvensis | Filago arvensis L. | FIAR2 |
| Logfia arvensis | Gnaphalium arvense L. | GNAR2 |
| Logfia arvensis | Oglifa arvensis (L.) Cass. | OGAR2 |
| Logfia californica | Filago californica Nutt. | FICA2 |
| Logfia californica | Oglifa californica (Nutt.) Rydb. | OGCA |
| Logfia depressa | Filago depressa Gray | FIDE |
| Logfia depressa | Oglifa depressa (Gray) Chrtek & Holub | OGDE |
| Logfia gallica | Filago gallica L. | FIGA |
| Logfia gallica | Oglifa gallica (L.) Chrtek & Holub | OGGA |
| Logfia minima | Filago minima (Sm.) Pers. | FIMI3 |
| Logfia minima | Oglifa minima (Sm.) Reichenb. | OGMI |
| lone fleabane | Erigeron uncialis Blake | ERUN2 |
| lone fleabane | Erigeron uncialis Blake ssp. conjugans (Blake) Cronq. | ERUNC |
| lone fleabane | Erigeron uncialis Blake ssp. uncialis | ERUNU |
| Lonestar gumweed | Grindelia adenodonta (Steyermark) Nesom | GRAD2 |
| longbeard hawkweed | Hieracium longiberbe T.J. Howell | HILO |
| longdisk sneezeweed | Helenium quadridentatum Labill. | HEQU |
| longflower rabbitbrush | Chrysothamnus depressus Nutt. | CHDE2 |
| longleaf arnica | Arnica lonchophylla Greene | ARLO5 |
| longleaf arnica | Arnica lonchophylla Greene ssp. lonchophylla | ARLOL |
| longleaf aster | Symphyotrichum robynsianum (Rouss.) L. Brouillet & Labrecque | SYRO3 |
| longleaf brickellbush | Brickellia longifolia S. Wats. | BRLO |
| longleaf brickellbush | Brickellia longifolia S. Wats. var. longifolia | BRLOL3 |
| longleaf brickellbush | Brickellia longifolia S. Wats. var. multiflora (Kellogg) Cronq. | BRLOM |
| longleaf camphorweed | Pluchea longifolia Nash | PLLO2 |
| longleaf crownbeard | Verbesina longifolia (Gray) Gray | VELO |
| longleaf false goldeneye | Heliomeris longifolia (Robins. & Greenm.) Cockerell | HELO6 |
| longleaf false goldeneye | Heliomeris longifolia (Robins. & Greenm.) Cockerell var. annua (M.E. Jones) Yates | HELOA2 |
| longleaf false goldeneye | Heliomeris longifolia (Robins. & Greenm.) Cockerell var. longifolia | HELOL |
| longleaf fleabane | Erigeron corymbosus Nutt. | ERCO5 |
| longleaf sunflower | Helianthus longifolius Pursh | HELO3 |
| longleaf wormwood | Artemisia longifolia Nutt. | ARLO7 |
| longshoot | Vernonia sericea L.C. Rich. | VESE2 |
| longspine horsebrush | Tetradymia axillaris A. Nels. | TEAX |
| longspine horsebrush | Tetradymia axillaris A. Nels. var. axillaris | TEAXA |
| longspine horsebrush | Tetradymia axillaris A. Nels. var. longispina (M.E. Jones) Strother | TEAXL |
| longstalk cinchweed | Pectis longipes Gray | PELO |
| longstalk greenthread | Thelesperma longipes Gray | THLO |
| longstyle thistle | Cirsium longistylum Moore & Frankton | CILO2 |
| Loomis's thimblehead | Hymenothrix loomisii Blake | HYLO |
| Louisiana goldenrod | Solidago ludoviciana (Gray) Small | SOLU |
| Louisiana nerveray | Tetragonotheca ludoviciana (Torr. & Gray) Gray ex Hall | TELU |
| low alpine hawkweed | Hieracium gracile Hook. var. detonsum (Gray) Gray | HIGRD |
| low greenthread | Thelesperma caespitosum Dorn | THCA11 |
| low pussytoes | Antennaria dimorpha (Nutt.) Torr. & Gray | ANDI2 |
| low rough aster | Eurybia radula (Ait.) Nesom | EURA10 |
| low starburr | Acanthospermum humile (Sw.) DC. | ACHU |
| Lowrie's blue wood aster | Symphyotrichum lowrieanum (Porter) Nesom | SYLO2 |
| Lucy Braun's rosinweed | Silphium terebinthinaceum Jacq. var. luciae-brauniae Steyermark | SITEL2 |
| Lucy Braun's snakeroot | Ageratina luciae-brauniae (Fern.) King & H.E. Robins. | AGLU |
| Luquillo Mountain hempvine | Mikania pachyphylla Urban | MIPA9 |
| Lyall aster | Symphyotrichum hendersonii (Fern.) Nesom | SYHE5 |
| Lyall's goldenweed | Tonestus lyallii (Gray) A. Nels. | TOLY |
| Lygodesmia arizonica | Lygodesmia grandiflora (Nutt.) Torr. & Gray var. arizonica (S. Tomb) Welsh | LYGRA |
| Lygodesmia dianthopsis | Lygodesmia grandiflora (Nutt.) Torr. & Gray var. dianthopsis (Eat. ex King) Welsh | LYGRD |
| Lygodesmia doloresensis | Lygodesmia grandiflora (Nutt.) Torr. & Gray var. doloresensis (S. Tomb) Welsh | LYGRD2 |
| Lygodesmia entrada | Lygodesmia grandiflora (Nutt.) Torr. & Gray var. entrada (Welsh & Goodrich) Welsh | LYGRE |
| Lygodesmia grandiflora | Erythremia grandiflora Nutt. | ERGR17 |
| Lygodesmia grandiflora | Lygodesmia grandiflora (Nutt.) Torr. & Gray var. stricta Maguire | LYGRS |
| Lygodesmia texana | Lygodesmia aphylla (Nutt.) DC. var. texana Torr. & Gray | LYAPT |
| Lynn Haven goldenaster | Chrysopsis lanuginosa Small | CHLA21 |
| Lyon's pygmydaisy | Pentachaeta lyonii Gray | PELY4 |
| lyreleaf greeneyes | Berlandiera lyrata Benth. | BELY |
| MacDougal's ragwort | Senecio eremophilus Richards. var. macdougalii (Heller) Cronq. | SEERM |
| Macdougal's yellowtops | Flaveria macdougalii Theroux, Pinkava & Keil | FLMA |
| machaeranthera | Machaeranthera pinnatifida (Hook.) Shinners var. scabrella (Greene) B.L. Turner & Hartman [excluded] | MAPIS |
| Machaeranthera arida | Machaeranthera ammophila Reveal | MAAM10 |
| Machaeranthera arida | Machaeranthera arizonica Jackson & Johnston | MAAR6 |
| Machaeranthera arida | Machaeranthera coulteri (Gray) B.L. Turner & Horne var. arida (B.L. Turner & Horne) B.L. Turner | MACOA |
| Machaeranthera arida | Psilactis coulteri auct. p.p., non Gray | PSCO7 |
| Machaeranthera asteroides var. asteroides | Aster amplifolius (Woot. & Standl.) Kittell | ASAM9 |
| Machaeranthera asteroides var. asteroides | Aster canescens Pursh var. latifolius (Gray) Gray | ASCAL2 |
| Machaeranthera asteroides var. asteroides | Dieteria asteroides Torr. | DIAS |
| Machaeranthera asteroides var. asteroides | Machaeranthera amplifolia Woot. & Standl. | MAAM4 |
| Machaeranthera asteroides var. asteroides | Machaeranthera canescens (Pursh) Gray var. latifolia Gray | MACAL2 |
| Machaeranthera asteroides var. asteroides | Machaeranthera pruinosa Gray | MAPR6 |
| Machaeranthera asteroides var. asteroides | Machaeranthera simplex Woot. & Standl. | MASI7 |
| Machaeranthera asteroides var. asteroides | Machaeranthera verna A. Nels. | MAVE3 |
| Machaeranthera asteroides var. glandulosa | Machaeranthera hansonii A. Nels. | MAHA6 |
| Machaeranthera asteroides var. lagunensis | Machaeranthera lagunensis Keck | MALA |
| Machaeranthera bigelovii var. bigelovii | Aster aquifolius (Greene ex Woot. & Standl.) Blake | ASAQ3 |
| Machaeranthera bigelovii var. bigelovii | Aster bigelovii Gray | ASBI9 |
| Machaeranthera bigelovii var. bigelovii | Aster pattersonii Gray | ASPA26 |
| Machaeranthera bigelovii var. bigelovii | Aster rubrotinctus Blake | ASRU10 |
| Machaeranthera bigelovii var. bigelovii | Machaeranthera aquifolia Greene ex Woot. & Standl. | MAAQ |
| Machaeranthera bigelovii var. bigelovii | Machaeranthera centaureoides Greene ex Woot. & Standl. | MACE |
| Machaeranthera bigelovii var. bigelovii | Machaeranthera pattersonii (Gray) Greene | MAPA10 |
| Machaeranthera bigelovii var. bigelovii | Machaeranthera rubricaulis Rydb. | MARU3 |
| Machaeranthera bigelovii var. commixta | Machaeranthera canescens (Pursh) Gray var. commixta (Greene) Welsh | MACAC4 |
| Machaeranthera bigelovii var. commixta | Machaeranthera commixta Greene | MACO2 |
| Machaeranthera bigelovii var. mucronata | Aster adenolepis Blake | ASAD8 |
| Machaeranthera bigelovii var. mucronata | Machaeranthera mucronata Greene | MAMU |
| Machaeranthera blephariphylla | Aster gymnocephalus auct. non (DC.) Gray [misapplied] | ASGY2 |
| Machaeranthera blephariphylla | Haplopappus blephariphyllus Gray | HABL7 |
| Machaeranthera blephariphylla | Haplopappus gymnocephalus DC. | HAGY2 |
| Machaeranthera blephariphylla | Machaeranthera correllii Shinners | MACO16 |
| Machaeranthera blephariphylla | Machaeranthera gymnocephala auct. non (DC.) Shinners [misapplied] | MAGY |
| Machaeranthera canescens ssp. canescens var. ambigua | Machaeranthera angustifolia Woot. & Standl. | MAAN10 |
| Machaeranthera canescens ssp. canescens var. ambigua | Machaeranthera oxylepis Greene | MAOX |
| Machaeranthera canescens ssp. canescens var. ambigua | Machaeranthera scoparia Greene | MASC2 |
| Machaeranthera canescens ssp. canescens var. canescens | Aster canescens Pursh | ASCA25 |
| Machaeranthera canescens ssp. canescens var. canescens | Aster canescens Pursh var. viscosus (Nutt.) Gray | ASCAV3 |
| Machaeranthera canescens ssp. canescens var. canescens | Aster glossophyllus Piper | ASGL8 |
| Machaeranthera canescens ssp. canescens var. canescens | Aster leiodes Blake | ASLE21 |
| Machaeranthera canescens ssp. canescens var. canescens | Aster shastensis (Gray) Gray var. glossophyllus (Piper) Cronq. | ASSHG |
| Machaeranthera canescens ssp. canescens var. canescens | Aster shastensis (Gray) Gray var. latifolius Cronq. | ASSHL |
| Machaeranthera canescens ssp. canescens var. canescens | Dieteria canescens Nutt. | DICA18 |
| Machaeranthera canescens ssp. canescens var. canescens | Dieteria divaricata Nutt. | DIDI11 |
| Machaeranthera canescens ssp. canescens var. canescens | Dieteria pulverulenta Nutt. | DIPU5 |
| Machaeranthera canescens ssp. canescens var. canescens | Dieteria viscosa Nutt. | DIVI10 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera angustifolia Rydb., non Woot. & Standl. | MAAN11 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera canescens (Pursh) Gray var. latifolia (A. Nels.) Welsh, non Gray | MACAL3 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera canescens (Pursh) Gray var. monticola Dorn | MACAM |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera canescens (Pursh) Gray var. viscosa (Nutt.) Piper | MACAV |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera divaricata (Nutt.) Greene | MADI7 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera glabella Greene ex Rydb. | MAGL10 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera laetevirens Greene, non Aster laetevirens (Greene) Greene | MALA3 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera latifolia A. Nels. | MALA11 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera leptophylla Rydb. | MALE6 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera linearis Rydb., non Greene | MALI |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera montana Greene | MAMO5 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera paniculata A. Nels. | MAPA19 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera pinosa Elmer | MAPI4 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera pulverulenta (Nutt.) Greene | MAPU8 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera ramosa A. Nels. | MARA8 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera selbyi Rydb. | MASE4 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera shastensis Gray var. glossophylla (Piper) Cronq. & Keck | MASHG |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera shastensis Gray var. latifolia (Cronq.) Cronq. & Keck | MASHL |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera shastensis Gray var. montana (Greene) Cronq. & Keck | MASHM |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera spinulosa (Greene) Cory, non Amellus spinulosa Pursh | MASP4 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera subalpina Greene | MASU3 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera superba A. Nels. | MASU6 |
| Machaeranthera canescens ssp. canescens var. canescens | Machaeranthera viscosa (Nutt.) Greene | MAVI7 |
| Machaeranthera canescens ssp. canescens var. incana | Aster attenuatus (T.J. Howell) M.E. Peck, non Lindl. ex Hook. | ASAT5 |
| Machaeranthera canescens ssp. canescens var. incana | Aster tephrodes (Gray) Blake | ASTE18 |
| Machaeranthera canescens ssp. canescens var. incana | Dieteria incana (Lindl.) Torr. & Gray | DIIN3 |
| Machaeranthera canescens ssp. canescens var. incana | Diplopappus incanus Lindl. | DIIN4 |
| Machaeranthera canescens ssp. canescens var. incana | Machaeranthera attenuata T.J. Howell | MAAT |
| Machaeranthera canescens ssp. canescens var. incana | Machaeranthera canescens (Pursh) Gray var. tephrodes Gray | MACAT |
| Machaeranthera canescens ssp. canescens var. incana | Machaeranthera incana (Lindl.) Greene | MAIN9 |
| Machaeranthera canescens ssp. canescens var. incana | Machaeranthera tephrodes (Gray) Greene | MATE |
| Machaeranthera canescens ssp. canescens var. leucanthemifolia | Aster leucanthemifolius Greene | ASLE19 |
| Machaeranthera canescens ssp. canescens var. leucanthemifolia | Machaeranthera hiemalis A. Nels. | MAHI4 |
| Machaeranthera canescens ssp. canescens var. leucanthemifolia | Machaeranthera leucanthemifolia (Greene) Greene | MALE |
| Machaeranthera canescens ssp. canescens var. sessiliflora | Dieteria sessiliflora (Nutt.) Greene | DISE13 |
| Machaeranthera canescens ssp. canescens var. sessiliflora | Machaeranthera magna A. Nels. | MAMA23 |
| Machaeranthera canescens ssp. canescens var. sessiliflora | Machaeranthera sessiliflora (Nutt.) Greene | MASE2 |
| Machaeranthera canescens ssp. canescens var. shastensis | Aster inornatus Greene | ASIN23 |
| Machaeranthera canescens ssp. canescens var. shastensis | Aster shastensis (Gray) Gray | ASSH10 |
| Machaeranthera canescens ssp. canescens var. shastensis | Aster shastensis (Gray) Gray var. eradiatus Gray | ASSHE |
| Machaeranthera canescens ssp. canescens var. shastensis | Machaeranthera eradiata (Gray) T.J. Howell | MAER |
| Machaeranthera canescens ssp. canescens var. shastensis | Machaeranthera inops A. Nels. & J.F. Macbr. | MAIN11 |
| Machaeranthera canescens ssp. canescens var. shastensis | Machaeranthera inops A. Nels. & J.F. Macbr. var. atrata A. Nels. & J.F. Macbr. | MAINA2 |
| Machaeranthera canescens ssp. canescens var. shastensis | Machaeranthera inornata (Greene) Greene | MAIN10 |
| Machaeranthera canescens ssp. canescens var. shastensis | Machaeranthera shastensis Gray | MASH |
| Machaeranthera canescens ssp. canescens var. shastensis | Machaeranthera shastensis Gray var. eradiata (Gray) Cronq. & Keck | MASHE |
| Machaeranthera canescens ssp. canescens var. ziegleri | Machaeranthera canescens (Pursh) Gray ssp. ziegleri Munz | MACAZ |
| Machaeranthera canescens ssp. glabra var. aristata | Aster canescens Pursh var. aristatus Eastw. | ASCAA3 |
| Machaeranthera canescens ssp. glabra var. aristata | Aster cichoriaceus (Greene) Blake | ASCI8 |
| Machaeranthera canescens ssp. glabra var. aristata | Machaeranthera canescens (Pursh) Gray var. vacans (A. Nels.) Welsh | MACAV3 |
| Machaeranthera canescens ssp. glabra var. aristata | Machaeranthera cichoriacea Greene | MACI3 |
| Machaeranthera canescens ssp. glabra var. aristata | Machaeranthera pulverulenta (Nutt.) Greene var. vacans A. Nels. | MAPUV |
| Machaeranthera canescens ssp. glabra var. aristata | Machaeranthera rigida Greene | MARI2 |
| Machaeranthera canescens ssp. glabra var. glabra | Aster linearis (Greene) Cory | ASLI8 |
| Machaeranthera canescens ssp. glabra var. glabra | Machaeranthera canescens (Pursh) Gray var. viridis Gray | MACAV2 |
| Machaeranthera canescens ssp. glabra var. glabra | Machaeranthera fremontii Rydb. | MAFR4 |
| Machaeranthera canescens ssp. glabra var. glabra | Machaeranthera linearis Greene | MALI4 |
| Machaeranthera carnosa var. carnosa | Leucosyris carnosa (Gray) Greene | LECA59 |
| Machaeranthera carnosa var. carnosa | Linosyris carnosa Gray | LICA20 |
| Machaeranthera carnosa var. intricata | Aster intricatus (Gray) Blake | ASIN4 |
| Machaeranthera carnosa var. intricata | Bigelovia intricata Gray | BIIN3 |
| Machaeranthera carnosa var. intricata | Leucosyris carnosa (Gray) Greene var. intricata (Gray) Cronq. | LECAI2 |
| Machaeranthera coloradoensis var. coloradoensis | Aster coloradoensis Gray | ASCO28 |
| Machaeranthera coloradoensis var. coloradoensis | Eriocarpum coloradoense (Gray) Greene | ERCO30 |
| Machaeranthera coloradoensis var. coloradoensis | Haplopappus coloradoensis (Gray) R.L. Hartman ex Dorn | HACO5 |
| Machaeranthera coloradoensis var. coloradoensis | Xylorhiza coloradoensis (Gray) Rydb. | XYCO4 |
| Machaeranthera gracilis | Dieteria gracilis Nutt., non Aster gracilis Nutt. | DIGR8 |
| Machaeranthera gracilis | Haplopappus gracilis (Nutt.) Gray | HAGR11 |
| Machaeranthera gracilis | Haplopappus ravenii R.C. Jackson | HARA3 |
| Machaeranthera gracilis | Sideranthus gracilis (Nutt.) A. Nels. | SIGR9 |
| Machaeranthera grindelioides var. depressa | Haplopappus nuttallii Torr. & Gray var. depressus Maguire | HANUD |
| Machaeranthera grindelioides var. grindelioides | Eriocarpum grindelioides Nutt. | ERGR14 |
| Machaeranthera grindelioides var. grindelioides | Haplopappus nuttallii Torr. & Gray | HANU2 |
| Machaeranthera grindelioides var. grindelioides | Sideranthus grindelioides (Nutt.) Britt. | SIGR12 |
| Machaeranthera gypsitherma | Aster blepharophyllus Gray | ASBL2 |
| Machaeranthera juncea | Haplopappus junceus Greene | HAJU |
| Machaeranthera parviflora | Aster parviflorus Gray, non Nees | ASPA20 |
| Machaeranthera parviflora | Aster parvulus Blake | ASPA30 |
| Machaeranthera parviflora | Machaeranthera pygmaea (Gray) Woot. & Standl. | MAPY2 |
| Machaeranthera pinnatifida ssp. gooddingii var. gooddingii | Haplopappus gooddingii (A. Nels.) Munz & Johnston | HAGO2 |
| Machaeranthera pinnatifida ssp. gooddingii var. gooddingii | Haplopappus spinulosus (Pursh) DC. var. gooddingii (A. Nels.) Blake | HASPG |
| Machaeranthera pinnatifida ssp. gooddingii var. gooddingii | Sideranthus gooddingii A. Nels. | SIGO |
| Machaeranthera pinnatifida ssp. gooddingii var. paradoxa | Haplopappus spinulosus (Pursh) DC. var. paradoxa (B.L. Turner & R.L. Hartman) Cronq. | HASPP |
| Machaeranthera pinnatifida ssp. pinnatifida var. chihuahuana | Haplopappus spinulosus (Pursh) DC. var. chihuahuanus (B.L. Turner & R.L. Hartman) Gandhi | HASPC3 |
| Machaeranthera pinnatifida ssp. pinnatifida var. glaberrima | Haplopappus spinulosus (Pursh) DC. ssp. glaberrimus (Rydb.) Hall | HASPG4 |
| Machaeranthera pinnatifida ssp. pinnatifida var. glaberrima | Haplopappus spinulosus (Pursh) DC. var. glaberrimus (Rydb.) Blake | HASPG2 |
| Machaeranthera pinnatifida ssp. pinnatifida var. glaberrima | Sideranthus glaberrimus Rydb. | SIGL7 |
| Machaeranthera pinnatifida ssp. pinnatifida var. glaberrima | Sideranthus spinulosus (Pursh) Sweet ex Rydb. var. glaberrimus (Rydb.) A. Nels. | SISPG |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Amellus spinulosus Pursh, non Machaeranthera spinulosus Greene | AMSP5 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Aster pinnatifidus (Hook.) Kuntze | ASPI10 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Dieteria spinulosa (Pursh) Nutt. | DISP5 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Diplopappus pinnatifidus Hook. | DIPI4 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Eriocarpum australe Greene | ERAU5 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Eriocarpum spinulosum (Pursh) Greene | ERSP14 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Eriocarpum wootonii Greene | ERWO |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus coulteri Harvey & Gray ex Gray | HACO6 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. | HASP3 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. ssp. australis (Greene) Hall | HASPA |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. ssp. cotulus (Small) Hall | HASPC |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. ssp. laevis (Woot. & Standl.) Hall | HASPL |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. var. canescens Gray | HASPC2 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. var. glaber Gray | HASPG3 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus spinulosus (Pursh) DC. var. turbinellus (Rydb.) Blake | HASPT |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Haplopappus texensis R.C. Jackson | HATE5 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Machaeranthera australis (Greene) Shinners | MAAU4 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Machaeranthera laevis (Woot. & Standl.) Shinners | MALA12 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Machaeranthera pinnata (Nutt.) Shinners | MAPI5 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Machaeranthera texensis (R.C. Jackson) Shinners | MATE12 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus australis (Greene) Rydb. | SIAU5 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus cotula Small | SICO10 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus laevis Woot. & Standl. | SILA12 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus machaerantherus Small | SIMA9 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus puberulus Rydb. | SIPU6 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus spinulosus (Pursh) Sweet ex Rydb. | SISP4 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus turbinellus Rydb. | SITU3 |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Sideranthus wootonii (Greene) Standl. | SIWO |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Starkea pinnata Nutt. | STPI4 |
| Machaeranthera pinnatifida var. scabrella | Eriocarpum scabrellum Greene [excluded] | ERSC12 |
| Machaeranthera pinnatifida var. scabrella | Haplopappus spinulosus (Pursh) DC. ssp. scabrellus (Greene) Hall [excluded] | HASPS |
| Machaeranthera pinnatifida var. scabrella | Haplopappus spinulosus (Pursh) DC. var. scabrellus (Greene) Blake [excluded] | HASPS2 |
| Machaeranthera pinnatifida var. scabrella | Machaeranthera scabrella (Greene) Shinners [excluded] | MASC10 |
| Machaeranthera riparia | Aster riparius Kunth | ASRI3 |
| Machaeranthera riparia | Aster sonorae Gray | ASSO7 |
| Machaeranthera riparia | Machaeranthera sonorae (Gray) J. Stucky | MASO7 |
| Machaeranthera tagetina | Aster tagetinus (Greene) Blake | ASTA3 |
| Machaeranthera tanacetifolia | Aster tanacetifolius Kunth | ASTA4 |
| Machaeranthera tanacetifolia | Machaeranthera coronopifolia (Nutt.) A. Nels. | MACO15 |
| Machaeranthera tanacetifolia | Machaeranthera parthenium Greene | MAPA11 |
| Machaeranthera viscida | Haplopappus havardii Waterfall | HAHA7 |
| Machaeranthera viscida | Machaeranthera havardii (Waterfall) Shinners | MAHA3 |
| Macoun's cudweed | Pseudognaphalium macounii (Greene) Kartesz | PSMA11 |
| Madagascar ragwort | Senecio madagascariensis Poir. | SEMA15 |
| Madia elegans ssp. densifolia | Madia elegans D. Don ex Lindl. var. densifolia (Greene) Jepson | MAELD2 |
| Madia gracilis | Madia dissitiflora (Nutt.) Torr. & Gray | MADI8 |
| Madia gracilis | Madia gracilis (Sm.) Keck & J. Clausen ex Applegate ssp. collina Keck | MAGRC |
| Madia gracilis | Madia gracilis (Sm.) Keck & J. Clausen ex Applegate ssp. pilosa Keck | MAGRP |
| Madia sativa | Madia capitata Nutt. | MACA10 |
| Madia sativa | Madia sativa Molina ssp. capitata (Nutt.) Piper | MASAC2 |
| Madia sativa | Madia sativa Molina var. congesta Torr. & Gray | MASAC3 |
| Maguire's fleabane | Erigeron maguirei Cronq. | ERMA8 |
| Malacothrix coulteri | Malacothrix coulteri Harvey & Gray var. cognata Jepson | MACOC3 |
| Malacothrix coulteri | Zollikoferia elquiensis Phil. | ZOEL |
| Malacothrix floccifera | Malacothrix obtusa Benth. | MAOB5 |
| Malacothrix floccifera | Malacothrix parviflora Benth. | MAPA12 |
| Malacothrix floccifera | Malacothrix senecioides Reiche | MASE5 |
| Malacothrix floccifera | Senecio flocciferus DC. | SEFL5 |
| Malacothrix glabrata | Malacothrix californica DC. var. glabrata Gray ex D.C. Eat. | MACAG3 |
| Malacothrix incana | Malacothrix incana (Nutt.) Torr. & Gray var. succulenta (Elmer) E. Williams | MAINS |
| Malacothrix incana | Malacothrix succulenta Elmer | MASU10 |
| Malacothrix indecora | Malacothrix foliosa Gray var. indecora (Greene) E. Williams | MAFOI |
| Malacothrix saxatilis var. arachnoidea | Malacothrix arachnoidea McGregor | MAAR11 |
| Malacothrix saxatilis var. implicata | Malacothrix implicata Eastw. | MAIM |
| Malacothrix saxatilis var. tenuifolia | Malacothrix altissima Greene | MAAL12 |
| Malacothrix saxatilis var. tenuifolia | Malacothrix saxatilis (Nutt.) Torr. & Gray var. altissima (Greene) Ferris | MASAA2 |
| Malacothrix saxatilis var. tenuifolia | Malacothrix saxatilis (Nutt.) Torr. & Gray var. tenuissima Munz | MASAT2 |
| Malacothrix saxatilis var. tenuifolia | Malacothrix tenuifolia (Nutt.) Torr. & Gray | MATE13 |
| Malacothrix sonchoides | Leptoseris sonchoides Nutt. | LESO2 |
| Malacothrix squalida | Malacothrix foliosa Gray var. squalida (Greene) E. Williams | MAFOS |
| Malacothrix squalida | Malacothrix insularis Greene var. squalida (Greene) Ferris | MAINS2 |
| Malacothrix stebbinsii | Malacothrix clevelandii Gray var. stebbinsii (W.S. Davis & Raven) Cronq. | MACLS |
| Malacothrix torreyi | Malacothrix sonchoides (Nutt.) Torr. & Gray var. torreyi (Gray) E. Williams | MASOT |
| Malheur wirelettuce | Stephanomeria malheurensis Gottlieb | STMA5 |
| Malibu baccharis | Baccharis malibuensis Beauchamp & Henderson | BAMA13 |
| malperia | Malperia S. Wats. | MALPE |
| Maltese star-thistle | Centaurea melitensis L. | CEME2 |
| maluco | Acmella iodiscaea (A.H. Moore) R.K. Jansen | ACIO |
| manazanilla del monte | Wedelia reticulata DC. | WERE |
| mantisalca | Mantisalca Cass. | MANTI |
| Mantisalca salmantica | Centaurea salmantica L. | CESA5 |
| many stem cudweed | Gnaphalium polycaulon Pers. | GNPO |
| many-stemmed goldenweed | Pyrrocoma integrifolia (Porter ex Gray) Greene | PYIN3 |
| manyawn pricklyleaf | Thymophylla aurea (Gray) Greene ex Britt. | THAU4 |
| manyawn pricklyleaf | Thymophylla aurea (Gray) Greene ex Britt. var. aurea | THAUA |
| manyawn pricklyleaf | Thymophylla aurea (Gray) Greene ex Britt. var. polychaeta (Gray) Strother | THAUP |
| manybristle cinchweed | Pectis papposa Harvey & Gray | PEPA2 |
| manybristle cinchweed | Pectis papposa Harvey & Gray var. grandis Keil | PEPAG |
| manybristle cinchweed | Pectis papposa Harvey & Gray var. papposa | PEPAP3 |
| manyflower false threadleaf | Schkuhria multiflora Hook. & Arn. | SCMU6 |
| manyflower leastdaisy | Chaetopappa bellioides (Gray) Shinners | CHBE3 |
| manyflower sunflower | Helianthus ?multiflorus L. (pro sp.) [annuus ? decapetalus] | HEMU2 |
| manyflowered aster | Symphyotrichum ericoides (L.) Nesom var. pansum (Blake) Nesom | SYERP2 |
| manyhead desertdandelion | Malacothrix foliosa Gray ssp. polycephala W.S. Davis | MAFOP2 |
| manyhead hymenopappus | Hymenopappus filifolius Hook. var. polycephalus (Osterhout) B.L. Turner | HYFIP3 |
| manyray aster | Symphyotrichum anomalum (Engelm.) Nesom | SYAN2 |
| manyray goldenrod | Solidago multiradiata Ait. var. scopulorum Gray | SOMUS |
| manyray gumweed | Grindelia grandiflora Hook. | GRGR |
| manystem woolly sunflower | Eriophyllum multicaule (DC.) Gray | ERMU6 |
| manzanilla horseweed | Conyza laevigata (L.C. Rich) Pruski | COLA21 |
| manzanilla trepador | Bidens reptans (L.) G. Don | BIRE |
| manzanilla trepador | Bidens reptans (L.) G. Don var. reptans | BIRER |
| marguerite | Argyranthemum frutescens (L.) Schultz-Bip. | ARFR11 |
| Maricao River hempvine | Mikania stevensiana Britt. | MIST6 |
| marigold | Calendula L. | CALEN |
| marigold | Tagetes L. | TAGET |
| mariola | Parthenium incanum Kunth | PAIN2 |
| Mariposa erigeron | Erigeron mariposanus Congdon | ERMA15 |
| maroon blanketflower | Gaillardia amblyodon J. Gay | GAAM |
| marsh cudweed | Gnaphalium uliginosum L. | GNUL |
| marsh dandelion | Taraxacum palustre (Lyons) Symons | TAPA9 |
| marsh fleabane | Senecio congestus (R. Br.) DC. | SECO2 |
| marsh jaumea | Jaumea carnosa (Less.) Gray | JACA4 |
| marsh silverpuffs | Microseris paludosa (Greene) J.T. Howell | MIPA |
| marsh sowthistle | Sonchus palustris L. | SOPA10 |
| marsh thistle | Cirsium palustre (L.) Scop. | CIPA6 |
| Marshallia graminifolia var. cynanthera | Marshallia graminifolia (Walt.) Small ssp. tenuifolia (Raf.) L. Watson | MAGRT2 |
| Marshallia graminifolia var. cynanthera | Marshallia tenuifolia Raf. | MATE6 |
| Marshallia graminifolia var. graminifolia | Marshallia laciniarioides Small | MALA4 |
| Marshallia graminifolia var. graminifolia | Marshallia tenuifolia Raf. var. graminifolia (Walt.) Gandhi & Thomas | MATEG |
| Marshallia graminifolia var. graminifolia | Marshallia williamsonii Small | MAWI4 |
| Marshallia obovata var. obovata | Marshallia obovata (Walt.) Beadle & F.E. Boynt. var. platyphylla (M.A. Curtis) Beadle & F.E. Boynt. | MAOBP |
| marshelder | Iva L. | IVA |
| Maryland goldenaster | Chrysopsis mariana (L.) Ell. | CHMA14 |
| Maryland hawkweed | Hieracium greenii Porter & Britt. | HIGR5 |
| Maryland hawkweed | Hieracium marianum Willd. | HIMA10 |
| Marysvale fleabane | Erigeron nauseosus (M.E. Jones) A. Nels. | ERNA6 |
| Mason's neststraw | Stylocline masonii Morefield | STMA10 |
| Matricaria discoidea | Artemisia matricarioides auct. non Less. [misapplied] | ARMA17 |
| Matricaria discoidea | Chamomilla suaveolens (Pursh) Rydb. | CHSU5 |
| Matricaria discoidea | Lepidanthus suaveolens (Pursh) Nutt. | LESU2 |
| Matricaria discoidea | Lepidotheca suaveolens (Pursh) Nutt. | LESU3 |
| Matricaria discoidea | Matricaria matricarioides auct. non (Less.) Porter [misapplied] | MAMA11 |
| Matricaria discoidea | Matricaria suaveolens (Pursh) Buch., non L. | MASU9 |
| Matricaria discoidea | Santolina suaveolens Pursh | SASU14 |
| Matricaria discoidea | Tanacetum suaveolens (Pursh) Hook. | TASU2 |
| Matricaria occidentalis | Chamomilla occidentalis (Greene) Rydb. | CHOC3 |
| Matricaria recutita | Chamomilla chamomilla (L.) Rydb. | CHCH8 |
| Matricaria recutita | Chamomilla recutita (L.) Rauschert | CHRE2 |
| Matricaria recutita | Matricaria chamomilla L. 1755 & 1763, non 1753 | MACH2 |
| Matricaria recutita | Matricaria chamomilla L. var. coronata (J. Gay) Coss. & Germ. | MACHC |
| Matricaria recutita | Matricaria suaveolens L. | MASU8 |
| Maui beggarticks | Bidens mauiensis (Gray) Sherff | BIMA4 |
| Maui dubautia | Dubautia dolosa (O. Deg. & Sherff) G.D. Carr | DUDO |
| Maui island-aster | Hesperomannia arbuscula Hbd. | HEAR10 |
| Maui nehe | Lipochaeta kamolensis O. Deg. & Sherff | LIKA |
| Maui remya | Remya mauiensis Hbd. | REMA2 |
| Maui tetramolopium | Tetramolopium arenarium (Gray) Hbd. | TEAR3 |
| Maui tetramolopium | Tetramolopium arenarium (Gray) Hbd. ssp. arenarium | TEARA |
| Maui tetramolopium | Tetramolopium arenarium (Gray) Hbd. ssp. arenarium var. arenarium | TEARA2 |
| Maui tetramolopium | Tetramolopium arenarium (Gray) Hbd. ssp. arenarium var. confertum Sherff | TEARC |
| Maui tetramolopium | Tetramolopium arenarium (Gray) Hbd. ssp. laxum Lowrey | TEARL |
| Maui wormwood | Artemisia mauiensis (Gray) Skottsberg | ARMA10 |
| Mauna Kea dubautia | Dubautia arborea (Gray) Keck | DUAR |
| Mauna Loa beggarticks | Bidens menziesii (Gray) Sherff | BIME |
| Mauna Loa beggarticks | Bidens menziesii (Gray) Sherff ssp. filiformis (Sherff) Ganders & Nagata | BIMEF2 |
| Mauna Loa beggarticks | Bidens menziesii (Gray) Sherff ssp. menziesii | BIMEM |
| max chrysanthemum | Leucanthemum maximum (Ramond) DC. | LEMA8 |
| Maximilian sunflower | Helianthus maximiliani Schrad. | HEMA2 |
| mayweed | Matricaria L. | MATRI |
| mayweed | Tripleurospermum Schultz-Bip. | TRIPL4 |
| meadow false fleabane | Pulicaria dysenterica (L.) Bernh. | PUDY |
| meadow hawkweed | Hieracium caespitosum Dumort. | HICA10 |
| meadow knapweed | Centaurea ?moncktonii C. E. Britton | CEMO6 |
| meadow knapweed | Centaurea debeauxii Gren. & Godr. [excluded] | CEDE5 |
| meadow prairie-dandelion | Nothocalais nigrescens (Henderson) Heller | NONI |
| meadow thistle | Cirsium scariosum Nutt. | CISC2 |
| meadow woollyheads | Psilocarphus elatior (Gray) Gray | PSEL |
| meager pygmydaisy | Pentachaeta exilis (Gray) Gray | PEEX4 |
| meager pygmydaisy | Pentachaeta exilis (Gray) Gray ssp. aeolica Van Horn & Ornduff | PEEXA |
| meager pygmydaisy | Pentachaeta exilis (Gray) Gray ssp. exilis | PEEXE |
| Mecca woodyaster | Xylorhiza cognata (Hall) T.J. Wats. | XYCO2 |
| medicineplant | Adenostemma J.R. & G. Forst. | ADENO4 |
| Melampodium divaricatum | Dysodium divaricatum L.C. Rich. | DYDI |
| Melampodium perfoliatum | Alcina perfoliata Cav. | ALPE8 |
| Melampodium sericeum | Melampodium hispidum Kunth | MEHI2 |
| Melanthera aspera var. aspera | Calea aspera Jacq. | CAAS6 |
| Melanthera aspera var. aspera | Melanthera canescens (Kuntze) O.E. Schulz | MECA12 |
| Melanthera aspera var. aspera | Melanthera deltoidea Michx. | MEDE8 |
| Melanthera aspera var. aspera | Melanthera montana O.E. Schulz | MEMO9 |
| Melanthera aspera var. glabriuscula | Melanthera calcicola Britt. | MECA13 |
| Melanthera aspera var. glabriuscula | Melanthera confusa Britt. | MECO6 |
| Melanthera nivea | Bidens nivea L. | BINI |
| Melanthera nivea | Melanthera carpenteri Small | MECA18 |
| Melanthera nivea | Melanthera hastata Michx. | MEHA6 |
| Melanthera parvifolia | Melanthera radiata Small | MERA3 |
| Mendocino erigeron | Erigeron foliosus Nutt. var. mendocinus (Greene) Nesom | ERFOM |
| Mendocino lessingia | Lessingia nemaclada Greene var. mendocina (Greene) J.T. Howell | LENEM |
| Menzies's goldenbush | Isocoma menziesii (Hook. & Arn.) Nesom | ISME5 |
| Menzies's goldenbush | Isocoma menziesii (Hook. & Arn.) Nesom var. decumbens (Greene) Nesom | ISMED |
| Menzies's goldenbush | Isocoma menziesii (Hook. & Arn.) Nesom var. diabolica Nesom | ISMED2 |
| Menzies's goldenbush | Isocoma menziesii (Hook. & Arn.) Nesom var. menziesii | ISMEM |
| Menzies's goldenbush | Isocoma menziesii (Hook. & Arn.) Nesom var. sedoides (Greene) Nesom | ISMES |
| Menzies's goldenbush | Isocoma menziesii (Hook. & Arn.) Nesom var. vernonioides (Nutt.) Nesom | ISMEV |
| mesa tansyaster | Machaeranthera tagetina Greene | MATA |
| Metcalf's groundsel | Packera neomexicana (Gray) W.A. Weber & A. L?ve var. metcalfei (Greene) D.K. Trock & T.M. Barkl. | PANEM2 |
| Mex's fleabane | Erigeron mexiae K. Becker | ERME7 |
| Mexican alpinegold | Hulsea mexicana Rydb. | HUME |
| Mexican blazing star | Liatris punctata Hook. var. mexicana Gaiser | LIPUM |
| Mexican bonebract | Sclerocarpus uniserialis (Benth.) Hemsl. | SCUN2 |
| Mexican bonebract | Sclerocarpus uniserialis (Benth.) Hemsl. var. austrotexanus B.L. Turner | SCUNA |
| Mexican bonebract | Sclerocarpus uniserialis (Benth.) Hemsl. var. uniserialis | SCUNU |
| Mexican brassbuttons | Cotula mexicana (DC.) Cabrera | COME15 |
| Mexican creeping zinnia | Sanvitalia procumbens Lam. | SAPR6 |
| Mexican flamevine | Pseudogynoxys chenopodioides Kunth | PSCH |
| Mexican gumweed | Grindelia oxylepis Greene | GROX |
| Mexican tansyaster | Psilactis gentryi (Standl.) D. Morgan | PSGE |
| Mexican thistle | Cirsium mexicanum DC. | CIME4 |
| Mexican woollywhite | Hymenopappus mexicanus Gray | HYME |
| Michaux's wormwood | Artemisia michauxiana Bess. | ARMI4 |
| Micropus amphibolus | Micropus amphibola Gray [orthographic variant] | MIAM2 |
| Micropus amphibolus | Stylocline amphibola (Gray) J.T. Howell | STAM14 |
| Micropus amphibolus | Stylocline amphiloba (Gray) J.T. Howell [orthographic error] | STAM11 |
| Microseris borealis | Apargidium boreale (Bong.) Torr. & Gray | APBO |
| Microseris decipiens | Stebbinsoseris decipiens (Chambers) Chambers nom. illeg. | STDE7 |
| Microseris douglasii ssp. platycarpha | Microseris douglasii (DC.) Schultz-Bip. var. platycarpha (Gray) B.L. Turner | MIDOP2 |
| Microseris heterocarpa | Stebbinsoseris heterocarpa (Nutt.) Chambers nom. illeg. | STHE10 |
| Microseris laciniata ssp. laciniata | Scorzonella laciniata (Hook.) Schultz-Bip. | SCLA7 |
| Microseris laciniata ssp. laciniata | Scorzonella laciniata (Hook.) Schultz-Bip. var. pratensis (Greene) Jepson | SCLAP |
| Microseris laciniata ssp. laciniata | Scorzonella procera Greene | SCPR2 |
| Microseris laciniata ssp. leptosepala | Scorzonella laciniata (Hook.) Schultz-Bip. var. bolanderi (Gray) Jepson | SCLAB |
| Microseris laciniata ssp. leptosepala | Scorzonella leachiana M.E. Peck | SCLE2 |
| Microseris laciniata ssp. leptosepala | Scorzonella leptosepala Nutt. | SCLE4 |
| Microseris laciniata var. siskiyouensis | Microseris nutans (Hook.) Schultz-Bip. ssp. siskiyouensis Chambers | MINUS |
| Microseris lindleyi | Microseris linearifolia (Nutt.) Schultz-Bip. | MILI |
| Microseris lindleyi | Uropappus lindleyi (DC.) Nutt. | URLI5 |
| Microseris lindleyi | Uropappus linearifolius Nutt. | URLI2 |
| Microseris nutans | Ptilocalais nutans (Hook.) Greene | PTNU2 |
| Microseris nutans | Scorzonella nutans Hook. | SCNU4 |
| Microseris nutans | Scorzonella nutans Hook. var. major (Gray) M.E. Peck | SCNUM |
| Mikania cordata | Eupatorium cordatum Burm. f. [excluded] | EUCO42 |
| Mikania cordifolia | Cacalia cordifolia L. f. | CACO59 |
| Mikania cordifolia | Willoughbya halei Small | WIHA3 |
| Mikania scandens | Mikania angulosa Raf. | MIAN6 |
| Mikania scandens | Mikania batatifolia auct. non DC. [misapplied] | MIBA5 |
| Mikania scandens | Mikania scandens (L.) Willd. var. pubescens (Nutt.) Torr. & Gray | MISCP |
| Mikania scandens | Willoughbya heterophylla Small | WIHE2 |
| milkthistle | Silybum Adans. | SILYB |
| Mill Creek agoseris | Agoseris lackschewitzii D. Henderson & R. Moseley | AGLA9 |
| miniature marigold | Tagetes minima L. | TAMI2 |
| Missouri goldenrod | Solidago missouriensis Nutt. | SOMI2 |
| Missouri goldenrod | Solidago missouriensis Nutt. var. fasciculata Holz. | SOMIF |
| Missouri goldenrod | Solidago missouriensis Nutt. var. missouriensis | SOMIM |
| Missouri goldenrod | Solidago missouriensis Nutt. var. tenuissima (Woot. & Standl.) C.& J. Taylor | SOMIT2 |
| Missouri ironweed | Vernonia missurica Raf. | VEMI2 |
| Missouri orange coneflower | Rudbeckia missouriensis Engelm. ex C.L. Boynt. & Beadle | RUMI |
| mock dandelion | Phalacroseris Gray | PHALA |
| mock goldenweed | Stenotus Nutt. | STENO7 |
| mock leopardbane | Arnica dealbata (Gray) B.G. Baldwin | ARDE11 |
| Modoc hawksbeard | Crepis modocensis Greene | CRMO4 |
| Modoc hawksbeard | Crepis modocensis Greene ssp. glareosa (Piper) Babcock & Stebbins | CRMOG3 |
| Modoc hawksbeard | Crepis modocensis Greene ssp. modocensis | CRMOM |
| Modoc hawksbeard | Crepis modocensis Greene ssp. rostrata (Coville) Babcock & Stebbins | CRMOR |
| Modoc hawksbeard | Crepis modocensis Greene ssp. subacaulis (Kellogg) Babcock & Stebbins | CRMOS |
| Mogollon hawkweed | Hieracium fendleri Schultz-Bip. var. mogollense Gray | HIFEM |
| Mogollon Mountain ragwort | Packera quaerens (Greene) W.A. Weber & A. L?ve | PAQU7 |
| Mogollon thistle | Cirsium parryi (Gray) Petrak ssp. mogollonicum C. Schaack & G. Goodwin | CIPAM |
| Mohr's Barbara's buttons | Marshallia mohrii Beadle & F.E. Boynt. | MAMO3 |
| Mohr's coneflower | Rudbeckia mohrii Gray | RUMO6 |
| Mohr's ironweed | Vernonia angustifolia Michx. ssp. mohrii (S.B. Jones) S.B. Jones & Faust | VEANM |
| Mohr's rosinweed | Silphium mohrii Small | SIMO4 |
| Mohr's thoroughwort | Eupatorium mohrii Greene | EUMO4 |
| moist sowthistle | Sonchus arvensis L. ssp. uliginosus (Bieb.) Nyman | SOARU |
| Mojave brickellbush | Brickellia oblongifolia Nutt. | BROB |
| Mojave brickellbush | Brickellia oblongifolia Nutt. var. oblongifolia | BROBO |
| Mojave cottonthorn | Tetradymia stenolepis Greene | TEST2 |
| Mojave desertstar | Monoptilon bellioides (Gray) Hall | MOBE2 |
| Mojave hole-in-the-sand plant | Nicolletia occidentalis Gray | NIOC |
| Mojave rabbitbrush | Ericameria paniculata (Gray) Rydb. | ERPA29 |
| Mojave ragwort | Senecio mohavensis Gray | SEMO3 |
| Mojave tarweed | Deinandra mohavensis (Keck) B.G. Baldwin | DEMO5 |
| Mojave thistle | Cirsium mohavense (Greene) Petrak | CIMO |
| Mojave woodyaster | Xylorhiza tortifolia (Torr. & Gray) Greene | XYTO2 |
| Mojave woodyaster | Xylorhiza tortifolia (Torr. & Gray) Greene var. tortifolia | XYTOT |
| Mojave woolly sunflower | Eriophyllum mohavense (I.M. Johnston) Jepson | ERMO6 |
| Molokai beggarticks | Bidens molokaiensis (Hbd.) Sherff | BIMO |
| Molokai nehe | Lipochaeta degeneri Sherff | LIDE5 |
| Mona Island thoroughwort | Chromolaena oteroi (Monachino) King & H.E. Robins. | CHOT |
| monarch of the veld | Venidium fastuosum (Jacq.) Stapf | VEFA |
| monarch thistle | Cirsium chuskaense Moore & Frankton | CICH3 |
| Mono ragwort | Senecio flaccidus Less. var. monoensis (Greene) B.L. Turner & T.M. Barkl. | SEFLM |
| monolopia | Monolopia DC. | MONOL2 |
| Monolopia congdonii | Eatonella congdonii Gray | EACO2 |
| Monolopia congdonii | Lembertia congdonii (Gray) Greene | LECO9 |
| Monongahela Barbara's buttons | Marshallia grandiflora Beadle & F.E. Boynt. | MAGR7 |
| montane coneflower | Rudbeckia montana Gray | RUMO9 |
| montanoa | Montanoa Llave & Lex. | MONTA |
| Montanoa hibiscifolia | Montagnaea hibiscifolia Benth. | MOHI2 |
| Monte Torrecilla thoroughwort | Koanophyllon droserolepis (B.L. Robins.) King & H.E. Robins. | KODR2 |
| Morefield's neststraw | Stylocline intertexta Morefield | STIN4 |
| Morocco knapweed | Cyanopsis muricata (L.) Dost | CYMU7 |
| Moscow salsify | Tragopogon miscellus Ownbey | TRMI8 |
| mountain arnica | Arnica montana L. | ARMO8 |
| mountain ashdaisy | Piptocarpha tetrantha Urban | PITE6 |
| mountain aster | Canadanthus Nesom | CANAD |
| mountain aster | Eurybia chlorolepis (Burgess) Nesom | EUCH12 |
| mountain big sagebrush | Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle | ARTRV |
| mountain crownbeard | Verbesina oreophila Woot. & Standl. | VEOR |
| mountain decumbent goldenrod | Solidago curtisii Torr. & Gray | SOCU |
| mountain dubautia | Dubautia menziesii (Gray) Keck | DUME4 |
| mountain dwarfdandelion | Krigia montana (Michx.) Nutt. | KRMO |
| mountain goldenrod | Solidago flaccidifolia Small | SOFL |
| mountain hawksbeard | Crepis monticola Coville | CRMO5 |
| mountain neststraw | Stylocline gnaphalioides Nutt. | STGN |
| mountain oxeye | Heliopsis parvifolia Gray | HEPA4 |
| mountain ragwort | Senecio parryi Gray | SEPA2 |
| mountain slope thistle | Cirsium scapanolepis Petrak | CISC |
| mountain sneezeweed | Helenium autumnale L. var. montanum (Nutt.) Fern. | HEAUM |
| mountain tail-leaf | Pericome caudata Gray | PECA10 |
| mountain tarweed | Madia glomerata Hook. | MAGL2 |
| mountain thistle | Cirsium scopulorum (Greene) Cockerell ex Daniels | CISC3 |
| mouseear hawkweed | Hieracium pilosella L. | HIPI |
| mouseear hawkweed | Hieracium pilosella L. var. niveum Muell.-Arg. | HIPIN |
| mouseear hawkweed | Hieracium pilosella L. var. pilosella | HIPIP |
| Mt Hamilton thistle | Cirsium fontinale (Greene) Jepson var. campylon (H.K. Sharsmith) Pilz ex Keil & C. Turner | CIFOC |
| Mt. Albert goldenrod | Solidago simplex Kunth | SOSI3 |
| Mt. Albert goldenrod | Solidago simplex Kunth ssp. simplex | SOSIS |
| Mt. Albert goldenrod | Solidago simplex Kunth ssp. simplex var. simplex | SOSIS3 |
| Mt. Albert goldenrod | Solidago simplex Kunth ssp. simplex var. spathulata (DC.) Cronq. | SOSIS4 |
| Mt. Davis brickellbush | Brickellia parvula Gray | BRPA |
| Mt. Diablo cottonseed | Micropus amphibolus Gray | MIAM3 |
| Mt. Diablo helianthella | Helianthella castanea Greene | HECA2 |
| Mt. Hamilton tickseed | Coreopsis hamiltonii (Elmer) H.K. Sharsmith | COHA2 |
| Mt. Kahili beggarticks | Bidens valida Sherff | BIVA |
| Mt. Lassen fleabane | Erigeron lassenianus Greene | ERLA2 |
| Mt. Lassen fleabane | Erigeron lassenianus Greene var. deficiens Cronq. | ERLAD |
| Mt. Lassen fleabane | Erigeron lassenianus Greene var. lassenianus | ERLAL4 |
| Mt. Shasta arnica | Arnica viscosa Gray | ARVI6 |
| Mt. Tamalpais lessingia | Lessingia micradenia Greene | LEMI5 |
| Mt. Tamalpais lessingia | Lessingia micradenia Greene var. micradenia | LEMIM |
| Mt. Waialeale island-daisy | Keysseria helenae (Forbes & Lydgate) Cabrera | KEHE |
| muck sunflower | Helianthus simulans E.E. Wats. | HESI2 |
| Mueller's hawkbit | Leontodon muelleri (Schultz-Bip.) Fiori | LEMU13 |
| Muir's fleabane | Erigeron muirii Gray | ERMU8 |
| Muir's raillardiopsis | Carlquistia muirii (Gray) B.G. Baldwin | CAMU27 |
| Mule Mountain brickellbush | Asanthus squamulosus (Gray) King & H.E. Robins. | ASSQ |
| mule's fat | Baccharis salicifolia (Ruiz & Pav?n) Pers. | BASA4 |
| mule-ears | Wyethia amplexicaulis (Nutt.) Nutt. | WYAM |
| mule-ears | Wyethia Nutt. | WYETH |
| Munz's tidytips | Layia munzii Keck | LAMU2 |
| Murdock's thistle | Cirsium murdockii (Welsh) Cronq. | CIMU2 |
| Musinea ragwort | Senecio musiniensis Welsh | SEMU12 |
| muster John Henry | Tagetes minuta L. | TAMI3 |
| Mutis's burrweed | Soliva mutisii Kunth | SOMU2 |
| mycelis | Mycelis Cass. | MYCEL |
| Mycelis muralis | Lactuca muralis (L.) Fresen. | LAMU |
| na'ena'e 'ula | Dubautia raillardioides Hbd. | DURA |
| na'ena'e pua kea | Dubautia paleata Gray | DUPA3 |
| na'ena'e pua melemele | Dubautia laxa Hook. & Arn. | DULA4 |
| na'ena'e pua melemele | Dubautia laxa Hook. & Arn. ssp. bryanii (O. Deg. & Sherff) G.D. Carr | DULAB3 |
| na'ena'e pua melemele | Dubautia laxa Hook. & Arn. ssp. hirsuta (Hbd.) G.D. Carr | DULAH3 |
| na'ena'e pua melemele | Dubautia laxa Hook. & Arn. ssp. laxa | DULAL |
| na'ena'e pua melemele | Dubautia laxa Hook. & Arn. ssp. pseudoplantaginea (Skottsberg) G.D. Carr | DULAP4 |
| naked Mexicanhat | Ratibida peduncularis (Torr. & Gray) Barnh. | RAPE3 |
| naked Mexicanhat | Ratibida peduncularis (Torr. & Gray) Barnh. var. peduncularis | RAPEP2 |
| naked Mexicanhat | Ratibida peduncularis (Torr. & Gray) Barnh. var. picta (Gray) Sharp | RAPEP |
| naked turtleback | Psathyrotopsis scaposa (Gray) H.E. Robins. | PSSC14 |
| nakedstem hawksbeard | Crepis pleurocarpa Gray | CRPL |
| nakedstem sunray | Enceliopsis nudicaulis (Gray) A. Nels. | ENNU |
| nakedstem sunray | Enceliopsis nudicaulis (Gray) A. Nels. var. corrugata Cronq. | ENNUC |
| nakedstem sunray | Enceliopsis nudicaulis (Gray) A. Nels. var. nudicaulis | ENNUN |
| narrow-leaved rockdaisy | Perityle angustifolia (Gray) Shinners | PEAN6 |
| narrowleaf arnica | Arnica angustifolia Vahl | ARAN5 |
| narrowleaf arnica | Arnica angustifolia Vahl ssp. angustifolia | ARANA |
| narrowleaf arnica | Arnica angustifolia Vahl ssp. tomentosa (Macoun) G.W. Douglas & G. Ruyle-Douglas | ARANT |
| narrowleaf brickellbush | Brickellia oblongifolia Nutt. var. linifolia (D.C. Eat.) B.L. Robins. | BROBL |
| narrowleaf cottonrose | Logfia gallica (L.) Coss. & Germ. | LOGA2 |
| narrowleaf goldenaster | Chrysopsis linearifolia Semple | CHLI4 |
| narrowleaf goldenaster | Chrysopsis linearifolia Semple ssp. linearifolia | CHLIL |
| narrowleaf goldenbush | Ericameria linearifolia (DC.) Urbatsch & Wussow | ERLI6 |
| narrowleaf gumweed | Grindelia lanceolata Nutt. | GRLA3 |
| narrowleaf gumweed | Grindelia lanceolata Nutt. var. lanceolata | GRLAL |
| narrowleaf hawksbeard | Crepis tectorum L. | CRTE3 |
| narrowleaf hawkweed | Hieracium umbellatum L. | HIUM |
| narrowleaf ironweed | Vernonia lettermannii Engelm. ex Gray | VELE |
| narrowleaf laphamia | Perityle intricata (Brandeg.) Shinners | PEIN12 |
| narrowleaf marshelder | Iva angustifolia Nutt. ex DC. | IVAN |
| narrowleaf mock goldenweed | Stenotus stenophyllus (Gray) Greene | STST5 |
| narrowleaf pectis | Pectis angustifolia Torr. var. angustifolia | PEANA |
| narrowleaf purple everlasting | Gamochaeta falcata (Lam.) Cabrera | GAFA3 |
| narrowleaf pussytoes | Antennaria stenophylla (Gray) Gray | ANST2 |
| narrowleaf saw-wort | Saussurea angustifolia (Willd.) DC. | SAAN3 |
| narrowleaf saw-wort | Saussurea angustifolia (Willd.) DC. var. angustifolia | SAANA3 |
| narrowleaf saw-wort | Saussurea angustifolia (Willd.) DC. var. yukonensis Porsild | SAANY |
| narrowleaf silkgrass | Pityopsis graminifolia (Michx.) Nutt. | PIGR4 |
| narrowleaf silkgrass | Pityopsis graminifolia (Michx.) Nutt. var. aequilifolia Bowers & Semple | PIGRA |
| narrowleaf silkgrass | Pityopsis graminifolia (Michx.) Nutt. var. graminifolia | PIGRG |
| narrowleaf silkgrass | Pityopsis graminifolia (Michx.) Nutt. var. latifolia (Fern.) Semple & Bowers | PIGRL |
| narrowleaf silkgrass | Pityopsis graminifolia (Michx.) Nutt. var. tenuifolia (Torr.) Semple & Bowers | PIGRT |
| narrowleaf whitetop aster | Sericocarpus linifolius (L.) B.S.P. | SELI5 |
| narrowleaf wirelettuce | Stephanomeria minor (Hook.) Nutt. var. minor | STMIM |
| narrowleaf wirelettuce | Stephanomeria minor (Hook.) Nutt. var. myrioclada (D.C. Eat.) Kartesz | STMIM2 |
| narrowleaf yellowtops | Flaveria linearis Lag. | FLLI |
| narrowleaf zinnia | Zinnia angustifolia Kunth | ZIAN2 |
| Navajo fleabane | Erigeron concinnus (Hook. & Arn.) Torr. & Gray | ERCO27 |
| Navajo fleabane | Erigeron concinnus (Hook. & Arn.) Torr. & Gray var. concinnus | ERCOC3 |
| Navajo fleabane | Erigeron concinnus (Hook. & Arn.) Torr. & Gray var. condensatus D.C. Eat. | ERCOC4 |
| Navajo fleabane | Erigeron concinnus (Hook. & Arn.) Torr. & Gray var. subglaber (Cronq.) Nesom | ERCOS |
| Navajo tea | Thelesperma subnudum Gray | THSU |
| Navajo tea | Thelesperma subnudum Gray var. marginatum (Rydb.) T.E. Melchert ex Cronq. | THSUM |
| Navajo tea | Thelesperma subnudum Gray var. subnudum | THSUS |
| Navajo thistle | Cirsium navajoense Moore & Frankton | CINA |
| Nebraska aster | Symphyotrichum praealtum (Poir.) Nesom var. nebraskense (Britt.) Nesom | SYPRN |
| Nebraska blazing star | Liatris punctata Hook. var. nebraskana Gaiser | LIPUN |
| Nebraska tansyaster | Machaeranthera canescens (Pursh) Gray ssp. glabra (Gray) B.L. Turner var. nebraskana B.L. Turner | MACAN |
| needle goldfields | Lasthenia gracilis (DC.) Greene | LAGR10 |
| needleleaf fleabane | Erigeron nematophyllus Rydb. | ERNE2 |
| neglected balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. neglecta (Sharp) Cronq. | BAHON |
| neglected sunflower | Helianthus neglectus Heiser | HENE |
| nehe | Lipochaeta connata (Gaud.) DC. | LICO10 |
| nehe | Lipochaeta connata (Gaud.) DC. var. acris (Sherff) R.C. Gardner | LICOA |
| nehe | Lipochaeta connata (Gaud.) DC. var. connata | LICOC |
| nehe | Lipochaeta DC. | LIPOC2 |
| Nelson's brickellbush | Brickellia nelsonii B.L. Robins. [excluded] | BRNE |
| nerveray | Tetragonotheca L. | TETRA5 |
| neststraw | Ancistrocarphus Gray | ANCIS2 |
| neststraw | Stylocline Nutt. | STYLO |
| nettle-leaf soldier | Galinsoga urticifolia (Kunth) Benth. | GAUR4 |
| netvein dubautia | Dubautia reticulata (Sherff) Keck | DURE2 |
| netvein goldeneye | Viguiera reticulata S. Wats. | VIRE |
| neurolaena | Neurolaena R. Br. | NEURO2 |
| Neurolaena lobata | Conyza lobata L. | COLO8 |
| Neurolaena lobata | Pluchea symphytifolia (P. Mill.) Gillis | PLSY2 |
| Nevada arnica | Arnica nevadensis Gray | ARNE3 |
| Nevada broomsage | Lepidospartum latisquamum S. Wats. | LELA4 |
| Nevada dustymaiden | Chaenactis nevadensis (Kellogg) Gray | CHNE |
| Nevada goldeneye | Heliomeris multiflora Nutt. var. nevadensis (A. Nels.) Yates | HEMUN |
| Nevada goldenrod | Solidago spectabilis (D.C. Eat.) Gray | SOSP3 |
| Nevada goldenrod | Solidago spectabilis (D.C. Eat.) Gray var. confinis (Gray) Cronq. | SOSPC |
| Nevada goldenrod | Solidago spectabilis (D.C. Eat.) Gray var. spectabilis | SOSPS6 |
| Nevada helianthella | Helianthella californica Gray ssp. nevadensis (Greene) W.A. Weber | HECAN2 |
| Nevada rockdaisy | Perityle megalocephala (S. Wats.) J.F. Macbr. | PEME6 |
| Nevada rockdaisy | Perityle megalocephala (S. Wats.) J.F. Macbr. var. megalocephala | PEMEM |
| Nevada sumpweed | Chorisiva nevadensis (M.E. Jones) Rydb. | CHNE12 |
| Nevin's brickellbush | Brickellia nevinii Gray | BRNE2 |
| Nevin's woolly sunflower | Constancea nevinii (Gray) B.G. Baldwin | CONE9 |
| New England aster | Symphyotrichum novae-angliae (L.) Nesom | SYNO2 |
| New England blazing star | Liatris scariosa (L.) Willd. var. novae-angliae Lunell | LISCN2 |
| New England hawkweed | Hieracium sabaudum L. | HISA4 |
| New Mexican gumweed | Grindelia arizonica Gray var. neomexicana (Woot. & Standl.) Nesom | GRARN |
| New Mexico fleabane | Erigeron neomexicanus Gray | ERNE3 |
| New Mexico groundsel | Packera neomexicana (Gray) W.A. Weber & A. L?ve | PANE7 |
| New Mexico groundsel | Packera neomexicana (Gray) W.A. Weber & A. L?ve var. mutabilis (Greene) W.A. Weber & A. L?ve | PANEM |
| New Mexico groundsel | Packera neomexicana (Gray) W.A. Weber & A. L?ve var. neomexicana | PANEN |
| New Mexico plumeseed | Rafinesquia neomexicana Gray | RANE |
| New Mexico rockdaisy | Perityle staurophylla (Barneby) Shinners | PEST8 |
| New Mexico rockdaisy | Perityle staurophylla (Barneby) Shinners var. homoflora T.K. Todsen | PESTH |
| New Mexico rockdaisy | Perityle staurophylla (Barneby) Shinners var. staurophylla | PESTS2 |
| New Mexico sunflower | Helianthus praetermissus E.E. Wats. | HEPR5 |
| New Mexico tansyaster | Psilactis asteroides Gray | PSAS2 |
| New Mexico thistle | Cirsium neomexicanum Gray | CINE |
| New York aster | Symphyotrichum novi-belgii (L.) Nesom | SYNO3 |
| New York aster | Symphyotrichum novi-belgii (L.) Nesom var. elodes (Torr. & Gray) Nesom | SYNOE |
| New York aster | Symphyotrichum novi-belgii (L.) Nesom var. novi-belgii | SYNON |
| New York ironweed | Vernonia noveboracensis (L.) Michx. | VENO |
| Newberry's hymenopappus | Hymenopappus newberryi (Gray) I.M. Johnston | HYNE |
| Newberry's tickseed | Coreopsis californica (Nutt.) H.K. Sharsmith var. newberryi (Gray) E.B. Sm. | COCAN |
| ngai camphor | Blumea balsamifera (L.) DC. | BLBA2 |
| Nieuwland's blazing star | Liatris scariosa (L.) Willd. var. nieuwlandii (Lunell) E.G. Voss | LISCN |
| nipplewort | Lapsana L. | LAPSA |
| nipplewort | Lapsanastrum J.K. Pak & K. Bremer | LAPSA2 |
| Nippon daisy | Nipponanthemum nipponicum (Franch. ex Maxim.) Kitam. | NINI |
| Nipponanthemum nipponicum | Chrysanthemum nipponicum (Franch. ex Maxim.) Spreng. | CHNI4 |
| Nipponanthemum nipponicum | Leucanthemum nipponicum Franch. ex Maxim. | LENI2 |
| noble yarrow | Achillea nobilis L. | ACNO |
| nodding arnica | Arnica lessingii Greene | ARLE2 |
| nodding beggartick | Bidens cernua L. | BICE |
| nodding madia | Harmonia nutans (Greene) B.G. Baldwin | HANU3 |
| nodding microceris | Microseris nutans (Hook.) Schultz-Bip. | MINU |
| nodding plumeless thistle | Carduus nutans L. | CANU4 |
| nodding ragwort | Senecio bigelovii Gray | SEBI2 |
| nodding ragwort | Senecio bigelovii Gray var. bigelovii | SEBIB |
| nodding rattlesnakeroot | Prenanthes crepidinea Michx. | PRCR |
| nodding sunray | Encelia nutans Eastw. | ENNU4 |
| nodeweed | Synedrella nodiflora (L.) Gaertn. | SYNO |
| North African knapweed | Centaurea diluta Ait. | CEDI4 |
| northern bog aster | Symphyotrichum boreale (Torr. & Gray) A.& D. L?ve | SYBO2 |
| northern dandelion | Taraxacum phymatocarpum J. Vahl | TAPH |
| northern groundsel | Packera hyperborealis (Greenm.) A.& D. L?ve | PAHY5 |
| northwestern groundsel | Packera contermina (Greenm.) J.F. Bain | PACO53 |
| Nothocalais alpestris | Agoseris alpestris (Gray) Greene | AGAL10 |
| Nothocalais alpestris | Agoseris barbellulata (Greene ex Gray) Greene | AGBA4 |
| Nothocalais alpestris | Microseris alpestris (Gray) Q. Jones ex Cronq. | MIAL7 |
| Nothocalais cuspidata | Agoseris cuspidata (Pursh) Raf. | AGCU2 |
| Nothocalais cuspidata | Microseris cuspidata (Pursh) Schultz-Bip. | MICU6 |
| Nothocalais nigrescens | Microseris nigrescens Henderson | MINI3 |
| Nothocalais troximoides | Microseris troximoides Gray | MITR5 |
| Nothocalais troximoides | Scorzonella troximoides (Gray) Jepson | SCTR6 |
| Nuttall's horsebrush | Tetradymia nuttallii Torr. & Gray | TENU2 |
| Nuttall's rayless goldenrod | Bigelowia nuttallii L.C. Anders. | BINU2 |
| Nuttall's sunflower | Helianthus nuttallii Torr. & Gray | HENU |
| Nuttall's sunflower | Helianthus nuttallii Torr. & Gray ssp. nuttallii | HENUN |
| Nuttall's thistle | Cirsium nuttallii DC. | CINU |
| Nuttall's Townsend daisy | Townsendia nuttallii Dorn | TONU |
| nutty saw-wort | Saussurea nuda Ledeb. | SANU |
| Oahu beggarticks | Bidens populifolia Sherff | BIPO2 |
| Oahu tetramolopium | Tetramolopium tenerrimum (Less.) Nees | TETE5 |
| Oahu wormwood | Artemisia australis Less. | ARAU3 |
| Oak Creek ragwort | Packera quercetorum (Greene) C. Jeffrey | PAQU8 |
| oakleaf fleabane | Erigeron quercifolius Lam. | ERQU |
| oblongleaf basindaisy | Platyschkuhria integrifolia (Gray) Rydb. var. oblongifolia (Gray) W. Ellison | PLINO |
| Oclemena ?blakei | Aster blakei (Porter) House | ASBL7 |
| Oclemena acuminata | Aster acuminatus Michx. | ASAC6 |
| Oclemena acuminata | Aster acuminatus Michx. var. magdalenensis Fern. | ASACM |
| Oclemena nemoralis | Aster nemoralis Ait. | ASNE |
| Oclemena reticulata | Aster reticulatus Pursh | ASRE8 |
| Oclemena reticulata | Doellingeria reticulata (Pursh) Greene | DORE2 |
| ogiera | Eleutheranthera ruderalis (Sw.) Schultz-Bip. | ELRU2 |
| Ogotoruk Creek ragwort | Packera ogotorukensis (Packer) A.& D. L?ve | PAOG |
| Ohio goldenrod | Oligoneuron ohioense (Frank ex Riddell) G.N. Jones | OLOH |
| oil neststraw | Stylocline citroleum Morefield | STCI10 |
| Ojo Alamo fleabane | Erigeron bistiensis Nesom & Hevron | ERBI9 |
| Old Cahaba rosinweed | Silphium perplexum J. Allison | SIPE10 |
| old-man-in-the-Spring | Senecio vulgaris L. | SEVU |
| oldfield sneezeweed | Helenium campestre Small | HECA13 |
| oldplainsman | Hymenopappus artemisiifolius DC. | HYAR3 |
| oldplainsman | Hymenopappus artemisiifolius DC. var. artemisiifolius | HYARA |
| oldplainsman | Hymenopappus artemisiifolius DC. var. riograndensis B.L. Turner | HYARR2 |
| oldwoman | Artemisia stelleriana Bess. | ARST6 |
| Oligoneuron ?bernardii | Solidago ?bernardii Boivin | SOBE2 |
| Oligoneuron ?krotkovii | Solidago ?krotkovii Boivin | SOKR |
| Oligoneuron ?lutescens | Aster lutescens (Lindl. ex DC.) Torr. & Gray | ASLU3 |
| Oligoneuron ?lutescens | Aster ptarmicoides (Nees) Torr. & Gray var. lutescens (Lindl. ex DC.) Gray | ASPTL |
| Oligoneuron ?lutescens | Diplopappus lutescens Lindl. ex DC. | DILU2 |
| Oligoneuron ?lutescens | Solidago ?lutescens (Lindl. ex DC.) Boivin | SOLU4 |
| Oligoneuron ?lutescens | Unamia lutescens (Lindl. ex DC.) Rydb. | UNLU |
| Oligoneuron album | Aster ptarmicoides (Nees) Torr. & Gray | ASPT4 |
| Oligoneuron album | Aster ptarmicoides (Nees) Torr. & Gray var. georgianus Gray | ASPTG |
| Oligoneuron album | Doellingeria ptarmicoides Nees | DOPT |
| Oligoneuron album | Inula alba Nutt. | INAL |
| Oligoneuron album | Solidago asteroides Semple | SOAS5 |
| Oligoneuron album | Solidago ptarmicoides (Nees) Boivin | SOPT4 |
| Oligoneuron album | Unamia alba (Nutt.) Rydb. | UNAL |
| Oligoneuron houghtonii | Solidago houghtonii Torr. & Gray ex Gray | SOHO |
| Oligoneuron nitidum | Solidago nitida Torr. & Gray | SONI2 |
| Oligoneuron ohioense | Solidago ohioensis Frank ex Riddell | SOOH |
| Oligoneuron riddellii | Solidago riddellii Frank ex Riddell | SORI |
| Oligoneuron rigidum var. glabratum | Oligoneuron jacksonii (Kuntze) Small | OLJA |
| Oligoneuron rigidum var. glabratum | Solidago corymbosa Ell. | SOCO3 |
| Oligoneuron rigidum var. glabratum | Solidago jacksonii (Kuntze) Fern. | SOJA4 |
| Oligoneuron rigidum var. glabratum | Solidago rigida L. ssp. glabrata (E.L. Braun) Heard & Semple | SORIG2 |
| Oligoneuron rigidum var. glabratum | Solidago rigida L. var. glabrata E.L. Braun | SORIG |
| Oligoneuron rigidum var. glabratum | Solidago rigida L. var. laevicaulis Shinners | SORIL |
| Oligoneuron rigidum var. humile | Oligoneuron canescens Rydb. | OLCA3 |
| Oligoneuron rigidum var. humile | Oligoneuron corymbosum (Ell.) Small var. humile (Porter) Beaudry & Kapoor | OLCOH |
| Oligoneuron rigidum var. humile | Solidago canescens (Rydb.) Friesner | SOCA12 |
| Oligoneuron rigidum var. humile | Solidago jacksonii (Kuntze) Fern. var. humilis (Porter) Beaudry | SOJAH |
| Oligoneuron rigidum var. humile | Solidago parvirigida Beaudry | SOPA7 |
| Oligoneuron rigidum var. humile | Solidago rigida L. ssp. humilis (Porter) Heard & Semple | SORIH2 |
| Oligoneuron rigidum var. humile | Solidago rigida L. var. humilis Porter | SORIH |
| Oligoneuron rigidum var. rigidum | Oligoneuron grandiflorum (Raf.) Small | OLGR3 |
| Oligoneuron rigidum var. rigidum | Solidago grandiflora Raf. | SOGR5 |
| Oligoneuron rigidum var. rigidum | Solidago rigida L. | SORI2 |
| Olokele Canyon nehe | Lipochaeta fauriei Levl. | LIFA2 |
| Olympic Mountain aster | Eucephalus paucicapitatus (B.L. Robins.) Greene | EUPA22 |
| Olympic Mountain ragwort | Senecio neowebsteri Blake | SENE6 |
| Omalotheca supina | Gnaphalium supinum L. | GNSU2 |
| Omalotheca sylvatica | Gnaphalium sylvaticum L. | GNSY2 |
| oncosiphon | Oncosiphon K?llersj? | ONCOS |
| Oncosiphon piluliferum | Matricaria globifera (Thunb.) Fenzl ex Harv. | MAGL13 |
| Oncosiphon suffruticosum | Matricaria suffruticosa (L.) Druce | MASU4 |
| oneflower fleabane | Erigeron uniflorus L. | ERUN4 |
| oneflower fleabane | Erigeron uniflorus L. ssp. eriocephalus (J. Vahl) Cronq. | ERUNE |
| oneflower helianthella | Helianthella uniflora (Nutt.) Torr. & Gray | HEUN |
| oneflower helianthella | Helianthella uniflora (Nutt.) Torr. & Gray var. uniflora | HEUNU |
| oneflower honeycombhead | Balduina uniflora Nutt. | BAUN |
| onefruit | Haplocarpha Less. | HAPLO10 |
| onehead brittlebush | Encelia scaposa (Gray) Gray | ENSC |
| onestem fleabane | Erigeron simplex Greene | ERSI3 |
| onion blanketflower | Gaillardia multiceps Greene | GAMU |
| onion blanketflower | Gaillardia multiceps Greene var. microcephala B.L. Turner | GAMUM |
| onion blanketflower | Gaillardia multiceps Greene var. multiceps | GAMUM2 |
| Onopordum acanthium | Onopordum acanthium L. ssp. acanthium L. [superfluous autonym] | ONACA |
| Ontario blazing star | Liatris cylindracea Michx. | LICY |
| Ontario goatsbeard | Tragopogon mirabilis Rouy | TRMI10 |
| Ontario goldenrod | Solidago simplex Kunth ssp. randii (Porter) Ringius var. ontarioensis (Ringius) Ringius | SOSIO |
| Oonopsis engelmannii | Haplopappus engelmannii (Gray) Hall | HAEN |
| Oonopsis foliosa var. foliosa | Haplopappus fremontii (Gray) Greene | HAFR2 |
| Oonopsis foliosa var. foliosa | Haplopappus fremontii (Gray) Greene ssp. typicus Hall | HAFRT |
| Oonopsis foliosa var. monocephala | Haplopappus fremontii (Gray) Greene ssp. monocephalus (A. Nels.) Hall | HAFRM |
| Oonopsis multicaulis | Haplopappus multicaulis (Nutt.) Gray | HAMU3 |
| Oonopsis wardii | Haplopappus fremontii (Gray) Greene ssp. wardii (Gray) Hall | HAFRW |
| Oonopsis wardii | Haplopappus wardii (Gray) Dorn | HAWA2 |
| openwoods ragwort | Senecio rapifolius Nutt. | SERA |
| oppositeleaf bahia | Picradeniopsis oppositifolia (Nutt.) Rydb. ex Britt. | PIOP |
| oppositeleaf spotflower | Acmella oppositifolia (Lam.) R.K. Jansen | ACOP |
| oppositeleaf spotflower | Acmella oppositifolia (Lam.) R.K. Jansen var. repens (Walt.) R.K. Jansen | ACOPR |
| oppositeleaved tarweed | Hemizonella minima (Gray) Gray | HEMI20 |
| orange agoseris | Agoseris aurantiaca (Hook.) Greene | AGAU2 |
| orange agoseris | Agoseris aurantiaca (Hook.) Greene var. aurantiaca | AGAUA |
| orange agoseris | Agoseris aurantiaca (Hook.) Greene var. purpurea (Gray) Cronq. | AGAUP |
| orange coneflower | Rudbeckia fulgida Ait. | RUFU2 |
| orange coneflower | Rudbeckia fulgida Ait. var. fulgida | RUFUF |
| orange coneflower | Rudbeckia fulgida Ait. var. speciosa (Wenderoth) Perdue | RUFUS3 |
| orange coneflower | Rudbeckia fulgida Ait. var. umbrosa (C.L. Boynt. & Beadle) Cronq. | RUFUU |
| orange daisy | Erigeron aurantiacus Regel | ERAU7 |
| orange hawkweed | Hieracium aurantiacum L. | HIAU |
| Orcutt's aster | Xylorhiza orcuttii (Vasey & Rose) Greene | XYOR |
| Orcutt's bristleweed | Hazardia orcuttii (Gray) Greene | HAOR3 |
| Orcutt's yellow pincushion | Chaenactis glabriuscula DC. var. orcuttiana (Greene) Hall | CHGLO |
| oreganillo | Koanophyllon dolicholepis (Urban) King & H.E. Robins. | KODO |
| Oregon false goldenaster | Heterotheca oregona (Nutt.) Shinners | HEOR2 |
| Oregon false goldenaster | Heterotheca oregona (Nutt.) Shinners var. compacta (Keck) Semple | HEORC |
| Oregon false goldenaster | Heterotheca oregona (Nutt.) Shinners var. oregona | HEORO |
| Oregon false goldenaster | Heterotheca oregona (Nutt.) Shinners var. rudis (Greene) Semple | HEORR |
| Oregon false goldenaster | Heterotheca oregona (Nutt.) Shinners var. scaberrima (Gray) Semple | HEORS |
| Oregon gumweed | Grindelia stricta DC. | GRST3 |
| Oregon gumweed | Grindelia stricta DC. var. angustifolia (Gray) M.A. Lane | GRSTA2 |
| Oregon gumweed | Grindelia stricta DC. var. platyphylla (Greene) M.A. Lane | GRSTP2 |
| Oregon gumweed | Grindelia stricta DC. var. stricta | GRSTS2 |
| Oregon western rosinweed | Calycadenia truncata DC. | CATR3 |
| Oregon western rosinweed | Calycadenia truncata DC. ssp. microcephala Hall ex Keck | CATRM |
| Oregon western rosinweed | Calycadenia truncata DC. ssp. scabrella (E. Drew) Keck | CATRS |
| Oregon western rosinweed | Calycadenia truncata DC. ssp. truncata | CATRT |
| Oregon whitetop aster | Sericocarpus oregonensis Nutt. | SEOR6 |
| Oregon whitetop aster | Sericocarpus oregonensis Nutt. var. californicus (Dur.) Nesom | SEORC2 |
| Oregon whitetop aster | Sericocarpus oregonensis Nutt. var. oregonensis | SEORO2 |
| Oregon woollyheads | Psilocarphus oregonus Nutt. | PSOR |
| Oreochrysum parryi | Aster minor Kuntze | ASMI18 |
| Oreochrysum parryi | Haplopappus parryi Gray | HAPA9 |
| Oreochrysum parryi | Solidago parryi (Gray) Greene | SOPA4 |
| Oreostemma alpigenum var. alpigenum | Aster alpigenus (Torr. & Gray) Gray | ASAL2 |
| Oreostemma alpigenum var. alpigenum | Haplopappus alpigenus Torr. & Gray | HAAL5 |
| Oreostemma alpigenum var. andersonii | Aster alpigenus (Torr. & Gray) Gray ssp. andersonii (Gray) Onno | ASALA3 |
| Oreostemma alpigenum var. andersonii | Aster alpigenus (Torr. & Gray) Gray var. andersonii (Gray) Onno ex M.E. Peck | ASALA |
| Oreostemma alpigenum var. andersonii | Aster andersonii (Gray) Gray | ASAN12 |
| Oreostemma alpigenum var. andersonii | Erigeron andersonii Gray | ERAN11 |
| Oreostemma alpigenum var. haydenii | Aster alpigenus (Torr. & Gray) Gray ssp. haydenii (Porter) Cronq. | ASALH2 |
| Oreostemma alpigenum var. haydenii | Aster alpigenus (Torr. & Gray) Gray var. haydenii (Porter) Cronq. | ASALH |
| Oreostemma alpigenum var. haydenii | Aster haydenii Porter | ASHA12 |
| Oreostemma alpigenum var. haydenii | Oreostemma alpigenum (Torr. & Gray) Greene ssp. haydenii (Porter) Semple | ORALH2 |
| Oreostemma elatum | Aster elatus (Greene) Cronq. | ASEL2 |
| Oreostemma elatum | Oreastrum elatum Greene | OREL |
| Oreostemma peirsonii | Aster peirsonii C.W. Sharsmith | ASPE2 |
| Organ Mountain rockdaisy | Perityle cernua (Greene) Shinners | PECE3 |
| Oriental false hawksbeard | Youngia japonica (L.) DC. | YOJA |
| Ornduff's goldfields | Lasthenia ornduffii R. Chan | LAOR3 |
| orochaenactis | Orochaenactis Coville | OROCH |
| osmadenia | Osmadenia Nutt. | OSMAD |
| Osmadenia tenella | Calycadenia tenella (Nutt.) Torr. & Gray | CATE |
| Osmadenia tenella | Hemizonia tenella (Nutt.) Gray | HETE17 |
| Osteospermum ecklonis | Dimorphotheca ecklonis DC. | DIEC2 |
| Osterhout's thistle | Cirsium osterhoutii (Rydb.) Petrak | CIOS |
| Otay tarweed | Deinandra conjugens (Keck) B.G. Baldwin | DECO13 |
| othake | Palafoxia sphacelata (Nutt. ex Torr.) Cory | PASP |
| Ouachita Mountain goldenrod | Solidago ouachitensis C.& J. Taylor | SOOU |
| ovateleaf cacalia | Arnoglossum ovatum (Walt.) H.E. Robins. | AROV |
| owl's crown | Gamochaeta sphacilata (Kunth) Cabrera | GASP9 |
| owl's-claws | Hymenoxys hoopesii (Gray) Bierner | HYHO |
| Ownbey's thistle | Cirsium ownbeyi Welsh | CIOW |
| Owyhee sage | Artemisia papposa Blake & Cronq. | ARPA16 |
| ox eye | Buphthalmum L. | BUPHT |
| ox-eye | Buphthalmum salicifolium L. | BUSA7 |
| oxeye | Heteranthemis Schott | HETER18 |
| oxeye daisy | Leucanthemum vulgare Lam. | LEVU |
| oxford ragwort | Senecio squalidus L. | SESQ |
| oxtongue | Picris L. | PICRI |
| Oxytenia acerosa | Iva acerosa (Nutt.) R.C. Jackson | IVAC |
| Pacific alpine wormwood | Artemisia glomerata Ledeb. | ARGL9 |
| Pacific alpine wormwood | Artemisia glomerata Ledeb. var. glomerata | ARGLG |
| Pacific alpine wormwood | Artemisia glomerata Ledeb. var. subglabrata Hult | ARGLS |
| Pacific aster | Symphyotrichum chilense (Nees) Nesom | SYCH4 |
| Pacific aster | Symphyotrichum chilense (Nees) Nesom var. chilense | SYCHC |
| Pacific aster | Symphyotrichum chilense (Nees) Nesom var. invenustum (Greene) Nesom | SYCHI |
| Pacific aster | Symphyotrichum chilense (Nees) Nesom var. medium (Jepson) Nesom | SYCHM |
| Pacific hulsea | Hulsea algida Gray | HUAL |
| Pacific yarrow | Achillea millefolium L. var. pacifica (Rydb.) G.N. Jones | ACMIP |
| Packard's wormwood | Artemisia packardiae J. Grimes & Ertter | ARPA20 |
| Packera anonyma | Senecio anonymus Wood | SEAN2 |
| Packera anonyma | Senecio smallii Britt. | SESM3 |
| Packera antennariifolia | Senecio antennariifolius Britt. | SEAN3 |
| Packera aurea | Senecio aureus L. | SEAU2 |
| Packera aurea | Senecio aureus L. var. aquilonius Fern. | SEAUA |
| Packera aurea | Senecio aureus L. var. gracilis (Pursh) Hook. | SEAUG |
| Packera aurea | Senecio aureus L. var. intercursus Fern. | SEAUI |
| Packera aurea | Senecio gracilis Pursh | SEGR8 |
| Packera bernardina | Senecio bernardinus Greene | SEBE |
| Packera bernardina | Senecio ionophyllus Greene var. sparsilobatus (Parish) Hall | SEIOS |
| Packera bolanderi var. bolanderi | Senecio bolanderi Gray | SEBO |
| Packera bolanderi var. harfordii | Senecio bolanderi Gray var. harfordii (Greenm.) T.M. Barkl. | SEBOH |
| Packera bolanderi var. harfordii | Senecio harfordii Greenm. | SEHA10 |
| Packera breweri | Senecio breweri Burtt-Davy | SEBR |
| Packera cana | Senecio canus Hook. | SECA2 |
| Packera cana | Senecio convallium Greenm. | SECO11 |
| Packera cana | Senecio hallii Britt. | SEHA7 |
| Packera cana | Senecio hallii Britt. var. discoidea W.A. Weber | SEHAD |
| Packera cana | Senecio harbourii Rydb. | SEHA9 |
| Packera cana | Senecio howellii Greene | SEHO2 |
| Packera cana | Senecio purshianus Nutt. | SEPU9 |
| Packera cardamine | Senecio cardamine Greene | SECA6 |
| Packera castoreus | Senecio castoreus Welsh | SECA24 |
| Packera clevelandii | Senecio clevelandii Greene | SECL2 |
| Packera clevelandii | Senecio clevelandii Greene var. heterophyllus Hoover | SECLH |
| Packera contermina | Senecio conterminus Greenm. | SECO14 |
| Packera crocata | Senecio crocatus Rydb. | SECR2 |
| Packera crocata | Senecio crocatus Rydb. var. wolfii Greenm. | SECRW |
| Packera cymbalaria | Packera fernaldii (Greenm.) A.& D. L?ve | PAFE3 |
| Packera cymbalaria | Packera resedifolia (Less.) A.& D. L?ve | PARE8 |
| Packera cymbalaria | Senecio cymbalaria Pursh | SECY2 |
| Packera cymbalaria | Senecio resedifolius Less. | SERE5 |
| Packera cynthioides | Senecio cynthioides Greene | SECY3 |
| Packera cynthioides | Senecio wrightii Greenm. | SEWR3 |
| Packera debilis | Senecio debilis Nutt. | SEDE3 |
| Packera debilis | Senecio fedifolius Rydb. | SEFE2 |
| Packera dimorphophylla var. dimorphophylla | Packera dimorphophylla (Greene) W.A. Weber & A. L?ve ssp. dimorphophylla | PADID2 |
| Packera dimorphophylla var. dimorphophylla | Senecio dimorphophyllus Greene | SEDI4 |
| Packera dimorphophylla var. dimorphophylla | Senecio heterodoxus Greene ex Rydb. | SEHE4 |
| Packera dimorphophylla var. intermedia | Packera dimorphophylla (Greene) W.A. Weber & A. L?ve ssp. intermedia (T.M. Barkl.) W.A. Weber & A. L?ve | PADII3 |
| Packera dimorphophylla var. intermedia | Senecio dimorphophyllus Greene var. intermedius T.M. Barkl. | SEDII |
| Packera dimorphophylla var. paysonii | Senecio dimorphophyllus Greene var. paysonii T.M. Barkl. | SEDIP |
| Packera eurycephala var. eurycephala | Senecio eurycephalus Torr. & Gray ex Gray | SEEU |
| Packera eurycephala var. lewisrosei | Senecio eurycephalus Torr. & Gray ex Gray var. lewisrosei (J.T. Howell) T.M. Barkl. | SEEUL |
| Packera eurycephala var. lewisrosei | Senecio lewisrosei J.T. Howell | SELE11 |
| Packera fendleri | Senecio fendleri Gray | SEFE |
| Packera fendleri | Senecio fendleri Gray var. lanatus Osterhout | SEFEL |
| Packera flettii | Senecio flettii Wieg. | SEFL |
| Packera franciscana | Senecio franciscanus Greene | SEFR2 |
| Packera ganderi | Senecio ganderi T.M. Barkl. & Beauchamp | SEGA |
| Packera glabella | Senecio glabellus Poir. | SEGL |
| Packera glabella | Senecio lobatus Pers. | SELO5 |
| Packera greenei | Senecio greenei Gray | SEGR3 |
| Packera hartiana | Senecio hartianus Heller | SEHA5 |
| Packera hesperia | Senecio hesperius Greene | SEHE2 |
| Packera hyperborealis | Senecio hyperborealis Greenm. | SEHY3 |
| Packera indecora | Senecio indecorus Greene | SEIN |
| Packera indecora | Senecio pauciflorus Pursh var. fallax (Greenm.) Greenm. | SEPAF |
| Packera ionophylla | Senecio ionophyllus Greene | SEIO |
| Packera layneae | Senecio layneae Greene | SELA4 |
| Packera macounii | Senecio ligulifolius Greene | SELI8 |
| Packera macounii | Senecio macounii Greene | SEMA |
| Packera malmstenii | Senecio malmstenii Blake ex Tidestrom | SEMA16 |
| Packera millefolia | Senecio memmingeri Britt. | SEME5 |
| Packera millefolia | Senecio millefolium Torr. & Gray | SEMI2 |
| Packera millelobata | Senecio millelobatus Rydb. | SEMI3 |
| Packera moresbiensis | Senecio cymbalarioides Buek ssp. moresbiensis Calder & Taylor | SECYM |
| Packera moresbiensis | Senecio moresbiensis (Calder & Taylor) G.W. Douglas & G. Ruyle-Douglas | SEMO10 |
| Packera moresbiensis | Senecio streptanthifolius Greene var. moresbiensis (Calder & Taylor) Boivin | SESTM2 |
| Packera multilobata | Senecio lynceus Greene | SELY2 |
| Packera multilobata | Senecio lynceus Greene var. leucoreus (Greenm.) Blake | SELYL |
| Packera multilobata | Senecio multilobatus Torr. & Gray ex Gray | SEMU3 |
| Packera multilobata | Senecio stygius Greene | SEST6 |
| Packera multilobata | Senecio thornberi Greenm. | SETH |
| Packera multilobata | Senecio uintahensis (A. Nels.) Greenm. | SEUI |
| Packera neomexicana var. metcalfei | Senecio metcalfei Greene | SEME7 |
| Packera neomexicana var. metcalfei | Senecio neomexicanus Gray var. metcalfei (Greene) T.M. Barkl. | SENEM |
| Packera neomexicana var. mutabilis | Senecio mutabilis Greene | SEMU8 |
| Packera neomexicana var. mutabilis | Senecio neomexicanus Gray var. mutabilis (Greene) T.M. Barkl. | SENEM2 |
| Packera neomexicana var. neomexicana | Senecio eurypterus Greenm. | SEEU2 |
| Packera neomexicana var. neomexicana | Senecio neomexicanus Gray | SENE4 |
| Packera neomexicana var. neomexicana | Senecio neomexicanus Gray var. griffithsii Greenm. | SENEG2 |
| Packera neomexicana var. neomexicana | Senecio oresbius Greenm. | SEOR7 |
| Packera neomexicana var. neomexicana | Senecio thurberi Gray | SETH2 |
| Packera neomexicana var. toumeyi | Senecio neomexicanus Gray var. toumeyi (Greene) T.M. Barkl. | SENET |
| Packera neomexicana var. toumeyi | Senecio toumeyi Greene | SETO8 |
| Packera obovata | Senecio obovatus Muhl. ex Willd. | SEOB2 |
| Packera obovata | Senecio obovatus Muhl. ex Willd. var. elliottii (Torr. & Gray) Fern. | SEOBE |
| Packera obovata | Senecio obovatus Muhl. ex Willd. var. rotundus Britt. | SEOBR2 |
| Packera obovata | Senecio rotundus (Britt.) Small | SERO5 |
| Packera ogotorukensis | Senecio ogotorukensis Packer | SEOG |
| Packera pauciflora | Senecio discoideus (Hook.) Britt. | SEDI9 |
| Packera pauciflora | Senecio pauciflorus Pursh | SEPA4 |
| Packera paupercula | Senecio balsamitae Muhl. ex Willd. | SEBA4 |
| Packera paupercula | Senecio crawfordii (Britt.) G.W. Douglas & G. Ruyle-Douglas | SECR6 |
| Packera paupercula | Senecio gaspensis Greenm. | SEGA3 |
| Packera paupercula | Senecio gaspensis Greenm. var. firmifolius (Greenm.) Fern. | SEGAF |
| Packera paupercula | Senecio pauperculus Michx. | SEPA5 |
| Packera paupercula | Senecio pauperculus Michx. var. balsamitae (Muhl. ex Willd.) Fern. | SEPAB |
| Packera paupercula | Senecio pauperculus Michx. var. crawfordii (Britt.) T.M. Barkl. | SEPAC |
| Packera paupercula | Senecio pauperculus Michx. var. firmifolius (Greenm.) Greenm. | SEPAF2 |
| Packera paupercula | Senecio pauperculus Michx. var. neoscoticus Fern. | SEPAN2 |
| Packera paupercula | Senecio pauperculus Michx. var. praelongus (Greenm.) House | SEPAP |
| Packera paupercula | Senecio pauperculus Michx. var. thompsoniensis (Greenm.) Boivin | SEPAT |
| Packera paupercula | Senecio tweedyi Rydb. | SETW |
| Packera plattensis | Senecio plattensis Nutt. | SEPL |
| Packera plattensis | Senecio pseudotomentosus Mackenzie & Bush | SEPS3 |
| Packera porteri | Ligularia porteri (Greene) W.A. Weber | LIPO5 |
| Packera porteri | Senecio porteri Greene | SEPO |
| Packera pseudaurea var. flavula | Packera pseudaurea (Rydb.) W.A. Weber & A. L?ve ssp. flavula (Greene) W.A. Weber & A. L?ve | PAPSF2 |
| Packera pseudaurea var. flavula | Senecio flavulus Greene | SEFL6 |
| Packera pseudaurea var. flavula | Senecio pseudaureus Rydb. ssp. flavulus (Greene) G.W. Douglas & G. Ruyle-Douglas | SEPSF2 |
| Packera pseudaurea var. flavula | Senecio pseudaureus Rydb. var. flavulus (Greene) Greenm. | SEPSF |
| Packera pseudaurea var. pseudaurea | Senecio pauciflorus Pursh var. jucundulus Jepson | SEPAJ |
| Packera pseudaurea var. pseudaurea | Senecio pseudaureus Rydb. | SEPS2 |
| Packera pseudaurea var. semicordata | Senecio aureus L. var. semicordatus (Mackenzie & Bush) Greenm. | SEAUS |
| Packera pseudaurea var. semicordata | Senecio pseudaureus Rydb. ssp. semicordatus (Mackenzie & Bush) G.W. Douglas & G. Ruyle-Douglas | SEPSS2 |
| Packera pseudaurea var. semicordata | Senecio pseudaureus Rydb. var. semicordatus (Mackenzie & Bush) T.M. Barkl. | SEPSS |
| Packera pseudaurea var. semicordata | Senecio semicordatus Mackenzie & Bush | SESE15 |
| Packera quaerens | Senecio quaerens Greene | SEQU2 |
| Packera quercetorum | Senecio quercetorum Greene | SEQU |
| Packera sanguisorboides | Senecio sanguisorboides Rydb. | SESA6 |
| Packera schweinitziana | Senecio robbinsii Oakes ex Rusby | SERO6 |
| Packera schweinitziana | Senecio schweinitzianus Nutt. | SESC4 |
| Packera spellenbergii | Senecio spellenbergii T.M. Barkl. | SESP7 |
| Packera streptanthifolia | Packera cymbalarioides (Nutt.) W.A. Weber & A. L?ve nom. illeg. | PACY2 |
| Packera streptanthifolia | Packera oodes (Rydb.) W.A. Weber | PAOO |
| Packera streptanthifolia | Packera streptanthifolia (Greene) W.A. Weber & A. L?ve var. rubricaulis (Greene) Dorn | PASTR |
| Packera streptanthifolia | Packera streptanthifolia (Greene) W.A. Weber & A. L?ve var. streptanthifolia (Greene) W.A. Weber & A. L?ve [superfluous autonym] | PASTS |
| Packera streptanthifolia | Senecio acutidens Rydb. | SEAC6 |
| Packera streptanthifolia | Senecio adamsii T.J. Howell | SEAD2 |
| Packera streptanthifolia | Senecio aureus L. var. borealis Torr. & Gray | SEAUB |
| Packera streptanthifolia | Senecio cymbalarioides Nutt. var. borealis (Torr. & Gray) Greenm. | SECYB |
| Packera streptanthifolia | Senecio cymbalarioides Nutt. var. suksdorfii (Greenm.) M.E. Peck | SECYS |
| Packera streptanthifolia | Senecio cymbalarioides Nutt., non Buek | SECY4 |
| Packera streptanthifolia | Senecio fulgens Rydb. | SEFU2 |
| Packera streptanthifolia | Senecio jonesii Rydb. | SEJO2 |
| Packera streptanthifolia | Senecio laetiflorus Greene | SELA7 |
| Packera streptanthifolia | Senecio leonardii Rydb. | SELE10 |
| Packera streptanthifolia | Senecio longipetiolatus Rydb. | SELO3 |
| Packera streptanthifolia | Senecio oodes Rydb. | SEOO |
| Packera streptanthifolia | Senecio pammelii Greenm. | SEPA13 |
| Packera streptanthifolia | Senecio platylobus Rydb. | SEPL5 |
| Packera streptanthifolia | Senecio rubricaulis Greene | SERU7 |
| Packera streptanthifolia | Senecio streptanthifolius Greene | SEST3 |
| Packera streptanthifolia | Senecio streptanthifolius Greene var. borealis (Torr. & Gray) J.F. Bain | SESTB |
| Packera streptanthifolia | Senecio streptanthifolius Greene var. kluanei J.F. Bain | SESTK |
| Packera streptanthifolia | Senecio streptanthifolius Greene var. laetiflorus (Greene) J.F. Bain | SESTL |
| Packera streptanthifolia | Senecio streptanthifolius Greene var. oodes (Rydb.) J.F. Bain | SESTO |
| Packera streptanthifolia | Senecio streptanthifolius Greene var. rubricaulis (Greene) J.F. Bain | SESTR |
| Packera streptanthifolia | Senecio streptanthifolius Greene var. wallowensis J.F. Bain | SESTW |
| Packera streptanthifolia | Senecio subcuneatus Rydb. | SESU6 |
| Packera streptanthifolia | Senecio suksdorfii Greenm. | SESU8 |
| Packera streptanthifolia | Senecio wardii Greene | SEWA4 |
| Packera subnuda | Packera buekii D.K. Trock & T.M. Barkl. | PABU6 |
| Packera subnuda | Senecio cymbalarioides Buek | SECY |
| Packera subnuda | Senecio subnudus DC. | SESU5 |
| Packera tampicana | Senecio greggii Rydb. | SEGR9 |
| Packera tampicana | Senecio imparipinnatus Klatt | SEIM |
| Packera tampicana | Senecio tampicanus DC. | SETA2 |
| Packera tomentosa | Senecio alabamensis Britt. ex Small | SEAL7 |
| Packera tomentosa | Senecio tomentosus Michx. | SETO2 |
| Packera tridenticulata | Senecio densus Greene | SEDE6 |
| Packera tridenticulata | Senecio manitobensis Greenm. | SEMA8 |
| Packera tridenticulata | Senecio tridenticulatus Rydb. | SETR2 |
| Packera werneriifolia | Senecio aureus L. var. werneriifolius Gray | SEAUW |
| Packera werneriifolia | Senecio molinarius Greenm. | SEMO8 |
| Packera werneriifolia | Senecio muirii Greenm. | SEMU7 |
| Packera werneriifolia | Senecio saxosus Klatt | SESA7 |
| Packera werneriifolia | Senecio saxosus Klatt var. toiyabensis Greenm. | SESAT |
| Packera werneriifolia | Senecio werneriifolius (Gray) Gray | SEWE2 |
| Packera werneriifolia | Senecio werneriifolius (Gray) Gray var. alpinus (Gray) Dorn | SEWEA |
| Packera werneriifolia | Senecio werneriifolius (Gray) Gray var. incertus Greenm. | SEWEI |
| palafox | Palafoxia Lag. | PALAF |
| Palafoxia arida var. gigantea | Palafoxia linearis (Cav.) Lag. var. gigantea M.E. Jones | PALIG |
| Palafoxia callosa | Othake callosa (Nutt.) Bush | OTCA |
| Palafoxia callosa | Palafoxia callosa (Nutt.) Torr. & Gray var. bella (Cory) Shinners | PACAB4 |
| Palafoxia callosa | Polypteris callosa (Nutt.) Gray | POCA18 |
| Palafoxia integrifolia | Polypteris integrifolia Nutt. | POIN18 |
| Palafoxia rosea var. macrolepis | Palafoxia macrolepis (Rydb.) Cory | PAMA9 |
| Palafoxia rosea var. macrolepis | Palafoxia texana DC. var. macrolepis (Rydb.) Shinners | PATEM3 |
| Palafoxia sphacelata | Othake sphacelata (Nutt. ex Torr.) Rydb. | OTSP |
| Palafoxia sphacelata | Polypteris hookeriana Gray | POHO9 |
| Palafoxia sphacelata | Polypteris sphacelata (Nutt. ex Torr.) Trel. | POSP11 |
| Palafoxia texana var. ambigua | Palafoxia rosea (Bush) Cory var. ambigua Shinners | PAROA |
| Palafoxia texana var. texana | Palafoxia rosea (Bush) Cory var. papposa Shinners | PAROP |
| pale agoseris | Agoseris glauca (Pursh) Raf. | AGGL |
| pale agoseris | Agoseris glauca (Pursh) Raf. var. agrestis (Osterhout) Q. Jones ex Cronq. | AGGLA |
| pale agoseris | Agoseris glauca (Pursh) Raf. var. cronquistii Welsh | AGGLC |
| pale agoseris | Agoseris glauca (Pursh) Raf. var. dasycephala (Torr. & Gray) Jepson | AGGLD |
| pale agoseris | Agoseris glauca (Pursh) Raf. var. glauca | AGGLG |
| pale agoseris | Agoseris glauca (Pursh) Raf. var. monticola (Greene) Q. Jones ex Cronq. | AGGLM |
| pale fleabane | Erigeron pallens Cronq. | ERPA34 |
| pale Indian plaintain | Arnoglossum atriplicifolium (L.) H.E. Robins. | ARAT |
| pale purple coneflower | Echinacea pallida (Nutt.) Nutt. | ECPA |
| pale thistle | Cirsium pallidum Woot. & Standl. | CIPA5 |
| paleleaf woodland sunflower | Helianthus strumosus L. | HEST |
| paleyellow ragwort | Senecio integerrimus Nutt. var. ochroleucus (Gray) Cronq. | SEINO |
| paleyellow tidytips | Layia heterotricha (DC.) Hook. & Arn. | LAHE |
| Palmer's goldenbush | Ericameria palmeri (Gray) Hall | ERPA15 |
| Palmer's goldenrod | Solidago ulmifolia Muhl. ex Willd. var. palmeri Cronq. | SOULP2 |
| Palmer's rabbitbrush | Ericameria palmeri (Gray) Hall var. pachylepis (Hall) Nesom | ERPAP |
| Palmer's rabbitbrush | Ericameria palmeri (Gray) Hall var. palmeri | ERPAP2 |
| Palmer's zinnia | Zinnia maritima Kunth | ZIMA2 |
| Palmer's zinnia | Zinnia maritima Kunth var. palmeri (Gray) B.L. Turner | ZIMAP |
| palmleaf thoroughwort | Conoclinium greggii (Gray) Small | COGR10 |
| Palo Alto thistle | Cirsium praeteriens J.F. Macbr. | CIPR2 |
| Palouse thistle | Cirsium brevifolium Nutt. | CIBR |
| pamakani | Tetramolopium capillare (Gaud.) St. John | TECA7 |
| Panamint daisy | Enceliopsis covillei (A. Nels.) Blake | ENCO |
| Panamint rock goldenrod | Chrysothamnus gramineus Hall | CHGR13 |
| paperflower | Psilostrophe DC. | PSILO3 |
| pappose tarweed | Centromadia parryi (Greene) Greene ssp. australis (Keck) B.G. Baldwin | CEPAA |
| pappose tarweed | Centromadia parryi (Greene) Greene ssp. parryi | CEPAP4 |
| pappose tarweed | Centromadia parryi (Greene) Greene ssp. rudis (Greene) B.G. Baldwin | CEPAR4 |
| para cress | Spilanthes acmella (L.) L. | SPAC2 |
| parachute plant | Atrichoseris platyphylla (Gray) Gray | ATPL |
| paradox sunflower | Helianthus paradoxus Heiser | HEPA2 |
| Paraguayan starburr | Acanthospermum australe (Loefl.) Kuntze | ACAU2 |
| Parasenecio auriculata | Cacalia auriculata DC. | CAAU9 |
| Parasenecio auriculata | Cacalia auriculata DC. ssp. kamtschatica (Maxim.) Hult | CAAUK |
| Parasenecio auriculata | Cacalia kamtschatica (Maxim.) Kudo | CAKA9 |
| Parasenecio auriculata | Koyamacalia auriculata (DC.) H.E. Robins. & Brett. | KOAU |
| parasol whitetop | Doellingeria umbellata (P. Mill.) Nees | DOUM2 |
| parasol whitetop | Doellingeria umbellata (P. Mill.) Nees var. pubens (Gray) Britt. | DOUMP2 |
| parasol whitetop | Doellingeria umbellata (P. Mill.) Nees var. umbellata | DOUMU |
| Parish's chaenactis | Chaenactis parishii Gray | CHPA |
| Parish's fleabane | Erigeron parishii Gray | ERPA3 |
| Parish's goldeneye | Viguiera parishii Greene | VIPA14 |
| Parish's rabbitbrush | Ericameria parishii (Greene) Hall | ERPA24 |
| Parish's sunflower | Helianthus nuttallii Torr. & Gray ssp. parishii (Gray) Heiser | HENUP |
| Parlin's pussytoes | Antennaria parlinii Fern. | ANPA9 |
| Parlin's pussytoes | Antennaria parlinii Fern. ssp. fallax (Greene) Bayer & Stebbins | ANPAF |
| Parlin's pussytoes | Antennaria parlinii Fern. ssp. parlinii | ANPAP |
| Parry's alpinegold | Hulsea vestita Gray ssp. parryi (Gray) Wilken | HUVEP |
| Parry's arnica | Arnica parryi Gray | ARPA13 |
| Parry's arnica | Arnica parryi Gray ssp. parryi | ARPAP3 |
| Parry's aster | Symphyotrichum foliaceum (Lindl. ex DC.) Nesom var. parryi (D.C. Eat.) Nesom | SYFOP |
| Parry's blanketflower | Gaillardia parryi Greene | GAPA |
| Parry's dwarf-sunflower | Helianthella parryi Gray | HEPA |
| Parry's false tarplant | Centromadia parryi (Greene) Greene | CEPA21 |
| Parry's goldenrod | Oreochrysum parryi (Gray) Rydb. | ORPA3 |
| Parry's leastdaisy | Chaetopappa parryi Gray | CHPA2 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird | ERPA30 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. affinis (A. Nels.) Nesom & Baird | ERPAA2 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. aspra (Greene) Nesom & Baird | ERPAA3 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. attenuata (M.E. Jones) Nesom & Baird | ERPAA4 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. howardii (Parry ex Gray) Nesom & Baird | ERPAH |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. imula (Hall & Clements) Nesom & Baird | ERPAI |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. latior (Hall & Clements) Nesom & Baird | ERPAL3 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. monocephala (A. Nels & Kennedy) Nesom & Baird | ERPAM3 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. montana (L.C. Anders.) Nesom & Baird | ERPAM4 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. nevadensis (Gray) Nesom & Baird | ERPAN2 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. parryi | ERPAP10 |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. salmonensis (L.C. Anders.) Nesom & Baird | ERPAS |
| Parry's rabbitbrush | Ericameria parryi (Gray) Nesom & Baird var. vulcanica (Greene) Nesom & Baird | ERPAV |
| Parry's rockdaisy | Perityle parryi Gray | PEPA12 |
| Parry's thistle | Cirsium parryi (Gray) Petrak | CIPA |
| Parry's thistle | Cirsium parryi (Gray) Petrak ssp. parryi | CIPAP2 |
| Parry's Townsend daisy | Townsendia parryi D.C. Eat. | TOPA2 |
| Parry's wirelettuce | Stephanomeria parryi Gray | STPA3 |
| Parry's wormwood | Artemisia parryi Gray | ARPA17 |
| parthenice | Parthenice Gray | PARTH |
| Parthenium alpinum | Bolophyta alpina Nutt. | BOAL5 |
| Parthenium auriculatum | Parthenium hispidum Raf. var. auriculatum (Britt.) Rollins | PAHIA |
| Parthenium auriculatum | Parthenium integrifolium L. var. auriculatum (Britt.) Cornelius ex Cronq. | PAINA |
| Parthenium confertum var. lyratum | Parthenium hysterophorus L. var. lyratum Gray | PAHYL |
| Parthenium confertum var. lyratum | Parthenium lyratum (Gray) Gray | PALY2 |
| Parthenium hispidum | Parthenium integrifolium L. var. hispidum (Raf.) Mears | PAINH2 |
| Parthenium hispidum | Parthenium repens Eggert | PARE7 |
| Parthenium hysterophorus | Parthenium lobatum Buckl. | PALO7 |
| Parthenium integrifolium var. integrifolium | Parthenium integrifolium L. var. henryanum Mears | PAINH |
| Parthenium integrifolium var. mabryanum | Parthenium radfordii Mears | PARA9 |
| Parthenium ligulatum | Bolophyta ligulata (M.E. Jones) W.A. Weber | BOLI5 |
| Parthenium ligulatum | Parthenium alpinum (Nutt.) Torr. & Gray var. ligulatum M.E. Jones | PAALL |
| Parthenium tetraneuris | Bolophyta tetraneuris (Barneby) W.A. Weber | BOTE7 |
| Parthenium tetraneuris | Parthenium alpinum (Nutt.) Torr. & Gray var. tetraneuris (Barneby) Rollins | PAALT |
| Pascalia | Pascalia Ortega | PASCA |
| Pascalia glauca | Wedelia glauca (Ortega) Hoffmann ex Hicken | WEGL |
| pasture goatsbeard | Tragopogon hybridus L. | TRHY7 |
| pasture hawksbeard | Crepis pannonica (Jacq.) K. Koch | CRPA20 |
| pasture knapweed | Centaurea bovina Velen. | CEBO |
| pasture thistle | Cirsium pumilum Spreng. | CIPU4 |
| Patterson's senecio | Senecio pattersonensis Hoover | SEPA3 |
| Patterson's wormwood | Artemisia pattersonii Gray | ARPA18 |
| Payson's groundsel | Packera dimorphophylla (Greene) W.A. Weber & A. L?ve var. paysonii (T.M. Barkl.) D.K. Trock & T.M. Barkl. | PADIP2 |
| pearlhead | Isocarpha R. Br. | ISOCA |
| pearly everlasting | Anaphalis DC. | ANAPH |
| pearly pussytoes | Antennaria anaphaloides Rydb. | ANAN2 |
| pebble pincushion | Chaenactis carphoclinia Gray | CHCA |
| pebble pincushion | Chaenactis carphoclinia Gray var. carphoclinia | CHCAC |
| Pecos River skeletonplant | Lygodesmia ramosissima Greenm. | LYRA2 |
| Pectis angustifolia var. fastigiata | Pectis texana Cory | PETE12 |
| Pectis angustifolia var. tenella | Pectis tenella DC. | PETE |
| Pectis ciliaris | Pectis portoricensis Urban | PEPO3 |
| Pectis cylindrica | Pectis prostrata Cav. var. cylindrica Fern. | PEPRC |
| Pectis elongata var. floribunda | Pectis floribunda A. Rich. | PEFL12 |
| Pectis glaucescens | Chthonia glaucescens Cass. | CHGL8 |
| Pectis glaucescens | Pectis leptocephala (Cass.) Urban | PELE10 |
| Pectis linearis | Pectis febrifuga van Hall | PEFE3 |
| Pectis prostrata | Pectis multisetosa Rydb. | PEMU10 |
| Pectis prostrata | Pectis prostrata Cav. var. urceolata Fern. | PEPRU |
| Pectis rusbyi | Pectis palmeri S. Wats. | PEPA34 |
| Peirson's aster | Oreostemma peirsonii (C.W. Sharsmith) Nesom | ORPE4 |
| Peirson's lessingia | Lessingia lemmonii Gray var. peirsonii (J.T. Howell) Ferris | LELEP |
| Peirson's pincushion | Chaenactis carphoclinia Gray var. peirsonii (Jepson) Munz | CHCAP2 |
| Peirson's serpentweed | Tonestus peirsonii (Keck) Nesom & D. Morgan | TOPE |
| Pennsylvania everlasting | Gamochaeta pensylvanica (Willd.) Cabrera | GAPE2 |
| Pensacola marshelder | Iva asperifolia Less. | IVAS |
| Pentachaeta alsinoides | Chaetopappa alsinoides (Greene) Keck | CHAL3 |
| Pentachaeta aurea | Chaetopappa aurea (Nutt.) Keck | CHAU |
| Pentachaeta aurea | Pentachaeta orcuttii Gray | PEOR8 |
| Pentachaeta aurea | Pentachaeta paleacea Greene | PEPA35 |
| Pentachaeta bellidiflora | Chaetopappa bellidiflora (Greene) Keck | CHBE |
| Pentachaeta bellidiflora | Pentachaeta exilis (Gray) Gray var. grayi Jepson | PEEXG |
| Pentachaeta exilis ssp. exilis | Aphantochaeta exilis Gray | APEX |
| Pentachaeta exilis ssp. exilis | Chaetopappa exilis (Gray) Keck | CHEX |
| Pentachaeta exilis ssp. exilis | Pentachaeta aphantochaeta Greene | PEAP2 |
| Pentachaeta exilis ssp. exilis | Pentachaeta exilis (Gray) Gray var. aphantochaeta Gray | PEEXA2 |
| Pentachaeta exilis ssp. exilis | Pentachaeta exilis (Gray) Gray var. discoidea Gray | PEEXD |
| Pentachaeta fragilis | Chaetopappa fragilis (Brandeg.) Keck | CHFR2 |
| Pentachaeta lyonii | Chaetopappa lyonii (Gray) Keck | CHLY |
| pentzia | Pentzia Thunb. | PENTZ |
| Pentzia incana | Pentzia virgata Less. | PEVI15 |
| peregrine thistle | Cirsium cymosum (Greene) J.T. Howell | CICY |
| perennial cornflower | Centaurea montana L. | CEMO |
| perennial goldfields | Lasthenia californica DC. ex Lindl. ssp. macrantha (Gray) R. Chan | LACAM3 |
| perennial saltmarsh aster | Symphyotrichum tenuifolium (L.) Nesom | SYTE6 |
| Perezia multiflora ssp. sonchifolia | Perezia sonchifolia Baker | PESO3 |
| perfoliate blackfoot | Melampodium perfoliatum (Cav.) Kunth | MEPE2 |
| perfumeballs | Gaillardia suavis (Gray & Engelm.) Britt. & Rusby | GASU |
| Pericallis hybrida | Pericallis cuneata (L'H?r.) Bolle | PECU4 |
| Pericallis hybrida | Senecio cruentus DC. | SECR4 |
| Pericallis hybrida | Senecio hybridus (Willd.) Regel | SEHY5 |
| pericome | Pericome Gray | PERIC |
| Pericome caudata | Pericome caudata Gray var. glandulosa (Goodman) Harrington | PECAG |
| Pericome caudata | Pericome glandulosa Goodman | PEGL22 |
| Perityle angustifolia | Laphamia angustifolia Gray | LAAN4 |
| Perityle angustifolia | Laphamia angustifolia Gray ssp. laciniata (Gray) Niles | LAANL |
| Perityle bisetosa var. bisetosa | Laphamia bisetosa Torr. ex Gray | LABI4 |
| Perityle californica | Perityle plumigera Harvey & Gray [excluded] | PEPL9 |
| Perityle cernua | Laphamia cernua Greene | LACE2 |
| Perityle cinerea | Laphamia cinerea Gray | LACI2 |
| Perityle cochisensis | Laphamia cochisensis Niles | LACO11 |
| Perityle congesta | Laphamia congesta M.E. Jones | LACO10 |
| Perityle dissecta | Laphamia dissecta Torr. | LADI8 |
| Perityle emoryi | Perityle emoryi Torr. var. nuda (Torr.) Gray | PEEMN |
| Perityle gilensis var. gilensis | Laphamia gilensis M.E. Jones | LAGI |
| Perityle gilensis var. salensis | Laphamia gilensis M.E. Jones ssp. longilobus Niles | LAGIL |
| Perityle gracilis | Laphamia fastigiata Brandeg. | LAFA3 |
| Perityle gracilis | Laphamia gracilis M.E. Jones | LAGR6 |
| Perityle gracilis | Perityle fastigiata (Brandeg.) Shinners | PEFA3 |
| Perityle intricata | Laphamia intricata Brandeg. | LAIN10 |
| Perityle intricata | Laphamia megalocephala S. Wats. ssp. intricata (Brandeg.) Keck | LAMEI |
| Perityle intricata | Perityle megalocephala (S. Wats.) J.F. Macbr. var. intricata (Brandeg.) A. Powell | PEMEI |
| Perityle inyoensis | Laphamia inyoensis Ferris | LAIN9 |
| Perityle lindheimeri var. halimifolia | Laphamia halimifolia Gray | LAHA2 |
| Perityle lindheimeri var. halimifolia | Perityle halimifolia (Gray) Shinners | PEHA13 |
| Perityle lindheimeri var. lindheimeri | Laphamia halimifolia Gray ssp. lindheimeri (Gray) Niles | LAHAL |
| Perityle lindheimeri var. lindheimeri | Laphamia rotundata Rydb. | LARO |
| Perityle lindheimeri var. lindheimeri | Perityle rotundata (Rydb.) Shinners | PERO2 |
| Perityle megalocephala var. megalocephala | Laphamia megalocephala S. Wats. | LAME3 |
| Perityle microglossa | Perityle spilanthoides (Schultz-Bip.) Rydb. | PESP6 |
| Perityle quinqueflora | Laphamia quinqueflora Steyermark | LAQU |
| Perityle rupestris var. rupestris | Laphamia rupestris Gray | LARU3 |
| Perityle saxicola | Laphamia saxicola Eastw. | LASA5 |
| Perityle stansburyi | Laphamia stansburii Gray [orthographic variant] | LAST5 |
| Perityle stansburyi | Laphamia stansburyi Gray | LAST12 |
| Perityle stansburyi | Perityle stansburii (Gray) J.F. Macbr. [orthographic variant] | PEST7 |
| Perityle staurophylla var. staurophylla | Laphamia staurophylla Barneby | LAST4 |
| Perityle tenella | Laphamia palmeri Gray | LAPA9 |
| Perityle tenella | Laphamia palmeri Gray var. tenella M.E. Jones | LAPAT2 |
| Perityle villosa | Laphamia villosa Blake | LAVI5 |
| perkysue | Tetraneuris argentea (Gray) Greene | TEAR4 |
| Peruvian ragweed | Ambrosia peruviana Willd. | AMPE2 |
| Peruvian zinnia | Zinnia peruviana (L.) L. | ZIPE |
| pestilence wort | Petasites hybridus (L.) P.G. Gaertn., B. Mey. & Scherb. | PEHY |
| Petasites frigidus var. frigidus | Petasites alaskanus Rydb. | PEAL16 |
| Petasites frigidus var. frigidus | Petasites corymbosus (R. Br.) Rydb. | PECO24 |
| Petasites frigidus var. frigidus | Petasites frigidus (L.) Fries ssp. nivalis (Greene) Cody | PEFRN2 |
| Petasites frigidus var. frigidus | Petasites frigidus (L.) Fries var. corymbosus (R. Br.) Cronq. | PEFRC |
| Petasites frigidus var. frigidus | Petasites frigidus (L.) Fries var. hyperboreoides Hult | PEFRH |
| Petasites frigidus var. frigidus | Petasites frigidus (L.) Fries var. nivalis (Greene) Cronq. | PEFRN |
| Petasites frigidus var. frigidus | Petasites gracilis Britt. | PEGR18 |
| Petasites frigidus var. frigidus | Petasites hyperboreus Rydb. | PEHY5 |
| Petasites frigidus var. frigidus | Petasites nivalis Greene | PENI4 |
| Petasites frigidus var. palmatus | Nardosmia arctica (Porsild) A.& D. L?ve | NAAR3 |
| Petasites frigidus var. palmatus | Petasites arcticus Porsild | PEAR5 |
| Petasites frigidus var. palmatus | Petasites frigidus (L.) Fries ssp. arcticus (Porsild) Cody | PEFRA3 |
| Petasites frigidus var. palmatus | Petasites frigidus (L.) Fries ssp. palmatus (Ait.) Cody | PEFRP2 |
| Petasites frigidus var. palmatus | Petasites hookerianus (Nutt.) Rydb. | PEHO7 |
| Petasites frigidus var. palmatus | Petasites palmatus (Ait.) Gray | PEPA31 |
| Petasites frigidus var. palmatus | Petasites speciosus (Nutt.) Piper | PESP7 |
| Petasites frigidus var. sagittatus | Petasites dentatus Blank. | PEDE19 |
| Petasites frigidus var. sagittatus | Petasites sagittatus (Banks ex Pursh) Gray | PESA5 |
| Petasites frigidus var. vitifolius | Nardosmia vitifolia (Greene) A.& D. L?ve | NAVI2 |
| Petasites frigidus var. vitifolius | Petasites ?vitifolius Greene (pro sp.) | PEVI14 |
| Petasites frigidus var. vitifolius | Petasites nivalis Greene ssp. vitifolius (Greene) Toman | PENIV |
| Petasites frigidus var. vitifolius | Petasites palmatus (Ait.) Gray var. frigidus Macoun | PEPAF |
| Petasites frigidus var. vitifolius | Petasites trigonophylla Greene | PETR9 |
| Petasites frigidus var. vitifolius | Petasites warrenii St. John | PEWA15 |
| Petasites hybridus | Petasites officinalis Moench | PEOF |
| Petasites hybridus | Petasites vulgaris Hill | PEVU3 |
| Petasites japonicus | Nardosmia japonica Sieb. & Zucc. | NAJA3 |
| petite desertdandelion | Malacothrix foliosa Gray ssp. crispifolia W.S. Davis | MAFOC |
| Petradoria pumila ssp. graminea | Petradoria pumila (Nutt.) Greene var. graminea (Woot. & Standl.) Welsh | PEPUG2 |
| Petradoria pumila ssp. graminea | Solidago graminea (Woot. & Standl.) Blake | SOGR10 |
| Petradoria pumila ssp. pumila | Solidago petradoria Blake | SOPE7 |
| Philadelphia fleabane | Erigeron philadelphicus L. | ERPH |
| Philadelphia fleabane | Erigeron philadelphicus L. var. philadelphicus | ERPHP |
| Philadelphia fleabane | Erigeron philadelphicus L. var. provancheri (Victorin & Rouss.) Boivin | ERPHP2 |
| Philbrick's desertdandelion | Malacothrix foliosa Gray ssp. philbrickii W.S. Davis | MAFOP |
| Phoebanthus grandiflorus | Helianthella grandiflora Torr. & Gray | HEGR16 |
| Phoebanthus tenuifolius | Helianthella tenuifolia Torr. & Gray | HETE19 |
| Picradeniopsis oppositifolia | Bahia oppositifolia (Nutt.) Gray | BAOP2 |
| Picradeniopsis woodhousei | Bahia woodhousei (Gray) Gray | BAWO2 |
| Picris hieracioides ssp. kamtschatica | Picris kamtschatica Ledeb. | PIKA4 |
| Picrothamnus desertorum | Artemisia spinescens D.C. Eat. | ARSP5 |
| piedmont marshelder | Iva microcephala Nutt. | IVMI |
| piedmont ragwort | Packera millefolia (Torr. & Gray) W.A. Weber & A. L?ve | PAMI25 |
| pigeoncoop | Spilanthes urens Jacq. | SPUR |
| pili nehe | Lipochaeta bryanii Sherff | LIBR6 |
| pillar false gumweed | Vanclevea stylosa (Eastw.) Greene | VAST3 |
| Pinaleno Mountain rubberweed | Hymenoxys ambigens (Blake) Bierner | HYAM8 |
| Pinaleno Mountain rubberweed | Hymenoxys ambigens (Blake) Bierner var. ambigens | HYAMA |
| Pinaropappus roseus var. roseus | Achyrophorus roseus Less. | ACRO2 |
| pincushion | Chaenactis DC. | CHAEN |
| pincushion flower | Chaenactis fremontii Gray | CHFR |
| pine barren goldenrod | Solidago fistulosa P. Mill. | SOFI |
| pine barren thoroughwort | Eupatorium resinosum Torr. ex DC. | EURE8 |
| pine barren whitetop aster | Oclemena reticulata (Pursh) Nesom | OCRE2 |
| pinebush | Ericameria pinifolia (Gray) Hall | ERPI7 |
| pineland chaffhead | Carphephorus carnosus (Small) C.W. James | CACA59 |
| pineland daisy | Chaptalia dentata (L.) Cass. | CHDE4 |
| pineland false sunflower | Phoebanthus tenuifolius (Torr. & Gray) Blake | PHTE7 |
| pineland goldenaster | Chrysopsis latisquamea Pollard | CHLA7 |
| pineland marshtail | Laennecia schiedeana (Less.) Nesom | LASC3 |
| pineland nerveray | Tetragonotheca helianthoides L. | TEHE2 |
| pineland rayless goldenrod | Bigelowia nudata (Michx.) DC. | BINU |
| pineland rayless goldenrod | Bigelowia nudata (Michx.) DC. ssp. australis L.C. Anders. | BINUA |
| pineland rayless goldenrod | Bigelowia nudata (Michx.) DC. ssp. nudata | BINUN |
| pineland silkgrass | Pityopsis aspera (Shuttlw. ex Small) Small | PIAS2 |
| pineland silkgrass | Pityopsis aspera (Shuttlw. ex Small) Small var. aspera | PIASA2 |
| pineland squarestem | Melanthera ligulata Small | MELI6 |
| pinewoods pussytoes | Antennaria geyeri Gray | ANGE3 |
| pingue rubberweed | Hymenoxys richardsonii (Hook.) Cockerell | HYRI |
| pingue rubberweed | Hymenoxys richardsonii (Hook.) Cockerell var. richardsonii | HYRIR |
| pink bogbutton | Sclerolepis uniflora (Walt.) B.S.P. | SCUN3 |
| pink cudweed | Pseudognaphalium ramosissimum (Nutt.) A. Anderb. | PSRA5 |
| pink thoroughwort | Fleischmannia incarnata (Walt.) King & H.E. Robins. | FLIN2 |
| pink tickseed | Coreopsis rosea Nutt. | CORO |
| pinkray Fremont's-gold | Syntrichopappus lemmonii (Gray) Gray | SYLE |
| pinkscale blazing star | Liatris elegans (Walt.) Michx. | LIEL |
| pinkscale blazing star | Liatris elegans (Walt.) Michx. var. carizzana Gaiser | LIELC |
| pinkscale blazing star | Liatris elegans (Walt.) Michx. var. elegans | LIELE |
| pinkscale blazing star | Liatris elegans (Walt.) Michx. var. flabellata (Small) Gaiser | LIELF |
| pinnate dahlia | Dahlia pinnata Cav. | DAPI3 |
| pinnate false threadleaf | Schkuhria pinnata (Lam.) Kuntze ex Thell. | SCPI3 |
| pinnate false threadleaf | Schkuhria pinnata (Lam.) Kuntze ex Thell. var. pinnata | SCPIP |
| pinnate prairie coneflower | Ratibida pinnata (Vent.) Barnh. | RAPI |
| pintwater rabbitbrush | Chrysothamnus eremobius L.C. Anders. | CHER3 |
| Piper's fleabane | Erigeron piperianus Cronq. | ERPI3 |
| Piptocoma antillana | Piptocoma rufescens auct. non Cass. [misapplied] | PIRU4 |
| pitchfork | Dicranocarpus parviflorus Gray | DIPA3 |
| Pityopsis aspera var. adenolepis | Chrysopsis adenolepis Fern. | CHAD4 |
| Pityopsis aspera var. adenolepis | Heterotheca adenolepis (Fern.) Ahles | HEAD2 |
| Pityopsis aspera var. adenolepis | Pityopsis adenolepis (Fern.) Semple | PIAD2 |
| Pityopsis aspera var. aspera | Chrysopsis aspera Shuttlw. ex Small | CHAS3 |
| Pityopsis aspera var. aspera | Chrysopsis graminifolia (Michx.) Ell. var. aspera (Shuttlw. ex Small) Gray | CHGRA3 |
| Pityopsis aspera var. aspera | Heterotheca aspera (Shuttlw. ex Small) Shinners | HEAS |
| Pityopsis falcata | Chrysopsis falcata (Pursh) Ell. | CHFA5 |
| Pityopsis falcata | Heterotheca falcata (Pursh) Harms | HEFA3 |
| Pityopsis flexuosa | Chrysopsis flexuosa Nash | CHFL5 |
| Pityopsis flexuosa | Heterotheca flexuosa (Nash) Harms | HEFL7 |
| Pityopsis graminifolia var. graminifolia | Chrysopsis graminifolia (Michx.) Ell. | CHGR14 |
| Pityopsis graminifolia var. graminifolia | Chrysopsis nervosa (Willd.) Fern. | CHNE11 |
| Pityopsis graminifolia var. graminifolia | Heterotheca correllii (Fern.) Ahles | HECO16 |
| Pityopsis graminifolia var. graminifolia | Heterotheca graminifolia (Michx.) Shinners | HEGR10 |
| Pityopsis graminifolia var. graminifolia | Heterotheca nervosa (Willd.) Shinners | HENE3 |
| Pityopsis graminifolia var. latifolia | Chrysopsis graminifolia (Michx.) Ell. var. latifolia Fern. | CHGRL |
| Pityopsis graminifolia var. tenuifolia | Chrysopsis graminifolia (Michx.) Ell. var. microcephala (Small) Cronq. | CHGRM |
| Pityopsis graminifolia var. tenuifolia | Chrysopsis microcephala Small | CHMI12 |
| Pityopsis graminifolia var. tenuifolia | Heterotheca graminifolia (Michx.) Shinners var. tenuifolia (Torr.) Gandhi & Thomas | HEGRT3 |
| Pityopsis graminifolia var. tenuifolia | Heterotheca microcephala (Small) Shinners | HEMI12 |
| Pityopsis graminifolia var. tenuifolia | Heterotheca nervosa (Willd.) Shinners var. microcephala (Small) Shinners ex Ahles | HENEM |
| Pityopsis graminifolia var. tenuifolia | Pityopsis graminifolia (Michx.) Nutt. var. microcephala (Small) Semple | PIGRM |
| Pityopsis graminifolia var. tenuifolia | Pityopsis microcephala (Small) Small | PIMI4 |
| Pityopsis graminifolia var. tracyi | Chrysopsis tracyi Small | CHTR8 |
| Pityopsis graminifolia var. tracyi | Heterotheca graminifolia (Michx.) Shinners var. tracyi (Small) R.W. Long | HEGRT2 |
| Pityopsis graminifolia var. tracyi | Pityopsis tracyi (Small) Small | PITR6 |
| Pityopsis oligantha | Chrysopsis oligantha Chapman ex Torr. & Gray | CHOL4 |
| Pityopsis oligantha | Heterotheca oligantha (Chapman ex Torr. & Gray) Harms | HEOL |
| Pityopsis pinifolia | Chrysopsis pinifolia Ell. | CHPI7 |
| Pityopsis pinifolia | Heterotheca pinifolia (Ell.) Ahles | HEPI6 |
| Pityopsis ruthii | Chrysopsis ruthii Small | CHRU3 |
| Pityopsis ruthii | Heterotheca ruthii (Small) Harms | HERU2 |
| plains blackfoot | Melampodium leucanthum Torr. & Gray | MELE2 |
| plains dozedaisy | Aphanostephus ramosissimus DC. | APRA |
| plains dozedaisy | Aphanostephus ramosissimus DC. var. humilis (Benth.) B.L. Turner & Birdsong | APRAH |
| plains dozedaisy | Aphanostephus ramosissimus DC. var. ramosissimus | APRAR |
| plains fleabane | Erigeron modestus Gray | ERMO2 |
| plains gumweed | Grindelia oolepis Blake | GROO |
| plains ironweed | Vernonia marginata (Torr.) Raf. | VEMA2 |
| plainsdaisy | Dichaetophora campestris Gray | DICA2 |
| plantain false leopardbane | Doronicum plantagineum L. | DOPL |
| plantain goldenweed | Pyrrocoma uniflora (Hook.) Greene | PYUN2 |
| plantain goldenweed | Pyrrocoma uniflora (Hook.) Greene var. gossypina (Greene) Kartesz & Gandhi | PYUNG |
| plantain goldenweed | Pyrrocoma uniflora (Hook.) Greene var. uniflora | PYUNU |
| plantainleaf dubautia | Dubautia plantaginea Gaud. | DUPL |
| plantainleaf dubautia | Dubautia plantaginea Gaud. ssp. humilis G.D. Carr | DUPLH |
| plantainleaf dubautia | Dubautia plantaginea Gaud. ssp. magnifolia (Sherff) G.D. Carr | DUPLM |
| plantainleaf dubautia | Dubautia plantaginea Gaud. ssp. plantaginea | DUPLP3 |
| Platyschkuhria integrifolia var. desertorum | Bahia nudicaulis Gray var. desertorum (M.E. Jones) Cronq. | BANUD |
| Platyschkuhria integrifolia var. integrifolia | Bahia nudicaulis Gray | BANU |
| Platyschkuhria integrifolia var. oblongifolia | Bahia nudicaulis Gray var. oblongifolia (Gray) Cronq. | BANUO |
| Platyschkuhria integrifolia var. oblongifolia | Bahia oblongifolia (Gray) Gray | BAOB2 |
| Platyschkuhria integrifolia var. oblongifolia | Platyschkuhria oblongifolia (Gray) Rydb. | PLOB3 |
| Platyschkuhria integrifolia var. ourolepis | Bahia nudicaulis Gray var. ourolepis (Blake) Cronq. | BANUO2 |
| Platyschkuhria integrifolia var. ourolepis | Bahia ourolepis Blake | BAOU |
| Pleiacanthus spinosus | Lygodesmia spinosa Nutt. | LYSP2 |
| Pleiacanthus spinosus | Stephanomeria spinosa (Nutt.) S. Tomb | STSP6 |
| pleurocoronis | Pleurocoronis King & H.E. Robins. | PLEUR4 |
| Pleurocoronis laphamioides | Hofmeisteria laphamioides Rose [excluded] | HOLA8 |
| Pleurocoronis pluriseta | Hofmeisteria pluriseta Gray | HOPL4 |
| Pluchea camphorata | Pluchea petiolata Cass. | PLPE2 |
| Pluchea camphorata | Pluchea viscida (Raf.) House | PLVI2 |
| Pluchea carolinensis | Conyza carolinensis Jacq. | COCA22 |
| Pluchea carolinensis | Conyza cortesii Kunth | COCO24 |
| Pluchea carolinensis | Pluchea ?fosbergii Cooperrider & Galang | PLFO4 |
| Pluchea carolinensis | Pluchea cortesii (Kunth) DC. | PLCO9 |
| Pluchea carolinensis | Pluchea odorata auct. non (L.) Cass. [misapplied] | PLOD2 |
| Pluchea carolinensis | Pluchea symphytifolia auct. non Gillis, non Conyza symphytifolia P. Mill. [misapplied] | PLSY |
| Pluchea foetida var. foetida | Pluchea tenuifolia Small | PLTE4 |
| Pluchea foetida var. imbricata | Pluchea imbricata (Kearney) Nash | PLIM |
| Pluchea odorata var. odorata | Conyza odorata L. | COOD2 |
| Pluchea odorata var. odorata | Pluchea purpurascens (Sw.) DC. | PLPU2 |
| Pluchea odorata var. succulenta | Pluchea purpurascens (Sw.) DC. var. succulenta Fern. | PLPUS |
| Pluchea sagittalis | Pluchea quitoc DC. | PLQU2 |
| Pluchea sagittalis | Pluchea suaveolens (Vell.) Kuntze | PLSU |
| Pluchea sericea | Berthelotia sericea (Nutt.) Rydb. | BESE2 |
| Pluchea sericea | Polypappus sericeus Nutt. | POSE13 |
| Pluchea sericea | Tessaria sericea (Nutt.) Shinners | TESE4 |
| Plumas alpine aster | Oreostemma elatum (Greene) Greene | OREL4 |
| plumed brickellbush | Brickellia brachyphylla (Gray) Gray | BRBR2 |
| plumed goldenrod | Solidago plumosa Small | SOPL |
| plumeless saw-wort | Serratula L. | SERRA |
| plumeless thistle | Carduus L. | CARDU |
| plumeseed | Rafinesquia Nutt. | RAFIN |
| plumeweed | Carminatia tenuiflora DC. | CATE8 |
| Plummer's baccharis | Baccharis plummerae Gray | BAPL |
| Plummer's baccharis | Baccharis plummerae Gray ssp. plummerae | BAPLP |
| Plummer's candyleaf | Stevia plummerae Gray | STPL |
| Plummer's candyleaf | Stevia plummerae Gray var. alba Gray | STPLA |
| Plummer's candyleaf | Stevia plummerae Gray var. plummerae | STPLP |
| plumpseeded madia | Madia anomala Greene | MAAN2 |
| Podunk ragwort | Packera malmstenii (Blake ex Tidestrom) Kartesz | PAMA36 |
| pointed gumweed | Grindelia fastigiata Greene | GRFA |
| polar hawkweed | Hieracium atratum Fries | HIAT2 |
| polymnia | Polymnia L. | POLYM |
| Polymnia canadensis | Polymnia canadensis L. var. radiata Gray | POCAR |
| Polymnia canadensis | Polymnia radiata (Gray) Small | PORA9 |
| porcupine thistle | Cirsium laterifolium (Osterhout) Petrak | CILA5 |
| poreleaf | Porophyllum Adans. | POROP |
| poreleaf dogweed | Adenophyllum porophyllum (Cav.) Hemsl. | ADPO2 |
| Porophyllum gracile | Porophyllum caesium Greene | POCA37 |
| Porophyllum gracile | Porophyllum junciforme Greene | POJU4 |
| Porophyllum gracile | Porophyllum nodosum M.E. Jones | PONO7 |
| Porophyllum gracile | Porophyllum putidum A. Nels. | POPU15 |
| Porophyllum gracile | Porophyllum vaseyi Greene | POVA7 |
| Porophyllum leiocarpum | Porophyllum macrocephalum DC. var. leiocarpum Urban | POMAL |
| Porophyllum ruderale ssp. macrocephalum | Kleinia glandulosa Moc. & Sess | KLGL |
| Porophyllum ruderale ssp. macrocephalum | Porophyllum latifolium Benth. | POLA13 |
| Porophyllum ruderale ssp. macrocephalum | Porophyllum macrocephalum DC. | POMA30 |
| Porophyllum ruderale ssp. macrocephalum | Porophyllum ruderale (Jacq.) Cass. var. macrocephalum (DC.) Cronq. | PORUM |
| Porophyllum ruderale ssp. ruderale | Cacalia porophyllum L. | CAPO14 |
| Porophyllum ruderale ssp. ruderale | Kleinia ruderalis Jacq. | KLRU |
| Porophyllum ruderale ssp. ruderale | Porophyllum porophyllum (L.) Kuntze | POPO20 |
| Porter's goldenrod | Solidago porteri Small | SOPO2 |
| Porter's groundsel | Packera porteri (Greene) C. Jeffrey | PAPO12 |
| Porter's sunflower | Helianthus porteri (Gray) Pruski | HEPO3 |
| Porter's wormwood | Artemisia porteri Cronq. | ARPO5 |
| Portuguese daisy | Leucanthemum lacustre (Brot.) Samp. | LELA10 |
| pot marigold | Calendula officinalis L. | CAOF |
| potato dwarfdandelion | Krigia dandelion (L.) Nutt. | KRDA |
| povertyweed | Iva axillaris Pursh | IVAX |
| prairie blazing star | Liatris pycnostachya Michx. | LIPY |
| prairie blazing star | Liatris pycnostachya Michx. var. lasiophylla Shinners | LIPYL |
| prairie blazing star | Liatris pycnostachya Michx. var. pycnostachya | LIPYP |
| prairie broomweed | Amphiachyris dracunculoides (DC.) Nutt. | AMDR |
| prairie coneflower | Ratibida Raf. | RATIB |
| prairie coneflower | Rudbeckia fulgida Ait. var. palustris (Eggert ex C.L. Boynt. & Beadle) Perdue | RUFUP |
| prairie false willow | Baccharis texana (Torr. & Gray) Gray | BATE |
| prairie fleabane | Erigeron strigosus Muhl. ex Willd. | ERST3 |
| prairie fleabane | Erigeron strigosus Muhl. ex Willd. var. septentrionalis (Fern. & Wieg.) Fern. | ERSTS |
| prairie fleabane | Erigeron strigosus Muhl. ex Willd. var. strigosus | ERSTS2 |
| prairie goldenrod | Oligoneuron album (Nutt.) Nesom | OLAL2 |
| prairie groundsel | Packera plattensis (Nutt.) W.A. Weber & A. L?ve | PAPL12 |
| prairie ironweed | Vernonia fasciculata Michx. | VEFA2 |
| prairie ironweed | Vernonia fasciculata Michx. ssp. corymbosa (Schwein. ex Keating) S.B. Jones | VEFAC |
| prairie ironweed | Vernonia fasciculata Michx. ssp. fasciculata | VEFAF |
| prairie rosinweed | Silphium terebinthinaceum Jacq. | SITE |
| prairie rosinweed | Silphium terebinthinaceum Jacq. var. terebinthinaceum | SITET |
| prairie sagewort | Artemisia frigida Willd. | ARFR4 |
| prairie sunflower | Helianthus petiolaris Nutt. | HEPE |
| prairie sunflower | Helianthus petiolaris Nutt. ssp. fallax Heiser | HEPEF |
| prairie sunflower | Helianthus petiolaris Nutt. ssp. petiolaris | HEPEP |
| prairie thistle | Cirsium canescens Nutt. | CICA11 |
| prairie-dandelion | Nothocalais (Gray) Greene | NOTHO5 |
| prairiedawn | Hymenoxys texana (Coult. & Rose) Cockerell | HYTE5 |
| prenanthella | Prenanthella Rydb. | PRENA2 |
| Prenanthella exigua | Lygodesmia exigua (Gray) Gray | LYEX3 |
| Prenanthes alata | Prenanthes lessingii Hult | PRLE |
| Prenanthes alba | Nabalus albus (L.) Hook. | NAAL2 |
| Prenanthes altissima | Nabalus altissimus (L.) Hook. | NAAL3 |
| Prenanthes altissima | Prenanthes altissima L. var. cinnamomea Fern. | PRALC |
| Prenanthes aspera | Nabalus asperus (Michx.) Torr. & Gray | NAAS |
| Prenanthes autumnalis | Nabalus virgatus (Michx.) DC. | NAVI3 |
| Prenanthes autumnalis | Prenanthes virgata Michx. | PRVI4 |
| Prenanthes barbata | Prenanthes serpentaria Pursh var. barbata Torr. & Gray | PRSEB |
| Prenanthes boottii | Nabalus boottii DC. | NABO |
| Prenanthes crepidinea | Nabalus crepidineus (Michx.) DC. | NACR |
| Prenanthes nana | Nabalus nanus (Bigelow) DC. | NANA |
| Prenanthes nana | Prenanthes trifoliolata (Cass.) Fern. var. nana (Bigelow) Fern. | PRTRN |
| Prenanthes racemosa var. multiflora | Prenanthes racemosa Michx. ssp. multiflora Cronq. | PRRAM |
| Prenanthes racemosa var. racemosa | Nabalus racemosus (Michx.) DC. | NARA2 |
| Prenanthes racemosa var. racemosa | Prenanthes racemosa Michx. ssp. racemosa | PRRAR |
| Prenanthes racemosa var. racemosa | Prenanthes racemosa Michx. var. pinnatifida Gray | PRRAP2 |
| Prenanthes roanensis | Nabalus cylindricus Small | NACY |
| Prenanthes roanensis | Nabalus roanensis Chickering | NARO3 |
| Prenanthes roanensis | Prenanthes cylindrica (Small) E.L. Braun | PRCY |
| Prenanthes sagittata | Prenanthes alata (Hook.) D. Dietr. var. sagittata Gray | PRALS |
| Prenanthes serpentaria | Nabalus integrifolius Cass. | NAIN4 |
| Prenanthes serpentaria | Nabalus serpentarius (Pursh) Hook. | NASE3 |
| Prenanthes serpentaria | Prenanthes integrifolia (Cass.) Small | PRIN7 |
| Prenanthes trifoliolata | Nabalus trifoliolatus Cass. | NATR |
| pretty sneezeweed | Helenium elegans DC. | HEEL |
| pretty sneezeweed | Helenium elegans DC. var. amphilobum (Gray) Bierner | HEELA |
| pretty sneezeweed | Helenium elegans DC. var. elegans | HEELE2 |
| prickleleaf | Hecastocleis shockleyi Gray | HESH |
| prickly goldenfleece | Urospermum picroides (L.) Scop. ex F.W. Schmidt | URPI |
| prickly gousblom | Berkheya heterophylla O. Hoffmann | BEHE |
| prickly hawkweed | Hieracium horridum Fries | HIHO |
| prickly lettuce | Lactuca serriola L. | LASE |
| pricklyleaf | Thymophylla Lag. | THYMO |
| pricklyleaf dogweed | Thymophylla acerosa (DC.) Strother | THAC |
| primroseleaf horseweed | Conyza primulifolia (Lam.) Cuatrec. & Lourteig | COPR5 |
| Pringle's aster | Symphyotrichum pilosum (Willd.) Nesom var. pringlei (Gray) Nesom | SYPIP2 |
| Pringle's brickellbush | Brickellia pringlei Gray | BRPR |
| Pringle's cudweed | Pseudognaphalium pringlei (Gray) A. Anderb. | PSPR2 |
| Pringle's fleabane | Erigeron pringlei Gray | ERPR10 |
| Pringle's hawkweed | Hieracium pringlei Gray | HIPR2 |
| Pringle's tarwort | Flourensia pringlei (Gray) Blake | FLPR2 |
| Pringle's woolly sunflower | Eriophyllum pringlei Gray | ERPR4 |
| Proctor's ironweed | Vernonia proctori Urbatsch | VEPR |
| professor's fleabane | Erigeron proselyticus Nesom | ERPR11 |
| prostrate chamomile | Anthemis secundiramea Biv. | ANSE6 |
| prostrate tropic daisy | Egletes prostrata (Sw.) Kuntze | EGPR |
| proustia | Proustia Lag. | PROUS |
| Proustia vanillosma | Proustia krugiana Urban | PRKR |
| Psacalium decompositum | Cacalia decomposita Gray | CADE |
| Psacalium decompositum | Odontotrichum decompositum (Gray) Rydb. | ODDE2 |
| Psathyrotes annua | Bulbostylis annua Nutt. | BUAN4 |
| Psathyrotes ramosissima | Tetradymia ramosissima Torr. | TERA4 |
| Psathyrotopsis scaposa | Psathyrotes scaposa Gray | PSSC |
| Pseudelephantopus spicatus | Elephantopus spicatus Juss. ex Aubl. | ELSP5 |
| Pseudobahia heermannii | Pseudobahia bahiifolia (Benth.) Rydb. var. pinnatifida Gray | PSBAP |
| Pseudognaphalium arizonicum | Gnaphalium arizonicum Gray | GNAR |
| Pseudognaphalium attenuatum | Gnaphalium attenuatum DC. | GNAT |
| Pseudognaphalium biolettii | Gnaphalium bicolor Bioletti | GNBI |
| Pseudognaphalium brachypterum | Gnaphalium brachypterum DC. [excluded] | GNBR3 |
| Pseudognaphalium californicum | Gnaphalium californicum DC. | GNCA |
| Pseudognaphalium canescens ssp. beneolens | Gnaphalium beneolens A. Davids. | GNBE |
| Pseudognaphalium canescens ssp. beneolens | Gnaphalium canescens DC. ssp. beneolens (A. Davids.) Stebbins & Keil | GNCAB2 |
| Pseudognaphalium canescens ssp. canescens | Gnaphalium canescens DC. | GNCA2 |
| Pseudognaphalium canescens ssp. canescens | Gnaphalium canescens DC. ssp. canescens DC. [superfluous autonym] | GNCAC2 |
| Pseudognaphalium canescens ssp. canescens | Gnaphalium wrightii Gray | GNWR |
| Pseudognaphalium canescens ssp. microcephalum | Gnaphalium canescens DC. ssp. microcephalum (Nutt.) Stebbins & Keil | GNCAM2 |
| Pseudognaphalium canescens ssp. microcephalum | Gnaphalium microcephalum Nutt. | GNMI |
| Pseudognaphalium canescens ssp. microcephalum | Pseudognaphalium microcephalum (Nutt.) A. Anderb. | PSMI4 |
| Pseudognaphalium canescens ssp. thermale | Gnaphalium canescens DC. ssp. thermale (E. Nels.) Stebbins & Keil | GNCAT |
| Pseudognaphalium canescens ssp. thermale | Gnaphalium microcephalum Nutt. ssp. thermale (E. Nels.) G.W. Douglas | GNMIT2 |
| Pseudognaphalium canescens ssp. thermale | Gnaphalium microcephalum Nutt. var. thermale (E. Nels.) Cronq. | GNMIT |
| Pseudognaphalium canescens ssp. thermale | Gnaphalium thermale E. Nels. | GNTH |
| Pseudognaphalium canescens ssp. thermale | Pseudognaphalium microcephalum (Nutt.) A. Anderb. var. thermale (E. Nels.) Dorn | PSMIT |
| Pseudognaphalium domingense | Gnaphalium domingense Lam. | GNDO |
| Pseudognaphalium domingense | Gnaphalium portoricense Urban | GNPO2 |
| Pseudognaphalium elegans | Gnaphalium elegans Kunth | GNEL |
| Pseudognaphalium helleri ssp. helleri | Gnaphalium helleri Britt. | GNHE |
| Pseudognaphalium helleri ssp. helleri | Gnaphalium obtusifolium L. var. helleri (Britt.) Blake | GNOBH |
| Pseudognaphalium helleri ssp. micradenium | Gnaphalium helleri Britt. var. micradenium (Weatherby) Mahler | GNHEM |
| Pseudognaphalium helleri ssp. micradenium | Gnaphalium obtusifolium L. var. micradenium Weatherby | GNOBM |
| Pseudognaphalium helleri ssp. micradenium | Pseudognaphalium micradenium (Weatherby) Nesom | PSMI6 |
| Pseudognaphalium jaliscense | Gnaphalium jaliscense Greenm. | GNJA5 |
| Pseudognaphalium leucocephalum | Gnaphalium leucocephalum Gray | GNLE |
| Pseudognaphalium luteoalbum | Gnaphalium luteoalbum L. | GNLU |
| Pseudognaphalium macounii | Gnaphalium decurrens Ives, non L. | GNDE |
| Pseudognaphalium macounii | Gnaphalium macounii Greene | GNMA |
| Pseudognaphalium macounii | Pseudognaphalium viscosum auct. non (Kunth) W.A. Weber [misapplied] | PSVI5 |
| Pseudognaphalium obtusifolium ssp. obtusifolium | Gnaphalium obtusifolium L. | GNOB |
| Pseudognaphalium obtusifolium ssp. praecox | Gnaphalium obtusifolium L. var. praecox Fern. | GNOBP |
| Pseudognaphalium obtusifolium ssp. saxicola | Gnaphalium obtusifolium L. var. saxicola (Fassett) Cronq. | GNOBS |
| Pseudognaphalium obtusifolium ssp. saxicola | Gnaphalium saxicola Fassett | GNSA2 |
| Pseudognaphalium pringlei | Gnaphalium pringlei Gray | GNPR |
| Pseudognaphalium ramosissimum | Gnaphalium ramosissimum Nutt. | GNRA |
| Pseudognaphalium roseum | Gnaphalium roseum Kunth | GNRO |
| Pseudognaphalium sandwicensium var. hawaiiense | Gnaphalium hawaiiense O. Deg. & Sherff | GNHA |
| Pseudognaphalium sandwicensium var. hawaiiense | Gnaphalium sandwicensium Gaud. var. hawaiiense O. Deg. & Sherff | GNSAH2 |
| Pseudognaphalium sandwicensium var. hawaiiense | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. ssp. hawaiiense (O. Deg. & Sherff) Kartesz, comb. nov. ined. | PSSAH |
| Pseudognaphalium sandwicensium var. kilaueanum | Gnaphalium sandwicensium Gaud. var. kilaueanum O. Deg. & Sherff | GNSAK |
| Pseudognaphalium sandwicensium var. kilaueanum | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. ssp. kilaueanum (O. Deg. & Sherff) Kartesz, comb. nov. ined. | PSSAK |
| Pseudognaphalium sandwicensium var. molokaiense | Gnaphalium sandwicensium Gaud. var. molokaiense O. Deg. & Sherff | GNSAM |
| Pseudognaphalium sandwicensium var. molokaiense | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. ssp. molokaiense (O. Deg. & Sherff) Kartesz, comb. nov. ined. | PSSAM |
| Pseudognaphalium sandwicensium var. sandwicensium | Gnaphalium sandwicensium Gaud. | GNSA |
| Pseudognaphalium sandwicensium var. sandwicensium | Gnaphalium sandwicensium Gaud. var. flagellare Sherff | GNSAF |
| Pseudognaphalium sandwicensium var. sandwicensium | Gnaphalium sandwicensium Gaud. var. lineatum Sherff | GNSAL |
| Pseudognaphalium sandwicensium var. sandwicensium | Pseudognaphalium sandwicensium (Gaud.) A. Anderb. ssp. sandwicensium | PSSAS2 |
| Pseudognaphalium stramineum | Gnaphalium chilense Spreng. | GNCH |
| Pseudognaphalium stramineum | Gnaphalium chilense Spreng. var. confertifolium Greene | GNCHC |
| Pseudognaphalium stramineum | Gnaphalium stramineum Kunth | GNST |
| Pseudognaphalium viscosum | Gnaphalium viscosum Kunth | GNVI |
| pseudogynoxys | Pseudogynoxys (Greenm.) Cabrera | PSEUD15 |
| Pseudogynoxys chenopodioides | Senecio confusus Britten | SECO8 |
| Psilactis asteroides | Aster boltoniae Greene | ASBO4 |
| Psilactis asteroides | Machaeranthera boltoniae (Greene) B.L. Turner & Horne | MABO2 |
| Psilactis asteroides | Psilactis leptos Shinners | PSLE5 |
| Psilactis brevilingulata | Machaeranthera brevilingulata (Schultz-Bip. ex Hemsl.) B.L. Turner & Horne | MABR3 |
| Psilactis gentryi | Machaeranthera mexicana B.L. Turner & Horne | MAME4 |
| Psilactis heterocarpa | Machaeranthera heterocarpa R.L. Hartman & M.A. Lane | MAHE3 |
| Psilactis tenuis | Machaeranthera tenuis (S. Wats.) B.L. Turner & Horne | MATE11 |
| Psilocarphus tenellus var. globiferus | Psilocarphus tenellus Nutt. var. tenuis (Eastw.) Cronq. | PSTET |
| Psilostrophe cooperi | Riddellia cooperi Gray | RICO4 |
| Psilostrophe sparsiflora | Riddellia tagetina (Nutt.) Greene var. sparsiflora Gray | RITAS |
| Psilostrophe tagetina var. cerifera | Psilostrophe villosa Rydb. | PSVI |
| Psilostrophe tagetina var. tagetina | Psilostrophe tagetina (Nutt.) Greene var. grandiflora (Rydb.) Heiser | PSTAG |
| Psilostrophe tagetina var. tagetina | Psilostrophe tagetina (Nutt.) Greene var. lanata A. Nels. | PSTAL |
| Psilostrophe tagetina var. tagetina | Riddellia tagetina (Nutt.) Greene | RITA |
| Pterocaulon alopecuroidies | Pterocaulon alopecuroideum (Lam.) DC. [orthographic variant] | PTAL2 |
| Pterocaulon pycnostachyum | Pterocaulon undulatum (Walt.) C. Mohr | PTUN |
| Pterocaulon virgatum | Gnaphalium virgatum L. | GNVI2 |
| Puerto Rico hempvine | Mikania porosa Urban | MIPO3 |
| Puerto Rico ironweed | Vernonia borinquensis Urban | VEBO2 |
| Puerto Rico thoroughwort | Critonia portoricensis (Urban) Britt. & P. Wilson | CRPO7 |
| puffballs | Marshallia caespitosa Nutt. ex DC. | MACA7 |
| puffballs | Marshallia caespitosa Nutt. ex DC. var. caespitosa | MACAC2 |
| puffballs | Marshallia caespitosa Nutt. ex DC. var. signata Beadle & F.E. Boynt. | MACAS |
| Puget Sound gumweed | Grindelia integrifolia DC. | GRIN |
| Pulicaria arabica | Vicoa auriculata auct. non Cass. [misapplied] | VIAU2 |
| Pulicaria dysenterica | Inula dysenterica L. | INDY |
| Pulicaria paludosa | Pulicaria hispanica (Boiss.) Boiss. | PUHI2 |
| pulvinate pussytoes | Antennaria rosea Greene ssp. pulvinata (Greene) Bayer | ANROP |
| pumice alpinegold | Hulsea vestita Gray | HUVE |
| pumice alpinegold | Hulsea vestita Gray ssp. callicarpha (Hall) Wilken | HUVEC |
| pumice alpinegold | Hulsea vestita Gray ssp. gabrielensis Wilken | HUVEG |
| pumice alpinegold | Hulsea vestita Gray ssp. inyoensis (Keck) Wilken | HUVEI |
| pumice alpinegold | Hulsea vestita Gray ssp. vestita | HUVEV |
| pungent brickellbush | Brickellia arguta B.L. Robins. | BRAR2 |
| pungent brickellbush | Brickellia arguta B.L. Robins. var. arguta | BRARA |
| pungent brickellbush | Brickellia arguta B.L. Robins. var. odontolepis B.L. Robins. | BRARO |
| pungent false tarplant | Centromadia pungens (Hook. & Arn.) Greene | CEPU14 |
| purple coneflower | Echinacea Moench | ECHIN |
| purple cushion fleabane | Erigeron poliospermus Gray | ERPO2 |
| purple cushion fleabane | Erigeron poliospermus Gray var. cereus Cronq. | ERPOC |
| purple cushion fleabane | Erigeron poliospermus Gray var. poliospermus | ERPOP |
| purple fleabane | Erigeron purpuratus Greene | ERPU3 |
| purple fleabane | Erigeron purpuratus Greene var. purpuratus | ERPUP8 |
| purple rattlesnakeroot | Prenanthes racemosa Michx. | PRRA |
| purple rattlesnakeroot | Prenanthes racemosa Michx. var. multiflora (Cronq.) Dorn | PRRAM2 |
| purple rattlesnakeroot | Prenanthes racemosa Michx. var. racemosa | PRRAR3 |
| purple wormwood | Artemisia globularia Cham. ex Bess. | ARGL8 |
| purpledisk helianthella | Helianthella microcephala (Gray) Gray | HEMI2 |
| purpledisk honeycombhead | Balduina atropurpurea Harper | BAAT |
| purpledisk sunflower | Helianthus atrorubens L. | HEAT |
| purplehead sneezeweed | Helenium flexuosum Raf. | HEFL |
| purplestem aster | Symphyotrichum puniceum (L.) A.& D. L?ve | SYPU |
| purplestem aster | Symphyotrichum puniceum (L.) A.& D. L?ve var. puniceum | SYPUP |
| purplestem aster | Symphyotrichum puniceum (L.) A.& D. L?ve var. scabricaule (Shinners) Nesom | SYPUS |
| purplestem beggarticks | Bidens connata Muhl. ex Willd. | BICO5 |
| pussytoes | Antennaria Gaertn. | ANTEN |
| pygmy alpinegold | Hulsea vestita Gray ssp. pygmaea (Gray) Wilken | HUVEP2 |
| pygmy cudweed | Evax Gaertn. | EVAX |
| pygmy fleabane | Erigeron pygmaeus (Gray) Greene | ERPY |
| pygmy goldenweed | Tonestus pygmaeus (Torr. & Gray) A. Nels. | TOPY |
| pygmy pussytoes | Antennaria monocephala DC. | ANMO9 |
| pygmy pussytoes | Antennaria monocephala DC. ssp. angustata (Greene) Hult | ANMOA |
| pygmy pussytoes | Antennaria monocephala DC. ssp. monocephala | ANMOM |
| pygmy sagebrush | Artemisia pygmaea Gray | ARPY2 |
| pygmycedar | Peucephyllum Gray | PEUCE2 |
| pygmydaisy | Pentachaeta Nutt. | PENTA5 |
| Pyrenean thistle | Cirsium pyrenaicum (Jacq.) All. | CIPY2 |
| pyrethrum | Chrysanthemum cinerariifolium (Trevir.) Vis. | CHCI5 |
| pyrethum daisy | Tanacetum coccineum (Willd.) Grierson | TACO6 |
| Pyrrhopappus carolinianus | Pyrrhopappus carolinianus (Walt.) DC. var. georgianus (Shinners) Ahles | PYCAG |
| Pyrrhopappus carolinianus | Pyrrhopappus georgianus Shinners | PYGE2 |
| Pyrrhopappus carolinianus | Sitilias caroliniana (Walt.) Raf. | SICA10 |
| Pyrrhopappus grandiflorus | Pyrrhopappus scaposus DC. | PYSC |
| Pyrrhopappus grandiflorus | Sitilias grandiflora (Nutt.) Greene | SIGR15 |
| Pyrrhopappus pauciflorus | Pyrrhopappus geiseri Shinners | PYGE4 |
| Pyrrhopappus pauciflorus | Pyrrhopappus multicaulis DC. | PYMU2 |
| Pyrrhopappus pauciflorus | Pyrrhopappus multicaulis DC. var. geiseri (Shinners) Northington | PYMUG |
| Pyrrhopappus pauciflorus | Pyrrhopappus rothrockii Gray | PYRO2 |
| Pyrrhopappus pauciflorus | Sitilias multicaulis (DC.) Greene | SIMU5 |
| Pyrrocoma apargioides | Haplopappus apargioides Gray | HAAP |
| Pyrrocoma carthamoides var. carthamoides | Haplopappus carthamoides (Hook.) Gray | HACA5 |
| Pyrrocoma carthamoides var. carthamoides | Haplopappus carthamoides (Hook.) Gray ssp. rigidus (Rydb.) Hall | HACAR |
| Pyrrocoma carthamoides var. carthamoides | Haplopappus carthamoides (Hook.) Gray var. erythropappus (Rydb.) St. John | HACAE |
| Pyrrocoma carthamoides var. carthamoides | Haplopappus carthamoides (Hook.) Gray var. rigidus (Rydb.) M.E. Peck | HACAR2 |
| Pyrrocoma carthamoides var. carthamoides | Haplopappus carthamoides (Hook.) Gray var. typicus (Hall) Cronq. | HACAT |
| Pyrrocoma carthamoides var. cusickii | Haplopappus carthamoides (Hook.) Gray ssp. cusickii (Gray) Hall | HACAC2 |
| Pyrrocoma carthamoides var. cusickii | Haplopappus carthamoides (Hook.) Gray var. cusickii Gray | HACAC |
| Pyrrocoma carthamoides var. subsquarrosa | Haplopappus carthamoides (Hook.) Gray var. subsquarrosus (Greene) Dorn | HACAS |
| Pyrrocoma carthamoides var. subsquarrosa | Pyrrocoma subsquarrosa Greene | PYSU |
| Pyrrocoma clementis var. clementis | Haplopappus clementis (Rydb.) Blake | HACL2 |
| Pyrrocoma clementis var. villosa | Pyrrocoma villosa Rydb. | PYVI6 |
| Pyrrocoma crocea var. crocea | Haplopappus croceus Gray | HACR2 |
| Pyrrocoma crocea var. crocea | Haplopappus croceus Gray ssp. typicus Hall | HACRT |
| Pyrrocoma crocea var. genuflexa | Haplopappus croceus Gray var. genuflexus (Greene) Blake | HACRG |
| Pyrrocoma crocea var. genuflexa | Pyrrocoma genuflexa Greene | PYGE3 |
| Pyrrocoma hirta var. hirta | Haplopappus hirtus Gray | HAHI |
| Pyrrocoma hirta var. hirta | Haplopappus hirtus Gray ssp. typicus Hall | HAHIT |
| Pyrrocoma hirta var. lanulosa | Haplopappus hirtus Gray ssp. lanulosus (Greene) Hall | HAHIL2 |
| Pyrrocoma hirta var. lanulosa | Haplopappus hirtus Gray var. lanulosus (Greene) M.E. Peck | HAHIL |
| Pyrrocoma hirta var. lanulosa | Pyrrocoma lanulosa Greene | PYLA3 |
| Pyrrocoma hirta var. sonchifolia | Haplopappus hirtus Gray ssp. sonchifolius (Greene) Hall | HAHIS2 |
| Pyrrocoma hirta var. sonchifolia | Haplopappus hirtus Gray var. sonchifolius (Greene) M.E. Peck | HAHIS |
| Pyrrocoma hirta var. sonchifolia | Pyrrocoma sonchifolia Greene | PYSO2 |
| Pyrrocoma insecticruris | Haplopappus insecticruris (Henderson) Heller | HAIN2 |
| Pyrrocoma insecticruris | Haplopappus integrifolius Porter ex Gray ssp. insecticruris (Henderson) Hall | HAINI |
| Pyrrocoma integrifolia | Haplopappus integrifolius Porter ex Gray | HAIN3 |
| Pyrrocoma integrifolia | Haplopappus integrifolius Porter ex Gray ssp. typicus Hall | HAINT |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray | HALA2 |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray ssp. solidagineus (Greene) Hall | HALAS |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray ssp. tenuicaulis (D.C. Eat.) Hall | HALAT |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray ssp. vaseyi (Parry ex D.C. Eat.) Hall | HALAV |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray var. sublanatus Cody | HALAS2 |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray var. tenuicaulis (D.C. Eat.) Gray | HALAT2 |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray var. typicus (Hall) Cronq. | HALAT3 |
| Pyrrocoma lanceolata var. lanceolata | Haplopappus lanceolatus (Hook.) Torr. & Gray var. vaseyi Parry ex D.C. Eat. | HALAV2 |
| Pyrrocoma lanceolata var. subviscosa | Haplopappus subviscosus (Greene) Blake | HASU2 |
| Pyrrocoma lanceolata var. subviscosa | Pyrrocoma subviscosa Greene | PYSU2 |
| Pyrrocoma liatriformis | Haplopappus integrifolius Porter ex Gray ssp. liatriformis (Greene) Hall | HAINL |
| Pyrrocoma liatriformis | Haplopappus integrifolius Porter ex Gray ssp. scaberulus (Greene) Hall | HAINS |
| Pyrrocoma liatriformis | Haplopappus liatriformis (Greene) St. John | HALI2 |
| Pyrrocoma liatriformis | Haplopappus racemosus (Nutt.) Torr. ssp. liatriformis (Greene) Keck | HARAL2 |
| Pyrrocoma linearis | Haplopappus uniflorus (Hook.) Torr. & Gray ssp. linearis Keck | HAUNL |
| Pyrrocoma lucida | Haplopappus lucidus (Keck) Keck | HALU |
| Pyrrocoma lucida | Haplopappus racemosus (Nutt.) Torr. ssp. lucidus Keck | HARAL |
| Pyrrocoma racemosa var. congesta | Haplopappus racemosus (Nutt.) Torr. ssp. congestus (Greene) Hall | HARAC |
| Pyrrocoma racemosa var. congesta | Pyrrocoma congesta Greene | PYCO7 |
| Pyrrocoma racemosa var. paniculata | Haplopappus paniculatus (Nutt.) Gray var. virgatus Gray | HAPAV |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. ssp. brachycephalus (A. Nels.) Hall | HARAB |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. ssp. duriuscula (Greene) Hall | HARAD |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. ssp. glomeratus (Nutt.) Hall | HARAG2 |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. ssp. halophilus (Greene) Hall | HARAH |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. ssp. prionophyllus (Greene) Hall | HARAP2 |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. var. glomerellus (Nutt.) Gray | HARAG |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. var. paniculatus (Nutt.) Cronq. | HARAP4 |
| Pyrrocoma racemosa var. paniculata | Haplopappus racemosus (Nutt.) Torr. var. prionophyllus (Greene) Welsh | HARAP3 |
| Pyrrocoma racemosa var. pinetorum | Haplopappus racemosus (Nutt.) Torr. ssp. pinetorum Keck | HARAP |
| Pyrrocoma racemosa var. racemosa | Haplopappus racemosus (Nutt.) Torr. | HARA |
| Pyrrocoma racemosa var. sessiliflora | Haplopappus racemosus (Nutt.) Torr. ssp. sessiliflorus (Greene) Hall | HARAS |
| Pyrrocoma racemosa var. sessiliflora | Haplopappus racemosus (Nutt.) Torr. var. sessiliflorus (Greene) Welsh | HARAS2 |
| Pyrrocoma racemosa var. sessiliflora | Pyrrocoma sessiliflora Greene | PYSE3 |
| Pyrrocoma radiata | Haplopappus carthamoides (Hook.) Gray var. maximus Gray | HACAM3 |
| Pyrrocoma radiata | Haplopappus radiatus (Nutt.) Cronq. | HARA2 |
| Pyrrocoma uniflora var. gossypina | Haplopappus uniflorus (Hook.) Torr. & Gray ssp. gossypinus (Greene) Hall | HAUNG |
| Pyrrocoma uniflora var. gossypina | Pyrrocoma gossypina Greene | PYGO2 |
| Pyrrocoma uniflora var. uniflora | Haplopappus contractus Hall | HACO2 |
| Pyrrocoma uniflora var. uniflora | Haplopappus uniflorus (Hook.) Torr. & Gray | HAUN2 |
| Pyrrocoma uniflora var. uniflora | Haplopappus uniflorus (Hook.) Torr. & Gray ssp. howellii (Gray) Hall | HAUNH2 |
| Pyrrocoma uniflora var. uniflora | Haplopappus uniflorus (Hook.) Torr. & Gray ssp. typicus Hall | HAUNT |
| Pyrrocoma uniflora var. uniflora | Haplopappus uniflorus (Hook.) Torr. & Gray var. howellii (Gray) M.E. Peck | HAUNH |
| Pyrrocoma uniflora var. uniflora | Pyrrocoma howellii (Gray) Greene | PYHO3 |
| q tips | Bombycilaena californica (Fisch. & C.A. Mey.) Holub var. californica | BOCAC |
| q tips | Bombycilaena californica (Fisch. & C.A. Mey.) Holub var. subvestita (Gray) Kartesz, comb. nov. ined. | BOCAS |
| Quayle's ragwort | Senecio quaylei T.M. Barkl. | SEQU3 |
| Queen Anne's thistle | Cirsium canum (L.) All. | CICA16 |
| queen thistle | Cirsium chellyense Moore & Frankton | CICH2 |
| queendevil | Hieracium gronovii L. | HIGR3 |
| quill fleabane | Erigeron gracilis Rydb. | ERGR2 |
| rabbit-tobacco | Pseudognaphalium obtusifolium (L.) Hilliard & Burtt | PSOB3 |
| rabbit-tobacco | Pseudognaphalium obtusifolium (L.) Hilliard & Burtt ssp. obtusifolium | PSOBO |
| rabbit-tobacco | Pseudognaphalium obtusifolium (L.) Hilliard & Burtt ssp. praecox (Fern.) Kartesz | PSOBP |
| rabbit-tobacco | Pseudognaphalium obtusifolium (L.) Hilliard & Burtt ssp. saxicola (Fassett) Kartesz | PSOBS |
| rabbitbrush | Chrysothamnus Nutt. | CHRYS9 |
| rabbitbush | Ericameria bloomeri (Gray) J.F. Macbr. | ERBL2 |
| rabbithead balsamroot | Balsamorhiza hookeri (Hook.) Nutt. var. lagocephala (Sharp) Cronq. | BAHOL |
| raceme pussytoes | Antennaria racemosa Hook. | ANRA |
| ragged marshelder | Hedosyne ambrosiifolia (Gray) Strother | HEAM11 |
| ragleaf | Crassocephalum Moench | CRASS2 |
| ragleaf bahia | Bahia dissecta (Gray) Britt. | BADI |
| ragweed | Ambrosia L. | AMBRO |
| ragweed sagebrush | Artemisia franserioides Greene | ARFR3 |
| ragwort | Packera A.& D. L?ve | PACKE |
| ragwort | Pericallis Webb | PERIC4 |
| ragwort | Senecio L. | SENEC |
| raillardella | Raillardella (Gray) Benth. | RAILL |
| Raillardella argentea | Raillardella minima Rydb. | RAMI5 |
| Raillardella argentea | Raillardia argentea Gray | RAAR6 |
| rainiera | Rainiera Greene | RAINI |
| Rainiera stricta | Luina stricta (Greene) B.L. Robins. | LUST9 |
| rambling fleabane | Erigeron vagus Payson | ERVA3 |
| Ramm's madia | Jensia rammii (Greene) B.G. Baldwin | JERA |
| ramtilla | Guizotia abyssinica (L. f.) Cass. | GUAB |
| Rand's goldenrod | Solidago simplex Kunth ssp. randii (Porter) Ringius | SOSIR |
| Rand's goldenrod | Solidago simplex Kunth ssp. randii (Porter) Ringius var. gillmanii (Gray) Ringius | SOSIG2 |
| Rand's goldenrod | Solidago simplex Kunth ssp. randii (Porter) Ringius var. monticola (Porter) Ringius | SOSIM |
| Rand's goldenrod | Solidago simplex Kunth ssp. randii (Porter) Ringius var. racemosa (Greene) Ringius | SOSIR2 |
| Rand's goldenrod | Solidago simplex Kunth ssp. randii (Porter) Ringius var. randii (Porter) Kartesz & Gandhi | SOSIR3 |
| Ratibida columnifera | Lepachys columnaris (Pursh) T. & G. | LECO48 |
| Ratibida columnifera | Lepachys columnifera (Nutt.) J.F. Macbr. | LECO13 |
| Ratibida columnifera | Ratibida columnaris D. Don | RACO7 |
| Ratibida columnifera | Ratibida columnaris D. Don var. pulcherrima (DC.) D. Don | RACOP |
| Ratibida columnifera | Rudbeckia columnaris Pursh, non Sims | RUCO23 |
| Ratibida columnifera | Rudbeckia columnifera Nutt. | RUCO24 |
| Ratibida peduncularis var. peduncularis | Lepachys peduncularis Torr. & Gray | LEPE7 |
| Ratibida peduncularis var. picta | Lepachys peduncularis Torr. & Gray var. picta Gray | LEPEP |
| Ratibida peduncularis var. picta | Ratibida picta (Gray) Small | RAPI2 |
| Ratibida pinnata | Lepachys pinnata (Vent.) T. & G. | LEPI14 |
| Ratibida pinnata | Rudbeckia pinnata Vent. | RUPI3 |
| Ratibida tagetes | Rudbeckia globosa Nutt. | RUGL4 |
| Ratibida tagetes | Rudbeckia tagetes James | RUTA4 |
| rattlesnakeroot | Prenanthes L. | PRENA |
| rattlesnakeweed | Hieracium venosum L. | HIVE |
| Raven Ridge false goldenweed | Oonopsis foliosa (Gray) Greene var. monocephala (A. Nels.) Kartesz & Gandhi | OOFOM |
| ray goldenweed | Pyrrocoma radiata Nutt. | PYRA2 |
| ray hymenopappus | Hymenopappus radiatus Rose | HYRA2 |
| Rayjacksonia annua | Haplopappus annuus (Rydb.) Cory | HAAN |
| Rayjacksonia annua | Haplopappus phyllocephalus DC. ssp. annuus (Rydb.) Hall | HAPHA |
| Rayjacksonia annua | Haplopappus phyllocephalus DC. var. annuus (Rydb.) Waterfall | HAPHA2 |
| Rayjacksonia annua | Machaeranthera annua (Rydb.) Shinners | MAAN8 |
| Rayjacksonia annua | Machaeranthera phyllocephala (DC.) Shinners var. annua (Rydb.) Shinners | MAPHA |
| Rayjacksonia annua | Sideranthus annuus Rydb. | SIAN6 |
| Rayjacksonia aurea | Haplopappus aureus Gray | HAAU3 |
| Rayjacksonia aurea | Machaeranthera aurea (Gray) Shinners | MAAU3 |
| Rayjacksonia aurea | Sideranthus aureus (Gray) Small | SIAU3 |
| Rayjacksonia phyllocephala | Eriocarpum megacephalum Nash | ERME13 |
| Rayjacksonia phyllocephala | Haplopappus phyllocephalus DC. | HAPH2 |
| Rayjacksonia phyllocephala | Haplopappus phyllocephalus DC. var. megacephalus (Nash) Waterfall | HAPHM |
| Rayjacksonia phyllocephala | Machaeranthera phyllocephala (DC.) Shinners | MAPH2 |
| Rayjacksonia phyllocephala | Machaeranthera phyllocephala (DC.) Shinners var. megacephala (Nash) Shinners | MAPHM |
| Rayjacksonia phyllocephala | Sideranthus megacephalus (Nash) Small | SIME3 |
| rayless alkali aster | Symphyotrichum ciliatum (Ledeb.) Nesom | SYCI2 |
| rayless arnica | Arnica ?diversifolia Greene (pro sp.) [amplexicaulis or mollis ? cordifolia or latifolia] | ARDI7 |
| rayless arnica | Arnica discoidea Benth. | ARDI6 |
| rayless aster | Eucephalus tomentellus (Greene) Greene | EUTO4 |
| rayless goldenhead | Acamptopappus sphaerocephalus (Harvey & Gray ex Gray) Gray | ACSP |
| rayless goldenhead | Acamptopappus sphaerocephalus (Harvey & Gray ex Gray) Gray var. hirtellus Blake | ACSPH |
| rayless goldenhead | Acamptopappus sphaerocephalus (Harvey & Gray ex Gray) Gray var. sphaerocephalus | ACSPS2 |
| rayless goldenrod | Bigelowia DC. | BIGEL |
| rayless mock goldenrod | Solidago discoidea Ell. | SODI3 |
| rayless ragwort | Senecio aronicoides DC. | SEAR4 |
| rayless shaggy fleabane | Erigeron aphanactis (Gray) Greene | ERAP |
| rayless shaggy fleabane | Erigeron aphanactis (Gray) Greene var. aphanactis | ERAPA2 |
| rayless shaggy fleabane | Erigeron aphanactis (Gray) Greene var. congestus (Greene) Cronq. | ERAPC |
| rayless sunflower | Helianthus radula (Pursh) Torr. & Gray | HERA |
| rayless tansyaster | Machaeranthera grindelioides (Nutt.) Shinners | MAGR2 |
| rayless tansyaster | Machaeranthera grindelioides (Nutt.) Shinners var. depressa (Maguire) Cronq. & Keck | MAGRD |
| rayless tansyaster | Machaeranthera grindelioides (Nutt.) Shinners var. grindelioides | MAGRG |
| rayless tidytips | Layia discoidea Keck | LADI4 |
| reclined gumweed | Grindelia decumbens Greene | GRDE |
| reclined gumweed | Grindelia decumbens Greene var. decumbens | GRDED |
| reclined gumweed | Grindelia decumbens Greene var. subincisa (Greene) Steyermark | GRDES |
| red dahlia | Dahlia coccinea Cav. [excluded] | DACO4 |
| red dome blanketflower | Gaillardia pinnatifida Torr. | GAPI |
| red dome blanketflower | Gaillardia pinnatifida Torr. var. linearis (Rydb.) Biddulph | GAPIL2 |
| red dome blanketflower | Gaillardia pinnatifida Torr. var. pinnatifida | GAPIP2 |
| red hawksbeard | Crepis rubra L. | CRRU9 |
| red star-thistle | Centaurea calcitrapa L. | CECA2 |
| redflower ragleaf | Crassocephalum crepidioides (Benth.) S. Moore | CRCR9 |
| redpurple ragwort | Senecio elegans L. | SEEL |
| redray alpinegold | Hulsea heterochroma Gray | HUHE |
| redrock tarweed | Deinandra arida (Keck) B.G. Baldwin | DEAR8 |
| redstem wormwood | Artemisia scoparia Waldst. & Kit. | ARSC4 |
| remarkable goatsbeard | Tragopogon mirus Ownbey | TRMI7 |
| remya | Remya Hbd. ex Benth. | REMYA |
| Remya kauaiensis | Remya kauaiensis Hbd. var. magnifica O. Deg. & Sherff | REKAM2 |
| Remya kauaiensis | Remya kauaiensis Hbd. var. magnifolia O. Deg. & Sherff | REKAM |
| resinbush | Viguiera stenoloba Blake | VIST |
| resinbush | Viguiera stenoloba Blake var. stenoloba | VISTS |
| resindot sunflower | Helianthus resinosus Small | HERE5 |
| resinleaf brickellbush | Brickellia baccharidea Gray | BRBA2 |
| resinous snakeroot | Ageratina resiniflua (Urban) King & H.E. Robins. | AGRE3 |
| Reverchon's palafox | Palafoxia reverchonii (Bush) Cory | PARE |
| Reverchon's rosinweed | Silphium reverchonii Bush | SIRE4 |
| rhagadiolus | Rhagadiolus Juss. | RHAGA |
| Rhagadiolus stellatus | Rhagadiolus edulis Gaertn. | RHED3 |
| rhizome fleabane | Erigeron rhizomatus Cronq. | ERRH2 |
| Rhodanthe chlorocephala ssp. rosea | Acroclinium roseum Hook. | ACRO8 |
| Rhodanthe chlorocephala ssp. rosea | Helipterum roseum (Hook.) Benth. | HERO8 |
| rice button aster | Symphyotrichum dumosum (L.) Nesom | SYDU2 |
| rice button aster | Symphyotrichum dumosum (L.) Nesom var. dumosum | SYDUD2 |
| rice button aster | Symphyotrichum dumosum (L.) Nesom var. gracilipes (Wieg.) Nesom | SYDUG |
| rice button aster | Symphyotrichum dumosum (L.) Nesom var. pergracile (Wieg.) Nesom | SYDUP |
| rice button aster | Symphyotrichum dumosum (L.) Nesom var. strictior (Torr. & Gray) Nesom | SYDUS |
| rice button aster | Symphyotrichum dumosum (L.) Nesom var. subulifolium (Torr. & Gray) Nesom | SYDUS2 |
| Riddell's dozedaisy | Aphanostephus riddellii Torr. & Gray | APRI |
| Riddell's goldenrod | Oligoneuron riddellii (Frank ex Riddell) Rydb. | OLRI2 |
| Riddell's ragwort | Senecio riddellii Torr. & Gray | SERI2 |
| ridge beggartick | Bidens gardneri Baker | BIGA |
| ridgetop tetramolopium | Tetramolopium filiforme Sherff | TEFI2 |
| ridgetop tetramolopium | Tetramolopium filiforme Sherff var. filiforme | TEFIF |
| ridgetop tetramolopium | Tetramolopium filiforme Sherff var. polyphyllum (Sherff) Lowrey | TEFIP |
| rigid whitetop aster | Symphyotrichum retroflexum (Lindl. ex DC.) Nesom | SYRE3 |
| rigiopappus | Rigiopappus Gray | RIGIO |
| rincon rubberweed | Hymenoxys quinquesquamata Rydb. | HYQU2 |
| Rio Grande bugheal | Trichocoronis rivularis Gray | TRRI6 |
| Rio Grande fleabane | Erigeron tenellus DC. | ERTE5 |
| Rio Grande greenthread | Thelesperma nuecense B.L. Turner | THNU |
| Rio Grande palafox | Palafoxia riograndensis Cory | PARI |
| Rio Grande pearlhead | Isocarpha oppositifolia (L.) Cass. | ISOP |
| Rio Grande ragweed | Ambrosia cheiranthifolia Gray | AMCH2 |
| Rio Grande tickseed | Coreopsis nuecensoides E.B. Sm. | CONU6 |
| riverbank creepingoxeye | Wedelia lanceolata DC. | WELA |
| Roan Mountain goldenrod | Solidago roanensis Porter | SORO2 |
| Roan Mountain rattlesnakeroot | Prenanthes roanensis (Chickering) Chickering | PRRO2 |
| robin's plantain | Erigeron pulchellus Michx. | ERPU |
| robin's plantain | Erigeron pulchellus Michx. var. pulchellus | ERPUP |
| Robinson's compassplant | Silphium laciniatum L. var. robinsonii Perry | SILAR |
| Robinson's hawkweed | Hieracium robinsonii (Zahn) Fern. | HIRO4 |
| rock dandelion | Taraxacum laevigatum (Willd.) DC. | TALA2 |
| rock fleabane | Erigeron saxatilis Nesom | ERSA18 |
| rock goldenrod | Solidago rupestris Raf. | SORU3 |
| rock ragwort | Senecio rupestris Waldst. & Kit. | SERU5 |
| rock tansy | Sphaeromeria capitata Nutt. | SPCA8 |
| rock tickseed | Coreopsis wrightii (Gray) H.M. Parker | COWR3 |
| Rock's nehe | Lipochaeta rockii Sherff | LIRO |
| rockcastle aster | Eurybia saxicastellii (J. Campbell & M. Medley) Nesom | EUSA15 |
| rockdaisy | Perityle Benth. | PERIT |
| rockgoldenrod | Petradoria Greene | PETRA |
| rocklettuce | Pinaropappus Less. | PINAR |
| rockloving erigeron | Erigeron petrophilus Greene | ERPE5 |
| rockloving erigeron | Erigeron petrophilus Greene var. petrophilus | ERPEP4 |
| rockloving erigeron | Erigeron petrophilus Greene var. viscidulus (Gray) Nesom | ERPEV |
| rockslide yellow fleabane | Erigeron leiomerus Gray | ERLE6 |
| Rocky Mountain aster | Ionactis stenomeres (Gray) Greene | IOST |
| Rocky Mountain beggarticks | Bidens heterosperma Gray | BIHE |
| Rocky Mountain blazing star | Liatris ligulistylis (A. Nels.) K. Schum. | LILI |
| Rocky Mountain goldenrod | Solidago multiradiata Ait. | SOMU |
| Rocky Mountain goldenrod | Solidago multiradiata Ait. var. multiradiata | SOMUM |
| Rocky Mountain groundsel | Packera streptanthifolia (Greene) W.A. Weber & A. L?ve | PAST10 |
| Rocky Mountain pussytoes | Antennaria media Greene | ANME2 |
| Rocky Mountain thistle | Cirsium perplexans (Rydb.) Petrak | CIPE5 |
| Rocky Mountain zinnia | Zinnia grandiflora Nutt. | ZIGR |
| rocky ragwort | Senecio megacephalus Nutt. | SEME |
| rockyscree false goldenaster | Heterotheca fulcrata (Greene) Shinners | HEFU3 |
| rockyscree false goldenaster | Heterotheca fulcrata (Greene) Shinners var. amplifolia (Rydb.) Semple | HEFUA2 |
| rockyscree false goldenaster | Heterotheca fulcrata (Greene) Shinners var. fulcrata | HEFUF |
| rockyscree false goldenaster | Heterotheca fulcrata (Greene) Shinners var. senilis (Woot. & Standl.) Semple | HEFUS |
| rod wirelettuce | Stephanomeria virgata Benth. | STVI2 |
| rod wirelettuce | Stephanomeria virgata Benth. ssp. virgata | STVIV |
| Rolandra fruticosa | Echinops fruticosus L. | ECFR2 |
| Roldana hartwegii | Roldana carlomasonii (B.L. Turner & T.M. Barkl.) C. Jeffrey | ROCA12 |
| Roldana hartwegii | Senecio carlomasonii B.L. Turner & T.M. Barkl. | SECA8 |
| Roldana hartwegii | Senecio hartwegii Benth. | SEHA6 |
| Roldana hartwegii | Senecio seemanii auct. non Schultz-Bip. ex Seem. [misapplied] | SESE11 |
| Roldana petasitis | Senecio petasitis (Sims) DC. | SEPE6 |
| rolled gumweed | Grindelia revoluta Steyermark | GRRE |
| Roman chamomile | Chamaemelum nobile (L.) All. | CHNO3 |
| Roman wormwood | Artemisia pontica L. | ARPO4 |
| romerillo | Bidens alba (L.) DC. | BIAL |
| romerillo | Bidens alba (L.) DC. var. radiata (Schultz-Bip.) Ballard ex T.E. Melchert | BIALR |
| romero macho | Pectis linifolia L. | PELI9 |
| Roosevelt Dam rockdaisy | Perityle saxicola (Eastw.) Shinners | PESA12 |
| Rooseveltweed | Baccharis neglecta Britt. | BANE2 |
| rose heath | Chaetopappa ericoides (Torr.) Nesom | CHER2 |
| rose rush | Lygodesmia aphylla (Nutt.) DC. | LYAP3 |
| rose thistle | Cirsium andersonii (Gray) Petrak | CIAN |
| rosilla | Helenium puberulum DC. | HEPU2 |
| rosinweed | Silphium L. | SILPH |
| rosinweed sunflower | Helianthus silphioides Nutt. | HESI |
| rosy balsamroot | Balsamorhiza rosea A. Nels. & J.F. Macbr. | BARO2 |
| rosy camphorweed | Pluchea rosea Godfrey | PLRO |
| rosy cudweed | Pseudognaphalium roseum (Kunth) A. Anderb. | PSRO |
| rosy palafox | Palafoxia rosea (Bush) Cory | PARO |
| rosy palafox | Palafoxia rosea (Bush) Cory var. macrolepis (Rydb.) B.L. Turner & Morris | PAROM |
| rosy palafox | Palafoxia rosea (Bush) Cory var. rosea | PAROR |
| rosy pussytoes | Antennaria rosea Greene | ANRO2 |
| rosy pussytoes | Antennaria rosea Greene ssp. arida (E. Nels.) Bayer | ANROA |
| rosy pussytoes | Antennaria rosea Greene ssp. confinis (Greene) Bayer | ANROC |
| rosy pussytoes | Antennaria rosea Greene ssp. rosea | ANROR |
| rosy sunray | Rhodanthe chlorocephala (Turcz.) P. Wilson | RHCH13 |
| Rothrock's crownbeard | Verbesina rothrockii Robins. & Greenm. | VERO2 |
| Rothrock's knapweed | Centaurea rothrockii Greenm. | CERO |
| Rothrock's snakeroot | Ageratina rothrockii (Gray) King & H.E. Robins. | AGRO5 |
| Rothrock's thistle | Cirsium rothrockii (Gray) Petrak | CIRO |
| Rothrock's Townsend daisy | Townsendia rothrockii Gray ex Rothrock | TORO |
| rough blackfoot | Melampodium sericeum Lag. | MESE2 |
| rough boneset | Eupatorium pilosum Walt. | EUPI2 |
| rough brickellbush | Brickellia microphylla (Nutt.) Gray var. scabra Gray | BRMIS |
| rough cockleburr | Xanthium strumarium L. | XAST |
| rough cockleburr | Xanthium strumarium L. var. glabratum (DC.) Cronq. | XASTG |
| rough cockleburr | Xanthium strumarium L. var. strumarium | XASTS |
| rough coneflower | Rudbeckia grandiflora (D. Don) J.F. Gmel. ex DC. | RUGR |
| rough coneflower | Rudbeckia grandiflora (D. Don) J.F. Gmel. ex DC. var. alismifolia (Torr. & Gray) Cronq. | RUGRA |
| rough coneflower | Rudbeckia grandiflora (D. Don) J.F. Gmel. ex DC. var. grandiflora | RUGRG |
| rough dubautia | Dubautia scabra (DC.) Keck | DUSC |
| rough dubautia | Dubautia scabra (DC.) Keck ssp. leiophylla (Gray) G.D. Carr | DUSCL2 |
| rough dubautia | Dubautia scabra (DC.) Keck ssp. scabra | DUSCS |
| rough eyelashweed | Blepharipappus scaber Hook. | BLSC |
| rough eyelashweed | Blepharipappus scaber Hook. ssp. laevis (Gray) Keck | BLSCL |
| rough eyelashweed | Blepharipappus scaber Hook. ssp. scaber | BLSCS |
| rough false goldeneye | Heliomeris hispida (Gray) Cockerell | HEHI6 |
| rough fleabane | Erigeron asper Nutt. | ERAS3 |
| rough gumweed | Grindelia scabra Greene | GRSC |
| rough hawksbeard | Crepis biennis L. | CRBI3 |
| rough hawkweed | Hieracium scabrum Michx. | HISC |
| rough hawkweed | Hieracium scabrum Michx. var. intonsum Fern. & St. John | HISCI |
| rough hawkweed | Hieracium scabrum Michx. var. scabrum | HISCS |
| rough hawkweed | Hieracium scabrum Michx. var. tonsum Fern. & St. John | HISCT |
| rough rattlesnakeroot | Prenanthes aspera Michx. | PRAS |
| rough star-thistle | Centaurea aspera L. | CEAS2 |
| rough thistle | Cirsium scabrum (Poir.) Bonnet & Barratte | CISC4 |
| roughleaf aster | Eurybia radulina (Gray) Nesom | EURA11 |
| roughleaf coneflower | Rudbeckia scabrifolia L.E. Brown | RUSC4 |
| roughleaf rosinweed | Silphium scaberrimum Ell. | SISC4 |
| roughstem hawkweed | Hieracium schultzii Fries | HISC10 |
| roughstem rosinweed | Silphium radula Nutt. | SIRA2 |
| roundleaf candyleaf | Stevia ovata Willd. | STOV3 |
| roundleaf candyleaf | Stevia ovata Willd. var. ovata Willd. [excluded] | STOVO2 |
| roundleaf goldenrod | Solidago patula Muhl. ex Willd. | SOPA2 |
| roundleaf goldenrod | Solidago patula Muhl. ex Willd. var. patula | SOPAP |
| roundleaf goldenrod | Solidago patula Muhl. ex Willd. var. strictula Torr. & Gray | SOPAS |
| roundleaf ragwort | Packera obovata (Muhl. ex Willd.) W.A. Weber & A. L?ve | PAOB6 |
| roundleaf snakeweed | Gutierrezia sphaerocephala Gray | GUSP |
| roundleaf thoroughwort | Eupatorium rotundifolium L. | EURO4 |
| roundleaf thoroughwort | Eupatorium rotundifolium L. var. cordigerum Fern. | EUROC |
| roundleaf thoroughwort | Eupatorium rotundifolium L. var. ovatum (Bigelow) Torr. | EUROO |
| roundleaf thoroughwort | Eupatorium rotundifolium L. var. rotundifolium | EUROR |
| roundleaf thoroughwort | Eupatorium rotundifolium L. var. scabridum (Ell.) Gray | EUROS |
| royal cudweed | Pseudognaphalium elegans (Kunth) Kartesz | PSEL4 |
| royal fleabane | Erigeron rybius Nesom | ERRY2 |
| royal goldfields | Lasthenia coronaria (Nutt.) Ornduff | LACO7 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird | ERNA10 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird | ERNAC2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. arenaria (L.C. Anders.) Nesom & Baird | ERNAA3 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. ceruminosa (Dur. & Hilg.) Nesom & Baird | ERNAC3 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. juncea (Greene) Nesom & Baird | ERNAJ |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. leiosperma (Gray) Nesom & Baird | ERNAL |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. mohavensis (Greene) Nesom & Baird | ERNAM |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. nitida (L.C. Anders.) Nesom & Baird | ERNAN2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. oreophila (A. Nels.) Nesom & Baird | ERNAO |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. turbinata (M.E. Jones) Nesom & Baird | ERNAT |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa | ERNAN3 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. bernardina (Hall) Nesom & Baird | ERNAB |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. bigelovii (Gray) Nesom & Baird | ERNAB2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. glabrata (Gray) Nesom & Baird | ERNAG |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. glareosa (M.E. Jones) Nesom & Baird | ERNAG2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. hololeuca (Gray) Nesom & Baird | ERNAH |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. iridis (L.C. Anders.) Nesom & Baird | ERNAI |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. latisquamea (Gray) Nesom & Baird | ERNAL2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. nana (Cronq.) Nesom & Baird | ERNAN4 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. nauseosa | ERNAN5 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. psilocarpa (Blake) Nesom & Baird | ERNAP |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. salicifolia (Rydb.) Nesom & Baird | ERNAS |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. speciosa (Nutt.) Nesom & Baird | ERNAS2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. texensis (L.C. Anders.) Nesom & Baird | ERNAT2 |
| rubber rabbitbrush | Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. nauseosa var. washoensis (L.C. Anders.) Nesom & Baird | ERNAW |
| rubberweed | Hymenoxys Cass. | HYMEN7 |
| Rudbeckia alpicola | Rudbeckia occidentalis Nutt. var. alpicola (Piper) Cronq. | RUOCA |
| Rudbeckia auriculata | Rudbeckia fulgida Ait. var. auriculata Perdue | RUFUA |
| Rudbeckia fulgida var. deamii | Rudbeckia deamii Blake | RUDE12 |
| Rudbeckia fulgida var. fulgida | Rudbeckia acuminata C.L. Boynt. & Beadle | RUAC9 |
| Rudbeckia fulgida var. fulgida | Rudbeckia foliosa C.L. Boynt. & Beadle | RUFO4 |
| Rudbeckia fulgida var. fulgida | Rudbeckia fulgida Ait. var. spathulata (Michx.) Perdue | RUFUS2 |
| Rudbeckia fulgida var. fulgida | Rudbeckia spathulata Michx. | RUSP7 |
| Rudbeckia fulgida var. fulgida | Rudbeckia tenax C.L. Boynt. & Beadle | RUTE3 |
| Rudbeckia fulgida var. fulgida | Rudbeckia truncata Small | RUTR10 |
| Rudbeckia fulgida var. palustris | Rudbeckia palustris Eggert ex C.L. Boynt. & Beadle | RUPA22 |
| Rudbeckia fulgida var. speciosa | Rudbeckia fulgida Ait. var. sullivantii (C.L. Boynt. & Beadle) Cronq. | RUFUS |
| Rudbeckia fulgida var. speciosa | Rudbeckia gloriosa hort. | RUGL6 |
| Rudbeckia fulgida var. speciosa | Rudbeckia speciosa Wenderoth | RUSP8 |
| Rudbeckia fulgida var. speciosa | Rudbeckia speciosa Wenderoth var. sullivantii (C.L. Boynt. & Beadle) B.L. Robins. | RUSPS2 |
| Rudbeckia fulgida var. speciosa | Rudbeckia sullivantii C.L. Boynt. & Beadle | RUSU7 |
| Rudbeckia fulgida var. umbrosa | Rudbeckia chapmanii C.L. Boynt. & Beadle | RUCH2 |
| Rudbeckia fulgida var. umbrosa | Rudbeckia umbrosa C.L. Boynt. & Beadle | RUUM |
| Rudbeckia glaucescens | Rudbeckia californica Gray var. glauca Blake | RUCAG |
| Rudbeckia grandiflora var. alismifolia | Rudbeckia alismifolia Torr. & Gray | RUAL16 |
| Rudbeckia hirta var. angustifolia | Rudbeckia divergens T.V. Moore | RUDI |
| Rudbeckia hirta var. angustifolia | Rudbeckia floridana T.V. Moore var. angustifolia T.V. Moore | RUFLA |
| Rudbeckia hirta var. floridana | Rudbeckia floridana T.V. Moore | RUFL10 |
| Rudbeckia hirta var. hirta | Rudbeckia amplectens T.V. Moore | RUAM8 |
| Rudbeckia hirta var. hirta | Rudbeckia brittonii Small | RUBR11 |
| Rudbeckia hirta var. hirta | Rudbeckia hirta L. var. brittonii (Small) Fern. | RUHIB |
| Rudbeckia hirta var. hirta | Rudbeckia hirta L. var. monticola (Small) Fern. | RUHIM |
| Rudbeckia hirta var. hirta | Rudbeckia monticola Small | RUMO7 |
| Rudbeckia hirta var. pulcherrima | Rudbeckia bicolor Nutt. | RUBI5 |
| Rudbeckia hirta var. pulcherrima | Rudbeckia hirta L. var. corymbifera Fern. | RUHIC |
| Rudbeckia hirta var. pulcherrima | Rudbeckia hirta L. var. lanceolata (Bisch.) Core | RUHIL |
| Rudbeckia hirta var. pulcherrima | Rudbeckia hirta L. var. sericea (T.V. Moore) Fern. | RUHIS |
| Rudbeckia hirta var. pulcherrima | Rudbeckia hirta L. var. serotina (Nutt.) Core | RUHIS2 |
| Rudbeckia hirta var. pulcherrima | Rudbeckia longipes T.V. Moore | RULO8 |
| Rudbeckia hirta var. pulcherrima | Rudbeckia sericea T.V. Moore | RUSE16 |
| Rudbeckia hirta var. pulcherrima | Rudbeckia serotina Nutt. | RUSE5 |
| Rudbeckia hirta var. pulcherrima | Rudbeckia serotina Nutt. var. corymbifera (Fern.) Fern. & Schub. | RUSEC |
| Rudbeckia hirta var. pulcherrima | Rudbeckia serotina Nutt. var. lanceolata (Bisch.) Fern. & Schub. | RUSEL |
| Rudbeckia hirta var. pulcherrima | Rudbeckia serotina Nutt. var. sericea (T.V. Moore) Fern. & Schub. | RUSES |
| Rudbeckia klamathensis | Rudbeckia californica Gray var. intermedia Perdue | RUCAI |
| Rudbeckia laciniata var. ampla | Rudbeckia ampla A. Nels. | RUAM9 |
| Rudbeckia laciniata var. ampla | Rudbeckia laciniata L. ssp. ampla (A. Nels.) W.A. Weber | RULAA2 |
| Rudbeckia laciniata var. digitata | Rudbeckia heterophylla Torr. & Gray | RUHE5 |
| Rudbeckia laciniata var. digitata | Rudbeckia laciniata L. var. humilis Gray | RULAH2 |
| Rudbeckia laciniata var. laciniata | Rudbeckia laciniata L. var. hortensis Bailey | RULAH |
| Rudbeckia missouriensis | Rudbeckia fulgida Ait. var. missouriensis (Engelm. ex C.L. Boynt. & Beadle) Cronq. | RUFUM |
| Rudbeckia montana | Rudbeckia occidentalis Nutt. var. montana (Gray) Perdue | RUOCM |
| Rudbeckia nitida | Rudbeckia glabra DC. | RUGL3 |
| Rudbeckia occidentalis | Rudbeckia occidentalis Nutt. var. occidentalis Nutt. [superfluous autonym] | RUOCO2 |
| Rudbeckia texana | Rudbeckia nitida Nutt. var. texana Perdue | RUNIT |
| Rudbeckia triloba var. pinnatiloba | Rudbeckia pinnatiloba (Torr. & Gray) Beadle | RUPI4 |
| Rudbeckia triloba var. rupestris | Rudbeckia beadlei Small p.p. | RUBE10 |
| Rudbeckia triloba var. rupestris | Rudbeckia rupestris Chickering | RURU6 |
| Rudbeckia triloba var. rupestris | Rudbeckia triloba L. var. beadlei (Small) Fern. p.p. | RUTRB |
| Rugel's Indianplantain | Rugelia nudicaulis Shuttlw. ex Chapman | RUNU2 |
| Rugel's Indianplantain | Rugelia Shuttlw. ex Chapman | RUGEL |
| Rugelia nudicaulis | Cacalia rugelia (Gray) T.M. Barkl. & Cronq. | CARU16 |
| Rugelia nudicaulis | Senecio rugelia Gray | SERU6 |
| running fleabane | Erigeron colomexicanus A. Nels. | ERCO28 |
| Runyon's sunflower | Helianthus praecox Engelm. & Gray ssp. runyonii (Heiser) Heiser | HEPRR |
| Rusby's cinchweed | Pectis rusbyi Greene ex Gray | PERU6 |
| Rusby's goldenbush | Isocoma rusbyi Greene | ISRU2 |
| Rusby's hawkweed | Hieracium rusbyi Greene | HIRU |
| Rusby's rubberweed | Hymenoxys rusbyi (Gray) Cockerell | HYRU |
| Rusby's thistle | Cirsium rusbyi (Greene) Petrak | CIRU2 |
| rush bristleweed | Machaeranthera juncea (Greene) Shinners | MAJU |
| rush pussytoes | Antennaria luzuloides Torr. & Gray | ANLU2 |
| rush pussytoes | Antennaria luzuloides Torr. & Gray ssp. aberrans (E. Nels.) Bayer & Stebbins | ANLUA2 |
| rush pussytoes | Antennaria luzuloides Torr. & Gray ssp. luzuloides | ANLUL |
| rush skeletonplant | Lygodesmia juncea (Pursh) D. Don ex Hook. | LYJU |
| rush skeletonweed | Chondrilla juncea L. | CHJU |
| rushpink skeletonplant | Lygodesmia entrada Welsh & Goodrich | LYEN |
| Ruth's goldaster | Pityopsis ruthii (Small) Small | PIRU3 |
| Rutter's false goldenaster | Heterotheca rutteri (Rothrock) Shinners | HERU3 |
| Rydberg's arnica | Arnica rydbergii Greene | ARRY |
| Rydberg's fleabane | Erigeron rydbergii Cronq. | ERRY |
| Rydberg's goldenbush | Ericameria obovata (Rydb.) Nesom | EROB3 |
| Rydberg's sunflower | Helianthus nuttallii Torr. & Gray ssp. rydbergii (Britt.) R.W. Long | HENUR |
| Rydberg's thistle | Cirsium rydbergii Petrak | CIRY |
| sacapellote | Acourtia microcephala DC. | ACMI3 |
| sachsia | Sachsia Griseb. | SACHS |
| Sachsia polycephala | Sachsia bahamensis Urban | SABA9 |
| Sacramento Mountain thistle | Cirsium vinaceum Woot. & Standl. | CIVI4 |
| Sacramento ragwort | Senecio sacramentanus Woot. & Standl. | SESA3 |
| safflower | Carthamus tinctorius L. | CATI |
| saffron ragwort | Packera crocata (Rydb.) W.A. Weber & A. L?ve | PACR5 |
| sagebrush | Artemisia L. | ARTEM |
| sagebrush fleabane | Erigeron austiniae Greene | ERAU6 |
| saints fleabane | Erigeron sanctarum S. Wats. | ERSA2 |
| salebrosa goldenrod | Solidago canadensis L. var. salebrosa (Piper) M.E. Jones | SOCAS |
| Salinas River tarweed | Deinandra pentactis (Keck) B.G. Baldwin | DEPE5 |
| Salinas Valley goldfields | Lasthenia leptalea (Gray) Ornduff | LALE4 |
| Salmea scandens | Bidens scandens L. | BISC2 |
| Salmon River fleabane | Erigeron salmonensis S.J. Brunsfeld & Nesom | ERSA19 |
| salsify | Tragopogon porrifolius L. | TRPO |
| Salt River rockdaisy | Perityle gilensis (M.E. Jones) J.F. Macbr. var. salensis A. Powell | PEGIS |
| saltmarsh baccharis | Baccharis douglasii DC. | BADO |
| saltwater false willow | Baccharis angustifolia Michx. | BAAN |
| San Bernardino aster | Symphyotrichum defoliatum (Parish) Nesom | SYDE |
| San Bernardino ragwort | Packera bernardina (Greene) W.A. Weber & A. L?ve | PABE7 |
| San Diego alpinegold | Hulsea californica Torr. & Gray | HUCA |
| San Diego burr ragweed | Ambrosia chenopodiifolia (Benth.) Payne | AMCH5 |
| San Diego povertyweed | Iva hayesiana Gray | IVHA |
| San Diego sagewort | Artemisia palmeri Gray | ARPA15 |
| San Diego tarweed | Hemizonia paniculata Gray | HEPA6 |
| San Felipe dogweed | Adenophyllum porophylloides (Gray) Strother | ADPO |
| San Francisco lessingia | Lessingia germanorum Cham. | LEGE |
| San Francisco Peaks ragwort | Packera franciscana (Greene) W.A. Weber & A. L?ve | PAFR6 |
| San Gabriel ragwort | Senecio astephanus Greene | SEAS2 |
| San Joaquin adobe sunburst | Pseudobahia peirsonii Munz | PSPE |
| San Joaquin silverpuffs | Microseris campestris Greene | MICA2 |
| San Joaquin snakeweed | Gutierrezia californica (DC.) Torr. & Gray | GUCA |
| San Joaquin tarweed | Holocarpha obconica (J.C. Clausen & Keck) Keck | HOOB |
| San Joaquin tarweed | Holocarpha obconica (J.C. Clausen & Keck) Keck ssp. autumnalis Keck | HOOBA |
| San Joaquin tarweed | Holocarpha obconica (J.C. Clausen & Keck) Keck ssp. obconica | HOOBO |
| San Joaquin woollythread | Monolopia congdonii (Gray) B.G. Baldwin | MOCO7 |
| San Mateo woolly sunflower | Eriophyllum latilobum Rydb. | ERLA8 |
| San Patricio tansyaster | Psilactis heterocarpa (R.L. Hartman & M.A. Lane) D. Morgan | PSHE5 |
| San Pedro daisy | Lasianthaea podocephala (Gray) K. Becker | LAPO4 |
| San Pedro matchweed | Xanthocephalum gymnospermoides (Gray) Benth. & Hook. f. | XAGY |
| San Pedro snakeweed | Gutierrezia petradoria (Welsh & Goodrich) Welsh | GUPE2 |
| sand dune thistle | Cirsium pitcheri (Torr. ex Eat.) Torr. & Gray | CIPI |
| sand fleabane | Erigeron arenarioides (D.C. Eat. ex Gray) Gray ex Rydb. | ERAR20 |
| sand palafox | Palafoxia hookeriana Torr. & Gray | PAHO |
| sand palafox | Palafoxia hookeriana Torr. & Gray var. hookeriana | PAHOH |
| sand palafox | Palafoxia hookeriana Torr. & Gray var. minor Shinners | PAHOM |
| sand sagebrush | Artemisia filifolia Torr. | ARFI2 |
| sandaster | Corethrogyne DC. | CORET |
| sanddune cinchweed | Pectis glaucescens (Cass.) Keil | PEGL16 |
| Sanderson's burrobrush | Hymenoclea sandersonii (Welsh) N. Holmgren | HYSA2 |
| sandhill thistle | Cirsium repandum Michx. | CIRE2 |
| Sandhill's blazing star | Liatris cokeri Pyne & Stucky | LICO17 |
| sandwort daisy fleabane | Erigeron bellidiastrum Nutt. var. arenarius (Greene) Nesom | ERBEA |
| sandywoods chaffhead | Carphephorus bellidifolius (Michx.) Torr. & Gray | CABE4 |
| sanguin purple coneflower | Echinacea sanguinea Nutt. | ECSA |
| Santa Barbara wirelettuce | Stephanomeria elata Nutt. | STEL3 |
| Santa Cruz desertdandelion | Malacothrix squalida Greene | MASQ |
| Santa Cruz Island desertdandelion | Malacothrix indecora Greene | MAIN2 |
| Santa Cruz silverpuffs | Microseris decipiens Chambers | MIDE |
| Santa Cruz tarplant | Holocarpha macradenia (DC.) Greene | HOMA |
| Santa Maria | Vernonia albicaulis Pers. | VEAL5 |
| Santa Maria feverfew | Parthenium hysterophorus L. | PAHY |
| Santa Rita Mountain aster | Symphyotrichum potosinum (Gray) Nesom | SYPO5 |
| Santa Rita snakeroot | Ageratina paupercula (Gray) King & H.E. Robins. | AGPA13 |
| Santa Susana tarweed | Deinandra minthornii (Jepson) B.G. Baldwin | DEMI4 |
| Santo Domingo false willow | Baccharis myrsinites (Lam.) Pers. | BAMY |
| Santolina pincushion | Chaenactis santolinoides Greene | CHSA |
| Santolina rosmarinifolia | Santolina virens Mill. | SAVI14 |
| santonica | Artemisia cina O. Berg & C. F. Schmidt | ARCI8 |
| Sanvitalia ocymoides | Calyptocarpus blepharolepis B.L. Robins. | CABL2 |
| Sanvitalia procumbens | Sanvitalia angustifolia Gray | SAAN11 |
| Sartwellia flaveriae | Sartwellia puberula Rydb. | SAPU12 |
| Saussurea alpina | Serratula alpina L. [excluded] | SEAL13 |
| Saussurea angustifolia var. yukonensis | Saussurea angustifolia (Willd.) DC. ssp. yukonensis (Porsild) Cody | SAANY2 |
| Saussurea angustifolia var. yukonensis | Saussurea viscida Hult?n var. yukonensis (Porsild) Hult | SAVIY |
| Saussurea densa | Saussurea nuda Ledeb. ssp. densa (Hook.) G.W. Douglas | SANUD2 |
| Saussurea densa | Saussurea nuda Ledeb. var. densa (Hook.) Hult | SANUD |
| Saussurea viscida | Saussurea angustifolia (Willd.) DC. var. viscida (Hult?n) Welsh | SAANV |
| savannah aster | Eurybia chapmanii (Torr. & Gray) Nesom | EUCH11 |
| savannah sneezeweed | Helenium vernale Walt. | HEVE |
| saw-wort | Saussurea DC. | SAUSS |
| sawtooth bristleweed | Hazardia squarrosa (Hook. & Arn.) Greene var. grindelioides (DC.) W.D. Clark | HASQG2 |
| sawtooth bristleweed | Hazardia squarrosa (Hook. & Arn.) Greene var. obtusa (Greene) Jepson | HASQO2 |
| sawtooth candyleaf | Stevia serrata Cav. | STSE2 |
| sawtooth goldenbush | Hazardia squarrosa (Hook. & Arn.) Greene | HASQ2 |
| sawtooth goldenbush | Hazardia squarrosa (Hook. & Arn.) Greene var. squarrosa | HASQS2 |
| sawtooth sunflower | Helianthus grosseserratus Martens | HEGR4 |
| sawtooth wormwood | Artemisia serrata Nutt. | ARSE4 |
| scabland fleabane | Erigeron bloomeri Gray | ERBL |
| scabland fleabane | Erigeron bloomeri Gray var. bloomeri | ERBLB |
| scabland fleabane | Erigeron bloomeri Gray var. nudatus (Gray) Cronq. | ERBLN |
| scabland fleabane | Erigeron bloomeri Gray var. pubens Keck | ERBLP |
| scabland sagebrush | Artemisia rigida (Nutt.) Gray | ARRI2 |
| Scabrethia scabra ssp. attenuata | Wyethia scabra Hook. var. attenuata W.A. Weber | WYSCA |
| Scabrethia scabra ssp. canescens | Wyethia scabra Hook. var. canescens W.A. Weber | WYSCC |
| Scabrethia scabra ssp. scabra | Wyethia scabra Hook. | WYSC |
| Scabrethia scabra ssp. scabra | Wyethia scabra Hook. var. scabra Hook. [superfluous autonym] | WYSCS |
| scalebud | Anisocoma acaulis Torr. & Gray | ANAC |
| scaleleaf aster | Symphyotrichum adnatum (Nutt.) Nesom | SYAD |
| scaly blazing star | Liatris squarrosa (L.) Michx. | LISQ |
| scaly blazing star | Liatris squarrosa (L.) Michx. var. compacta Torr. & Gray | LISQC |
| scaly blazing star | Liatris squarrosa (L.) Michx. var. glabrata (Rydb.) Gaiser | LISQG |
| scaly blazing star | Liatris squarrosa (L.) Michx. var. hirsuta (Rydb.) Gaiser | LISQH |
| scaly blazing star | Liatris squarrosa (L.) Michx. var. squarrosa | LISQS |
| scarlet tasselflower | Emilia coccinea (Sims) G. Don | EMCO |
| scented pussytoes | Antennaria aromatica Evert | ANAR10 |
| scentless false mayweed | Tripleurospermum perforata (Merat) M. Lainz | TRPE21 |
| scepterbearing fleabane | Erigeron sceptrifer Nesom | ERSC11 |
| Schaffner's bahia | Bahia schaffneri S. Wats. | BASC4 |
| Schkuhria anthemoidea var. wrightii | Schkuhria wislizeni Gray var. wrightii (Gray) Blake | SCWIW |
| Schkuhria multiflora | Bahia neomexicana (Gray) Gray | BANE |
| Schkuhria multiflora | Schkuhria multiflora Hook. & Arn. var. multiflora Hook. & Arn. [superfluous autonym] | SCMUM3 |
| Schkuhria pinnata var. guatemalensis | Schkuhria pinnata (Lam.) Kuntze ex Thell. var. wislizeni (Gray) B.L. Turner | SCPIW |
| Schkuhria pinnata var. guatemalensis | Schkuhria wislizeni Gray | SCWI |
| Schkuhria pinnata var. guatemalensis | Schkuhria wislizeni Gray var. frustrata Blake | SCWIF |
| Schott's pygmycedar | Peucephyllum schottii Gray | PESC4 |
| Schott's wirelettuce | Stephanomeria schottii Gray | STSC5 |
| Schreber's aster | Eurybia schreberi (Nees) Nees | EUSC5 |
| Schweinitz's ragwort | Packera schweinitziana (Nutt.) W.A. Weber & A. L?ve | PASC19 |
| Schweinitz's sunflower | Helianthus schweinitzii Torr. & Gray | HESC3 |
| Scolymus hispanicus | Scolymus grandiflorus Desf. | SCGR7 |
| scorzonera | Scorzonera L. | SCORZ |
| Scorzonera laciniata | Podospermum laciniatum (L.) DC. | POLA12 |
| Scotch cottonthistle | Onopordum acanthium L. | ONAC |
| Scouler's woollyweed | Hieracium scouleri Hook. | HISC2 |
| Scouler's woollyweed | Hieracium scouleri Hook. var. nudicaule (Gray) Cronq. | HISCN |
| Scouler's woollyweed | Hieracium scouleri Hook. var. scouleri | HISCS2 |
| scratchdaisy | Croptilon Raf. | CROPT |
| Scribner's hawkweed | Hieracium scribneri Small | HISC11 |
| Scribner's ragwort | Senecio integerrimus Nutt. var. scribneri (Rydb.) T.M. Barkl. | SEINS |
| scrubland goldenaster | Chrysopsis subulata Small | CHSU6 |
| sea aster | Tripolium Nees | TRIPO3 |
| sea aster | Tripolium pannonicum (Jacq.) Dobrocz. | TRPA26 |
| sea dahlia | Coreopsis maritima (Nutt.) Hook. f. | COMA10 |
| sea wormwood | Artemisia maritima L. | ARMA27 |
| seacliff beggarticks | Bidens hillebrandiana (Drake) O. Deg. | BIHI |
| seacliff beggarticks | Bidens hillebrandiana (Drake) O. Deg. ssp. hillebrandiana | BIHIH |
| seacliff beggarticks | Bidens hillebrandiana (Drake) O. Deg. ssp. polycephala Nagata & Ganders | BIHIP |
| seacliff tetramolopium | Tetramolopium sylvae Lowrey | TESY |
| seacoast marshelder | Iva imbricata Walt. | IVIM |
| seaside fleabane | Erigeron glaucus Ker-Gawl. | ERGL3 |
| seaside goldenrod | Solidago sempervirens L. | SOSE |
| seaside goldenrod | Solidago sempervirens L. var. mexicana (L.) Fern. | SOSEM |
| seaside goldenrod | Solidago sempervirens L. var. sempervirens | SOSES |
| seaside goldfields | Lasthenia maritima (Gray) Ornduff | LAMA8 |
| seaside nehe | Lipochaeta succulenta (Hook. & Arn.) DC. | LISU7 |
| seaside ragwort | Senecio pseudoarnica Less. | SEPS |
| seaside tansy | Borrichia Adans. | BORRI |
| seaside woolly sunflower | Eriophyllum stoechadifolium Lag. | ERST9 |
| Seeman's sunbonnets | Leibnitzia lyrata (D. Don) Nesom | LELY6 |
| seep arnica | Arnica lonchophylla Greene ssp. arnoglossa (Greene) Maguire | ARLOA |
| semaphore thoroughwort | Eupatorium mikanioides Chapman | EUMI7 |
| Senecio actinella | Packera actinella (Greene) W.A. Weber & A. L?ve | PAAC9 |
| Senecio actinella | Senecio actinella Greene var. mogollonicus (Greene) Greenm. | SEACM |
| Senecio amplectens var. amplectens | Ligularia amplectens (Gray) W.A. Weber | LIAM4 |
| Senecio amplectens var. holmii | Ligularia amplectens (Gray) W.A. Weber var. holmii (Greene) Dorn | LIAMH |
| Senecio amplectens var. holmii | Ligularia holmii (Greene) W.A. Weber | LIHO2 |
| Senecio amplectens var. holmii | Senecio holmii Greene | SEHO |
| Senecio aquaticus ssp. barbareifolius | Senecio erraticus Bertol. | SEER7 |
| Senecio bigelovii var. bigelovii | Ligularia bigelovii (Gray) W.A. Weber | LIBI8 |
| Senecio bigelovii var. hallii | Ligularia bigelovii (Gray) W.A. Weber var. hallii (Gray) Dorn | LIBIH |
| Senecio cineraria | Senecio bicolor (Willd.) Todaro nom. illeg. ssp. cineraria (DC.) Chater | SEBIC |
| Senecio cineraria | Senecio bicolor auct. non (Willd.) Todaro nom. illeg. [misapplied] | SEBI4 |
| Senecio congestus | Cineraria congesta R. Br. | CICO8 |
| Senecio congestus | Senecio congestus (R. Br.) DC. ssp. tonsus (Fern.) A.& D. L?ve | SECOT |
| Senecio congestus | Senecio congestus (R. Br.) DC. var. palustris (L.) Fern. | SECOP |
| Senecio congestus | Senecio congestus (R. Br.) DC. var. tonsus Fern. | SECOT2 |
| Senecio congestus | Senecio palustris (L.) Hook. | SEPA12 |
| Senecio crassulus | Senecio crassulus Gray var. cusickii (Piper) Greenm. ex Peck | SECRC |
| Senecio elmeri | Senecio crepidineus Greene | SECR5 |
| Senecio eremophilus var. eremophilus | Senecio glaucifolius Rydb. | SEGL5 |
| Senecio eremophilus var. kingii | Senecio ambrosioides Rydb. | SEAM3 |
| Senecio eremophilus var. kingii | Senecio eremophilus Richards. ssp. kingii (Rydb.) G.W. Douglas & G. Ruyle-Douglas | SEERK2 |
| Senecio eremophilus var. kingii | Senecio kingii Rydb. | SEKI |
| Senecio eremophilus var. macdougalii | Senecio eremophilus Richards. ssp. macdougalii (Heller) G.W. Douglas & G. Ruyle-Douglas | SEERM2 |
| Senecio eremophilus var. macdougalii | Senecio macdougalii Heller | SEMA12 |
| Senecio flaccidus var. douglasii | Senecio douglasii DC. | SEDO2 |
| Senecio flaccidus var. douglasii | Senecio douglasii DC. var. tularensis Munz | SEDOT |
| Senecio flaccidus var. flaccidus | Senecio douglasii DC. ssp. longilobus (Benth.) W.A. Weber | SEDOL2 |
| Senecio flaccidus var. flaccidus | Senecio douglasii DC. var. jamesii (Torr. & Gray) Ediger ex Correll & Johnston | SEDOJ |
| Senecio flaccidus var. flaccidus | Senecio douglasii DC. var. longilobus (Benth.) L. Benson | SEDOL |
| Senecio flaccidus var. flaccidus | Senecio filifolius Nutt., non Berg. | SEFI2 |
| Senecio flaccidus var. flaccidus | Senecio longilobus Benth. | SELO |
| Senecio flaccidus var. monoensis | Senecio douglasii DC. var. monoensis (Greene) Jepson | SEDOM |
| Senecio flaccidus var. monoensis | Senecio monoensis Greene | SEMO9 |
| Senecio fremontii var. blitoides | Senecio blitoides Greene | SEBL2 |
| Senecio fremontii var. blitoides | Senecio carthamoides Greene | SECA12 |
| Senecio fremontii var. blitoides | Senecio fremontii Torr. & Gray ssp. blitoides (Greene) W.A. Weber | SEFRB2 |
| Senecio fremontii var. occidentalis | Senecio fremontii Torr. & Gray ssp. occidentalis (Gray) G.W. Douglas & G. Ruyle-Douglas | SEFRO2 |
| Senecio hydrophiloides | Senecio foetidus J.T. Howell | SEFO |
| Senecio hydrophiloides | Senecio foetidus J.T. Howell var. hydrophiloides (Rydb.) T.M. Barkl. ex Cronq. | SEFOH |
| Senecio hydrophiloides | Senecio pereziifolius Rydb. | SEPE5 |
| Senecio hydrophilus | Senecio sandvicensis auct. non Less. [misapplied] | SESA5 |
| Senecio integerrimus var. exaltatus | Senecio columbianus Greene | SECO12 |
| Senecio integerrimus var. exaltatus | Senecio exaltatus Nutt. | SEEX2 |
| Senecio integerrimus var. exaltatus | Senecio hookeri Torr. & Gray | SEHO3 |
| Senecio integerrimus var. exaltatus | Senecio integerrimus Nutt. var. vaseyi (Greenm.) Cronq. | SEINV2 |
| Senecio integerrimus var. exaltatus | Senecio lugens Richards. var. exaltatus (Nutt.) Gray | SELUE2 |
| Senecio integerrimus var. exaltatus | Senecio vaseyi Greenm. | SEVA2 |
| Senecio integerrimus var. ochroleucus | Senecio lugens Richards. var. ochroleucus Gray | SELUO |
| Senecio integerrimus var. scribneri | Senecio scribneri Rydb. | SESC6 |
| Senecio lugens | Senecio integerrimus Nutt. var. lugens (Richards.) Boivin | SEINL2 |
| Senecio multidentatus var. huachucanus | Senecio huachucanus Gray | SEHU |
| Senecio neowebsteri | Ligularia websteri (Greenm.) W.A. Weber | LIWE4 |
| Senecio neowebsteri | Senecio websteri Greenm., non Hook. f. | SEWE5 |
| Senecio pudicus | Ligularia pudica (Greene) W.A. Weber | LIPU6 |
| Senecio pudicus | Senecio cernuus Gray, non L. f. | SECE2 |
| Senecio riddellii | Senecio spartioides Torr. & Gray var. fremontii (Torr. & Gray) Greenm. ex L.O. Williams | SESPF |
| Senecio riddellii | Senecio spartioides Torr. & Gray var. parksii (Cory) Shinners | SESPP3 |
| Senecio scorzonella | Senecio covillei Greene | SECO13 |
| Senecio scorzonella | Senecio covillei Greene var. scorzonella (Greene) Jepson | SECOS |
| Senecio serra var. admirabilis | Senecio admirabilis Greene | SEAD5 |
| Senecio serra var. serra | Senecio serra Hook. var. altior Jepson | SESEA2 |
| Senecio serra var. serra | Senecio serra Hook. var. integriusculus Gray | SESEI |
| Senecio soldanella | Ligularia soldanella (Gray) W.A. Weber | LISO |
| Senecio spartioides var. multicapitatus | Senecio multicapitatus Greenm. ex Rydb. | SEMU2 |
| Senecio spartioides var. spartioides | Senecio spartioides Torr. & Gray var. granularis Maguire & A. Holmgren ex Cronq. | SESPG |
| Senecio spartioides var. spartioides | Senecio toiyabensis Welsh & Goodrich | SETO6 |
| Senecio taraxacoides | Ligularia taraxacoides (Gray) W.A. Weber | LITA |
| Senecio taraxacoides | Senecio amplectens Gray var. taraxacoides Gray | SEAMT |
| Senecio triangularis | Senecio gibbsonsii Greene | SEGI4 |
| Senecio triangularis | Senecio triangularis Hook. var. angustifolius G.N. Jones | SETRA |
| separateleaf chickensage | Sphaeromeria diversifolia (D.C. Eat.) Rydb. | SPDI5 |
| sepi | Neurolaena lobata (L.) Cass. | NELO3 |
| Sequoia false goldenaster | Heterotheca monarchensis York, Shevock & Semple | HEMO14 |
| Sericocarpus asteroides | Aster asteroides (L.) MacMillan | ASAS10 |
| Sericocarpus asteroides | Aster paternus Cronq. | ASPA6 |
| Sericocarpus asteroides | Conyza asteroides L. | COAS4 |
| Sericocarpus linifolius | Aster solidagineus Michx. | ASSO2 |
| Sericocarpus linifolius | Conyza linifolia L. | COLI10 |
| Sericocarpus oregonensis var. californicus | Aster oregonensis (Nutt.) Cronq. ssp. californicus (Dur.) Keck | ASORC |
| Sericocarpus oregonensis var. californicus | Sericocarpus californicus Dur. | SECA13 |
| Sericocarpus oregonensis var. californicus | Sericocarpus oregonensis Nutt. ssp. californicus (Dur.) Ferris | SEORC |
| Sericocarpus oregonensis var. oregonensis | Aster oregonensis (Nutt.) Cronq. | ASOR |
| Sericocarpus rigidus | Aster curtus Cronq. | ASCU2 |
| Sericocarpus tortifolius | Aster bifoliatus (Walt.) Ahles | ASBI7 |
| Sericocarpus tortifolius | Aster tortifolius Michx. | ASTO6 |
| Sericocarpus tortifolius | Conyza bifoliata Walt. | COBI7 |
| Sericocarpus tortifolius | Sericocarpus acutisquamosus (Nash) Small | SEAC5 |
| Sericocarpus tortifolius | Sericocarpus bifoliatus (Walt.) Porter | SEBI7 |
| serpentine arnica | Arnica cernua T.J. Howell | ARCE |
| serpentine aster | Symphyotrichum depauperatum (Fern.) Nesom | SYDE2 |
| serpentine bristleweed | Hazardia stenolepis (Hall) Hoover | HAST4 |
| serpentine erigeron | Erigeron serpentinus Nesom | ERSE8 |
| serpentine fleabane | Erigeron angustatus Greene | ERAN19 |
| serpentine goldenbush | Ericameria ophitidis (J.T. Howell) Nesom | EROP2 |
| serpentine sunflower | Helianthus bolanderi Gray | HEBO3 |
| serpentine tarweed | Harmonia doris-nilesiae (T.W. & J.P. Nelson) B.G. Baldwin | HADO2 |
| serpentweed | Tonestus A. Nels. | TONES |
| serrate balsamroot | Balsamorhiza serrata A. Nels. & J.F. Macbr. | BASE2 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners | HESE |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. bolanderi (Gray) Semple | HESEB2 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. echioides (Benth.) Semple | HESEE2 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. echioides (Benth.) Semple var. bolanderioides Semple | HESEB3 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. echioides (Benth.) Semple var. camphorata (Eastw.) Semple | HESEC |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. echioides (Benth.) Semple var. echioides | HESEE3 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. fastigiata (Greene) Semple | HESEF2 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. fastigiata (Greene) Semple var. fastigiata | HESEF3 |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. fastigiata (Greene) Semple var. sanjacintensis Semple | HESES |
| sessileflower false goldenaster | Heterotheca sessiliflora (Nutt.) Shinners ssp. sessiliflora | HESES2 |
| sessileleaf false oxtongue | Blumea sessiliflora Dcne. | BLSE2 |
| shadowy goldenrod | Solidago sciaphila Steele | SOSC |
| shaggy blackfoot | Melampodium strigosum Stuessy | MEST8 |
| shaggy blazing star | Liatris pilosa (Ait.) Willd. | LIPI7 |
| shaggy blazing star | Liatris pilosa (Ait.) Willd. var. elegantula (Greene) comb. nov. ined. | LIPIE |
| shaggy blazing star | Liatris pilosa (Ait.) Willd. var. lasia (Fern. & Grisc.) comb. nov. ined. | LIPIL |
| shaggy blazing star | Liatris pilosa (Ait.) Willd. var. pilosa | LIPIP |
| shaggy fleabane | Erigeron pumilus Nutt. | ERPU2 |
| shaggy fleabane | Erigeron pumilus Nutt. ssp. intermedius Cronq. | ERPUI |
| shaggy fleabane | Erigeron pumilus Nutt. ssp. intermedius Cronq. var. gracilior Cronq. | ERPUG |
| shaggy fleabane | Erigeron pumilus Nutt. ssp. intermedius Cronq. var. intermedius (Cronq.) Cronq. | ERPUI2 |
| shaggy fleabane | Erigeron pumilus Nutt. ssp. pumilus | ERPUP3 |
| shaggy soldier | Galinsoga quadriradiata Cav. | GAQU |
| shale barren pussytoes | Antennaria virginica Stebbins | ANVI13 |
| shale barren ragwort | Packera antennariifolia (Britt.) W.A. Weber & A. L?ve | PAAN7 |
| sharp blazing star | Liatris acidota Engelm. & Gray | LIAC |
| sharpleaf gumweed | Grindelia acutifolia Steyermark | GRAC |
| sharppoint prairie-dandelion | Nothocalais cuspidata (Pursh) Greene | NOCU |
| Shasta chaenactis | Chaenactis suffrutescens Gray | CHSU |
| Shasta County arnica | Arnica venosa Hall | ARVE |
| Shasta helianthella | Helianthella californica Gray ssp. shastensis (W.A. Weber) W.A. Weber | HECAS4 |
| Shasta snakeroot | Ageratina shastensis (Taylor & Stebbins) King & H.E. Robins. | AGSH2 |
| Shasta tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. shastensis (Gray) B.L. Turner | MACAS3 |
| Shasta tarweed | Madia citrigracilis Keck | MACI |
| sheep fleabane | Erigeron ovinus Cronq. | EROV2 |
| shining fleabane | Erigeron barbellulatus Greene | ERBA3 |
| Shinnersoseris rostrata | Lygodesmia rostrata (Gray) Gray | LYRO2 |
| shiny coneflower | Rudbeckia nitida Nutt. | RUNI3 |
| shiny goldenrod | Oligoneuron nitidum (Torr. & Gray) Small | OLNI |
| Shockley's goldenhead | Acamptopappus shockleyi Gray | ACSH |
| shore aster | Symphyotrichum tradescantii (L.) Nesom | SYTR |
| short woollyheads | Psilocarphus brevissimus Nutt. | PSBR |
| short woollyheads | Psilocarphus brevissimus Nutt. var. brevissimus | PSBRB |
| Short's aster | Symphyotrichum shortii (Lindl.) Nesom | SYSH |
| Short's goldenrod | Solidago shortii Torr. & Gray | SOSH |
| short-rayed alkali aster | Symphyotrichum frondosum (Nutt.) Nesom | SYFR2 |
| shorthair goldenrod | Solidago canadensis L. var. gilvocanescens Rydb. | SOCAG |
| shortleaf alpinegold | Hulsea brevifolia Gray | HUBR |
| shortleaf baccharis | Baccharis brachyphylla Gray | BABR |
| shortleaf blazing star | Liatris tenuifolia Nutt. | LITE6 |
| shortleaf blazing star | Liatris tenuifolia Nutt. var. quadriflora Chapman | LITEQ |
| shortleaf blazing star | Liatris tenuifolia Nutt. var. tenuifolia | LITET2 |
| shortleaf dwarf-cudweed | Hesperevax sparsiflora (Gray) Greene var. brevifolia (Gray) Morefield | HESPB |
| shortleaf jefea | Jefea brevifolia (Gray) Strother | JEBR |
| shortleaf sneezeweed | Helenium brevifolium (Nutt.) Wood | HEBR |
| shortray fleabane | Erigeron lonchophyllus Hook. | ERLO |
| shortray rockdaisy | Perityle microglossa Benth. | PEMI5 |
| shortray zinnia | Zinnia anomala Gray | ZIAN |
| shortspine horsebrush | Tetradymia spinosa Hook. & Arn. | TESP2 |
| showy alpine ragwort | Senecio amplectens Gray | SEAM |
| showy alpine ragwort | Senecio amplectens Gray var. amplectens | SEAMA |
| showy coneflower | Rudbeckia alpicola Piper | RUAL17 |
| showy dandelion | Taraxacum spectabile Dahlst. | TASP4 |
| showy goldeneye | Heliomeris multiflora Nutt. | HEMU3 |
| showy goldeneye | Heliomeris multiflora Nutt. var. brevifolia (Greene ex Woot. & Standl.) Yates | HEMUB |
| showy goldeneye | Heliomeris multiflora Nutt. var. multiflora | HEMUM |
| showy goldenrod | Solidago erecta Pursh | SOER |
| showy goldenrod | Solidago speciosa Nutt. | SOSP2 |
| showy goldenrod | Solidago speciosa Nutt. var. jejunifolia (Steele) Cronq. | SOSPJ |
| showy goldenrod | Solidago speciosa Nutt. var. pallida Porter | SOSPP |
| showy goldenrod | Solidago speciosa Nutt. var. rigidiuscula Torr. & Gray | SOSPR |
| showy goldenrod | Solidago speciosa Nutt. var. speciosa | SOSPS4 |
| showy nerveray | Tetragonotheca repanda (Buckl.) Small | TERE2 |
| showy pussytoes | Antennaria pulcherrima (Hook.) Greene | ANPU |
| showy raillardella | Raillardella pringlei Greene | RAPR |
| showy sunflower | Helianthus niveus (Benth.) Brandeg. | HENI3 |
| showy sunflower | Helianthus niveus (Benth.) Brandeg. ssp. canescens (Gray) Heiser | HENIC |
| showy tarweed | Madia elegans D. Don ex Lindl. ssp. densifolia (Greene) Keck | MAELD |
| showy Townsend daisy | Townsendia florifer (Hook.) Gray | TOFL5 |
| shrubby alkaliaster | Machaeranthera carnosa (Gray) Nesom | MACA17 |
| shrubby alkaliaster | Machaeranthera carnosa (Gray) Nesom var. carnosa | MACAC5 |
| shrubby alkaliaster | Machaeranthera carnosa (Gray) Nesom var. intricata (Gray) Nesom | MACAI3 |
| shrubby brickellbush | Brickellia frutescens Gray | BRFR |
| shrubby bullseye | Gochnatia hypoleuca (DC.) Gray | GOHY |
| shrubby daisybush | Osteospermum fruticosum (L.) Norl. | OSFR4 |
| shrubby mayweed | Oncosiphon suffruticosum (L.) K?llersj? | ONSU2 |
| shrubby thoroughwort | Koanophyllon solidaginifolium (Gray) King & H.E. Robins. | KOSO |
| shrubland beggarticks | Bidens sandvicensis Less. | BISA2 |
| shrubland beggarticks | Bidens sandvicensis Less. ssp. confusa Nagata & Ganders | BISAC |
| shrubland beggarticks | Bidens sandvicensis Less. ssp. sandvicensis | BISAS2 |
| shrubland dubautia | Dubautia linearis (Gaud.) Keck | DULI |
| shrubland dubautia | Dubautia linearis (Gaud.) Keck ssp. linearis | DULIL |
| shrubland dubautia | Dubautia linearis (Gaud.) Keck ssp. opposita (Sherff) G.D. Carr | DULIO |
| shrubland nehe | Lipochaeta lobata (Gaud.) DC. | LILO2 |
| shrubland nehe | Lipochaeta lobata (Gaud.) DC. var. leptophylla O. Deg. & Sherff | LILOL |
| shrubland nehe | Lipochaeta lobata (Gaud.) DC. var. lobata | LILOL2 |
| Siberian wormwood | Artemisia laciniata Willd. | ARLA9 |
| Siberian yarrow | Achillea sibirica Ledeb. | ACSI |
| sickle tickseed | Coreopsis falcata Boynt. | COFA |
| sickleleaf silkgrass | Pityopsis falcata (Pursh) Nutt. | PIFA |
| Sierra Ancha fleabane | Erigeron anchana Nesom | ERAN17 |
| Sierra Blanca least-daisy | Ionactis elegans (Soreng & Spellenberg) Nesom | IOEL |
| Sierra erigeron | Erigeron petrophilus Greene var. sierrensis Nesom | ERPES2 |
| Sierra foothill silverpuffs | Microseris acuminata Greene | MIAC |
| Sierra lessingia | Lessingia leptoclada Gray | LELE7 |
| Sierra pussytoes | Antennaria pulchella Greene | ANPU8 |
| Sierra ragwort | Senecio scorzonella Greene | SESC |
| Sierra tidytips | Layia pentachaeta Gray | LAPE |
| Sierra tidytips | Layia pentachaeta Gray ssp. albida Keck | LAPEA |
| Sierra tidytips | Layia pentachaeta Gray ssp. pentachaeta | LAPEP |
| silkgrass | Pityopsis Nutt. | PITYO2 |
| silkleaf | Lagascea mollis Cav. | LAMO5 |
| silky balsamroot | Balsamorhiza sericea W.A. Weber | BASE4 |
| silky raillardella | Raillardella argentea (Gray) Gray | RAAR |
| Silphium asteriscus var. angustatum | Silphium angustum (Gray) Small | SIAN9 |
| Silphium asteriscus var. angustatum | Silphium dentatum Ell. var. angustatum (Gray) Perry | SIDEA |
| Silphium asteriscus var. asteriscus | Silphium asteriscus L. var. scabrum Nutt. | SIASS |
| Silphium asteriscus var. laevicaule | Silphium asteriscus L. var. dentata (Ell.) Chapman | SIASD2 |
| Silphium asteriscus var. laevicaule | Silphium dentatum Ell. | SIDE8 |
| Silphium asteriscus var. laevicaule | Silphium elliottii Small | SIEL4 |
| Silphium asteriscus var. laevicaule | Silphium incisum Greene | SIIN19 |
| Silphium asteriscus var. laevicaule | Silphium nodum Small | SINO2 |
| Silphium compositum var. compositum | Silphium orae Small | SIOR5 |
| Silphium compositum var. ovatifolium | Silphium compositum Michx. ssp. ovatifolium (Torr. & Gray) Sweeny & T.R. Fisher | SICOO |
| Silphium compositum var. ovatifolium | Silphium ovatifolium (Torr. & Gray) Small | SIOV2 |
| Silphium compositum var. reniforme | Silphium compositum Michx. ssp. reniforme (Raf. ex Nutt.) Sweeny & T.R. Fisher | SICOR |
| Silphium compositum var. reniforme | Silphium reniforme Raf. ex Nutt. | SIRE9 |
| Silphium compositum var. reniforme | Silphium terebinthinaceum Ell., non Jacq. | SITE3 |
| Silphium compositum var. venosum | Silphium compositum Michx. ssp. venosum (Small) Sweeny & T.R. Fisher | SICOV |
| Silphium compositum var. venosum | Silphium lapsuum Small | SILA14 |
| Silphium compositum var. venosum | Silphium venosum Small | SIVE2 |
| Silphium gracile | Silphium simpsonii Greene var. wrightii Perry | SISIW |
| Silphium integrifolium var. integrifolium | Silphium laevigatum Pursh | SILA13 |
| Silphium integrifolium var. laeve | Silphium speciosum Nutt. | SISP3 |
| Silphium perfoliatum var. connatum | Silphium connatum L. | SICO11 |
| Silphium perfoliatum var. connatum | Silphium perfoliatum L. ssp. connatum (L.) Cruden | SIPEC |
| Silphium perfoliatum var. connatum | Silphium scabrum Moench, non Walt. | SISC5 |
| Silphium pinnatifidum | Silphium chickamaugense Canby | SICH3 |
| Silphium pinnatifidum | Silphium terebinthinaceum Jacq. var. pinnatifidum (Ell.) Gray | SITEP |
| Silphium radula | Silphium asperrimum Hook. | SIAS |
| Silphium radula | Silphium dentatum Ell. var. gatesii (C. Mohr) Ahles | SIDEG |
| Silphium radula | Silphium gatesii C. Mohr | SIGA2 |
| Silphium terebinthinaceum var. terebinthinaceum | Silphium rumicifolium Small | SIRU3 |
| Silphium trifoliatum var. latifolium | Silphium confertifolium Small | SICO12 |
| Silphium trifoliatum var. latifolium | Silphium glabrum Eggert ex Small | SIGL8 |
| Silphium trifoliatum var. trifoliatum | Silphium atropurpureum Retz. ex Willd. | SIAT4 |
| Silphium trifoliatum var. trifoliatum | Silphium laevigatum Ell., non Pursh | SILA17 |
| silver burr ragweed | Ambrosia chamissonis (Less.) Greene | AMCH4 |
| silver chickensage | Sphaeromeria argentea Nutt. | SPAR2 |
| silver fleabane | Erigeron argentatus Gray | ERAR3 |
| silver pussytoes | Antennaria argentea Benth. | ANAR5 |
| silver pygmycudweed | Evax candida (Torr. & Gray) Gray | EVCA |
| silver ragwort | Senecio cineraria DC. | SECI2 |
| silver sagebrush | Artemisia cana Pursh | ARCA13 |
| silver sagebrush | Artemisia cana Pursh ssp. bolanderi (Gray) G.H. Ward | ARCAB3 |
| silver sagebrush | Artemisia cana Pursh ssp. cana | ARCAC5 |
| silver sagebrush | Artemisia cana Pursh ssp. viscidula (Osterhout) Beetle | ARCAV2 |
| silverback | Luina Benth. | LUINA |
| silvercrown | Cacaliopsis nardosmia (Gray) Gray | CANA5 |
| silverleaf sunflower | Helianthus argophyllus Torr. & Gray | HEAR3 |
| silverleaf sunray | Enceliopsis argophylla (D.C. Eat.) A. Nels. | ENAR |
| silverling | Baccharis glomeruliflora Pers. | BAGL |
| silverpuff | Chaptalia texana Greene | CHTE6 |
| silverpuffs | Microseris D. Don | MICRO6 |
| silversword | Argyroxiphium DC. | ARGYR |
| Silybum marianum | Carduus marianus L. | CAMA32 |
| Silybum marianum | Mariana mariana (L.) Hill | MAMA27 |
| Simmonds's aster | Symphyotrichum simmondsii (Small) Nesom | SYSI3 |
| simple-stem everlasting | Gamochaeta simplicicaulis (Willd. ex Spreng.) Cabrera | GASI5 |
| Simpson's rosinweed | Silphium simpsonii Greene | SISI |
| Simsia lagasceiformis | Simsia exaristata Gray | SIEX |
| Simsia lagasceiformis | Simsia exaristata Gray var. perplexa Blake | SIEXP |
| singleflower knapweed | Centaurea uniflora Turra | CEUN2 |
| singleflower knapweed | Centaurea uniflora Turra ssp. nervosa (Willd.) Bonnier & Layens | CEUNN |
| singlehead goldenbush | Ericameria suffruticosa (Nutt.) Nesom | ERSU13 |
| singlehead pussytoes | Antennaria solitaria Rydb. | ANSO |
| singlewhorl burrobrush | Hymenoclea monogyra Torr. & Gray ex Gray | HYMO |
| Siskiyou fleabane | Erigeron cervinus Greene | ERCE |
| Siskiyou Mountain ragwort | Packera macounii (Greene) W.A. Weber & A. L?ve | PAMA35 |
| Sivinsk's erigeron | Erigeron sivinskii Nesom | ERSI9 |
| skeletonleaf burr ragweed | Ambrosia tomentosa Nutt. | AMTO3 |
| skeletonplant | Lygodesmia D. Don | LYGOD |
| skeletonweed | Chaetadelpha Gray ex S. Wats. | CHAET |
| skyblue aster | Symphyotrichum oolentangiense (Riddell) Nesom | SYOO |
| skyblue aster | Symphyotrichum oolentangiense (Riddell) Nesom var. oolentangiense | SYOOO |
| skyblue aster | Symphyotrichum oolentangiense (Riddell) Nesom var. poaceum (Burgess) Nesom | SYOOP |
| sleepydaisy | Xanthisma DC. | XANTH |
| slender aster | Eurybia compacta Nesom | EUCO37 |
| slender blazing star | Liatris gracilis Pursh | LIGR9 |
| slender creeping-oxeye | Sphagneticola gracilis (L.C. Rich.) Pruski | SPGR10 |
| slender cudweed | Gnaphalium exilifolium A. Nels. | GNEX |
| slender fleabane | Erigeron tener (Gray) Gray | ERTE6 |
| slender goldentop | Euthamia caroliniana (L.) Greene ex Porter & Britt. | EUCA26 |
| slender goldentop | Euthamia galetorum Greene | EUGA2 |
| slender goldenweed | Machaeranthera gracilis (Nutt.) Shinners | MAGR10 |
| slender greenthread | Thelesperma simplicifolium Gray | THSI |
| slender hawksbeard | Crepis atribarba Heller | CRAT |
| slender hawksbeard | Crepis atribarba Heller ssp. atribarba | CRATA2 |
| slender hawksbeard | Crepis atribarba Heller ssp. originalis (Babcock & Stebbins) Babcock & Stebbins | CRATO |
| slender hawkweed | Hieracium gracile Hook. | HIGR |
| slender hawkweed | Hieracium gracile Hook. var. gracile | HIGRG |
| slender poreleaf | Porophyllum gracile Benth. | POGR5 |
| slender rattlesnakeroot | Prenanthes autumnalis Walt. | PRAU |
| slender rosinweed | Silphium gracile Gray | SIGR4 |
| slender scratchdaisy | Croptilon divaricatum (Nutt.) Raf. | CRDI17 |
| slender sowthistle | Sonchus tenerrimus L. | SOTE3 |
| slender sunflower | Helianthus gracilentus Gray | HEGR3 |
| slender tansyaster | Psilactis tenuis S. Wats. | PSTE6 |
| slender tarweed | Madia subspicata Keck | MASU |
| slender woollyheads | Psilocarphus tenellus Nutt. | PSTE |
| slender woollyheads | Psilocarphus tenellus Nutt. var. globiferus (Bertero ex DC.) Morefield | PSTEG |
| slender woollyheads | Psilocarphus tenellus Nutt. var. tenellus | PSTET2 |
| slenderleaf fleabane | Erigeron tenuis Torr. & Gray | ERTE7 |
| slenderstem lessingia | Lessingia nemaclada Greene | LENE3 |
| slenderstem lessingia | Lessingia nemaclada Greene var. albiflora (Eastw.) J.T. Howell | LENEA |
| slenderstem lessingia | Lessingia nemaclada Greene var. nemaclada | LENEN |
| slimleaf burr ragweed | Ambrosia tenuifolia Spreng. | AMTE5 |
| slimleaf sneezeweed | Helenium linifolium Rydb. | HELI |
| slimlobe bahia | Bahia biternata Gray | BABI3 |
| slimlobe beggarticks | Bidens tenuisecta Gray | BITE |
| slough thistle | Cirsium crassicaule (Greene) Jepson | CICR |
| small beggarticks | Bidens discoidea (Torr. & Gray) Britt. | BIDI |
| small blacktip ragwort | Senecio lugens Richards. | SELU |
| small palafox | Palafoxia callosa (Nutt.) Torr. & Gray | PACA3 |
| small pussytoes | Antennaria howellii Greene ssp. petaloidea (Fern.) Bayer | ANHOP |
| small rocklettuce | Pinaropappus parvus Blake | PIPA |
| small tarweed | Madia exigua (Sm.) Gray | MAEX |
| small wirelettuce | Stephanomeria exigua Nutt. | STEX |
| small wirelettuce | Stephanomeria exigua Nutt. ssp. exigua | STEXE |
| small woodland sunflower | Helianthus microcephalus Torr. & Gray | HEMI3 |
| Small's goldenrod | Solidago pinetorum Small | SOPI |
| Small's ragwort | Packera anonyma (Wood) W.A. Weber & A. L?ve | PAAN6 |
| small-leaf pussytoes | Antennaria parvifolia Nutt. | ANPA4 |
| small-leaf squarestem | Melanthera parvifolia Small | MEPA3 |
| small-leaved rockdaisy | Perityle megalocephala (S. Wats.) J.F. Macbr. var. oligophylla A. Powell | PEMEO |
| smallanthus | Smallanthus Mackenzie ex Small | SMALL |
| Smallanthus uvedalius | Osteospermum uvedalia L. | OSUV |
| Smallanthus uvedalius | Polymnia uvedalia (L.) L. | POUV2 |
| Smallanthus uvedalius | Polymnia uvedalia (L.) L. var. densipilis Blake | POUVD |
| Smallanthus uvedalius | Polymnia uvedalia (L.) L. var. floridana Blake | POUVF |
| smallflower creepingoxeye | Wedelia parviflora L.C. Rich. | WEPA |
| smallflower desert-chicory | Pyrrhopappus pauciflorus (D. Don) DC. | PYPA4 |
| smallflower hawksbeard | Crepis pulchra L. | CRPU3 |
| smallflower oxtongue | Picris pauciflora Willd. | PIPA9 |
| smallflower tansyaster | Machaeranthera parviflora Gray | MAPA |
| smallflower thoroughwort | Eupatorium semiserratum DC. | EUSE |
| smallflower western rosinweed | Calycadenia pauciflora Gray | CAPA6 |
| smallfruit beggarticks | Bidens mitis (Michx.) Sherff | BIMI |
| smallhead arnica | Arnica gracilis Rydb. | ARGR14 |
| smallhead aster | Symphyotrichum parviceps (Burgess) Nesom | SYPA10 |
| smallhead blazing star | Liatris microcephala (Small) K. Schum. | LIMI7 |
| smallhead catsear | Hypochaeris microcephala (Schultz-Bip.) Cabrera | HYMI5 |
| smallhead catsear | Hypochaeris microcephala (Schultz-Bip.) Cabrera var. albiflora (Kuntze) Cabrera | HYMIA |
| smallhead catsear | Hypochaeris microcephala (Schultz-Bip.) Cabrera var. microcephala (Schultz-Bip.) Cabrera [excluded] | HYMIM2 |
| smallhead doll's daisy | Boltonia diffusa Ell. | BODI |
| smallhead doll's daisy | Boltonia diffusa Ell. var. diffusa | BODID |
| smallhead doll's daisy | Boltonia diffusa Ell. var. interior Fern. & Grisc. | BODII |
| smallhead goldenweed | Pyrrocoma liatriformis Greene | PYLI |
| smallhead heathgoldenrod | Tonestus microcephalus (Cronq.) Nesom & D. Morgan | TOMI |
| smallhead sneezeweed | Helenium microcephalum DC. | HEMI |
| smallhead sneezeweed | Helenium microcephalum DC. var. microcephalum | HEMIM |
| smallhead sneezeweed | Helenium microcephalum DC. var. ooclinium (Gray) Bierner | HEMIO2 |
| smallhead star-thistle | Centaurea calcitrapoides L. | CECA5 |
| smallhead tetramolopium | Tetramolopium conyzoides (Gray) Hbd. | TECO6 |
| smallheaded Townsend daisy | Townsendia microcephala Dorn | TOMI4 |
| smallray goldfields | Lasthenia microglossa (DC.) Greene | LAMI4 |
| smallray swampwort | Enydra sessilis (Sw.) DC. | ENSE |
| Smith's sunflower | Helianthus smithii Heiser | HESM |
| smooth aster | Eucephalus glabratus (Greene) Greene | EUGL18 |
| smooth baccharis | Baccharis plummerae Gray ssp. glabrata Hoover | BAPLG |
| smooth beggartick | Bidens laevis (L.) B.S.P. | BILA |
| smooth blue aster | Symphyotrichum laeve (L.) A.& D. L?ve | SYLA3 |
| smooth blue aster | Symphyotrichum laeve (L.) A.& D. L?ve var. concinnum (Willd.) Nesom | SYLAC |
| smooth blue aster | Symphyotrichum laeve (L.) A.& D. L?ve var. laeve | SYLAL3 |
| smooth blue aster | Symphyotrichum laeve (L.) A.& D. L?ve var. purpuratum (Nees) Nesom | SYLAP |
| smooth catsear | Hypochaeris glabra L. | HYGL2 |
| smooth desertdandelion | Malacothrix glabrata (Gray ex D.C. Eat.) Gray | MAGL3 |
| smooth dubautia | Dubautia laevigata Gray | DULA2 |
| smooth elephantsfoot | Elephantopus nudatus Gray | ELNU |
| smooth goldfields | Lasthenia glaberrima DC. | LAGL3 |
| smooth hawksbeard | Crepis capillaris (L.) Wallr. | CRCA3 |
| smooth hawkweed | Hieracium laevigatum Willd. | HILA4 |
| smooth lessingia | Lessingia micradenia Greene var. glabrata (Keck) Ferris | LEMIG |
| smooth oxeye | Heliopsis helianthoides (L.) Sweet | HEHE5 |
| smooth oxeye | Heliopsis helianthoides (L.) Sweet var. gracilis (Nutt.) Gandhi & Thomas | HEHEG |
| smooth oxeye | Heliopsis helianthoides (L.) Sweet var. helianthoides | HEHEH |
| smooth oxeye | Heliopsis helianthoides (L.) Sweet var. occidentalis (T.R. Fisher) Steyermark | HEHEO |
| smooth oxeye | Heliopsis helianthoides (L.) Sweet var. scabra (Dunal) Fern. | HEHES |
| smooth purple coneflower | Echinacea laevigata (C.L. Boynt. & Beadle) Blake | ECLA |
| smooth sunflower | Helianthus laevigatus Torr. & Gray | HELA2 |
| smooth tidytips | Layia chrysanthemoides (DC.) Gray | LACH |
| smooth Townsend daisy | Townsendia formosa Greene | TOFO |
| smooth violet prairie aster | Symphyotrichum turbinellum (Lindl.) Nesom | SYTU2 |
| smooth white aster | Symphyotrichum porteri (Gray) Nesom | SYPO4 |
| smooth white oldfield aster | Symphyotrichum racemosum (Ell.) Nesom | SYRA5 |
| smooth woodyaster | Xylorhiza glabriuscula Nutt. | XYGL |
| smooth woodyaster | Xylorhiza glabriuscula Nutt. var. glabriuscula | XYGLG |
| smooth woodyaster | Xylorhiza glabriuscula Nutt. var. linearifolia T.J. Wats. | XYGLL |
| snake's head | Malacothrix coulteri Harvey & Gray | MACO3 |
| snakeroot | Ageratina Spach | AGERA2 |
| snakeweed | Gutierrezia Lag. | GUTIE |
| sneezeweed | Achillea ptarmica L. | ACPT |
| sneezeweed | Helenium L. | HELEN |
| snow arnica | Arnica frigida C.A. Mey. ex Iljin | ARFR2 |
| snow arnica | Arnica frigida C.A. Mey. ex Iljin ssp. frigida | ARFRF3 |
| snow squarestem | Melanthera nivea (L.) Small | MENI3 |
| snowy thistle | Cirsium occidentale (Nutt.) Jepson var. candidissimum (Greene) J.F. Macbr. | CIOCC |
| soft aster | Symphyotrichum molle (Rydb.) Nesom | SYMO2 |
| soft elephantsfoot | Elephantopus mollis Kunth | ELMO5 |
| soft goldenaster | Chrysopsis pilosa Nutt. | CHPI8 |
| soft greeneyes | Berlandiera pumila (Michx.) Nutt. | BEPU2 |
| soft greeneyes | Berlandiera pumila (Michx.) Nutt. var. pumila | BEPUP3 |
| soft thistle | Cirsium carolinianum (Walt.) Fern. & Schub. | CICA7 |
| soft western rosinweed | Calycadenia mollis Gray | CAMO4 |
| softhair coneflower | Rudbeckia mollis Ell. | RUMO |
| Solidago altissima | Solidago altissima L. var. altissima L. [superfluous autonym] | SOALA |
| Solidago altissima | Solidago altissima L. var. pluricephala M.C. Johnston | SOALP |
| Solidago altissima | Solidago altissima L. var. procera (Ait.) Fern. | SOALP2 |
| Solidago altissima | Solidago canadensis L. var. scabra Torr. & Gray | SOCAS5 |
| Solidago altissima | Solidago hirsutissima P. Mill. | SOHI7 |
| Solidago altissima | Solidago lunellii Rydb. | SOLU7 |
| Solidago arguta var. arguta | Solidago tarda Mackenzie | SOTA2 |
| Solidago arguta var. boottii | Solidago arguta Ait. ssp. boottii (Hook.) G. Morton | SOARB2 |
| Solidago arguta var. boottii | Solidago boottii Hook. | SOBO |
| Solidago arguta var. boottii | Solidago dispersa Small | SODI4 |
| Solidago arguta var. caroliniana | Solidago arguta Ait. ssp. caroliniana (Gray) G. Morton | SOARC2 |
| Solidago arguta var. caroliniana | Solidago arguta Ait. ssp. pseudoyadkinensis G. Morton | SOARP |
| Solidago arguta var. caroliniana | Solidago boottii Hook. var. caroliniana (Gray) Cronq. | SOBOC |
| Solidago arguta var. caroliniana | Solidago yadkinensis (Porter) Small | SOYA |
| Solidago arguta var. harrisii | Solidago harrisii Steele | SOHA4 |
| Solidago arguta var. neurolepis | Solidago neurolepis Fern. | SONE3 |
| Solidago auriculata | Solidago amplexicaulis Torr. & Gray ex Gray, non Martens | SOAM5 |
| Solidago auriculata | Solidago notabilis Mackenzie | SONO2 |
| Solidago brachyphylla | Solidago boottii Hook. var. brachyphylla (Chapman) Gray | SOBOB2 |
| Solidago caesia | Solidago axillaris Pursh | SOAX |
| Solidago caesia | Solidago caesia L. var. axillaris (Pursh) Gray | SOCAA |
| Solidago caesia | Solidago caesia L. var. caesia L. [superfluous autonym] | SOCAC |
| Solidago canadensis var. gilvocanescens | Solidago altissima L. var. gilvocanescens (Rydb.) Semple | SOALG |
| Solidago canadensis var. gilvocanescens | Solidago gilvocanescens (Rydb.) Smyth | SOGI2 |
| Solidago canadensis var. gilvocanescens | Solidago pruinosa Greene | SOPR |
| Solidago canadensis var. lepida | Solidago canadensis L. var. subserrata (DC.) Cronq. | SOCAS3 |
| Solidago canadensis var. lepida | Solidago lepida DC. | SOLE8 |
| Solidago canadensis var. lepida | Solidago lepida DC. var. molina Fern. | SOLEM |
| Solidago canadensis var. salebrosa | Solidago canadensis L. ssp. elongata (Nutt.) Keck | SOCAE |
| Solidago canadensis var. salebrosa | Solidago canadensis L. ssp. salebrosa (Piper) Keck | SOCAS4 |
| Solidago canadensis var. salebrosa | Solidago canadensis L. var. elongata (Nutt.) M.E. Peck | SOCAE2 |
| Solidago canadensis var. salebrosa | Solidago dumetorum Lunell | SODU3 |
| Solidago canadensis var. salebrosa | Solidago elongata Nutt. | SOEL4 |
| Solidago canadensis var. salebrosa | Solidago lepida DC. var. elongata (Nutt.) Fern. | SOLEE |
| Solidago canadensis var. salebrosa | Solidago lepida DC. var. fallax Fern. | SOLEF |
| Solidago curtisii | Solidago caesia L. var. curtisii (Torr. & Gray) Wood | SOCAC2 |
| Solidago curtisii | Solidago caesia L. var. hispida Wood | SOCAH3 |
| Solidago curtisii | Solidago curtisii Torr. & Gray var. pubens (M.A. Curtis) Gray | SOCUP |
| Solidago curtisii | Solidago monticola Torr. & Gray | SOMO3 |
| Solidago curtisii | Solidago pubens M.A. Curtis | SOPU5 |
| Solidago discoidea | Brintonia discoidea (Ell.) Greene | BRDI7 |
| Solidago erecta | Solidago speciosa Nutt. var. erecta (Pursh) MacM. | SOSPE |
| Solidago flaccidifolia | Solidago caesia L. var. paniculata Gray | SOCAP |
| Solidago flaccidifolia | Solidago gracilis Poir. | SOGR9 |
| Solidago flexicaulis | Solidago latifolia L. | SOLA7 |
| Solidago gigantea | Aster latissimifolius (P. Mill.) Kuntze var. serotinus Kuntze | ASLAS2 |
| Solidago gigantea | Solidago ?leiophallax Friesner | SOLE6 |
| Solidago gigantea | Solidago gigantea Ait. ssp. serotina (Kuntze) McNeill | SOGIS2 |
| Solidago gigantea | Solidago gigantea Ait. var. leiophylla Fern. | SOGIL |
| Solidago gigantea | Solidago gigantea Ait. var. pitcheri (Nutt.) Shinners | SOGIP |
| Solidago gigantea | Solidago gigantea Ait. var. serotina (Kuntze) Cronq. | SOGIS |
| Solidago gigantea | Solidago gigantea Ait. var. shinnersii Beaudry | SOGIS3 |
| Solidago gigantea | Solidago pitcheri Nutt. | SOPI5 |
| Solidago gigantea | Solidago serotina Ait., non Retz. | SOSE10 |
| Solidago gigantea | Solidago serotinoides A.& D. L?ve | SOSE9 |
| Solidago gracillima | Solidago austrina Small | SOAU3 |
| Solidago gracillima | Solidago flavovirens Chapman | SOFL3 |
| Solidago gracillima | Solidago perlonga Fern. | SOPE4 |
| Solidago hispida var. hispida | Solidago bicolor L. var. concolor Torr. & Gray | SOBIC2 |
| Solidago hispida var. hispida | Solidago bicolor L. var. ovalis Farw. | SOBIO |
| Solidago hispida var. lanata | Solidago bicolor L. var. lanata (Hook.) Seymour | SOBIL |
| Solidago hispida var. tonsa | Solidago bicolor L. var. tonsa (Fern.) Boivin | SOBIT |
| Solidago juliae | Solidago altissima L. var. canescens (Gray) M.C. Johnston | SOALC |
| Solidago juliae | Solidago canadensis L. var. canescens Gray | SOCAC5 |
| Solidago juncea | Solidago juncea Ait. var. neobohemica Fern. | SOJUN |
| Solidago juncea | Solidago juncea Ait. var. ramosa Porter & Britt. | SOJUR |
| Solidago latissimifolia | Solidago edisoniana Mackenzie | SOED |
| Solidago latissimifolia | Solidago elliottii Torr. & Gray | SOEL2 |
| Solidago latissimifolia | Solidago elliottii Torr. & Gray var. ascendens Fern. | SOELA |
| Solidago latissimifolia | Solidago elliottii Torr. & Gray var. edisoniana (Mackenzie) Fern. | SOELE |
| Solidago latissimifolia | Solidago elliottii Torr. & Gray var. pedicellata Fern. | SOELP |
| Solidago latissimifolia | Solidago elliptica Ait. | SOEL5 |
| Solidago latissimifolia | Solidago mirabilis Small | SOMI3 |
| Solidago ludoviciana | Solidago boottii Hook. var. ludoviciana Gray | SOBOL2 |
| Solidago macrophylla | Solidago macrophylla Pursh var. thyrsoidea (E. Mey.) Fern. | SOMAT |
| Solidago macrophylla | Solidago mensalis Fern. | SOME4 |
| Solidago missouriensis var. fasciculata | Solidago glaberrima Martens | SOGL4 |
| Solidago missouriensis var. fasciculata | Solidago glaberrima Martens var. moritura (Steele) Palmer & Steyermark | SOGLM |
| Solidago missouriensis var. fasciculata | Solidago missouriensis Nutt. var. glaberrima (Martens) Rosendahl & Cronq. | SOMIG |
| Solidago missouriensis var. missouriensis | Solidago missouriensis Nutt. var. extraria Gray | SOMIE |
| Solidago missouriensis var. missouriensis | Solidago missouriensis Nutt. var. montana Gray | SOMIM2 |
| Solidago missouriensis var. tenuissima | Solidago tenuissima Woot. & Standl. | SOTE6 |
| Solidago multiradiata var. arctica | Solidago virgauera L. var. arctica DC. | SOVIA |
| Solidago multiradiata var. multiradiata | Solidago anticostensis Fern. | SOAN5 |
| Solidago multiradiata var. scopulorum | Solidago ciliosa Greene | SOCI3 |
| Solidago multiradiata var. scopulorum | Solidago multiradiata Ait. ssp. scopulorum (Gray) W.A. Weber | SOMUS2 |
| Solidago multiradiata var. scopulorum | Solidago scopulorum (Gray) A. Nels. | SOSC3 |
| Solidago nemoralis var. longipetiolata | Solidago decemflora DC. | SODE4 |
| Solidago nemoralis var. longipetiolata | Solidago longipetiolata Mackenzie & Bush | SOLO |
| Solidago nemoralis var. longipetiolata | Solidago nemoralis Ait. ssp. decemflora (DC.) Brammall | SONED |
| Solidago nemoralis var. longipetiolata | Solidago nemoralis Ait. ssp. longipetiolata (Mackenzie & Bush) G.W. Douglas | SONEL2 |
| Solidago nemoralis var. longipetiolata | Solidago nemoralis Ait. var. decemflora (DC.) Fern. | SONED2 |
| Solidago nemoralis var. longipetiolata | Solidago pulcherrima A. Nels. | SOPU7 |
| Solidago nemoralis var. nemoralis | Solidago nemoralis Ait. ssp. haleana (Fern.) G.W. Douglas | SONEH2 |
| Solidago nemoralis var. nemoralis | Solidago nemoralis Ait. var. haleana Fern. | SONEH |
| Solidago odora var. chapmanii | Solidago chapmanii Torr. & Gray | SOCH5 |
| Solidago odora var. odora | Solidago suaveolens Schoepf | SOSU5 |
| Solidago patula var. strictula | Solidago arguta Ait. var. strigosa (Small) Steyermark | SOARS |
| Solidago patula var. strictula | Solidago salicina Ell. | SOSA2 |
| Solidago patula var. strictula | Solidago strigosa Small | SOST2 |
| Solidago petiolaris var. angusta | Solidago angusta Torr. & Gray | SOAN |
| Solidago petiolaris var. angusta | Solidago lindheimeriana Scheele | SOLI |
| Solidago petiolaris var. angusta | Solidago petiolaris Ait. var. wardii (Britt.) Fern. | SOPEW |
| Solidago petiolaris var. angusta | Solidago wardii Britt. | SOWA2 |
| Solidago petiolaris var. petiolaris | Solidago milleriana Mackenzie | SOMI5 |
| Solidago puberula var. pulverulenta | Solidago pulverulenta Nutt. | SOPU6 |
| Solidago radula var. radula | Solidago pendula Small | SOPE5 |
| Solidago radula var. radula | Solidago rotundifolia DC. | SORO4 |
| Solidago radula var. radula | Solidago scaberrima Torr. & Gray | SOSC5 |
| Solidago roanensis | Solidago maxonii Pollard | SOMA6 |
| Solidago roanensis | Solidago roanensis Porter var. monticola (Torr. & Gray) Fern. | SOROM |
| Solidago rugosa ssp. aspera | Solidago aspera Ait. | SOAS4 |
| Solidago rugosa ssp. aspera | Solidago celtidifolia Small | SOCE |
| Solidago rugosa ssp. aspera | Solidago drummondii Torr. & Gray | SODR |
| Solidago rugosa ssp. aspera | Solidago rugosa P. Mill. var. celtidifolia (Small) Fern. | SORUC |
| Solidago rugosa ssp. rugosa var. rugosa | Solidago scabra Muhl. ex Willd., non Muhl. | SOSC4 |
| Solidago rugosa ssp. rugosa var. sphagnophila | Solidago aestivalis Bickn. | SOAE |
| Solidago rupestris | Solidago canadensis L. var. rupestris (Raf.) Porter | SOCAR |
| Solidago sempervirens var. mexicana | Solidago angustifolia Ell. | SOAN4 |
| Solidago sempervirens var. mexicana | Solidago mexicana L. | SOME3 |
| Solidago sempervirens var. mexicana | Solidago petiolata auct. non P. Mill. [misapplied] | SOPE6 |
| Solidago simplex ssp. randii var. gillmanii | Solidago gillmanii (Gray) Steele | SOGI3 |
| Solidago simplex ssp. randii var. gillmanii | Solidago glutinosa Nutt. var. gillmanii (Gray) Cronq. | SOGLG |
| Solidago simplex ssp. randii var. gillmanii | Solidago racemosa Greene var. gillmanii (Gray) Fern. | SORAG |
| Solidago simplex ssp. randii var. gillmanii | Solidago spathulata DC. var. gillmanii (Gray) Gleason | SOSPG3 |
| Solidago simplex ssp. randii var. monticola | Solidago randii (Porter) Britt. var. monticola (Porter) Fern. | SORAM |
| Solidago simplex ssp. randii var. ontarioensis | Solidago glutinosa Nutt. var. ontarioensis Ringius | SOGLO |
| Solidago simplex ssp. randii var. racemosa | Solidago glutinosa Nutt. var. racemosa (Greene) Cronq. | SOGLR |
| Solidago simplex ssp. randii var. racemosa | Solidago racemosa Greene | SORA4 |
| Solidago simplex ssp. randii var. racemosa | Solidago spathulata DC. var. racemosa (Greene) Gleason | SOSPR4 |
| Solidago simplex ssp. randii var. randii | Solidago glutinosa Nutt. ssp. randii (Porter) Cronq. | SOGLR2 |
| Solidago simplex ssp. randii var. randii | Solidago randii (Porter) Britt. | SORA5 |
| Solidago simplex ssp. randii var. randii | Solidago spathulata DC. ssp. randii (Porter) Gleason | SOSPR2 |
| Solidago simplex ssp. simplex var. nana | Solidago bellidifolia Greene | SOBE4 |
| Solidago simplex ssp. simplex var. nana | Solidago decumbens Greene | SODE6 |
| Solidago simplex ssp. simplex var. nana | Solidago decumbens Greene var. oreophila (Rydb.) Fern. | SODEO |
| Solidago simplex ssp. simplex var. nana | Solidago glutinosa Nutt. var. nana (Gray) Cronq. | SOGLN |
| Solidago simplex ssp. simplex var. nana | Solidago oreophila Rydb. | SOOR |
| Solidago simplex ssp. simplex var. nana | Solidago spathulata DC. var. nana (Gray) Cronq. | SOSPN |
| Solidago simplex ssp. simplex var. simplex | Solidago glutinosa Nutt. | SOGL6 |
| Solidago simplex ssp. simplex var. simplex | Solidago neomexicana (Gray) Woot. & Standl. | SONE4 |
| Solidago simplex ssp. simplex var. simplex | Solidago spathulata DC. ssp. glutinosa (Nutt.) Keck | SOSPG2 |
| Solidago simplex ssp. simplex var. simplex | Solidago spathulata DC. var. neomexicana (Gray) Cronq. | SOSPN2 |
| Solidago simplex ssp. simplex var. spathulata | Solidago spathulata DC. | SOSP |
| Solidago simplex ssp. simplex var. spathulata | Solidago spathulata DC. ssp. spathulata DC. [superfluous autonym] | SOSPS8 |
| Solidago speciosa var. jejunifolia | Solidago jejunifolia Steele | SOJE |
| Solidago speciosa var. jejunifolia | Solidago uliginosa Nutt. var. jejunifolia (Steele) Boivin | SOULJ |
| Solidago speciosa var. pallida | Solidago pallida (Porter) Rydb. | SOPA8 |
| Solidago speciosa var. rigidiuscula | Solidago rigidiuscula (Torr. & Gray) Porter | SORI4 |
| Solidago speciosa var. rigidiuscula | Solidago speciosa Nutt. var. angustata Torr. & Gray | SOSPA |
| Solidago speciosa var. speciosa | Solidago conferta P. Mill. | SOCO4 |
| Solidago speciosa var. speciosa | Solidago harperi Mackenzie | SOHA3 |
| Solidago spectabilis var. confinis | Solidago confinis Gray | SOCO |
| Solidago sphacelata | Brachychaeta sphacelata (Raf.) Britt. | BRSP3 |
| Solidago uliginosa var. levipes | Solidago uniligulata (DC.) Porter var. levipes Fern. | SOUNL |
| Solidago uliginosa var. linoides | Solidago chrysolepis Fern. | SOCH3 |
| Solidago uliginosa var. linoides | Solidago farwellii Fern. | SOFA3 |
| Solidago uliginosa var. linoides | Solidago purshii Porter | SOPU8 |
| Solidago uliginosa var. linoides | Solidago uliginosa Nutt. var. peracuta (Fern.) Friesner | SOULP |
| Solidago uliginosa var. uliginosa | Solidago neglecta Torr. & Gray | SONE5 |
| Solidago uliginosa var. uliginosa | Solidago uliginosa Nutt. var. neglecta (Torr. & Gray) Fern. | SOULN |
| Solidago uliginosa var. uliginosa | Solidago uniligulata (DC.) Porter | SOUN |
| Solidago ulmifolia var. microphylla | Solidago delicatula Small | SODE2 |
| Solidago ulmifolia var. microphylla | Solidago helleri Small | SOHE4 |
| Solidago ulmifolia var. microphylla | Solidago microphylla (Gray) Engelm. ex Small | SOMI8 |
| Solidago velutina | Solidago arizonica (Gray) Woot. & Standl. | SOAR6 |
| Solidago velutina | Solidago californica Nutt. var. nevadensis Gray | SOCAN |
| Solidago velutina | Solidago canadensis L. var. arizonica Gray | SOCAA2 |
| Solidago velutina | Solidago howellii Woot. & Standl. | SOHO2 |
| Solidago velutina | Solidago sparsiflora Gray | SOSP5 |
| Solidago velutina | Solidago spathulata DC. var. subcinerea Gray | SOSPS3 |
| Solidago velutina | Solidago trinervata Greene | SOTR3 |
| Solidago velutina | Solidago velutina DC. var. nevadensis (Gray) C.& J. Taylor | SOVEN |
| Solidago wrightii var. adenophora | Solidago bigelovii Gray | SOBI3 |
| Solidago wrightii var. wrightii | Solidago bigelovii Gray var. wrightii (Gray) Gray | SOBIW |
| Soliva sessilis | Soliva daucifolia Nutt. | SODA |
| Soliva sessilis | Soliva pterosperma (Juss.) Less. | SOPT |
| Sonchus arvensis ssp. arvensis | Sonchus arvensis L. var. shumovichii Boivin | SOARS2 |
| Sonchus arvensis ssp. uliginosus | Sonchus arvensis L. var. glabrescens Guenth., Grab. & Wimmer | SOARG |
| Sonchus arvensis ssp. uliginosus | Sonchus uliginosus Bieb. | SOUL5 |
| Sonchus asper | Sonchus asper (L.) Hill ssp. asper (L.) Hill [superfluous autonym] | SOASA2 |
| Sonchus asper ssp. glaucescens | Sonchus nymanii Tineo & Guss. [excluded] | SONY2 |
| Sonne's arnica | Arnica parryi Gray ssp. sonnei (Greene) Maguire | ARPAS2 |
| Sonoma lessingia | Lessingia ramulosa Gray | LERA3 |
| Sonoma lessingia | Lessingia ramulosa Gray var. adenophora (Greene) Gray | LERAA |
| Sonoma lessingia | Lessingia ramulosa Gray var. ramulosa | LERAR |
| Sonora false goldenaster | Heterotheca marginata Semple | HEMA20 |
| Sonoran brickellbush | Brickellia simplex Gray | BRSI2 |
| Sonoran cinchweed | Pectis cylindrica (Fern.) Rydb. | PECY |
| Sonoran desertdandelion | Malacothrix sonorae W.S. Davis & Raven | MASO6 |
| Sonoran neststraw | Stylocline sonorensis Wiggins | STSO2 |
| Sonoran pricklyleaf | Thymophylla concinna (Gray) Strother | THCO10 |
| Sonoran thoroughwort | Fleischmannia sonorae (Gray) King & H.E. Robins. | FLSO |
| South American rubberweed | Hymenoxys anthemoides (Juss.) Cass. | HYAN |
| southeastern annual saltmarsh aster | Symphyotrichum squamatum (Spreng.) Nesom | SYSQ |
| southeastern sneezeweed | Helenium pinnatifidum (Nutt.) Rydb. | HEPI |
| southeastern sunflower | Helianthus agrestis Pollard | HEAG |
| southern annual saltmarsh aster | Symphyotrichum divaricatum (Nutt.) Nesom | SYDI2 |
| southern Barbara's buttons | Marshallia ramosa Beadle & F.E. Boynt. | MARA6 |
| southern globethistle | Echinops rito L. | ECRI |
| southern globethistle | Echinops rito L. ssp. ruthenicus (Bieb.) Nyman | ECRIR |
| southern goldenbush | Isocoma pluriflora (Torr. & Gray) Greene | ISPL |
| southern hawkweed | Hieracium argutum Nutt. | HIAR2 |
| southern mule-ears | Agnorhiza ovata (Torr. & Gray ex Torr.) W.A. Weber | AGOV |
| southern prairie aster | Eurybia hemispherica (Alexander) Nesom | EUHE10 |
| southern Sierra pincushion | Chaenactis alpigena C.W. Sharsmith | CHAL |
| southern swamp aster | Eurybia paludosa (Ait.) Nesom | EUPA23 |
| southern whitetop | Doellingeria sericocarpoides Small | DOSE |
| southernwood | Artemisia abrotanum L. | ARAB2 |
| southwestern annual saltmarsh aster | Symphyotrichum expansum (Poepp. ex Spreng.) Nesom | SYEX |
| southwestern brickellbush | Brickellia conduplicata (B.L. Robins.) B.L. Robins. | BRCO7 |
| southwestern cosmos | Cosmos parviflorus (Jacq.) Pers. | COPA12 |
| southwestern rabbitbrush | Chrysothamnus pulchellus (Gray) Greene | CHPU4 |
| sowthistle | Sonchus L. | SONCH |
| sowthistle desertdandelion | Malacothrix sonchoides (Nutt.) Torr. & Gray | MASO |
| Spanish false fleabane | Pulicaria paludosa Link | PUPA6 |
| Spanish gold | Grindelia papposa Nesom & Suh | GRPA8 |
| Spanish needles | Bidens bipinnata L. | BIBI7 |
| spearleaf agoseris | Agoseris retrorsa (Benth.) Greene | AGRE |
| spearleaf arnica | Arnica longifolia D.C. Eat. | ARLO6 |
| spearleaf brickellbush | Brickellia atractyloides Gray | BRAT |
| spearleaf rabbitbrush | Chrysothamnus linifolius Greene | CHLI3 |
| Sphaeromeria argentea | Tanacetum nuttallii Torr. & Gray | TANU2 |
| Sphaeromeria cana | Tanacetum canum D.C. Eat. | TACA15 |
| Sphaeromeria capitata | Tanacetum capitatum (Nutt.) Torr. & Gray | TACA13 |
| Sphaeromeria compacta | Tanacetum compactum Hall | TACO3 |
| Sphaeromeria diversifolia | Tanacetum diversifolium D.C. Eat. | TADI3 |
| Sphaeromeria simplex | Tanacetum simplex A. Nels. | TASI |
| Sphagneticola gracilis | Complaya gracilis (L.C. Rich.) Strother | COGR18 |
| Sphagneticola gracilis | Thelechitonia gracilis (L.C. Rich.) H.E. Robins. & Cuatrec. | THGR8 |
| Sphagneticola gracilis | Wedelia gracilis L.C. Rich. | WEGR |
| Sphagneticola trilobata | Complaya trilobata (L.) Strother | COTR14 |
| Sphagneticola trilobata | Silphium trilobatum L. | SITR4 |
| Sphagneticola trilobata | Thelechitonia trilobata (L.) H.E. Robins. & Cuatrec. | THTR10 |
| Sphagneticola trilobata | Wedelia trilobata (L.) A.S. Hitchc. | WETR |
| spherical blazing star | Liatris spheroidea Michx. | LISP4 |
| spiked western rosinweed | Calycadenia spicata (Greene) Greene | CASP2 |
| spilanthes | Spilanthes Jacq. | SPILA |
| spilanthes | Spilanthes oleracea L. | SPOL3 |
| spineless horsebrush | Tetradymia canescens DC. | TECA2 |
| spiny chloracantha | Chloracantha spinosa (Benth.) Nesom | CHSP11 |
| spiny cockleburr | Xanthium spinosum L. | XASP2 |
| spiny plumeless thistle | Carduus acanthoides L. | CAAC |
| spiny sowthistle | Sonchus asper (L.) Hill | SOAS |
| spiral dog's-tongue | Pseudelephantopus spirilis (Less.) Cronq. | PSSP7 |
| splitleaf brickellbush | Brickellia laciniata Gray | BRLA |
| splitleaf groundsel | Packera dimorphophylla (Greene) W.A. Weber & A. L?ve | PADI11 |
| splitleaf groundsel | Packera dimorphophylla (Greene) W.A. Weber & A. L?ve var. dimorphophylla | PADID3 |
| splitleaf groundsel | Packera dimorphophylla (Greene) W.A. Weber & A. L?ve var. intermedia (T.M. Barkl.) D.K. Trock & T.M. Barkl. | PADII4 |
| Spokane false goldenaster | Heterotheca barbata (Rydb.) Semple | HEBA2 |
| spoonleaf purple everlasting | Gamochaeta purpurea (L.) Cabrera | GAPU3 |
| spoonshape Barbara's buttons | Marshallia obovata (Walt.) Beadle & F.E. Boynt. | MAOB |
| spoonshape Barbara's buttons | Marshallia obovata (Walt.) Beadle & F.E. Boynt. var. obovata | MAOBO |
| spoonshape Barbara's buttons | Marshallia obovata (Walt.) Beadle & F.E. Boynt. var. scaposa Channell | MAOBS |
| spotflower | Acmella L.C. Rich. ex Pers. | ACMEL |
| spotted goldenthistle | Scolymus maculatus L. | SCMA5 |
| spotted hawkweed | Hieracium maculatum Sm. | HIMA3 |
| spotted joepyeweed | Eupatoriadelphus maculatus (L.) King & H.E. Robins. var. bruneri (Gray) King & H.E. Robins. | EUMAB |
| spotted joepyeweed | Eupatoriadelphus maculatus (L.) King & H.E. Robins. var. foliosum (Fern.) Kartesz, comb. nov. ined. | EUMAF2 |
| spotted knapweed | Centaurea stoebe L. | CEST8 |
| spotted knapweed | Centaurea stoebe L. ssp. micranthos (Gugler) Hayek | CESTM |
| spotted trumpetweed | Eupatoriadelphus maculatus (L.) King & H.E. Robins. | EUMA12 |
| spotted trumpetweed | Eupatoriadelphus maculatus (L.) King & H.E. Robins. var. maculatus | EUMAM3 |
| spreading cinchweed | Pectis prostrata Cav. | PEPR |
| spreading fleabane | Erigeron divergens Torr. & Gray | ERDI4 |
| spreading leastdaisy | Chaetopappa effusa (Gray) Shinners | CHEF |
| spreading nehe | Lipochaeta venosa Sherff | LIVE5 |
| spreading snakeroot | Ageratina riparia (Regel) King & H.E. Robins. | AGRI2 |
| spreading sneezeweed | Centipeda minima (L.) A. Braun & Aschers. | CEMI5 |
| spring lessingia | Lessingia tenuis (Gray) Coville | LETE8 |
| spring madia | Madia elegans D. Don ex Lindl. ssp. vernalis Keck | MAELV |
| Spring Mountain aster | Ionactis caelestis Leary & Nesom | IOCA2 |
| spring pygmycudweed | Evax verna Raf. | EVVE |
| spring pygmycudweed | Evax verna Raf. var. drummondii (Torr. & Gray) Kartesz & Gandhi | EVVED |
| spring pygmycudweed | Evax verna Raf. var. verna | EVVEV |
| spring thistle | Cirsium vernale (Osterhout) Cockerell | CIVE |
| spring-gold | Crocidium Hook. | CROCI |
| Springdale rockdaisy | Perityle tenella (M.E. Jones) J.F. Macbr. | PETE11 |
| springflowering goldenrod | Solidago verna M.A. Curtis ex Torr. & Gray | SOVE2 |
| sprucefir fleabane | Erigeron eximius Greene | EREX4 |
| squarebud daisy | Tetragonotheca texana Engelm. & Gray ex Gray | TETE2 |
| squarestem | Melanthera Rohr | MELAN2 |
| squarrose knapweed | Centaurea virgata Lam. | CEVI |
| squarrose knapweed | Centaurea virgata Lam. ssp. squarrosa (Willd.) Gugler | CEVIS2 |
| St. Paul's wort | Sigesbeckia L. | SIGES |
| stalked fleabane | Erigeron algidus Jepson | ERAL18 |
| Stansbury's rockdaisy | Perityle stansburyi (Gray) J.F. Macbr. | PEST14 |
| Star Peak fleabane | Erigeron salishii G.W. Douglas & Packer | ERSA17 |
| star tickseed | Coreopsis pubescens Ell. | COPU2 |
| star tickseed | Coreopsis pubescens Ell. var. debilis (Sherff) E.B. Sm. | COPUD |
| star tickseed | Coreopsis pubescens Ell. var. pubescens | COPUP |
| star tickseed | Coreopsis pubescens Ell. var. robusta Gray ex Eames | COPUR |
| starburr | Acanthospermum Schrank | ACANT3 |
| starry rosinweed | Silphium asteriscus L. | SIAS2 |
| starry rosinweed | Silphium asteriscus L. var. angustatum Gray | SIASA |
| starry rosinweed | Silphium asteriscus L. var. asteriscus | SIASA3 |
| starry rosinweed | Silphium asteriscus L. var. laevicaule DC. | SIASL2 |
| starved fleabane | Erigeron miser Gray | ERMI2 |
| Stebbins's desertdandelion | Malacothrix stebbinsii W.S. Davis & Raven | MAST2 |
| Stebbins's tarweed | Harmonia stebbinsii (T.W. & J.P. Nelson) B.G. Baldwin | HAST10 |
| Steele's eupatorium | Eupatorium steelei E. Lamont | EUST11 |
| Steen Mountain thistle | Cirsium peckii Henderson | CIPE4 |
| stem raillardella | Raillardella scaposa (Gray) Gray | RASC2 |
| stemless dwarf-cudweed | Hesperevax acaulis (Kellogg) Greene | HEAC8 |
| stemless dwarf-cudweed | Hesperevax acaulis (Kellogg) Greene var. acaulis | HEACA |
| stemless dwarf-cudweed | Hesperevax acaulis (Kellogg) Greene var. ambusticola Morefield | HEACA2 |
| stemless dwarf-cudweed | Hesperevax acaulis (Kellogg) Greene var. robustior Morefield | HEACR |
| stemless four-nerve daisy | Tetraneuris acaulis (Pursh) Greene | TEAC |
| stemless four-nerve daisy | Tetraneuris acaulis (Pursh) Greene var. acaulis | TEACA2 |
| stemless four-nerve daisy | Tetraneuris acaulis (Pursh) Greene var. epunctata (A. Nels.) Kartesz & Gandhi | TEACE |
| stemless four-nerve daisy | Tetraneuris acaulis (Pursh) Greene var. nana (Welsh) Kartesz & Gandhi | TEACN |
| stemless ironweed | Vernonia acaulis (Walt.) Gleason | VEAC |
| stemless mock goldenweed | Stenotus acaulis (Nutt.) Nutt. | STAC |
| stemless Townsend daisy | Townsendia exscapa (Richards.) Porter | TOEX2 |
| stemmy four-nerve daisy | Tetraneuris scaposa (DC.) Greene | TESC2 |
| stemmy four-nerve daisy | Tetraneuris scaposa (DC.) Greene var. argyrocaulon (Parker) Parker | TESCA |
| stemmy four-nerve daisy | Tetraneuris scaposa (DC.) Greene var. linearis (Nutt.) Parker | TESCL |
| stemmy four-nerve daisy | Tetraneuris scaposa (DC.) Greene var. scaposa | TESCS |
| Stenotus acaulis | Haplopappus acaulis (Nutt.) Gray | HAAC |
| Stenotus acaulis | Haplopappus acaulis (Nutt.) Gray ssp. typicus Hall | HAACT |
| Stenotus acaulis | Haplopappus acaulis (Nutt.) Gray var. glabratus D.C. Eat. | HAACG |
| Stenotus acaulis | Stenotus acaulis (Nutt.) Nutt. var. acaulis (Nutt.) Nutt. [superfluous autonym] | STACA |
| Stenotus acaulis | Stenotus acaulis (Nutt.) Nutt. var. glabratus (D.C. Eat.) Kartesz & Gandhi | STACG |
| Stenotus armerioides var. armerioides | Haplopappus armerioides (Nutt.) Gray | HAAR2 |
| Stenotus armerioides var. gramineus | Haplopappus armerioides (Nutt.) Gray var. gramineus Welsh & F.J. Sm. | HAARG |
| Stenotus lanuginosus | Haplopappus lanuginosus Gray | HALA3 |
| Stenotus lanuginosus | Haplopappus lanuginosus Gray ssp. andersonii (Rydb.) Hall | HALAA2 |
| Stenotus lanuginosus | Haplopappus lanuginosus Gray ssp. typicus Hall | HALAT4 |
| Stenotus lanuginosus | Haplopappus lanuginosus Gray var. andersonii (Rydb.) Cronq. | HALAA |
| Stenotus lanuginosus | Stenotus andersonii Rydb. | STAN4 |
| Stenotus lanuginosus | Stenotus lanuginosus (Gray) Greene var. andersonii (Rydb.) Hall | STLAA |
| Stenotus lanuginosus | Stenotus lanuginosus (Gray) Greene var. lanuginosus (Gray) Greene [superfluous autonym] | STLAL |
| Stenotus stenophyllus | Haplopappus stenophyllus Gray | HAST |
| Stephanomeria blairii | Malacothrix blairii (Munz & Johnston) Munz & Johnston | MABL3 |
| Stephanomeria blairii | Munzothamnus blairii (Munz & Johnston) Raven | MUBL |
| Stephanomeria exigua ssp. carotifera | Stephanomeria carotifera Hoover | STCA11 |
| Stephanomeria exigua ssp. coronaria | Stephanomeria coronaria Greene | STCO27 |
| Stephanomeria exigua ssp. coronaria | Stephanomeria exigua Nutt. var. coronaria (Greene) Jepson | STEXC |
| Stephanomeria exigua ssp. deanei | Stephanomeria exigua Nutt. var. deanei J.F. Macbr. | STEXD |
| Stephanomeria exigua ssp. exigua | Lygodesmia bigelovii (Gray) Shinners | LYBI |
| Stephanomeria exigua ssp. exigua | Stephanomeria exigua Nutt. ssp. pentachaeta D.C. Eat. | STEXP2 |
| Stephanomeria exigua ssp. exigua | Stephanomeria exigua Nutt. var. pentachaeta (D.C. Eat.) Hall | STEXP |
| Stephanomeria minor var. minor | Stephanomeria tenuifolia (Raf.) Hall | STTE2 |
| Stephanomeria minor var. myrioclada | Stephanomeria myrioclada D.C. Eat. | STMY |
| Stephanomeria minor var. myrioclada | Stephanomeria tenuifolia (Raf.) Hall var. myrioclada (D.C. Eat.) Cronq. | STTEM |
| Stephanomeria minor var. uintaensis | Lygodesmia tenuifolia (Raf.) Shinners | LYTE5 |
| Stephanomeria minor var. uintaensis | Stephanomeria minor (Hook.) Nutt. var. uintensis (Goodrich & Welsh) Kartesz, comb. nov. ined. [orthographic variant] | STMIU |
| Stephanomeria minor var. uintaensis | Stephanomeria tenuifolia (Raf.) Hall var. uintaensis Goodrich & Welsh | STTEU2 |
| Stephanomeria minor var. uintaensis | Stephanomeria tenuifolia (Raf.) Hall var. uintensis Goodrich & Welsh [orthographic variant] | STTEU |
| Stephanomeria pauciflora | Lygodesmia pauciflora (Torr.) Shinners | LYPA5 |
| Stephanomeria pauciflora | Ptiloria pauciflora (Torr.) Raf. | PTPA4 |
| Stephanomeria pauciflora | Stephanomeria cinerea (Blake) Blake | STCI5 |
| Stephanomeria pauciflora | Stephanomeria lygodesmoides M.E. Jones | STLY |
| Stephanomeria pauciflora | Stephanomeria neomexicana (Greene) Cory | STNE6 |
| Stephanomeria pauciflora | Stephanomeria pauciflora (Torr.) A. Nels. var. parishii (Jepson) Munz | STPAP3 |
| Stephanomeria pauciflora | Stephanomeria pauciflora (Torr.) A. Nelson var. pauciflora (Torr.) A. Nelson [superfluous autonym] | STPAP11 |
| Stephanomeria runcinata | Ptiloria ramosa Rydb. | PTRA |
| Stephanomeria thurberi | Lygodesmia thurberi (Gray) Shinners | LYTH4 |
| Stephanomeria virgata ssp. virgata | Stephanomeria virgata Benth. var. tomentosa (Greene) Munz | STVIT |
| Stephanomeria wrightii | Lygodesmia wrightii (Gray) Shinners | LYWR |
| Steve's dustymaiden | Chaenactis stevioides Hook. & Arn. | CHST |
| Stevia ovata var. texana | Stevia rhombifolia Kunth | STRH2 |
| Stevia salicifolia | Stevia salicifolia Cav. var. stenophylla (Gray) B.L. Robins. | STSAS |
| Stevia salicifolia | Stevia stenophylla Gray | STST9 |
| Stevia serrata | Stevia serrata Cav. var. haplopappa B.L. Robins. | STSEH3 |
| Stevia serrata | Stevia serrata Cav. var. ivifolia (Willd.) B.L. Robins. | STSEI |
| sticky brittlebush | Encelia resinifera C. Clark | ENRE |
| sticky desertsunflower | Geraea viscida (Gray) Blake | GEVI |
| sticky florestina | Florestina tripteris DC. | FLTR2 |
| sticky goldenweed | Pyrrocoma lucida (Keck) Kartesz & Gandhi | PYLU |
| sticky oxeye | Heteranthemis viscidehirta Schott | HEVI12 |
| sticky ragwort | Senecio viscosus L. | SEVI2 |
| sticky rosinweed | Silphium glutinosum J. Allison | SIGL10 |
| sticky saw-wort | Saussurea viscida Hult | SAVI4 |
| sticky snakeroot | Ageratina adenophora (Spreng.) King & H.E. Robins. | AGAD2 |
| sticky snakeweed | Gutierrezia texana (DC.) Torr. & Gray var. glutinosa (S. Schauer) M.A. Lane | GUTEG |
| sticky tansyaster | Machaeranthera viscida (Woot. & Standl.) R.L. Hartman | MAVI9 |
| sticky western rosinweed | Calycadenia multiglandulosa DC. | CAMU3 |
| stickyseed | Blennosperma Less. | BLENN |
| stiff goldenrod | Oligoneuron rigidum (L.) Small | OLRI |
| stiff goldenrod | Oligoneuron rigidum (L.) Small var. glabratum (E.L. Braun) Nesom | OLRIG |
| stiff goldenrod | Oligoneuron rigidum (L.) Small var. humile (Porter) Nesom | OLRIH |
| stiff goldenrod | Oligoneuron rigidum (L.) Small var. rigidum | OLRIR |
| stiff greenthread | Thelesperma filifolium (Hook.) Gray | THFI |
| stiff greenthread | Thelesperma filifolium (Hook.) Gray var. filifolium | THFIF |
| stiff greenthread | Thelesperma filifolium (Hook.) Gray var. intermedium (Rydb.) Shinners | THFII |
| stiff sunflower | Helianthus pauciflorus Nutt. | HEPA19 |
| stiff sunflower | Helianthus pauciflorus Nutt. ssp. pauciflorus | HEPAP2 |
| stiff sunflower | Helianthus pauciflorus Nutt. ssp. subrhomboideus (Rydb.) O. Spring & E. Schilling | HEPAS |
| stiff tickseed | Coreopsis palmata Nutt. | COPA10 |
| stiffleaf false goldenaster | Heterotheca stenophylla (Gray) Shinners | HEST3 |
| stiffleaf false goldenaster | Heterotheca stenophylla (Gray) Shinners var. angustifolia (Rydb.) Semple | HESTA |
| stiffleaf false goldenaster | Heterotheca stenophylla (Gray) Shinners var. stenophylla | HESTS |
| stiffleaf scratchdaisy | Croptilon rigidifolium (E.B. Sm.) E.B. Sm. | CRRI3 |
| Stillman's tickseed | Coreopsis stillmanii (Gray) Blake | COST3 |
| stinking brickellbush | Brickellia rusbyi Gray | BRRU |
| stinking camphorweed | Pluchea foetida (L.) DC. | PLFO |
| stinking camphorweed | Pluchea foetida (L.) DC. var. foetida | PLFOF |
| stinking camphorweed | Pluchea foetida (L.) DC. var. imbricata Kearney | PLFOI |
| stinking chamomile | Anthemis cotula L. | ANCO2 |
| stinking hawksbeard | Crepis foetida L. | CRFO2 |
| stinking hawksbeard | Crepis foetida L. var. foetida | CRFOF |
| stinking roger | Osteospermum calendulaceum L. f. | OSCA |
| stinking strawflower | Helichrysum foetidum (L.) Cass. | HEFO4 |
| stinking willie | Senecio jacobaea L. | SEJA |
| stinknet | Oncosiphon piluliferum (L. f.) K?llersj? | ONPI |
| stinkwort | Dittrichia graveolens (L.) W. Greuter | DIGR3 |
| Stokes's aster | Stokesia laevis (Hill) Greene | STLA6 |
| stokesia | Stokesia L'H?r. | STOKE |
| Stokesia laevis | Carthamus laevis Hill | CALA57 |
| stoloniferous pussytoes | Antennaria dioica (L.) Gaertn. | ANDI3 |
| stone rubberweed | Hymenoxys ?lapidicola Welsh & Neese | HYLA7 |
| stout goldenrod | Solidago squarrosa Nutt. | SOSQ |
| straggler daisy | Calyptocarpus vialis Less. | CAVI2 |
| strawflower | Helichrysum P. Mill. | HELIC4 |
| streaked burr ragweed | Ambrosia linearis (Rydb.) Payne | AMLI3 |
| streambed nehe | Lipochaeta tenuis O. Deg. & Sherff | LITE8 |
| streamside fleabane | Erigeron glabellus Nutt. | ERGL2 |
| streamside fleabane | Erigeron glabellus Nutt. var. glabellus | ERGLG |
| streamside fleabane | Erigeron glabellus Nutt. var. pubescens Hook. | ERGLP |
| strigose blacksamson | Echinacea angustifolia DC. var. strigosa R.L. McGregor | ECANS |
| striped cottonthorn | Tetradymia argyraea Munz & Roos | TEAR |
| striped hawksbeard | Crepis zacintha (L.) Babcock | CRZA2 |
| struchium | Struchium P. Br. | STRUC |
| Struchium sparganophorum | Ethulia sparganophora L. | ETSP |
| subalpine aster | Eurybia merita (A. Nels.) Nesom | EUME17 |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene | ERPE3 |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. callianthemus (Greene) Cronq. | ERPEC |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. callianthemus (Greene) Cronq. var. callianthemus | ERPEC2 |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. callianthemus (Greene) Cronq. var. hirsutus Cronq. | ERPEH |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. peregrinus | ERPEP |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. peregrinus var. dawsonii Greene | ERPED2 |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. peregrinus var. peregrinus | ERPEP3 |
| subalpine fleabane | Erigeron peregrinus (Banks ex Pursh) Greene ssp. peregrinus var. thompsonii (Blake ex J.W. Thompson) Cronq. | ERPET2 |
| subalpine goldenbush | Ericameria zionis (L.C. Anders.) Nesom | ERZI2 |
| subalpine gumweed | Grindelia subalpina Greene | GRSU |
| subalpine gumweed | Grindelia subalpina Greene var. erecta (A. Nels.) Steyermark | GRSUE |
| subalpine gumweed | Grindelia subalpina Greene var. subalpina | GRSUS |
| Suisun Marsh aster | Symphyotrichum lentum (Greene) Nesom | SYLE2 |
| Suisun thistle | Cirsium hydrophilum (Greene) Jepson | CIHY |
| Suisun thistle | Cirsium hydrophilum (Greene) Jepson var. hydrophilum | CIHYH |
| sulphur cosmos | Cosmos sulphureus Cav. | COSU5 |
| sulphur knapweed | Centaurea sulphurea Willd. | CESU |
| summer ragwort | Ligularia dentata (Gray) Hara | LIDE8 |
| sunbonnets | Leibnitzia Cass. | LEIBN |
| sunbonnetts | Chaptalia Vent. | CHAPT |
| sunburst | Pseudobahia Rydb. | PSEUD2 |
| sunfacing coneflower | Rudbeckia heliopsidis Torr. & Gray | RUHE |
| sunflower | Helianthus L. | HELIA3 |
| sunflower mule-ears | Wyethia helianthoides Nutt. | WYHE2 |
| sunray | Enceliopsis (Gray) A. Nels. | ENCEL2 |
| supple fleabane | Erigeron supplex Gray | ERSU4 |
| surf thistle | Cirsium rhothophilum Blake | CIRH |
| Svenson's beggarticks | Bidens hyperborea Greene var. svensonii Fassett | BIHYS |
| swamp boreal-daisy | Erigeron elatus (Hook.) Greene | EREL10 |
| swamp sunflower | Helianthus angustifolius L. | HEAN2 |
| swamp thistle | Cirsium muticum Michx. | CIMU |
| swampwort | Enydra Lour. | ENYDR |
| sweet coneflower | Rudbeckia subtomentosa Pursh | RUSU |
| sweet sagewort | Artemisia annua L. | ARAN3 |
| sweet yellowcrown | Proustia vanillosma C. Wright | PRVA |
| sweet-Nancy | Achillea ageratum L. | ACAG3 |
| sweetbush | Bebbia Greene | BEBBI |
| sweetbush | Bebbia juncea (Benth.) Greene | BEJU |
| sweetbush | Bebbia juncea (Benth.) Greene var. aspera Greene | BEJUA |
| sweetbush | Bebbia juncea Greene var. juncea Greene [excluded] | BEJUJ2 |
| sweetscent | Pluchea odorata (L.) Cass. | PLOD |
| sweetscent | Pluchea odorata (L.) Cass. var. odorata | PLODO |
| sweetscent | Pluchea odorata (L.) Cass. var. succulenta (Fern.) Cronq. | PLODS |
| sweetscented joepyeweed | Eupatorium purpureum L. | EUPU10 |
| sweetscented joepyeweed | Eupatorium purpureum L. var. purpureum | EUPUP |
| sweetscented marigold | Tagetes lucida Cav. | TALU3 |
| sweetsultan | Amberboa moschata (L.) DC. | AMMO |
| sword Townsend daisy | Townsendia spathulata Nutt. | TOSP |
| sylvan scorzonella | Microseris sylvatica (Benth.) Schultz-Bip. | MISY |
| Symphyotrichum ?amethystinum | Aster amethystinus Nutt. | ASAM13 |
| Symphyotrichum ?amethystinum | Lasallea ?amethystina (Nutt.) Semple & L. Brouillet | LAAM3 |
| Symphyotrichum ?amethystinum | Virgulus ?amethystinus (Nutt.) Reveal & Keener | VIAM2 |
| Symphyotrichum ?batesii | Aster ?batesii Rydb. (pro sp.) [not hybrid] | ASBA4 |
| Symphyotrichum ?columbianum | Aster ?columbianus Piper (pro sp.) [not hybrid] | ASCO37 |
| Symphyotrichum ?finkii | Aster finkii Rydb. | ASFI3 |
| Symphyotrichum ?gravesii | Aster gravesii Burgess | ASGR18 |
| Symphyotrichum ?longulum | Aster longulus Sheldon | ASLO15 |
| Symphyotrichum ?salignum | Aster ?salignus Willd. [excluded] | ASSA20 |
| Symphyotrichum ?schistosum | Aster ?schistosus Steele (pro sp.) [not hybrid] | ASSC10 |
| Symphyotrichum ?versicolor | Aster ?versicolor Willd. (pro sp.) [excluded] | ASVE14 |
| Symphyotrichum ?woldenii | Aster ?woldenii Rydb. (pro sp.) [not hybrid] | ASWO3 |
| Symphyotrichum adnatum | Aster adnatus Nutt. | ASAD4 |
| Symphyotrichum adnatum | Lasallea adnata (Nutt.) Semple & L. Brouillet | LAAD |
| Symphyotrichum adnatum | Virgulus adnatus (Nutt.) Reveal & Keener | VIAD3 |
| Symphyotrichum anomalum | Aster anomalus Engelm. | ASAN |
| Symphyotrichum anticostense | Aster anticostensis Fern. | ASAN13 |
| Symphyotrichum ascendens | Aster adscendens Lindl. | ASAD6 |
| Symphyotrichum ascendens | Aster ascendens Lindl. | ASAS5 |
| Symphyotrichum ascendens | Aster chilensis Nees ssp. adscendens (Lindl.) Cronq. | ASCHA |
| Symphyotrichum ascendens | Aster macounii Rydb. | ASMA14 |
| Symphyotrichum ascendens | Aster subgriseus Rydb. | ASSU15 |
| Symphyotrichum ascendens | Virgulaster ascendens (Lindl.) Semple | VIAS2 |
| Symphyotrichum bahamense | Aster subulatus Michx. var. elongatus Bosserd. | ASSUE2 |
| Symphyotrichum boreale | Aster borealis (Torr. & Gray) Prov. | ASBO7 |
| Symphyotrichum boreale | Aster franklinianus Rydb. | ASFR6 |
| Symphyotrichum boreale | Aster junceus auct. non Ait. [misapplied] | ASJU5 |
| Symphyotrichum boreale | Aster junciformis Rydb. | ASJU |
| Symphyotrichum boreale | Aster laxifolius Nees var. borealis Torr. & Gray | ASLAB2 |
| Symphyotrichum bracei | Aster bracei Britt. ex Small | ASBR16 |
| Symphyotrichum bracei | Aster tenuifolius L. var. aphyllus R.W. Long | ASTEA |
| Symphyotrichum campestre var. bloomeri | Aster bloomeri Gray | ASBL5 |
| Symphyotrichum campestre var. bloomeri | Aster campestris Nutt. var. bloomeri (Gray) Gray | ASCAB2 |
| Symphyotrichum campestre var. campestre | Aster campestris Nutt. | ASCA6 |
| Symphyotrichum campestre var. campestre | Virgulus campestris (Nutt.) Reveal & Keener | VICA14 |
| Symphyotrichum chilense var. chilense | Aster chilensis Nees | ASCH2 |
| Symphyotrichum chilense var. invenustum | Aster chilensis Nees var. invenustus (Greene) Jepson | ASCHI |
| Symphyotrichum chilense var. invenustum | Aster invenustus Greene | ASIN17 |
| Symphyotrichum chilense var. medium | Aster chilensis Nees var. medius Jepson | ASCHM |
| Symphyotrichum ciliatum | Aster brachyactis Blake | ASBR3 |
| Symphyotrichum ciliatum | Brachyactis angusta (Lindl.) Britt. | BRAN4 |
| Symphyotrichum ciliatum | Brachyactis ciliata (Ledeb.) Ledeb. | BRCI6 |
| Symphyotrichum ciliatum | Brachyactis ciliata (Ledeb.) Ledeb. ssp. angusta (Lindl.) A.G. Jones | BRCIA |
| Symphyotrichum ciliatum | Tripolium angustum Lindl. | TRAN7 |
| Symphyotrichum ciliolatum | Aster ciliolatus Lindl. | ASCI |
| Symphyotrichum ciliolatum | Aster ciliolatus Lindl. var. comatus (Fern.) A.G. Jones | ASCIC2 |
| Symphyotrichum ciliolatum | Aster ciliolatus Lindl. var. maccallae (Rydb.) A.G. Jones | ASCIM2 |
| Symphyotrichum ciliolatum | Aster ciliolatus Lindl. var. wilsonii (Rydb.) A.G. Jones | ASCIW |
| Symphyotrichum ciliolatum | Aster foliaceus Lindl. ex DC. var. subgeminatus Fern. | ASFOS2 |
| Symphyotrichum ciliolatum | Aster lindleyanus Torr. & Gray | ASLI9 |
| Symphyotrichum ciliolatum | Aster maccallae Rydb. | ASMA26 |
| Symphyotrichum ciliolatum | Aster saundersii Burgess | ASSA10 |
| Symphyotrichum ciliolatum | Aster subgeminatus (Fern.) Boivin | ASSU10 |
| Symphyotrichum ciliolatum | Aster wilsonii Rydb. | ASWI6 |
| Symphyotrichum ciliolatum | Symphyotrichum ciliolatum (Lindl.) A.& D. L?ve var. comatum (Fern.) Nesom | SYCIC |
| Symphyotrichum ciliolatum | Symphyotrichum ciliolatum (Lindl.) A.& D. L?ve var. maccallae (Rydb.) Nesom | SYCIM |
| Symphyotrichum ciliolatum | Symphyotrichum ciliolatum (Lindl.) A.& D. L?ve var. wilsonii (Rydb.) Nesom | SYCIW |
| Symphyotrichum ciliolatum | Symphyotrichum subgeminatum (Fern.) Nesom | SYSU3 |
| Symphyotrichum concolor | Aster concolor L. | ASCO2 |
| Symphyotrichum concolor | Aster concolor L. var. simulatus (Small) R.W. Long | ASCOS2 |
| Symphyotrichum concolor | Aster plumosus Small | ASPL7 |
| Symphyotrichum concolor | Aster simulatus Small | ASSI10 |
| Symphyotrichum concolor | Lasallea concolor (L.) Semple & L. Brouillet | LACO9 |
| Symphyotrichum concolor | Virgulus concolor (L.) Reveal & Keener | VICO15 |
| Symphyotrichum cordifolium | Aster cordifolius L. | ASCO4 |
| Symphyotrichum cordifolium | Aster cordifolius L. ssp. sagittifolius (Wedemeyer ex Willd.) A.G. Jones | ASCOS5 |
| Symphyotrichum cordifolium | Aster cordifolius L. var. furbishiae Fern. | ASCOF2 |
| Symphyotrichum cordifolium | Aster cordifolius L. var. incisus Britt. | ASCOI |
| Symphyotrichum cordifolium | Aster cordifolius L. var. lanceolatus Porter | ASCOL3 |
| Symphyotrichum cordifolium | Aster cordifolius L. var. moratus (Shinners) Shinners | ASCOM3 |
| Symphyotrichum cordifolium | Aster cordifolius L. var. polycephalus Porter | ASCOP2 |
| Symphyotrichum cordifolium | Aster cordifolius L. var. racemiflorus Fern. | ASCOR |
| Symphyotrichum cordifolium | Aster cordifolius L. var. sagittifolius (Wedemeyer ex Willd.) A.G. Jones | ASCOS3 |
| Symphyotrichum cordifolium | Aster finkii Rydb. var. moratus Shinners | ASFIM |
| Symphyotrichum cordifolium | Aster lowrieanus Porter var. incisus (Britt.) Porter | ASLOI |
| Symphyotrichum cordifolium | Aster lowrieanus Porter var. lanceolatus Porter | ASLOL |
| Symphyotrichum cordifolium | Aster plumarius Burgess | ASPL6 |
| Symphyotrichum cordifolium | Aster sagittifolius Wedemeyer ex Willd. | ASSA |
| Symphyotrichum cordifolium | Symphyotrichum cordifolium (L.) Nesom var. furbishiae (Fern.) Nesom | SYCOF |
| Symphyotrichum cordifolium | Symphyotrichum cordifolium (L.) Nesom var. lanceolatum (Porter) Nesom | SYCOL |
| Symphyotrichum cordifolium | Symphyotrichum cordifolium (L.) Nesom var. moratum (Shinners) Nesom | SYCOM |
| Symphyotrichum cordifolium | Symphyotrichum cordifolium (L.) Nesom var. polycephalum (Porter) Nesom | SYCOP |
| Symphyotrichum cordifolium | Symphyotrichum cordifolium (L.) Nesom var. racemiflorum (Fern.) Nesom | SYCOR |
| Symphyotrichum cordifolium | Symphyotrichum sagittifolium (Wedemeyer ex Willd.) Nesom | SYSA4 |
| Symphyotrichum cusickii | Aster cusickii Gray | ASCU11 |
| Symphyotrichum cusickii | Aster foliaceus Lindl. ex DC. var. cusickii (Gray) Cronq. | ASFOC2 |
| Symphyotrichum defoliatum | Aster bernardinus Hall | ASBE |
| Symphyotrichum defoliatum | Aster defoliatus Parish | ASDE10 |
| Symphyotrichum defoliatum | Aster deserticola J.F. Macbr. | ASDE17 |
| Symphyotrichum defoliatum | Virgulaster bernardinus (Hall) Semple | VIBE7 |
| Symphyotrichum depauperatum | Aster depauperatus Fern. | ASDE9 |
| Symphyotrichum depauperatum | Aster ericoides sensu Ait. var. pusillus Gray | ASERP3 |
| Symphyotrichum depauperatum | Aster pilosus Willd. var. pusillus (Gray) A.G. Jones | ASPIP5 |
| Symphyotrichum divaricatum | Aster divaricatus (Nutt.) Torr. & Gray, non L. | ASDI17 |
| Symphyotrichum divaricatum | Aster exilis Ell. nom. dub. | ASEX5 |
| Symphyotrichum divaricatum | Aster neomexicanus Woot. & Standl. | ASNE8 |
| Symphyotrichum divaricatum | Aster subulatus Michx. var. ligulatus Shinners | ASSUL |
| Symphyotrichum drummondii var. drummondii | Aster drummondii Lindl. | ASDR |
| Symphyotrichum drummondii var. drummondii | Aster sagittifolius Wedemeyer ex Willd. var. drummondii (Lindl.) Shinners | ASSAD2 |
| Symphyotrichum drummondii var. texanum | Aster drummondii Lindl. ssp. parviceps (Shinners) A.G. Jones | ASDRP2 |
| Symphyotrichum drummondii var. texanum | Aster drummondii Lindl. ssp. texanus (Burgess) A.G. Jones | ASDRT2 |
| Symphyotrichum drummondii var. texanum | Aster drummondii Lindl. var. parviceps (Shinners) A.G. Jones | ASDRP |
| Symphyotrichum drummondii var. texanum | Aster drummondii Lindl. var. texanus (Burgess) A.G. Jones | ASDRT |
| Symphyotrichum drummondii var. texanum | Aster texanus Burgess | ASTE3 |
| Symphyotrichum drummondii var. texanum | Aster texanus Burgess var. parviceps Shinners | ASTEP |
| Symphyotrichum drummondii var. texanum | Symphyotrichum drummondii (Lindl.) Nesom var. parviceps (Shinners) Nesom | SYDRP |
| Symphyotrichum dumosum var. dumosum | Aster coridifolius Michx. | ASCO38 |
| Symphyotrichum dumosum var. dumosum | Aster dumosus L. | ASDU |
| Symphyotrichum dumosum var. dumosum | Aster dumosus L. var. coridifolius (Michx.) Torr. & Gray | ASDUC |
| Symphyotrichum dumosum var. dumosum | Aster dumosus L. var. gracilentus Torr. & Gray | ASDUG2 |
| Symphyotrichum dumosum var. gracilipes | Aster dumosus L. var. gracilipes Wieg. | ASDUG |
| Symphyotrichum dumosum var. gracilipes | Aster gracilipes (Wieg.) Alexander | ASGR6 |
| Symphyotrichum dumosum var. pergracile | Aster dumosus L. var. pergracilis Wieg. | ASDUP |
| Symphyotrichum dumosum var. strictior | Aster dumosus L. var. dodgei Fern. | ASDUD |
| Symphyotrichum dumosum var. strictior | Aster dumosus L. var. strictior Torr. & Gray | ASDUS |
| Symphyotrichum dumosum var. strictior | Symphyotrichum dumosum (L.) Nesom var. dodgei (Fern.) Nesom | SYDUD |
| Symphyotrichum dumosum var. subulifolium | Aster dumosus L. var. subulifolius Torr. & Gray | ASDUS2 |
| Symphyotrichum eatonii | Aster bracteolatus auct. non Nutt. p.p. [misapplied] | ASBR11 |
| Symphyotrichum eatonii | Aster cordalenus Henderson | ASCO36 |
| Symphyotrichum eatonii | Aster eatonii (Gray) T.J. Howell | ASEA |
| Symphyotrichum eatonii | Aster foliaceus Lindl. ex DC. var. eatonii Gray | ASFOE |
| Symphyotrichum eatonii | Aster mearnsii Rydb. | ASME5 |
| Symphyotrichum eatonii | Aster oregonus auct. non (Nutt.) Torr. & Gray [misapplied] | ASOR4 |
| Symphyotrichum eatonii | Symphyotrichum bracteolatum auct. non (Nutt.) Nesom p.p. [misapplied] | SYBR2 |
| Symphyotrichum elliotii | Aster elliottii Torr. & Gray | ASEL4 |
| Symphyotrichum elliotii | Aster puniceus L. ssp. elliottii (Torr. & Gray) A.G. Jones | ASPUE2 |
| Symphyotrichum elliotii | Aster puniceus L. var. elliottii (Torr. & Gray) A.G. Jones | ASPUE |
| Symphyotrichum ericoides var. ericoides | Aster ericoides L. | ASER3 |
| Symphyotrichum ericoides var. ericoides | Aster ericoides L. var. prostratus (Kuntze) Blake | ASERP |
| Symphyotrichum ericoides var. ericoides | Aster exiguus Rydb. | ASEX6 |
| Symphyotrichum ericoides var. ericoides | Aster multiflorus Ait. | ASMU5 |
| Symphyotrichum ericoides var. ericoides | Aster multiflorus Ait. var. exiguus Fern. | ASMUE |
| Symphyotrichum ericoides var. ericoides | Aster multiflorus Ait. var. prostratus Kuntze | ASMUP |
| Symphyotrichum ericoides var. ericoides | Aster polycephalus Rydb. | ASPO7 |
| Symphyotrichum ericoides var. ericoides | Lasallea ericoides (L.) Semple & L. Brouillet | LAER3 |
| Symphyotrichum ericoides var. ericoides | Symphyotrichum ericoides (L.) Nesom var. prostratum (Kuntze) Nesom | SYERP |
| Symphyotrichum ericoides var. ericoides | Virgulus ericoides (L.) Reveal & Keener | VIER4 |
| Symphyotrichum ericoides var. pansum | Aster ericoides sensu Ait. ssp. pansus (Blake) A.G. Jones | ASERP7 |
| Symphyotrichum ericoides var. pansum | Aster ericoides sensu Ait. var. pansus (Blake) Boivin | ASERP2 |
| Symphyotrichum ericoides var. pansum | Aster multiflorus Ait. var. pansus Blake | ASMUP2 |
| Symphyotrichum ericoides var. pansum | Aster pansus (Blake) Cronq. | ASPA3 |
| Symphyotrichum ericoides var. stricticaule | Aster ericoides sensu Ait. var. stricticaulis (Torr. & Gray) F.C. Gates | ASERS |
| Symphyotrichum ericoides var. stricticaule | Aster multiflorus Ait. var. stricticaulis Torr. & Gray | ASMUS |
| Symphyotrichum ericoides var. stricticaule | Aster stricticaulis (Torr. & Gray) Rydb. | ASST19 |
| Symphyotrichum eulae | Aster eulae Shinners | ASEU |
| Symphyotrichum expansum | Aster inconspicuus Less. | ASIN15 |
| Symphyotrichum expansum | Aster subulatus Michx. var. cubensis (DC.) Shinners | ASSUC |
| Symphyotrichum expansum | Tripolium subulatum (L.) Nees var. parviflorum Nees | TRSUP |
| Symphyotrichum falcatum var. commutatum | Aster adsurgens auct. non Greene [misapplied] | ASAD7 |
| Symphyotrichum falcatum var. commutatum | Aster commutatus (Torr. & Gray) Gray | ASCO22 |
| Symphyotrichum falcatum var. commutatum | Aster commutatus (Torr. & Gray) Gray var. crassulus (Rydb.) Blake | ASCOC |
| Symphyotrichum falcatum var. commutatum | Aster commutatus (Torr. & Gray) Gray var. polycephalus Blake, non Aster polycephalus Rydb. | ASCOP |
| Symphyotrichum falcatum var. commutatum | Aster cordineri A. Nels. | ASCO27 |
| Symphyotrichum falcatum var. commutatum | Aster crassulus Rydb. | ASCR11 |
| Symphyotrichum falcatum var. commutatum | Aster ericoides L. var. commutatus (Torr. & Gray) Boivin p.p. | ASERC |
| Symphyotrichum falcatum var. commutatum | Aster falcatus Lindl. ssp. commutatus (Torr. & Gray) A.G. Jones | ASFAC3 |
| Symphyotrichum falcatum var. commutatum | Aster falcatus Lindl. var. commutatus (Torr. & Gray) A.G. Jones | ASFAC |
| Symphyotrichum falcatum var. commutatum | Aster falcatus Lindl. var. crassulus (Rydb.) Cronq. | ASFAC2 |
| Symphyotrichum falcatum var. commutatum | Aster multiflorus Ait. var. commutatus Torr. & Gray | ASMUC |
| Symphyotrichum falcatum var. commutatum | Aster nahanniensis Cody | ASNA4 |
| Symphyotrichum falcatum var. commutatum | Symphyotrichum falcatum (Lindl.) Nesom var. crassulum (Rydb.) Nesom | SYFAC2 |
| Symphyotrichum falcatum var. falcatum | Aster elegantulus Porsild | ASEL5 |
| Symphyotrichum falcatum var. falcatum | Aster ericoides L. var. commutatus (Torr. & Gray) Boivin p.p. | ASERC |
| Symphyotrichum falcatum var. falcatum | Aster falcatus Lindl. | ASFA2 |
| Symphyotrichum falcatum var. falcatum | Aster ramulosus Lindl. | ASRA9 |
| Symphyotrichum falcatum var. falcatum | Lasallea falcata (Lindl.) Semple & L. Brouillet | LAFA4 |
| Symphyotrichum falcatum var. falcatum | Virgulus falcatus (Lindl.) Reveal & Keener | VIFA2 |
| Symphyotrichum fendleri | Aster fendleri Gray | ASFE |
| Symphyotrichum fendleri | Virgulus fendleri (Gray) Reveal & Keener | VIFE3 |
| Symphyotrichum foliaceum var. apricum | Aster apricus (Gray) Rydb. | ASAP2 |
| Symphyotrichum foliaceum var. apricum | Aster foliaceus Lindl. ex DC. var. apricus Gray | ASFOA |
| Symphyotrichum foliaceum var. apricum | Aster subspicatus Nees var. apricus (Gray) Boivin | ASSUA2 |
| Symphyotrichum foliaceum var. canbyi | Aster foliaceus Lindl. ex DC. var. burkei Gray | ASFOB |
| Symphyotrichum foliaceum var. canbyi | Aster foliaceus Lindl. ex DC. var. canbyi Gray | ASFOC |
| Symphyotrichum foliaceum var. canbyi | Aster phyllodes Rydb. | ASPH4 |
| Symphyotrichum foliaceum var. canbyi | Aster tweedyi Rydb. | ASTW2 |
| Symphyotrichum foliaceum var. foliaceum | Aster foliaceus Lindl. ex DC. | ASFO |
| Symphyotrichum foliaceum var. foliaceum | Aster foliaceus Lindl. ex DC. var. sublinearis D.C. Eat. & Grisc. | ASFOS |
| Symphyotrichum foliaceum var. parryi | Aster ascendens Lindl. var. parryi D.C. Eat. | ASASP |
| Symphyotrichum foliaceum var. parryi | Aster diabolicus Piper | ASDI9 |
| Symphyotrichum foliaceum var. parryi | Aster foliaceus Lindl. ex DC. var. frondeus Gray | ASFOF2 |
| Symphyotrichum foliaceum var. parryi | Aster foliaceus Lindl. ex DC. var. parryi (D.C. Eat.) Gray | ASFOP |
| Symphyotrichum foliaceum var. parryi | Aster foliaceus Lindl. ex DC. var. subpetiolatus Fern. | ASFOS3 |
| Symphyotrichum foliaceum var. parryi | Aster frondeus (Gray) Greene | ASFR8 |
| Symphyotrichum fontinale | Aster fontinalis Alexander | ASFO4 |
| Symphyotrichum fontinale | Aster patens Ait. var. floridanus R.W. Long | ASPAF |
| Symphyotrichum frondosum | Aster frondosus (Nutt.) Torr. & Gray | ASFR |
| Symphyotrichum frondosum | Brachyactis frondosa (Nutt.) Gray | BRFR4 |
| Symphyotrichum frondosum | Tripolium frondosum Nutt. | TRFR3 |
| Symphyotrichum georgianum | Aster georgianus Alexander | ASGE2 |
| Symphyotrichum georgianum | Aster patens Ait. var. georgianus (Alexander) Cronq. | ASPAG |
| Symphyotrichum georgianum | Virgulus georgianus (Alexander) Semple | VIGE |
| Symphyotrichum georgianum | Virgulus patens (Ait.) Reveal & Keener var. georgianus (Alexander) Reveal & Keener | VIPAG |
| Symphyotrichum grandiflorum | Aster grandiflorus L. | ASGR |
| Symphyotrichum grandiflorum | Lasallea grandiflora (L.) Semple & L. Brouillet | LAGR5 |
| Symphyotrichum grandiflorum | Virgulus grandiflorus (L.) Reveal & Keener | VIGR5 |
| Symphyotrichum greatae | Aster greatae Parish | ASGR2 |
| Symphyotrichum hallii | Aster chilensis Nees ssp. hallii (Gray) Cronq. | ASCHH |
| Symphyotrichum hallii | Aster hallii Gray | ASHA7 |
| Symphyotrichum hendersonii | Aster cusickii Gray var. lyallii Gray | ASCUL |
| Symphyotrichum hendersonii | Aster foliaceus Lindl. ex DC. var. lyallii (Gray) Cronq. | ASFOL |
| Symphyotrichum hendersonii | Aster hendersonii Fern. | ASHE10 |
| Symphyotrichum jessicae | Aster jessicae Piper | ASJE |
| Symphyotrichum kralii | Aster pinifolius Alexander, non Nees | ASPI5 |
| Symphyotrichum laeve var. concinnum | Aster concinnus Willd. | ASCO23 |
| Symphyotrichum laeve var. concinnum | Aster laevis L. var. concinnus (Willd.) House | ASLAC |
| Symphyotrichum laeve var. geyeri | Aster geyeri (Gray) T.J. Howell | ASGE3 |
| Symphyotrichum laeve var. geyeri | Aster laevis L. var. geyeri Gray | ASLAG |
| Symphyotrichum laeve var. geyeri | Aster laevis L. var. guadalupensis A.G. Jones | ASLAG3 |
| Symphyotrichum laeve var. geyeri | Aster pickettianus Suksdorf | ASPI8 |
| Symphyotrichum laeve var. laeve | Aster falcidens Burgess | ASFA5 |
| Symphyotrichum laeve var. laeve | Aster laevis L. | ASLA5 |
| Symphyotrichum laeve var. laeve | Aster laevis L. var. falcatus Farw. | ASLAF2 |
| Symphyotrichum laeve var. laeve | Aster steeleorum Shinners | ASST18 |
| Symphyotrichum laeve var. purpuratum | Aster attenuatus auct. non Lindl. ex Hook. [misapplied] | ASAT3 |
| Symphyotrichum laeve var. purpuratum | Aster laevis L. var. purpuratus (Nees) A.G. Jones | ASLAP2 |
| Symphyotrichum laeve var. purpuratum | Aster purpuratus Nees | ASPU11 |
| Symphyotrichum laeve var. purpuratum | Aster virgatus Ell., non Moench | ASVI13 |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster hesperius Gray | ASHE |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster hesperius Gray var. laetevirens (Greene) Cronq. | ASHEL |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster hesperius Gray var. wootonii Greene | ASHEW |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster laetevirens Greene | ASLA11 |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster lanceolatus Willd. ssp. hesperius (Gray) Semple & Chmielewski | ASLAH2 |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster osterhoutii Rydb. | ASOS2 |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Aster wootonii (Greene) Greene | ASWO4 |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | Symphyotrichum hesperium (Gray) A.& D. L?ve | SYHE2 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. hirsuticaule | Aster lanceolatus Willd. var. hirsuticaulis Semple & Chmielewski | ASLAH5 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. interior | Aster interior Wieg. | ASIN18 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. interior | Aster lanceolatus Willd. ssp. interior (Wieg.) A.G. Jones | ASLAI3 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. interior | Aster lanceolatus Willd. var. interior (Wieg.) A.G. Jones | ASLAI4 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. interior | Aster simplex Willd. var. interior (Wieg.) Cronq. | ASSII |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster bellidiflorus Willd. | ASBE8 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster lamarckianus Nees | ASLA12 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster lanceolatus Willd. | ASLA80 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster lanceolatus Willd. ssp. simplex (Willd.) A.G. Jones | ASLAS3 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster lanceolatus Willd. var. simplex (Willd.) A.G. Jones | ASLAS4 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster laxus Willd. | ASLA17 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster paniculatus Lam. p.p., non P. Mill. | ASPA35 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster paniculatus Lam. var. simplex (Willd.) Burgess | ASPAS |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster simplex Willd. | ASSI2 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster simplex Willd. var. estuarinus Boivin | ASSIE |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster simplex Willd. var. ramosissimus (Torr. & Gray) Cronq. | ASSIR |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Aster tenuifolius L. var. ramosissimus Torr. & Gray | ASTER3 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. lanceolatum | Symphyotrichum simplex (Willd.) A.& D. L?ve | SYSI2 |
| Symphyotrichum lanceolatum ssp. lanceolatum var. latifolium | Aster lanceolatus Willd. var. latifolius Semple & Chmielewski | ASLAL5 |
| Symphyotrichum lateriflorum var. angustifolium | Aster agrostifolius Burgess | ASAG4 |
| Symphyotrichum lateriflorum var. angustifolium | Aster lateriflorus (L.) Britt. var. angustifolius Wieg. | ASLAA |
| Symphyotrichum lateriflorum var. flagellare | Aster lateriflorus (L.) Britt. var. flagellaris Shinners | ASLAF |
| Symphyotrichum lateriflorum var. flagellare | Aster lateriflorus (L.) Britt. var. indutus Shinners | ASLAI |
| Symphyotrichum lateriflorum var. horizontale | Aster horizontalis Desf. | ASHO7 |
| Symphyotrichum lateriflorum var. horizontale | Aster lateriflorus (L.) Britt. var. horizontalis (Desf.) Farw. | ASLAH |
| Symphyotrichum lateriflorum var. horizontale | Aster lateriflorus (L.) Britt. var. pendulus (Ait.) Burgess | ASLAP |
| Symphyotrichum lateriflorum var. horizontale | Aster pendulus Ait. | ASPE9 |
| Symphyotrichum lateriflorum var. lateriflorum | Aster hirsuticaulis Lindl. ex DC. | ASHI4 |
| Symphyotrichum lateriflorum var. lateriflorum | Aster lateriflorus (L.) Britt. | ASLA6 |
| Symphyotrichum lateriflorum var. lateriflorum | Aster lateriflorus (L.) Britt. var. hirsuticaulis (Lindl. ex DC.) Porter | ASLAH3 |
| Symphyotrichum lateriflorum var. lateriflorum | Aster vimineus Lam. | ASVI16 |
| Symphyotrichum lateriflorum var. lateriflorum | Solidago lateriflora L. | SOLA5 |
| Symphyotrichum lateriflorum var. lateriflorum | Symphyotrichum lateriflorum (L.) A.& D. L?ve var. hirsuticaule (DC.) Nesom | SYLAH4 |
| Symphyotrichum lateriflorum var. spatelliforme | Aster lateriflorus (L.) Britt. var. spatelliformis (Burgess) A.G. Jones | ASLAS |
| Symphyotrichum lateriflorum var. spatelliforme | Aster spatelliformis Burgess | ASSP10 |
| Symphyotrichum lateriflorum var. tenuipes | Aster acadiensis Shinners | ASAC10 |
| Symphyotrichum lateriflorum var. tenuipes | Aster lateriflorus (L.) Britt. var. tenuipes Wieg. | ASLAT2 |
| Symphyotrichum lentum | Aster chilensis Nees var. lentus (Greene) Jepson | ASCHL |
| Symphyotrichum lentum | Aster chilensis Nees var. sonomensis (Greene) Jepson | ASCHS |
| Symphyotrichum lentum | Aster lentus Greene | ASLE17 |
| Symphyotrichum lentum | Aster sonomensis Greene | ASSO6 |
| Symphyotrichum lowrieanum | Aster cordifolius L. ssp. laevigatus (Porter) A.G. Jones | ASCOL4 |
| Symphyotrichum lowrieanum | Aster cordifolius L. var. laevigatus Porter | ASCOL2 |
| Symphyotrichum lowrieanum | Aster lowrieanus Porter | ASLO9 |
| Symphyotrichum molle | Aster mollis Rydb. | ASMO13 |
| Symphyotrichum novae-angliae | Aster novae-angliae L. | ASNO |
| Symphyotrichum novae-angliae | Lasallea novae-angliae (L.) Semple & L. Brouillet | LANO |
| Symphyotrichum novae-angliae | Virgulus novae-angliae (L.) Reveal & Keener | VINO5 |
| Symphyotrichum novi-belgii var. elodes | Aster elodes Torr. & Gray | ASEL9 |
| Symphyotrichum novi-belgii var. elodes | Aster novi-belgii L. var. elodes (Torr. & Gray) Gray | ASNOE |
| Symphyotrichum novi-belgii var. novi-belgii | Aster eminens Willd. | ASEM3 |
| Symphyotrichum novi-belgii var. novi-belgii | Aster junceus Ait. | ASJU6 |
| Symphyotrichum novi-belgii var. novi-belgii | Aster longifolius Lam. | ASLO10 |
| Symphyotrichum novi-belgii var. novi-belgii | Aster novi-belgii L. | ASNO2 |
| Symphyotrichum novi-belgii var. novi-belgii | Aster salicifolius sensu Willd., non Lam. nec Ait. | ASSA12 |
| Symphyotrichum novi-belgii var. novi-belgii | Symphyotrichum longifolium (Lam.) Nesom, as to type | SYLO3 |
| Symphyotrichum novi-belgii var. villicaule | Aster gaspensis Victorin | ASGA7 |
| Symphyotrichum novi-belgii var. villicaule | Aster johannensis Fern. | ASJO2 |
| Symphyotrichum novi-belgii var. villicaule | Aster johannensis Fern. var. villicaulis (Gray) Fern. | ASJOV |
| Symphyotrichum novi-belgii var. villicaule | Aster longifolius Lam. var. villicaulis Gray | ASLOV |
| Symphyotrichum novi-belgii var. villicaule | Aster novi-belgii L. ssp. johannensis (Fern.) A.G. Jones | ASNOJ2 |
| Symphyotrichum novi-belgii var. villicaule | Aster novi-belgii L. var. johannensis (Fern.) A.G. Jones | ASNOJ |
| Symphyotrichum novi-belgii var. villicaule | Aster novi-belgii L. var. villicaulis (Gray) Boivin | ASNOV |
| Symphyotrichum novi-belgii var. villicaule | Aster tardiflorus L. var. vestitus Fern. | ASTAV |
| Symphyotrichum oblongifolium | Aster kumleinii Fries ex Gray | ASKU |
| Symphyotrichum oblongifolium | Aster oblongifolius Nutt. | ASOB2 |
| Symphyotrichum oblongifolium | Aster oblongifolius Nutt. var. angustatus Shinners | ASOBA |
| Symphyotrichum oblongifolium | Aster oblongifolius Nutt. var. orientis Shinners | ASOBO |
| Symphyotrichum oblongifolium | Aster oblongifolius Nutt. var. rigidulus Gray | ASOBR |
| Symphyotrichum oblongifolium | Lasallea oblongifolia (Nutt.) Semple & L. Brouillet | LAOB |
| Symphyotrichum oblongifolium | Virgulus oblongifolius (Nutt.) Reveal & Keener | VIOB5 |
| Symphyotrichum ontarionis | Aster diffusus Ait. var. thyrsoides Gray | ASDIT |
| Symphyotrichum ontarionis | Aster lateriflorus (L.) Britt. var. thyrsoides (Gray) Sheldon | ASLAT |
| Symphyotrichum ontarionis | Aster missouriensis Britt. var. thyrsoides (Gray) Wieg. | ASMIT2 |
| Symphyotrichum ontarionis | Aster missouriensis Britt., non Kuntze | ASMI14 |
| Symphyotrichum ontarionis | Aster ontarionis Wieg. | ASON |
| Symphyotrichum ontarionis | Aster ontarionis Wieg. var. glabratus Semple | ASONG |
| Symphyotrichum ontarionis | Aster pantotrichus Blake | ASPA23 |
| Symphyotrichum ontarionis | Aster pantotrichus Blake var. thyrsoides (Gray) Blake | ASPAT |
| Symphyotrichum ontarionis | Aster tradescantii L. var. thyrsoides (Gray) Boivin | ASTRT3 |
| Symphyotrichum ontarionis | Symphyotrichum ontarione (Wieg.) Nesom var. glabratum (Semple) L. Brouillet & Bouchard [orthographic variant] | SYONG |
| Symphyotrichum ontarionis | Symphyotrichum ontarione (Wieg.) Nesom [orthographic variant] | SYON |
| Symphyotrichum ontarionis | Symphyotrichum ontarionis (Wieg.) Nesom var. glabratum (Semple) L. Brouillet & Bouchard | SYONG2 |
| Symphyotrichum oolentangiense var. oolentangiense | Aster azureus Lindl. | ASAZ |
| Symphyotrichum oolentangiense var. oolentangiense | Aster oolentangiensis Riddell | ASOO4 |
| Symphyotrichum oolentangiense var. oolentangiense | Aster oolentangiensis Riddell var. laevicaulis (Fern.) A.G. Jones | ASOOL2 |
| Symphyotrichum oolentangiense var. poaceum | Aster azureus Lindl. var. poaceus (Burgess) Fern. | ASAZP |
| Symphyotrichum oolentangiense var. poaceum | Aster oolentangiensis Riddell var. poaceus (Burgess) A.G. Jones | ASOOP |
| Symphyotrichum oolentangiense var. poaceum | Aster poaceus Burgess | ASPO8 |
| Symphyotrichum oolentangiense var. poaceum | Aster vernalis Engelm. ex Burgess | ASVE4 |
| Symphyotrichum parviceps | Aster depauperatus Fern. var. parviceps (Burgess) Fern. | ASDEP2 |
| Symphyotrichum parviceps | Aster ericoides sensu Ait. var. parviceps Burgess | ASERP5 |
| Symphyotrichum parviceps | Aster parviceps (Burgess) Mackenzie & Bush | ASPA4 |
| Symphyotrichum parviceps | Aster pilosus Willd. ssp. parviceps (Burgess) A.G. Jones | ASPIP6 |
| Symphyotrichum patens var. gracile | Aster patens Ait. var. gracilis Hook. | ASPAG2 |
| Symphyotrichum patens var. gracile | Aster tenuicaulis (C. Mohr) Burgess | ASTE12 |
| Symphyotrichum patens var. gracile | Virgulus patens (Ait.) Reveal & Keener var. gracilis (Hook.) Reveal & Keener | VIPAG2 |
| Symphyotrichum patens var. patens | Aster patens Ait. | ASPA5 |
| Symphyotrichum patens var. patens | Lasallea patens (Ait.) Semple & L. Brouillet | LAPA8 |
| Symphyotrichum patens var. patens | Virgulus patens (Ait.) Reveal & Keener | VIPA10 |
| Symphyotrichum patens var. patentissimum | Aster continuus Small | ASCO25 |
| Symphyotrichum patens var. patentissimum | Aster patens Ait. var. patentissimus (Lindl. ex DC.) Torr. & Gray | ASPAP |
| Symphyotrichum patens var. patentissimum | Aster patentissimus Lindl. ex DC. | ASPA24 |
| Symphyotrichum patens var. patentissimum | Aster subsessilis Burgess | ASSU17 |
| Symphyotrichum patens var. patentissimum | Virgulus patens (Ait.) Reveal & Keener var. patentissimus (Lindl. ex DC.) Reveal & Keener | VIPAP3 |
| Symphyotrichum phlogifolium | Aster patens Ait. var. phlogifolius (Muhl. ex Willd.) Nees | ASPAP2 |
| Symphyotrichum phlogifolium | Aster phlogifolius Muhl. ex Willd. | ASPH6 |
| Symphyotrichum phlogifolium | Virgulus patens (Ait.) Reveal & Keener var. phlogifolius (Muhl. ex Willd.) Reveal & Keener | VIPAP4 |
| Symphyotrichum pilosum var. pilosum | Aster ericoides sensu Ait. var. platyphyllus Torr. & Gray | ASERP4 |
| Symphyotrichum pilosum var. pilosum | Aster ericoides sensu Ait. var. villosus (Michx.) Torr. & Gray | ASERV |
| Symphyotrichum pilosum var. pilosum | Aster juniperinus Burgess | ASJU3 |
| Symphyotrichum pilosum var. pilosum | Aster pilosus Willd. | ASPI2 |
| Symphyotrichum pilosum var. pilosum | Aster pilosus Willd. var. platyphyllus (Torr. & Gray) Blake | ASPIP7 |
| Symphyotrichum pilosum var. pilosum | Aster ramosissimus auct. non P. Mill. [misapplied] | ASRA10 |
| Symphyotrichum pilosum var. pilosum | Aster villosus Michx. | ASVI15 |
| Symphyotrichum pilosum var. pringlei | Aster ericoides sensu Ait. var. pringlei Gray | ASERP6 |
| Symphyotrichum pilosum var. pringlei | Aster faxonii Porter | ASFA4 |
| Symphyotrichum pilosum var. pringlei | Aster pilosus Willd. var. demotus Blake | ASPID3 |
| Symphyotrichum pilosum var. pringlei | Aster pilosus Willd. var. pringlei (Gray) Blake | ASPIP |
| Symphyotrichum pilosum var. pringlei | Aster polyphyllus Willd., non Moench | ASPO9 |
| Symphyotrichum pilosum var. pringlei | Aster pringlei (Gray) Britt. | ASPR13 |
| Symphyotrichum porteri | Aster ericoides L. var. strictus Porter | ASERS3 |
| Symphyotrichum porteri | Aster porteri Gray | ASPO5 |
| Symphyotrichum potosinum | Aster lemmonii Gray | ASLE14 |
| Symphyotrichum potosinum | Aster potosinus Gray | ASPO6 |
| Symphyotrichum praealtum var. angustior | Aster praealtus Poir. var. angustior Wieg. | ASPRA |
| Symphyotrichum praealtum var. nebraskense | Aster nebraskensis Britt. | ASNE7 |
| Symphyotrichum praealtum var. nebraskense | Aster praealtus Poir. var. nebraskensis (Britt.) Wieg. | ASPRN |
| Symphyotrichum praealtum var. praealtum | Aster caerulescens DC. | ASCA48 |
| Symphyotrichum praealtum var. praealtum | Aster coerulescens DC. [orthographic variant] | ASCO20 |
| Symphyotrichum praealtum var. praealtum | Aster novi-belgii L. var. litoreus Gray | ASNOL |
| Symphyotrichum praealtum var. praealtum | Aster praealtus Poir. | ASPR2 |
| Symphyotrichum praealtum var. praealtum | Aster praealtus Poir. var. caerulescens (DC.) A.G. Jones | ASPRC |
| Symphyotrichum praealtum var. praealtum | Aster praealtus Poir. var. imbricatior Wieg. | ASPRI |
| Symphyotrichum praealtum var. praealtum | Aster praealtus Poir. var. texicola Wieg. | ASPRT |
| Symphyotrichum praealtum var. praealtum | Aster salicifolius Ait., non Lam. | ASSA11 |
| Symphyotrichum praealtum var. praealtum | Symphyotrichum novi-belgii (L.) Nesom var. litoreum (Gray) Nesom | SYNOL |
| Symphyotrichum praealtum var. praealtum | Symphyotrichum praealtum (Poir.) Nesom var. texicola (Wieg.) Nesom | SYPRT |
| Symphyotrichum praealtum var. subasperum | Aster praealtus Poir. var. subasper (Lindl.) Wieg. | ASPRS |
| Symphyotrichum praealtum var. subasperum | Aster subasper Lindl. | ASSU16 |
| Symphyotrichum pratense | Aster phyllolepis Torr. & Gray | ASPH5 |
| Symphyotrichum pratense | Aster pratensis Raf. | ASPR3 |
| Symphyotrichum pratense | Aster sericeus Vent. var. microphyllus DC. | ASSEM |
| Symphyotrichum pratense | Lasallea sericea (Vent.) Greene ssp. pratensis (Raf.) Semple & L. Brouillet | LASEP2 |
| Symphyotrichum pratense | Virgulus pratensis (Raf.) Reveal & Keener | VIPR8 |
| Symphyotrichum prenanthoides | Aster prenanthoides Muhl. ex Willd. | ASPR4 |
| Symphyotrichum priceae | Aster kentuckiensis Britt. | ASKE4 |
| Symphyotrichum priceae | Aster pilosus Willd. var. priceae (Britt.) Cronq. | ASPIP2 |
| Symphyotrichum priceae | Aster priceae Britt. | ASPR17 |
| Symphyotrichum puniceum var. puniceum | Aster calderi Boivin | ASCA21 |
| Symphyotrichum puniceum var. puniceum | Aster conduplicatus Burgess | ASCO24 |
| Symphyotrichum puniceum var. puniceum | Aster firmus Nees | ASFI5 |
| Symphyotrichum puniceum var. puniceum | Aster forwoodii S. Wats. | ASFO8 |
| Symphyotrichum puniceum var. puniceum | Aster lucidulus (Gray) Wieg. | ASLU |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. | ASPU5 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. ssp. firmus (Nees) A.G. Jones | ASPUF2 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. calderi (Boivin) Lepage | ASPUC2 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. calvus Shinners | ASPUC3 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. compactus Fern. | ASPUC4 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. demissus Lindl. | ASPUD |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. firmus (Nees) Torr. & Gray | ASPUF |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. lucidulus Gray | ASPUL4 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. oligocephalus Fern. | ASPUO2 |
| Symphyotrichum puniceum var. puniceum | Aster puniceus L. var. perlongus Fern. | ASPUP3 |
| Symphyotrichum puniceum var. puniceum | Symphyotrichum firmum (Nees) Nesom | SYFI5 |
| Symphyotrichum puniceum var. puniceum | Symphyotrichum puniceum (L.) A.& D. L?ve var. calderi (Boivin) Nesom | SYPUC |
| Symphyotrichum puniceum var. scabricaule | Aster puniceus L. var. scabricaulis (Shinners) A.G. Jones | ASPUS2 |
| Symphyotrichum puniceum var. scabricaule | Aster scabricaulis Shinners | ASSC |
| Symphyotrichum racemosum | Aster brachypholis Small | ASBR10 |
| Symphyotrichum racemosum | Aster fragilis auct. non Willd. [misapplied] | ASFR2 |
| Symphyotrichum racemosum | Aster fragilis Willd. var. brachypholis (Small) A.G. Jones | ASFRB |
| Symphyotrichum racemosum | Aster fragilis Willd. var. subdumosus (Wieg.) A.G. Jones | ASFRS |
| Symphyotrichum racemosum | Aster racemosus Ell. | ASRA7 |
| Symphyotrichum racemosum | Aster vimineus auct. non Lam. [misapplied] | ASVI5 |
| Symphyotrichum racemosum | Aster vimineus Lam. var. subdumosus Wieg. | ASVIS |
| Symphyotrichum racemosum | Symphyotrichum racemosum (Ell.) Nesom var. subdumosum (Wieg.) Nesom | SYRAS |
| Symphyotrichum retroflexum | Aster curtisii Torr. & Gray | ASCU10 |
| Symphyotrichum retroflexum | Aster retroflexus Lindl. ex DC. | ASRE9 |
| Symphyotrichum robynsianum | Aster longifolius sensu Semple & Heard, non Lam. | ASLO14 |
| Symphyotrichum robynsianum | Aster robynsianus Rouss. | ASRO5 |
| Symphyotrichum robynsianum | Symphyotrichum longifolium sensu Nesom, non Lam. | SYLO6 |
| Symphyotrichum sericeum | Aster sericeus Vent. | ASSE2 |
| Symphyotrichum sericeum | Lasallea sericea (Vent.) Greene | LASE5 |
| Symphyotrichum sericeum | Virgulus sericeus (Vent.) Reveal & Keener | VISE8 |
| Symphyotrichum shortii | Aster camptosorus Small | ASCA32 |
| Symphyotrichum shortii | Aster shortii Lindl. | ASSH |
| Symphyotrichum simmondsii | Aster simmondsii Small | ASSI7 |
| Symphyotrichum simmondsii | Aster sulznerae Small | ASSU18 |
| Symphyotrichum spathulatum var. intermedium | Aster occidentalis (Nutt.) Torr. & Gray var. intermedius Gray | ASOCI |
| Symphyotrichum spathulatum var. spathulatum | Aster ascendens Lindl. var. fremontii Torr. & Gray | ASASF |
| Symphyotrichum spathulatum var. spathulatum | Aster delectabilis Hall | ASDE18 |
| Symphyotrichum spathulatum var. spathulatum | Aster fremontii (Torr. & Gray) Gray | ASFR7 |
| Symphyotrichum spathulatum var. spathulatum | Aster fremontii (Torr. & Gray) Gray var. parishii Gray | ASFRP |
| Symphyotrichum spathulatum var. spathulatum | Aster occidentalis (Nutt.) Torr. & Gray | ASOC |
| Symphyotrichum spathulatum var. spathulatum | Aster occidentalis (Nutt.) Torr. & Gray var. delectabilis (Hall) Ferris | ASOCD |
| Symphyotrichum spathulatum var. spathulatum | Aster occidentalis (Nutt.) Torr. & Gray var. fremontii (Torr. & Gray) A.G. Jones | ASOCF |
| Symphyotrichum spathulatum var. spathulatum | Aster occidentalis (Nutt.) Torr. & Gray var. parishii (Gray) Ferris | ASOCP |
| Symphyotrichum spathulatum var. spathulatum | Aster spathulatus Lindl. | ASSP16 |
| Symphyotrichum spathulatum var. spathulatum | Symphyotrichum spathulatum (Lindl.) Nesom var. fremontii (Torr. & Gray) Nesom | SYSPF |
| Symphyotrichum spathulatum var. spathulatum | Tripolium occidentale Nutt. | TROC3 |
| Symphyotrichum spathulatum var. yosemitanum | Aster ascendens Lindl. var. yosemitanus Gray | ASASY |
| Symphyotrichum spathulatum var. yosemitanum | Aster occidentalis (Nutt.) Torr. & Gray var. yosemitanus (Gray) Cronq. | ASOCY |
| Symphyotrichum spathulatum var. yosemitanum | Aster paludicola Piper | ASPA25 |
| Symphyotrichum spathulatum var. yosemitanum | Aster yosemitanus (Gray) Greene | ASYO2 |
| Symphyotrichum squamatum | Aster divaricatus (Nutt.) Torr. & Gray var. sandwicensis Gray | ASDIS |
| Symphyotrichum squamatum | Aster exilis Ell. var. australis Gray | ASEXA |
| Symphyotrichum squamatum | Aster sandwicensis (Gray) Hieron. | ASSA7 |
| Symphyotrichum squamatum | Aster squamatus (Spreng.) Hieron. | ASSQ4 |
| Symphyotrichum squamatum | Aster subulatus Michx. var. australis (Gray) Shinners | ASSUA |
| Symphyotrichum squamatum | Aster subulatus Michx. var. sandwicensis (Gray) A.G. Jones | ASSUS2 |
| Symphyotrichum subspicatum var. grayi | Aster grayi Suksdorf | ASGR11 |
| Symphyotrichum subspicatum var. grayi | Aster subspicatus Nees var. grayi (Suksdorf) Cronq. | ASSUG |
| Symphyotrichum subspicatum var. subspicatum | Aster douglasii Lindl. | ASDO2 |
| Symphyotrichum subspicatum var. subspicatum | Aster oregonum (Nutt.) Torr. & Gray | ASOR5 |
| Symphyotrichum subspicatum var. subspicatum | Aster subspicatus Nees | ASSU4 |
| Symphyotrichum subspicatum var. subspicatum | Tripolium oregonum Nutt. | TROR5 |
| Symphyotrichum subulatum | Aster subulatus Michx. | ASSU5 |
| Symphyotrichum subulatum | Aster subulatus Michx. var. euroauster Fern. & Grisc. | ASSUE |
| Symphyotrichum subulatum | Aster subulatus Michx. var. obtusifolius Fern. | ASSUO |
| Symphyotrichum tenuifolium | Aster tenuifolius L. | ASTE2 |
| Symphyotrichum tradescantii | Aster saxatilis (Fern.) Blanch. nom. illeg. | ASSA14 |
| Symphyotrichum tradescantii | Aster tradescantii L. | ASTR3 |
| Symphyotrichum tradescantii | Aster tradescantii L. var. saxatilis (Fern.) House | ASTRS |
| Symphyotrichum tradescantii | Aster vimineus Lam. var. saxatilis Fern. | ASVIS2 |
| Symphyotrichum turbinellum | Aster turbinellus Lindl. | ASTU2 |
| Symphyotrichum undulatum | Aster asperifolius Burgess | ASAS8 |
| Symphyotrichum undulatum | Aster claviger Burgess | ASCL5 |
| Symphyotrichum undulatum | Aster corrigiatus Burgess | ASCO41 |
| Symphyotrichum undulatum | Aster diversifolius Michx. | ASDI10 |
| Symphyotrichum undulatum | Aster gracilescens Burgess | ASGR12 |
| Symphyotrichum undulatum | Aster linguiformis Burgess | ASLI10 |
| Symphyotrichum undulatum | Aster loriformis (Burgess) Burgess | ASLO12 |
| Symphyotrichum undulatum | Aster mohrii Burgess | ASMO12 |
| Symphyotrichum undulatum | Aster proteus Burgess | ASPR11 |
| Symphyotrichum undulatum | Aster sylvestris Burgess | ASSY2 |
| Symphyotrichum undulatum | Aster triangularis (Burgess) Burgess | ASTR15 |
| Symphyotrichum undulatum | Aster truellius Burgess | ASTR16 |
| Symphyotrichum undulatum | Aster undulatus L. | ASUN2 |
| Symphyotrichum undulatum | Aster undulatus L. var. asperulus Wood | ASUNA |
| Symphyotrichum undulatum | Aster undulatus L. var. diversifolius (Michx.) Gray | ASUND |
| Symphyotrichum undulatum | Aster undulatus L. var. loriformis Burgess | ASUNL |
| Symphyotrichum undulatum | Aster undulatus L. var. triangularis Burgess | ASUNT |
| Symphyotrichum urophyllum | Aster hirtellus Lindl. | ASHI5 |
| Symphyotrichum urophyllum | Aster sagittifolius auct. non Wedemeyer ex Willd. [misapplied] | ASSA13 |
| Symphyotrichum urophyllum | Aster sagittifolius Wedemeyer ex Willd. var. urophyllus (Lindl.) Burgess | ASSAU |
| Symphyotrichum urophyllum | Aster urophyllus Lindl. | ASUR2 |
| Symphyotrichum vahlii var. vahlii | Aster vahlii (Gaudich.) Hook. & Arn. | ASVA7 |
| Symphyotrichum walteri | Aster squarrosus sensu Walt., non All. | ASSQ2 |
| Symphyotrichum walteri | Aster walteri Alexander | ASWA5 |
| Symphyotrichum walteri | Lasallea walteri (Alexander) Semple & L. Brouillet | LAWA4 |
| Symphyotrichum walteri | Virgulus walteri (Alexander) Reveal & Keener | VIWA3 |
| Symphyotrichum welshii | Aster welshii Cronq. | ASWE6 |
| Symphyotrichum yukonense | Aster yukonensis Cronq. | ASYU |
| Symphyotrichum yukonense | Virgulus yukonensis (Cronq.) Reveal & Keener | VIYU |
| synedrella | Synedrella Gaertn. | SYNED |
| Synedrella nodiflora | Verbesina nodiflora L. | VENO2 |
| Syrian knapweed | Centaurea babylonica (L.) L. | CEBA4 |
| table Townsend daisy | Townsendia mensana M.E. Jones | TOME2 |
| tackstem | Calycoseris Gray | CALYC4 |
| tacky goldenweed | Pyrrocoma hirta (Gray) Greene | PYHI |
| tacky goldenweed | Pyrrocoma hirta (Gray) Greene var. hirta | PYHIH |
| tacky goldenweed | Pyrrocoma hirta (Gray) Greene var. lanulosa (Greene) Mayes ex G. Brown & Keil | PYHIL |
| tacky goldenweed | Pyrrocoma hirta (Gray) Greene var. sonchifolia (Greene) Kartesz & Gandhi | PYHIS |
| Tagetes erecta | Tagetes major Gaertn. | TAMA2 |
| Tagetes lemmonii | Tagetes alamensis Rydb. | TAAL2 |
| Tagetes lemmonii | Tagetes palmeri Gray | TAPA11 |
| Tagetes micrantha | Tagetes fragrantissima Sess? & Moc. | TAFR2 |
| Tagetes minuta | Tagetes bonariensis Pers. | TABO2 |
| Tagetes minuta | Tagetes glandulifera Schrank | TAGL2 |
| Tagetes minuta | Tagetes glandulosa Schrank ex Link | TAGL3 |
| Tagetes minuta | Tagetes porophylla Vell. | TAPO2 |
| Tagetes patula | Tagetes corymbosa Sweet | TACO4 |
| Tagetes patula | Tagetes remotiflora Kunze | TARE3 |
| Tagetes patula | Tagetes signata Bartling | TASI3 |
| Tagetes patula | Tagetes tenuifolia Millsp. | TATE4 |
| tall agoseris | Agoseris elata (Nutt.) Greene | AGEL |
| tall blacktip ragwort | Senecio atratus Greene | SEAT |
| tall blazing star | Liatris aspera Michx. | LIAS |
| tall blazing star | Liatris aspera Michx. var. aspera | LIASA |
| tall blazing star | Liatris aspera Michx. var. intermedia (Lunell) Gaiser | LIASI |
| tall blazing star | Liatris aspera Michx. var. salutans (Lunell) Shinners | LIASS |
| tall blue lettuce | Lactuca biennis (Moench) Fern. | LABI |
| tall chamomile | Anthemis altissima L. | ANAL11 |
| tall elephantsfoot | Elephantopus elatus Bertol. | ELEL3 |
| tall fleabane | Erigeron elatior (Gray) Greene | EREL9 |
| tall globethistle | Echinops exaltatus Schrad. | ECEX |
| tall groundsel | Senecio hydrophiloides Rydb. | SEHY |
| tall hawkweed | Hieracium piloselloides Vill. | HIPI2 |
| tall ironweed | Vernonia angustifolia Michx. | VEAN |
| tall ironweed | Vernonia angustifolia Michx. ssp. angustifolia | VEANA |
| tall ironweed | Vernonia angustifolia Michx. ssp. scaberrima (Nutt.) S.B. Jones & Faust | VEANS |
| tall ragwort | Senecio serra Hook. | SESE2 |
| tall ragwort | Senecio serra Hook. var. admirabilis (Greene) A. Nels. | SESEA |
| tall ragwort | Senecio serra Hook. var. serra | SESES |
| tall rattlesnakeroot | Prenanthes altissima L. | PRAL3 |
| tall thistle | Cirsium altissimum (L.) Hill | CIAL2 |
| tall thoroughwort | Eupatorium altissimum L. | EUAL3 |
| tall tickseed | Coreopsis tripteris L. | COTR4 |
| tall tidytips | Layia hieracioides (DC.) Hook. & Arn. | LAHI3 |
| tall Townsend daisy | Townsendia eximia Gray | TOEX |
| tall yellowtop | Senecio magnificus F. Muell. | SEMA14 |
| Tamaulipa azurea | Eupatorium azureum DC. | EUAZ |
| Tanacetum balsamita | Balsamita major Desf. | BAMA8 |
| Tanacetum balsamita | Balsamita major Desf. var. tanacetoides (Boiss.) Moldenke | BAMAT2 |
| Tanacetum balsamita | Chrysanthemum balsamita (L.) Baill. var. tanacetoides Boiss. | CHBAT |
| Tanacetum balsamita | Chrysanthemum balsamita (L.) Baill., non L. | CHBA6 |
| Tanacetum balsamita | Pyrethrum majus (Desf.) Tzvelev | PYMA2 |
| Tanacetum bipinnatum ssp. bipinnatum | Chrysanthemum bipinnatum L. | CHBI4 |
| Tanacetum bipinnatum ssp. huronense | Chrysanthemum bipinnatum L. ssp. huronense (Nutt.) Hult | CHBIH |
| Tanacetum bipinnatum ssp. huronense | Tanacetum huronense Nutt. | TAHU |
| Tanacetum bipinnatum ssp. huronense | Tanacetum huronense Nutt. var. bifarium Fern. | TAHUB |
| Tanacetum bipinnatum ssp. huronense | Tanacetum huronense Nutt. var. floccosum Raup | TAHUF |
| Tanacetum bipinnatum ssp. huronense | Tanacetum huronense Nutt. var. johannense Fern. | TAHUJ |
| Tanacetum bipinnatum ssp. huronense | Tanacetum huronense Nutt. var. terrae-novae Fern. | TAHUT |
| Tanacetum camphoratum | Tanacetum douglasii DC. | TADO |
| Tanacetum coccineum | Chrysanthemum coccineum Willd. | CHCO14 |
| Tanacetum coccineum | Chrysanthemum roseum Adams | CHRO7 |
| Tanacetum corymbosum | Chrysanthemum corymbosum L. | CHCO26 |
| Tanacetum parthenium | Chrysanthemum parthenium (L.) Bernh. | CHPA33 |
| Tanacetum parthenium | Matricaria parthenium L. | MAPA18 |
| Tanacetum vulgare | Chrysanthemum vulgare (L.) Bernh. | CHVU3 |
| Tanacetum vulgare | Tanacetum boreale Fisch. ex DC. | TABO4 |
| Tanacetum vulgare | Tanacetum vulgare L. var. crispum DC. | TAVUC |
| tanseyleaf tansyaster | Machaeranthera tanacetifolia (Kunth) Nees | MATA2 |
| tansy | Tanacetum L. | TANAC |
| tansy rosinweed | Silphium pinnatifidum Ell. | SIPI2 |
| tansyaster | Machaeranthera Nees | MACHA |
| tansyaster | Psilactis Gray | PSILA2 |
| tansyaster | Rayjacksonia R.L. Hartman & M.A. Lane | RAYJA |
| tapered cudweed | Pseudognaphalium attenuatum (DC.) A. Anderb. | PSAT5 |
| tapertip hawksbeard | Crepis acuminata Nutt. | CRAC2 |
| tapertip hawksbeard | Crepis acuminata Nutt. ssp. acuminata | CRACA |
| tapertip hawksbeard | Crepis acuminata Nutt. ssp. pluriflora Babcock & Stebbins | CRACP |
| taproot fleabane | Erigeron radicatus Hook. | ERRA2 |
| Taraxacum eriophorum | Taraxacum olympicum G.N. Jones | TAOL |
| Taraxacum laevigatum | Leontodon erythrospermum (Andrz. ex Bess.) Britt. | LEER2 |
| Taraxacum laevigatum | Taraxacum disseminatum Hagl. | TADI7 |
| Taraxacum laevigatum | Taraxacum erythrospermum Andrz. ex Bess. | TAER3 |
| Taraxacum laevigatum | Taraxacum lacistophyllum (Dahlst.) Raunk. | TALA8 |
| Taraxacum laevigatum | Taraxacum scanicum Dahlst. | TASC |
| Taraxacum lyratum | Taraxacum kamtschaticum Dahlst. | TAKA |
| Taraxacum lyratum | Taraxacum scopulorum (Gray) Rydb. | TASC3 |
| Taraxacum lyratum | Taraxacum sibiricum Dahlst. | TASI2 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum ambigens Fern. | TAAM2 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum ambigens Fern. var. flutius Fern. | TAAMF |
| Taraxacum officinale ssp. ceratophorum | Taraxacum amphiphron B?cher | TAAM3 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum arctogenum Dahlst. | TAAR4 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum brachyceras Dahlst. | TABR4 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum carthamopsis Porsild | TACA10 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum ceratophorum (Ledeb.) DC. | TACE |
| Taraxacum officinale ssp. ceratophorum | Taraxacum dumetorum Greene | TADU |
| Taraxacum officinale ssp. ceratophorum | Taraxacum eurylepium Dahlst. | TAEU |
| Taraxacum officinale ssp. ceratophorum | Taraxacum hyperboreum Dahlst. | TAHY2 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum integratum Hagl. | TAIN3 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum lacerum Greene | TALA |
| Taraxacum officinale ssp. ceratophorum | Taraxacum lapponicum Kihlm. ex Hand.-Maz. | TALA4 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum latispinulosum M.P. Christens. | TALA7 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum laurentianum Fern. | TALA6 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum longii Fern. | TALO2 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum malteanum Dahlst. | TAMA5 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum maurolepium Hagl. | TAMA6 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum mitratum Hagl. | TAMI4 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum multesimum Hagl. | TAMU2 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum naevosum Dahlst. | TANA |
| Taraxacum officinale ssp. ceratophorum | Taraxacum ovinum Rydb. | TAOV |
| Taraxacum officinale ssp. ceratophorum | Taraxacum paucisquamosum M.E. Peck | TAPA7 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum pellianum Porsild | TAPE3 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum pseudonorvegicum Dahlst. | TAPS |
| Taraxacum officinale ssp. ceratophorum | Taraxacum purpuridens Dahlst. | TAPU2 |
| Taraxacum officinale ssp. ceratophorum | Taraxacum torngatense Fern. | TATO |
| Taraxacum officinale ssp. ceratophorum | Taraxacum trigonolobum Dahlst. | TATR |
| Taraxacum officinale ssp. ceratophorum | Taraxacum umbrinum Dahlst. | TAUM |
| Taraxacum officinale ssp. officinale | Leontodon latiloba (DC.) Britt. | LELA13 |
| Taraxacum officinale ssp. officinale | Leontodon taraxacum L. p.p. | LETA2 |
| Taraxacum officinale ssp. officinale | Taraxacum atroglaucum M.P. Christens. | TAAT |
| Taraxacum officinale ssp. officinale | Taraxacum campylodes Hagl. | TACA11 |
| Taraxacum officinale ssp. officinale | Taraxacum croceum auct. non Dahlst. [misapplied] | TACR |
| Taraxacum officinale ssp. officinale | Taraxacum curvidens M.P. Christens. | TACU2 |
| Taraxacum officinale ssp. officinale | Taraxacum cyclocentrum M.P. Christens. | TACY |
| Taraxacum officinale ssp. officinale | Taraxacum dahlstedtii Lindb. f. | TADA |
| Taraxacum officinale ssp. officinale | Taraxacum davidssonii M.P. Christens. | TADA2 |
| Taraxacum officinale ssp. officinale | Taraxacum devians Dahlst. | TADE |
| Taraxacum officinale ssp. officinale | Taraxacum dilutisquameum M.P. Christens. | TADI4 |
| Taraxacum officinale ssp. officinale | Taraxacum firmum Dahlst. | TAFI |
| Taraxacum officinale ssp. officinale | Taraxacum islandiciforme Dahlst. | TAIS |
| Taraxacum officinale ssp. officinale | Taraxacum kok-saghyz auct. non Rodin [misapplied] | TAKO80 |
| Taraxacum officinale ssp. officinale | Taraxacum latilobum DC. | TALA5 |
| Taraxacum officinale ssp. officinale | Taraxacum officinale G.H. Weber ex Wiggers ssp. vulgare (Lam.) Schinz & R. Keller | TAOFV |
| Taraxacum officinale ssp. officinale | Taraxacum officinale G.H. Weber ex Wiggers var. palustre (Lyons) Blytt p.p. | TAOFP |
| Taraxacum officinale ssp. officinale | Taraxacum palustre (Lyons) Symons var. vulgare (Lam.) Fern. | TAPAV |
| Taraxacum officinale ssp. officinale | Taraxacum pleniflorum M.P. Christens. | TAPL |
| Taraxacum officinale ssp. officinale | Taraxacum retroflexum Lindb. f. | TARE |
| Taraxacum officinale ssp. officinale | Taraxacum rhodolepis Dahlst. | TARH |
| Taraxacum officinale ssp. officinale | Taraxacum undulatum Lindb. f. & Marklund | TAUN |
| Taraxacum officinale ssp. officinale | Taraxacum vagans Hagl. | TAVA2 |
| Taraxacum officinale ssp. officinale | Taraxacum vulgare Lam. | TAVU2 |
| Taraxacum officinale ssp. officinale | Taraxacum xanthostigma Lindb. f. | TAXA |
| Taraxacum palustre | Taraxacum turfosum (Schultz-Bip.) Soest | TATU |
| Taraxacum phymatocarpum | Taraxacum alaskanum Rydb. | TAAL |
| Taraxacum phymatocarpum | Taraxacum arcticum (Trautv.) Dahlst. | TAAR5 |
| Taraxacum phymatocarpum | Taraxacum hyparcticum Dahlst. | TAHY |
| Taraxacum phymatocarpum | Taraxacum lateritium Dahlst. | TALA3 |
| Taraxacum phymatocarpum | Taraxacum mackenziense Porsild | TAMA3 |
| Taraxacum phymatocarpum | Taraxacum pumilum Dahlst. | TAPU3 |
| tarragon | Artemisia dracunculus L. | ARDR4 |
| tarweed | Hemizonia DC. | HEMIZ |
| tarweed | Holocarpha Greene | HOLOC |
| tarweed | Madia Molina | MADIA |
| tarwort | Flourensia DC. | FLOUR |
| tasselflower | Emilia Cass. | EMILI |
| tasselflower brickellbush | Brickellia grandiflora (Hook.) Nutt. | BRGR |
| Tatarian aster | Aster tataricus L. f. | ASTA |
| Taylor County goldaster | Pityopsis pinifolia (Ell.) Nutt. | PIPI4 |
| Tecate tarweed | Hemizonia floribunda Gray | HEFL4 |
| Tehachapi ragwort | Packera ionophylla (Greene) W.A. Weber & A. L?ve | PAIO4 |
| telegraphweed | Heterotheca grandiflora Nutt. | HEGR7 |
| Tenerife white marguerite | Argyranthemum gracilis Webb ex Sch. Bip. | ARGR20 |
| Tennessee ironweed | Vernonia flaccidifolia Small | VEFL |
| Tennessee leafcup | Polymnia laevigata Beadle | POLA8 |
| Tennessee purple coneflower | Echinacea tennesseensis (Beadle) Small | ECTE3 |
| Tephroseris atropurpurea ssp. atropurpurea | Senecio atropurpureus (Ledeb.) Fedtsch. | SEAT2 |
| Tephroseris atropurpurea ssp. atropurpurea | Tephroseris integrifolia (L.) Holub ssp. atropurpurea (Ledeb.) B. Nordenstam | TEINA |
| Tephroseris atropurpurea ssp. frigida | Senecio atropurpureus (Ledeb.) Fedtsch. ssp. frigidus (Richards.) Hult | SEATF2 |
| Tephroseris atropurpurea ssp. frigida | Senecio atropurpureus (Ledeb.) Fedtsch. var. ulmeri (Steffen) Porsild | SEATU2 |
| Tephroseris atropurpurea ssp. frigida | Senecio frigidus (Richards.) Less. | SEFR6 |
| Tephroseris kjellmanii | Senecio atropurpureus (Ledeb.) Fedtsch. ssp. tomentosus (Kjellm.) Hult | SEATT |
| Tephroseris kjellmanii | Senecio atropurpureus (Ledeb.) Fedtsch. var. dentatus (Gray) Hult | SEATD |
| Tephroseris kjellmanii | Senecio kjellmanii Porsild | SEKJ |
| Tephroseris kjellmanii | Senecio tichomirovii auct. non Schischkin [misapplied] | SETI |
| Tephroseris kjellmanii | Tephroseris atropurpurea (Ledeb.) Holub ssp. tomentosa (Kjellm.) A.& D. L?ve | TEATT |
| Tephroseris lindstroemii | Senecio bivestitus Cronq. | SEBI10 |
| Tephroseris lindstroemii | Senecio fuscatus auct. non Hayek [misapplied] | SEFU |
| Tephroseris lindstroemii | Senecio lindstroemii (Ostenf.) Porsild | SELI6 |
| Tephroseris lindstroemii | Senecio tundricola auct. non Tolm. [misapplied] | SETU |
| Tephroseris lindstroemii | Tephroseris tundricola (Tolm.) Holub var. lindstroemii (Ostenf.) V. Yu. | TETUL |
| Tephroseris yukonensis | Senecio alaskanus Hult | SEAL12 |
| Tephroseris yukonensis | Senecio yukonensis Porsild | SEYU |
| Terlingu brickellia | Brickellia hinckleyi Standl. var. terlinguensis (Flyr) B.L. Turner | BRHIT |
| Teton wirelettuce | Stephanomeria fluminea Gottlieb | STFL8 |
| Tetradymia axillaris var. longispina | Tetradymia spinosa Hook. & Arn. var. longispina M.E. Jones | TESPL |
| Tetradymia canescens | Tetradymia canescens DC. var. inermis (Rydb.) Payson | TECAI |
| Tetradymia tetrameres | Tetradymia comosa Gray ssp. tetrameres Blake | TECOT |
| Tetragonotheca helianthoides | Gonotheca helianthoides (L.) Raf. | GOHE |
| Tetragonotheca ludoviciana | Halea ludoviciana Torr. & Gray | HALU2 |
| Tetragonotheca repanda | Halea repanda Buckl. | HARE4 |
| tetramolopium | Tetramolopium Nees | TETRA16 |
| Tetramolopium arenarium ssp. laxum | Tetramolopium arenarium (Gray) Hbd. var. dentatum Hbd. | TEARD |
| Tetramolopium capillare | Luteidiscus capillaris (Gaud.) St. John | LUCA16 |
| Tetramolopium capillare | Senecio capillaris Gaud. | SECA10 |
| Tetramolopium conyzoides | Tetramolopium conyzoides (Gray) Hbd. var. dentatum (Mann) Sherff | TECOD |
| Tetramolopium filiforme var. polyphyllum | Tetramolopium polyphyllum Sherff | TEPO2 |
| Tetramolopium humile ssp. humile var. humile | Tetramolopium humile (Gray) Hbd. var. skottsbergii Sherff | TEHUS |
| Tetramolopium lepidotum ssp. arbusculum | Tetramolopium arbusculum (Gray) Sherff | TEAR2 |
| Tetramolopium lepidotum ssp. lepidotum | Tetramolopium lepidotum (Less.) Sherff var. luxurians (Hbd.) Sherff | TELEL |
| Tetramolopium remyi | Vittadinia remyi Gray | VIRE8 |
| Tetramolopium rockii var. calcisabulorum | Luteidiscus calcisabulorus St. John | LUCA17 |
| Tetramolopium rockii var. calcisabulorum | Tetramolopium calcisabulorum (St. John) St. John | TECA6 |
| Tetramolopium rockii var. rockii | Luteidiscus rockii (Sherff) St. John | LURO4 |
| Tetramolopium tenerrimum | Aster tenerrimus Less. | ASTE16 |
| Tetraneuris acaulis var. acaulis | Actinea acaulis (Pursh) Spreng. | ACAC2 |
| Tetraneuris acaulis var. acaulis | Actinella acaulis (Pursh) Nutt. | ACAC3 |
| Tetraneuris acaulis var. acaulis | Hymenoxys acaulis (Pursh) Parker | HYAC4 |
| Tetraneuris acaulis var. acaulis | Tetraneuris simplex A. Nels. | TESI |
| Tetraneuris acaulis var. arizonica | Actinea acaulis (Pursh) Spreng. var. arizonica (Greene) Blake | ACACA |
| Tetraneuris acaulis var. arizonica | Hymenoxys acaulis (Pursh) Parker var. arizonica (Greene) Parker | HYACA2 |
| Tetraneuris acaulis var. caespitosa | Hymenoxys acaulis (Pursh) Parker var. caespitosa (A. Nels.) Parker | HYACC2 |
| Tetraneuris acaulis var. caespitosa | Hymenoxys acaulis (Pursh) Parker var. lanata (Greene) Cronq. | HYACL |
| Tetraneuris acaulis var. caespitosa | Tetraneuris brevifolia Greene | TEBR2 |
| Tetraneuris acaulis var. epunctata | Hymenoxys acaulis (Pursh) Parker var. epunctata (A. Nels.) Cronq. | HYACE |
| Tetraneuris acaulis var. epunctata | Tetraneuris epunctata A. Nels. | TEEP |
| Tetraneuris acaulis var. nana | Hymenoxys acaulis (Pursh) Parker var. nana Welsh | HYACN |
| Tetraneuris argentea | Actinella argentea Gray | ACAR4 |
| Tetraneuris argentea | Hymenoxys argentea (Gray) Parker | HYAR5 |
| Tetraneuris brandegeei | Hymenoxys brandegeei Porter ex Gray | HYBR |
| Tetraneuris brandegeei | Rydbergia brandegeei (Porter ex Gray) Rydb. | RYBR |
| Tetraneuris grandiflora | Actinea grandiflora (Torr. & Gray ex Gray) Kuntze | ACGR4 |
| Tetraneuris grandiflora | Hymenoxys grandiflora (Torr. & Gray ex Gray) Parker | HYGR5 |
| Tetraneuris grandiflora | Rydbergia grandiflora (Torr. & Gray ex Gray) Greene | RYGR2 |
| Tetraneuris herbacea | Actinea herbacea (Greene) B.L. Robins. | ACHE2 |
| Tetraneuris herbacea | Hymenoxys acaulis (Pursh) Parker var. glabra (Gray) Parker | HYACG |
| Tetraneuris herbacea | Hymenoxys herbacea (Greene) Cusick | HYHE4 |
| Tetraneuris ivesiana | Hymenoxys acaulis (Pursh) Parker var. ivesiana (Greene) Parker | HYACI3 |
| Tetraneuris ivesiana | Hymenoxys argentea (Gray) Parker var. ivesiana (Greene) Cronq. | HYARI |
| Tetraneuris ivesiana | Hymenoxys ivesiana (Greene) Parker | HYIV |
| Tetraneuris ivesiana | Tetraneuris mancosensis A. Nels. | TEMA2 |
| Tetraneuris ivesiana | Tetraneuris pilosa Cockerell | TEPI2 |
| Tetraneuris linearifolia var. linearifolia | Hymenoxys linearifolia Hook. | HYLI7 |
| Tetraneuris scaposa var. argyrocaulon | Hymenoxys scaposa (DC.) Parker var. argyrocaulon Parker | HYSCA |
| Tetraneuris scaposa var. linearis | Hymenoxys scaposa (DC.) Parker var. linearis (Nutt.) Parker | HYSCL |
| Tetraneuris scaposa var. scaposa | Hymenoxys glabra (Nutt.) Shinners | HYGL5 |
| Tetraneuris scaposa var. scaposa | Hymenoxys scaposa (DC.) Parker | HYSC3 |
| Tetraneuris scaposa var. scaposa | Hymenoxys scaposa (DC.) Parker var. glabra (Nutt.) Parker | HYSCG |
| Tetraneuris scaposa var. scaposa | Tetraneuris fastigiata Greene | TEFA2 |
| Tetraneuris scaposa var. scaposa | Tetraneuris glabra (Nutt.) Greene | TEGL3 |
| Tetraneuris scaposa var. scaposa | Tetraneuris stenophylla Rydb. | TEST5 |
| Tetraneuris scaposa var. villosa | Hymenoxys scaposa (DC.) Parker var. villosa Shinners | HYSCV |
| Tetraneuris torreyana | Hymenoxys depressa (Torr. & Gray ex Gray) Welsh & Reveal | HYDE5 |
| Tetraneuris torreyana | Hymenoxys torreyana (Nutt.) Parker | HYTO2 |
| Tetraneuris torreyana | Tetraneuris depressa (Torr. & Gray ex Gray) Greene | TEDE |
| Tetraneuris turneri | Hymenoxys turneri Parker | HYTU3 |
| Texan candyleaf | Stevia ovata Willd. var. texana Grashoff | STOVT |
| Texan great ragweed | Ambrosia trifida L. var. texana Scheele | AMTRT |
| Texan gumweed | Grindelia lanceolata Nutt. var. texana (Scheele) Shinners | GRLAT |
| Texas aster | Symphyotrichum eulae (Shinners) Nesom | SYEU |
| Texas blueweed | Helianthus ciliaris DC. | HECI |
| Texas bristleleaf | Thymophylla tenuiloba (DC.) Small var. texana (Cory) Strother | THTET2 |
| Texas broomweed | Amphiachyris amoena (Shinners) Solbrig | AMAM3 |
| Texas chrysopsis | Chrysopsis texana Nesom | CHTE10 |
| Texas coneflower | Rudbeckia texana (Perdue) P. Cox & Urbatsch | RUTE4 |
| Texas crownbeard | Verbesina microptera DC. | VEMI |
| Texas desert goldenrod | Xylothamia palmeri (Gray) Nesom | XYPA3 |
| Texas false broomweed | Haploesthes greggii Gray var. texana (Coult.) I.M. Johnston | HAGRT |
| Texas goldentop | Euthamia gymnospermoides Greene | EUGY |
| Texas greeneyes | Berlandiera betonicifolia (Hook.) Small | BEBE4 |
| Texas ironweed | Vernonia texana (Gray) Small | VETE3 |
| Texas marshelder | Iva texensis R.C. Jackson | IVTE |
| Texas palafox | Palafoxia texana DC. | PATE |
| Texas palafox | Palafoxia texana DC. var. ambigua (Shinners) B.L. Turner & Morris | PATEA |
| Texas palafox | Palafoxia texana DC. var. texana | PATET |
| Texas pricklyleaf | Thymophylla setifolia Lag. | THSE4 |
| Texas pricklyleaf | Thymophylla setifolia Lag. var. radiata (Gray) Strother | THSER |
| Texas pricklyleaf | Thymophylla setifolia Lag. var. setifolia Lag. [excluded] | THSES2 |
| Texas rabbit-tobacco | Pseudognaphalium austrotexanum Nesom | PSAU3 |
| Texas ragwort | Senecio ampullaceus Hook. | SEAM2 |
| Texas skeletonplant | Lygodesmia texana (Torr. & Gray) Greene | LYTE |
| Texas sleepydaisy | Xanthisma texanum DC. | XATE |
| Texas sleepydaisy | Xanthisma texanum DC. ssp. texanum | XATET |
| Texas snakeweed | Gutierrezia texana (DC.) Torr. & Gray | GUTE2 |
| Texas snakeweed | Gutierrezia texana (DC.) Torr. & Gray var. texana | GUTET |
| Texas sunflower | Helianthus praecox Engelm. & Gray | HEPR2 |
| Texas sunflower | Helianthus praecox Engelm. & Gray ssp. hirtus (Heiser) Heiser | HEPRH |
| Texas sunflower | Helianthus praecox Engelm. & Gray ssp. praecox | HEPRP |
| Texas tansyaster | Machaeranthera blephariphylla (Gray) Shinners | MABL2 |
| Texas thistle | Cirsium texanum Buckl. | CITE2 |
| Texas tickseed | Coreopsis linifolia Nutt. | COLI5 |
| Texas Townsend daisy | Townsendia texensis Larsen | TOTE2 |
| Texas varilla | Varilla texana Gray | VATE2 |
| Texas western daisy | Astranthium robustum (Shinners) DeJong | ASRO2 |
| Texas yellowstar | Lindheimera texana Gray & Engelm. | LITE3 |
| Thelesperma ambiguum | Thelesperma fraternum Shinners | THFR |
| Thelesperma ambiguum | Thelesperma megapotamicum (Spreng.) Kuntze var. ambiguum (Gray) Shinners | THMEA |
| Thelesperma caespitosum | Thelesperma subnudum Gray var. caespitosum (Dorn) Welsh | THSUC |
| Thelesperma filifolium var. filifolium | Thelesperma trifidum (Poir.) Britt. | THTR2 |
| Thelesperma filifolium var. intermedium | Thelesperma intermedium Rydb. | THIN5 |
| Thelesperma megapotamicum | Bidens megapotamica Spreng. | BIME2 |
| Thelesperma megapotamicum | Thelesperma gracile (Torr.) Gray | THGR4 |
| Thelesperma pubescens | Thelesperma subnudum Gray var. alpinum Welsh | THSUA |
| Thelesperma subnudum var. marginatum | Thelesperma marginatum Rydb. | THMA5 |
| thickleaf ragwort | Senecio crassulus Gray | SECR |
| thickstem aster | Eurybia integrifolia (Nutt.) Nesom | EUIN9 |
| thimblehead | Hymenothrix Gray | HYMEN6 |
| thinleaf goldenhead | Pyrrocoma linearis (Keck) Kartesz & Gandhi | PYLI2 |
| thinleaf late purple aster | Symphyotrichum phlogifolium (Muhl. ex Willd.) Nesom | SYPH3 |
| thinleaf sunflower | Helianthus decapetalus L. | HEDE |
| thistle | Cirsium P. Mill. | CIRSI |
| thistleleaf aster | Eurybia eryngiifolia (Torr. & Gray) Nesom | EUER7 |
| Thompson's pincushion | Chaenactis thompsonii Cronq. | CHTH |
| thorn skeletonweed | Pleiacanthus spinosus (Nutt.) Rydb. | PLSP7 |
| thoroughwort | Chromolaena DC. | CHROM3 |
| thoroughwort | Conoclinium DC. | CONOC4 |
| thoroughwort | Critonia P. Br. | CRITO2 |
| thoroughwort | Eupatorium L. | EUPAT |
| thoroughwort | Fleischmannia Schultz-Bip. | FLEIS2 |
| thoroughwort | Hebeclinium DC. | HEBEC2 |
| thoroughwort | Koanophyllon Arruda | KOANO2 |
| threadleaf fleabane | Erigeron filifolius (Hook.) Nutt. | ERFI2 |
| threadleaf fleabane | Erigeron filifolius (Hook.) Nutt. var. filifolius | ERFIF |
| threadleaf fleabane | Erigeron filifolius (Hook.) Nutt. var. robustior M.E. Peck | ERFIR |
| threadleaf glowwort | Sartwellia flaveriae Gray | SAFL5 |
| threadleaf horsebrush | Tetradymia filifolia Greene | TEFI |
| threadleaf ragwort | Senecio flaccidus Less. | SEFL3 |
| threadleaf ragwort | Senecio flaccidus Less. var. flaccidus | SEFLF |
| threadleaf snakeweed | Gutierrezia microcephala (DC.) Gray | GUMI |
| three-lobed rockdaisy | Perityle gracilis (M.E. Jones) Rydb. | PEGR15 |
| threeflower snakeweed | Thurovia triflora Rose | THTR7 |
| threefold | Trixis P. Br. | TRIXI |
| threelobe beggarticks | Bidens tripartita L. | BITR |
| threenerve fleabane | Erigeron subtrinervis Rydb. ex Porter & Britt. | ERSU2 |
| threenerve fleabane | Erigeron subtrinervis Rydb. ex Porter & Britt. var. conspicuus (Rydb.) Cronq. | ERSUC |
| threenerve fleabane | Erigeron subtrinervis Rydb. ex Porter & Britt. var. subtrinervis | ERSUS |
| threenerve goldenrod | Solidago velutina DC. | SOVE6 |
| threeray tarweed | Hemizonia lobbii Greene | HELO4 |
| threetip sagebrush | Artemisia tripartita Rydb. | ARTR4 |
| threetip sagebrush | Artemisia tripartita Rydb. ssp. tripartita | ARTRT2 |
| threetooth ragwort | Packera tridenticulata (Rydb.) W.A. Weber & A. L?ve | PATR7 |
| thrift mock goldenweed | Stenotus armerioides Nutt. | STAR10 |
| thrift mock goldenweed | Stenotus armerioides Nutt. var. armerioides | STARA |
| Thurber's desertpeony | Acourtia thurberi (Gray) Reveal & King | ACTH |
| Thurber's sneezeweed | Helenium thurberi Gray | HETH |
| Thurber's wirelettuce | Stephanomeria thurberi Gray | STTH |
| thurovia | Thurovia Rose | THURO2 |
| Thurovia triflora | Gutierrezia triflora (Rose) M.A. Lane | GUTR2 |
| Thymophylla acerosa | Dyssodia acerosa DC. | DYAC |
| Thymophylla aurea var. aurea | Dyssodia aurea (Gray) A. Nels. | DYAU |
| Thymophylla aurea var. aurea | Lowellia aurea Gray | LOAU2 |
| Thymophylla aurea var. polychaeta | Dyssodia aurea (Gray) A. Nels. var. polychaeta (Gray) M.C. Johnston | DYAUP |
| Thymophylla aurea var. polychaeta | Dyssodia polychaeta (Gray) B.L. Robins. | DYPO2 |
| Thymophylla aurea var. polychaeta | Thymophylla polychaeta Gray | THPO10 |
| Thymophylla concinna | Dyssodia concinna (Gray) B.L. Robins. | DYCO |
| Thymophylla micropoides | Dyssodia micropoides (DC.) Loes. | DYMI |
| Thymophylla pentachaeta var. belenidium | Dyssodia belenidium (DC.) Macloskie | DYBE2 |
| Thymophylla pentachaeta var. belenidium | Dyssodia pentachaeta (DC.) B.L. Robins. var. belenidium (DC.) Strother | DYPEB |
| Thymophylla pentachaeta var. belenidium | Dyssodia thurberi (Gray) B.L. Robins. | DYTH2 |
| Thymophylla pentachaeta var. hartwegii | Dyssodia hartwegii (Gray) B.L. Robins. | DYHA2 |
| Thymophylla pentachaeta var. hartwegii | Dyssodia pentachaeta (DC.) B.L. Robins. ssp. hartwegii (Gray) Strother | DYPEH2 |
| Thymophylla pentachaeta var. hartwegii | Dyssodia pentachaeta (DC.) B.L. Robins. var. hartwegii (Gray) Strother | DYPEH |
| Thymophylla pentachaeta var. pentachaeta | Dyssodia pentachaeta (DC.) B.L. Robins. | DYPE |
| Thymophylla pentachaeta var. pentachaeta | Hymenatherum pentachaetum DC. | HYPE5 |
| Thymophylla pentachaeta var. puberula | Dyssodia pentachaeta (DC.) B.L. Robins. var. puberula (Rydb.) Strother | DYPEP |
| Thymophylla setifolia var. radiata | Dyssodia setifolia (Lag.) B.L. Robins. var. greggii (Gray) M.C. Johnston | DYSEG |
| Thymophylla setifolia var. radiata | Dyssodia setifolia (Lag.) B.L. Robins. var. radiata (Gray) Strother | DYSER |
| Thymophylla setifolia var. setifolia | Dyssodia setifolia (Lag.) B.L. Robins. [excluded] | DYSE2 |
| Thymophylla tenuiloba var. tenuiloba | Dyssodia tenuiloba (DC.) B.L. Robins. | DYTE |
| Thymophylla tenuiloba var. texana | Dyssodia tenuiloba (DC.) B.L. Robins. var. texana (Cory) Strother | DYTET |
| Thymophylla tenuiloba var. texana | Dyssodia texana Cory | DYTE4 |
| Thymophylla tenuiloba var. treculii | Dyssodia tenuiloba (DC.) B.L. Robins. var. treculii (Gray) Strother | DYTET2 |
| Thymophylla tenuiloba var. treculii | Dyssodia treculii (Gray) B.L. Robins. | DYTR2 |
| Thymophylla tenuiloba var. wrightii | Dyssodia tenuiloba (DC.) B.L. Robins. ssp. wrightii (Gray) Strother | DYTEW |
| Thymophylla tenuiloba var. wrightii | Dyssodia wrightii (Gray) B.L. Robins. | DYWR |
| Thymophylla tephroleuca | Dyssodia tephroleuca Blake | DYTE2 |
| tickseed | Coreopsis L. | COREO2 |
| tidytips | Layia Hook. & Arn. ex DC. | LAYIA |
| Tilesius's wormwood | Artemisia tilesii Ledeb. | ARTI |
| Tilesius's wormwood | Artemisia tilesii Ledeb. ssp. elatior (Torr. & Gray) Hult | ARTIE |
| Tilesius's wormwood | Artemisia tilesii Ledeb. ssp. gormanii (Rydb.) Hult | ARTIG |
| Tilesius's wormwood | Artemisia tilesii Ledeb. ssp. tilesii | ARTIT |
| Tilesius's wormwood | Artemisia tilesii Ledeb. ssp. unalaschcensis (Bess.) Hult | ARTIU2 |
| timberline sagebrush | Artemisia rothrockii Gray | ARRO4 |
| tiny pygmydaisy | Pentachaeta alsinoides Greene | PEAL19 |
| tithonia | Tithonia Desf. ex Juss. | TITHO |
| Tithonia diversifolia | Mirasolia diversifolia Hemsl. | MIDI7 |
| Tithonia rotundifolia | Tagetes rotundifolia P. Mill. | TARO2 |
| Tithonia rotundifolia | Tithonia speciosa (Hook.) Griseb. | TISP2 |
| Tolmies's goldenrod | Solidago missouriensis Nutt. var. tolmieana (Gray) Cronq. | SOMIT |
| Tolpis barbata | Crepis barbata L. | CRBA7 |
| Tolpis barbata | Tolpis umbellata Bertol. | TOUM |
| Tolstead's erigeron | Erigeron pulchellus Michx. var. tolsteadii Cronq. | ERPUT |
| Tonestus aberrans | Haplopappus aberrans (A. Nels.) Hall | HAAB |
| Tonestus aberrans | Macronema aberrans A. Nels. | MAAB3 |
| Tonestus alpinus | Haplopappus alpinus L.C. Anders. & Goodrich | HAAL3 |
| Tonestus eximius | Haplopappus eximius Hall | HAEX |
| Tonestus graniticus | Haplopappus graniticus Tiehm & L. Shultz | HAGR7 |
| Tonestus kingii var. barnebyana | Aster kingii D.C. Eat. var. barnebyana (Welsh & Goodrich) Welsh | ASKIB |
| Tonestus kingii var. barnebyana | Machaeranthera kingii (D.C. Eat.) Cronq. & Keck var. barnebyana Welsh & Goodrich | MAKIB |
| Tonestus kingii var. kingii | Aster kingii D.C. Eat. | ASKI |
| Tonestus kingii var. kingii | Machaeranthera kingii (D.C. Eat.) Cronq. & Keck | MAKI |
| Tonestus lyallii | Haplopappus lyallii Gray | HALY |
| Tonestus microcephalus | Haplopappus microcephalus Cronq. | HAMI2 |
| Tonestus peirsonii | Haplopappus eximius Hall ssp. peirsonii Keck | HAEXP2 |
| Tonestus peirsonii | Haplopappus peirsonii (Keck) J.T. Howell | HAPE3 |
| Tonestus pygmaeus | Haplopappus pygmaeus (Torr. & Gray) Gray | HAPY |
| toothed whitetop aster | Sericocarpus asteroides (L.) B.S.P. | SEAS3 |
| toothleaf goldeneye | Viguiera dentata (Cav.) Spreng. | VIDE3 |
| toothleaf goldeneye | Viguiera dentata (Cav.) Spreng. var. dentata | VIDED3 |
| toothleaf goldeneye | Viguiera dentata (Cav.) Spreng. var. lancifolia Blake | VIDEL2 |
| Topeka purple coneflower | Echinacea atrorubens Nutt. | ECAT |
| torhleaf goldeneye | Viguiera laciniata Gray | VILA3 |
| Torrey's desertdandelion | Malacothrix torreyi Gray | MATO2 |
| Torrey's four-nerve daisy | Tetraneuris torreyana (Nutt.) Greene | TETO |
| Toumey's groundsel | Packera neomexicana (Gray) W.A. Weber & A. L?ve var. toumeyi (Greene) D.K. Trock & T.M. Barkl. | PANET2 |
| Tournefort's gundelia | Gundelia tournefortii L. | GUTO |
| Townsend daisy | Townsendia Hook. | TOWNS |
| Townsendia alpigena var. alpigena | Townsendia montana M.E. Jones | TOMO |
| Townsendia alpigena var. caelilinensis | Townsendia montana M.E. Jones var. caelilinensis Welsh | TOMOC |
| Townsendia alpigena var. minima | Townsendia minima Eastw. | TOMI2 |
| Townsendia alpigena var. minima | Townsendia montana M.E. Jones var. minima (Eastw.) Beaman | TOMOM |
| Townsendia aprica | Townsendia jonesii (Beaman) Reveal var. lutea Welsh | TOJOL |
| Townsendia condensata var. anomala | Townsendia anomala Heiser | TOAN2 |
| Townsendia eximia | Townsendia vreelandii Rydb. | TOVR |
| Townsendia exscapa | Aster exscapus Richards. | ASEX7 |
| Townsendia exscapa | Townsendia intermedia Rydb. | TOIN2 |
| Townsendia exscapa | Townsendia sericea Hook. | TOSE |
| Townsendia florifer | Townsendia florifer (Hook.) Gray var. watsonii (Gray) Cronq. | TOFLW2 |
| Townsendia florifer | Townsendia florifera (Hook.) Gray var. watsonii (Gray) Cronq. [orthographic error] | TOFLW |
| Townsendia florifer | Townsendia florifera (Hook.) Gray [orthographic error] | TOFL2 |
| Townsendia formosa | Townsendia pinetorum Greene ex A. Nels. | TOPI |
| Townsendia incana | Townsendia arizonica Gray | TOAR3 |
| Townsendia jonesii var. jonesii | Townsendia mensana M.E. Jones var. jonesii Beaman | TOMEJ |
| Townsendia leptotes | Townsendia sericea Hook. var. leptotes Gray | TOSEL |
| Tracy's silkgrass | Pityopsis graminifolia (Michx.) Nutt. var. tracyi (Small) Semple | PIGRT2 |
| Tracy's thistle | Cirsium undulatum (Nutt.) Spreng. var. tracyi (Rydb.) Welsh | CIUNT |
| Tragopogon dubius | Tragopogon dubius Scop. ssp. major (Jacq.) Voll. | TRDUM |
| Tragopogon dubius | Tragopogon major Jacq. | TRMA9 |
| Tragopogon lamottei | Tragopogon pratensis L. | TRPR |
| Tragopogon pratensis ssp. orientalis | Tragopogon orientalis L. [excluded] | TROR11 |
| trailing fleabane | Erigeron flagellaris Gray | ERFL |
| trailplant | Adenocaulon Hook. | ADENO |
| trampweed | Facelis Cass. | FACEL |
| tranquil goldenweed | Pyrrocoma clementis Rydb. | PYCL2 |
| tranquil goldenweed | Pyrrocoma clementis Rydb. var. clementis | PYCLC |
| tranquil goldenweed | Pyrrocoma clementis Rydb. var. villosa (Rydb.) Mayes ex G. Brown & Keil | PYCLV |
| Trans-Pecos tansyaster | Psilactis brevilingulata Schultz-Bip. ex Hemsl. | PSBR5 |
| TransPecos desert goldenrod | Xylothamia triantha (Blake) Nesom | XYTR |
| TransPecos false clapdaisy | Pseudoclappia arenaria Rydb. | PSAR |
| Transpecos marshtail | Laennecia filaginoides DC. | LAFI |
| TransPecos poreleaf | Porophyllum scoparium Gray | POSC6 |
| TransPecos thimblehead | Hymenothrix wislizeni Gray | HYWI |
| Transvaal daisy | Gerbera Gmel. | GERBE |
| treasure-flower | Gazania rigens (L.) Gaertn. | GARI2 |
| treasureflower | Gazania linearis (Thunb.) Druce | GALI4 |
| Trecul's pricklyleaf | Thymophylla tenuiloba (DC.) Small var. treculii (Gray) Strother | THTET3 |
| tree marigold | Tithonia diversifolia (Hemsl.) Gray | TIDI2 |
| tree seaside tansy | Borrichia arborescens (L.) DC. | BOAR2 |
| treedaisy | Montanoa hibiscifolia (Benth.) Standl. | MOHI |
| triangle burr ragweed | Ambrosia deltoidea (Torr.) Payne | AMDE4 |
| Trichocoronis rivularis | Shinnersia rivularis (Gray) King & H.E. Robins. | SHRI |
| Trichocoronis wrightii | Trichocoronis riparia (Greene) Greene | TRRI7 |
| Trichocoronis wrightii | Trichocoronis wrightii (Torr. & Gray) Gray var. wrightii (Torr. & Gray) Gray [superfluous autonym] | TRWRW3 |
| trichoptilium | Trichoptilium Gray | TRICH8 |
| tricolor daisy | Glebionis carinatum (Schousboe) Tzvelev | GLCA5 |
| tridax | Tridax L. | TRIDA |
| Tripleurospermum maritima ssp. maritima | Chamomilla maritima (L.) Rydb. | CHMA13 |
| Tripleurospermum maritima ssp. maritima | Matricaria maritima L. | MAMA10 |
| Tripleurospermum maritima ssp. phaeocephala | Matricaria ambigua (Ledeb.) Krylov | MAAM8 |
| Tripleurospermum maritima ssp. phaeocephala | Matricaria grandiflora (Hook.) Britt. | MAGR13 |
| Tripleurospermum maritima ssp. phaeocephala | Matricaria hookeri (Schultz-Bip.) Czern. | MAHO2 |
| Tripleurospermum maritima ssp. phaeocephala | Matricaria maritima L. ssp. phaeocephala (Rupr.) Rauschert | MAMAP |
| Tripleurospermum maritima ssp. phaeocephala | Matricaria maritima L. var. nana (Hook.) Boivin | MAMAN |
| Tripleurospermum maritima ssp. phaeocephala | Tripleurospermum phaeocephalum (Rupr.) Pobed. | TRPH2 |
| Tripleurospermum perforata | Chamomilla inodora (L.) Gilib. | CHIN7 |
| Tripleurospermum perforata | Matricaria inodora L. | MAIN12 |
| Tripleurospermum perforata | Matricaria maritima L. ssp. inodora (L.) Clapham | MAMAI |
| Tripleurospermum perforata | Matricaria maritima L. var. agrestis (Knaf) Wilmott | MAMAA |
| Tripleurospermum perforata | Matricaria perforata M?rat | MAPE2 |
| Tripleurospermum perforata | Tripleurospermum inodorum (L.) Schultz-Bip. | TRIN11 |
| Tripolium pannonicum | Aster tripolium L. | ASTR80 |
| Tripolium pannonicum | Aster tripolium L. ssp. pannonicus (Jacq.) Soo | ASTRP2 |
| Trixis californica | Trixis californica Kellogg var. californica Kellogg [superfluous autonym] | TRCAC5 |
| Trixis inula | Trixis radialis (L.) Kuntze | TRRA7 |
| tropic daisy | Egletes Cass. | EGLET |
| tropical burnweed | Erechtites valerianifolia (Link ex Spreng.) DC. | ERVA6 |
| tropical cinchweed | Pectis elongata Kunth | PEEL6 |
| tropical cinchweed | Pectis elongata Kunth var. floribunda (A. Rich.) Keil | PEELF |
| tropical creeping cudweed | Euchiton sphaericus (Willd.) A. Anderb. | EUSP5 |
| tropical false goldeneye | Heliomeris soliceps (Barneby) Yates | HESO2 |
| tropical medicineplant | Adenostemma verbesina (L.) Schultz-Bip. | ADVE2 |
| tropical thoroughwort | Fleischmannia microstemon (Cass.) King & H.E. Robins. | FLMI |
| tropical threefold | Trixis inula Crantz | TRIN6 |
| tropical whiteweed | Ageratum conyzoides L. | AGCO |
| Truckee rabbitbrush | Chrysothamnus humilis Greene | CHHU2 |
| trumpetweed | Eupatoriadelphus fistulosus (Barratt) King & H.E. Robins. | EUFI2 |
| tuberous desert-chicory | Pyrrhopappus grandiflorus (Nutt.) Nutt. | PYGR2 |
| Tucson burr ragweed | Ambrosia cordifolia (Gray) Payne | AMCO4 |
| tufted fleabane | Erigeron caespitosus Nutt. | ERCA2 |
| tufted Townsend daisy | Townsendia scapigera D.C. Eat. | TOSC |
| tufted wirelettuce | Stephanomeria paniculata Nutt. | STPA2 |
| tundra aster | Oreostemma alpigenum (Torr. & Gray) Greene | ORAL4 |
| tundra aster | Oreostemma alpigenum (Torr. & Gray) Greene var. alpigenum | ORALA2 |
| tundra aster | Oreostemma alpigenum (Torr. & Gray) Greene var. andersonii (Gray) Nesom | ORALA3 |
| tundra aster | Oreostemma alpigenum (Torr. & Gray) Greene var. haydenii (Porter) Nesom | ORALH |
| tundra fleabane | Erigeron hyperboreus Greene | ERHY2 |
| turgid blazing star | Liatris turgida Gaiser | LITU3 |
| Turkish hawksbeard | Crepis nicaeensis Balbis ex Pers. | CRNI2 |
| Turner's four-nerve daisy | Tetraneuris turneri (Parker) Parker | TETU2 |
| Turner's marshtail | Laennecia turnerorum Nesom | LATU2 |
| turpentine bush | Ericameria laricifolia (Gray) Shinners | ERLA12 |
| turtleback | Psathyrotes Gray | PSATH |
| Tweedy's catsear | Hypochaeris brasiliensis (Less.) Benth. & Hook. ex Griseb. var. tweediei (Hook. & Arn.) Baker | HYBRT2 |
| Tweedy's fleabane | Erigeron tweedyi Canby | ERTW |
| twin arnica | Arnica sororia Greene | ARSO2 |
| twin desertdandelion | Malacothrix similis W.S. Davis & Raven | MASI5 |
| twinbugs | Dicoria Torr. ex Gray | DICOR |
| twistleaf goldenrod | Solidago tortifolia Ell. | SOTO2 |
| two-color rabbit-tobacco | Pseudognaphalium biolettii A. Anderb. | PSBI3 |
| twobristle rockdaisy | Perityle bisetosa (Torr. ex Gray) Shinners | PEBI |
| twobristle rockdaisy | Perityle bisetosa (Torr. ex Gray) Shinners var. appressa A. Powell | PEBIA |
| twobristle rockdaisy | Perityle bisetosa (Torr. ex Gray) Shinners var. bisetosa | PEBIB |
| twobristle rockdaisy | Perityle bisetosa (Torr. ex Gray) Shinners var. scalaris A. Powell | PEBIS |
| twoflower dwarfdandelion | Krigia biflora (Walt.) Blake | KRBI |
| twoflower dwarfdandelion | Krigia biflora (Walt.) Blake var. biflora | KRBIB |
| twoflower dwarfdandelion | Krigia biflora (Walt.) Blake var. viridis (Standl.) Kim | KRBIV |
| Tyrol knapweed | Centaurea nigrescens Willd. | CENI3 |
| Uinta fleabane | Erigeron uintahensis Cronq. | ERUI |
| Uinta Mountain fleabane | Erigeron goodrichii Welsh | ERGO3 |
| Uinta ragwort | Packera millelobata (Rydb.) W.A. Weber & A. L?ve | PAMI26 |
| Uinta wirelettuce | Stephanomeria minor (Hook.) Nutt. var. uintaensis (Goodrich & Welsh) Kartesz | STMIU2 |
| umber pussytoes | Antennaria umbrinella Rydb. | ANUM |
| umbrella milkwort | Tolpis Adans. | TOLPI |
| upland boneset | Eupatorium sessilifolium L. | EUSE3 |
| upland boneset | Eupatorium sessilifolium L. var. brittonianum Porter | EUSEB |
| upland boneset | Eupatorium sessilifolium L. var. sessilifolium | EUSES |
| upland boneset | Eupatorium sessilifolium L. var. vaseyi (Porter) Fern. & Grisc. | EUSEV |
| upright prairie coneflower | Ratibida columnifera (Nutt.) Woot. & Standl. | RACO3 |
| Urban's beggartick | Bidens reptans (L.) G. Don var. urbanii (Greenm.) O.E. Schulz | BIREU |
| urospermum | Urospermum Scop. | UROSP |
| Utah fleabane | Erigeron utahensis Gray | ERUT |
| Utah fleabane | Erigeron utahensis Gray var. sparsifolius (Eastw.) Cronq. | ERUTS |
| Utah fleabane | Erigeron utahensis Gray var. utahensis | ERUTU |
| valley lessingia | Lessingia glandulifera Gray | LEGL18 |
| valley lessingia | Lessingia glandulifera Gray var. glandulifera | LEGLG |
| valley lessingia | Lessingia glandulifera Gray var. pectinata (Greene) Jepson | LEGLP |
| valley mayweed | Matricaria occidentalis Greene | MAOC |
| vanclevea | Vanclevea Greene | VANCL |
| Vanclevea stylosa | Grindelia stylosa Eastw. | GRST2 |
| vanillaleaf | Carphephorus odoratissimus (J.F. Gmel.) Herbert | CAOD3 |
| variableleaf Indian plaintain | Arnoglossum diversifolium (Torr. & Gray) H.E. Robins. | ARDI9 |
| variableleaf sunflower | Helianthus heterophyllus Nutt. | HEHE4 |
| varilla | Varilla Gray | VARIL |
| Vasey's rabbitbrush | Chrysothamnus vaseyi (Gray) Greene | CHVA2 |
| Vasey's rockdaisy | Perityle vaseyi Coult. | PEVA |
| Vasey's rubberweed | Hymenoxys vaseyi (Gray) Cockerell | HYVA |
| Vasey's thistle | Cirsium hydrophilum (Greene) Jepson var. vaseyi (Gray) J.T. Howell | CIHYV |
| veiny brickellbush | Brickellia venosa (Woot. & Standl.) B.L. Robins. | BRVE |
| velvet groundsel | Roldana petasitis (Sims) H. Rob. & Brettell | ROPE6 |
| velvet turtleback | Psathyrotes ramosissima (Torr.) Gray | PSRA |
| velvetplant | Gynura aurantiaca (Blume) DC. | GYAU |
| velvetshrub | Piptocoma Cass. | PIPTO3 |
| velvety goldenrod | Solidago mollis Bartl. | SOMO |
| velvety goldenrod | Solidago mollis Bartl. var. angustata Shinners | SOMOA |
| velvety goldenrod | Solidago mollis Bartl. var. mollis | SOMOM |
| venegasia | Venegasia DC. | VENEG |
| venidium | Venidium Less. | VENID |
| Verbesina alata | Hamulium alatum (L.) Cass. | HAAL4 |
| Verbesina alata | Tepion alatum (L.) Britt. | TEAL2 |
| Verbesina alternifolia | Actinomeris alternifolia (L.) DC. | ACAL12 |
| Verbesina alternifolia | Ridan alternifolia (L.) Britt. | RIAL |
| Verbesina aristata | Actinomeris nudicaulis Nutt. | ACNU |
| Verbesina aristata | Helianthus aristatus Ell. | HEAR15 |
| Verbesina aristata | Pterophyton aristatum (Ell.) Alexander | PTAR3 |
| Verbesina aristata | Verbesina nudicaulis (Nutt.) Gray | VENU |
| Verbesina encelioides ssp. encelioides | Verbesina microptera (DC.) Herter, non DC. | VEMI4 |
| Verbesina encelioides ssp. encelioides | Ximenesia encelioides Cav. | XIEN |
| Verbesina encelioides ssp. encelioides | Ximenesia encelioides Cav. var. cana DC. p.p. | XIENC |
| Verbesina encelioides ssp. encelioides | Ximenesia microptera DC. | XIMI |
| Verbesina encelioides ssp. exauriculata | Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray var. exauriculata Robins. & Greenm. | VEENE |
| Verbesina encelioides ssp. exauriculata | Verbesina exauriculata (Robins. & Greenm.) Cockerell | VEEX |
| Verbesina encelioides ssp. exauriculata | Ximenesia encelioides Cav. var. exauriculata (Robins. & Greenm.) F.C. Gates | XIENE |
| Verbesina encelioides ssp. exauriculata | Ximenesia exauriculata (Robins. & Greenm.) Rydb. | XIEX |
| Verbesina helianthoides | Actinomeris helianthoides (Michx.) Nutt. | ACHE3 |
| Verbesina helianthoides | Actinomeris helianthoides (Michx.) Nutt. var. elliottii DC. | ACHEE |
| Verbesina helianthoides | Actinomeris helianthoides (Michx.) Nutt. var. nuttallii DC. | ACHEN |
| Verbesina helianthoides | Actinomeris oppositifolia DC. | ACOP2 |
| Verbesina helianthoides | Phaethusa helianthoides (Michx.) Britt. | PHHE16 |
| Verbesina helianthoides | Pterophyton helianthoides (Michx.) Alexander | PTHE2 |
| Verbesina heterophylla | Actinomeris heterophylla Chapman | ACHE4 |
| Verbesina heterophylla | Actinomeris pauciflora Nutt. | ACPA3 |
| Verbesina heterophylla | Pterophyton heterophyllum (Chapman) Alexander | PTHE3 |
| Verbesina heterophylla | Pterophyton pauciflorum (Nutt.) Alexander | PTPA2 |
| Verbesina heterophylla | Verbesina pauciflora (Nutt.) Small, non Hemsl. | VEPA4 |
| Verbesina heterophylla | Verbesina warei Gray | VEWA2 |
| Verbesina longifolia | Actinomeris longifolia Gray | ACLO4 |
| Verbesina microptera | Verbesina microptera DC. var. mollissima Robins. & Greenm. | VEMIM |
| Verbesina microptera | Verbesina texana Buckl. | VETE5 |
| Verbesina nana | Wootonella nana (Gray) Standl. | WONA |
| Verbesina nana | Ximenesia encelioides Cav. var. nana Gray | XIENN |
| Verbesina nana | Ximenesia nana (Gray) Shinners | XINA |
| Verbesina occidentalis | Phaethusa occidentalis (L.) Britt. | PHOC4 |
| Verbesina virginica var. laciniata | Phaethusa laciniata (Poir.) Small | PHLA16 |
| Verbesina virginica var. laciniata | Sigesbeckia laciniata Poir. | SILA15 |
| Verbesina virginica var. laciniata | Verbesina laciniata (Poir.) Nutt. | VELA5 |
| Verbesina virginica var. laciniata | Verbesina sinuata Ell. | VESI3 |
| Verbesina virginica var. laciniata | Verbesina virginica L. var. insularis Robins. & Greenm. | VEVII |
| Verbesina virginica var. virginica | Phaethusa virginica (L.) Britt. | PHVI6 |
| Verbesina walteri | Ridan paniculata (Walt.) Small | RIPA2 |
| Vernonia albicaulis | Lepidaploa glabra (Willd.) H. Rob. | LEGL23 |
| Vernonia angustifolia ssp. mohrii | Vernonia angustifolia Michx. var. mohrii S.B. Jones | VEANM2 |
| Vernonia angustifolia ssp. scaberrima | Vernonia angustifolia Michx. var. scaberrima (Nutt.) Gray | VEANS2 |
| Vernonia angustifolia ssp. scaberrima | Vernonia recurva Gleason | VERE2 |
| Vernonia angustifolia ssp. scaberrima | Vernonia scaberrima Nutt. | VESC3 |
| Vernonia arkansana | Vernonia crinita Raf. | VECR2 |
| Vernonia baldwinii ssp. interior | Vernonia interior Small | VEIN2 |
| Vernonia fasciculata ssp. corymbosa | Vernonia fasciculata Michx. var. corymbosa (Schwein. ex Keating) Daniels | VEFAC2 |
| Vernonia galamensis | Vernonia pauciflora (Willd.) Less. | VEPA6 |
| Vernonia gigantea ssp. gigantea | Vernonia altissima Nutt. | VEAL7 |
| Vernonia gigantea ssp. gigantea | Vernonia altissima Nutt. var. lilacina Clute | VEALL |
| Vernonia gigantea ssp. gigantea | Vernonia altissima Nutt. var. taeniotricha Blake | VEALT |
| Vernonia gigantea ssp. ovalifolia | Vernonia ovalifolia Torr. & Gray | VEOV |
| Vernonia glauca | Vernonia noveboracensis (L.) Michx. var. tomentosa (Ell.) Britt. | VENOT |
| Vernonia larsenii | Vernonia lindheimeri Gray & Engelm. var. leucophylla Larsen | VELIL |
| Vernonia marginata | Vernonia marginata (Torr.) Raf. var. tenuifolia (Small) Shinners | VEMAT |
| Vernonia missurica | Vernonia aborigina Gleason | VEAB2 |
| Vernonia noveboracensis | Vernonia harperi Gleason | VEHA4 |
| Vernonia sericea | Lepidaploa sericea (L.C. Rich.) H. Rob. | LESE16 |
| veronicaleaf brickellbush | Brickellia veronicifolia (Kunth) Gray | BRVE2 |
| veronicaleaf brickellbush | Brickellia veronicifolia (Kunth) Gray var. petrophila (B.L. Robins.) B.L. Robins. | BRVEP |
| veronicaleaf brickellbush | Brickellia veronicifolia (Kunth) Gray var. veronicifolia | BRVEV |
| Vesicarpa potentilloides var. nitrophilum | Sphaeromeria potentilloides (Gray) Heller var. nitrophila (Cronq.) A. Holmgren, L. Shultz & Lowrey | SPPON |
| Vesicarpa potentilloides var. nitrophilum | Tanacetum potentilloides (Gray) Gray var. nitrophilum Cronq. | TAPON |
| Vesicarpa potentilloides var. potentilloides | Sphaeromeria potentilloides (Gray) Heller | SPPO4 |
| Vesicarpa potentilloides var. potentilloides | Sphaeromeria potentilloides (Gray) Heller var. potentilloides (Gray) Heller [superfluous autonym] | SPPOP |
| Vesicarpa potentilloides var. potentilloides | Tanacetum potentilloides (Gray) Gray | TAPO3 |
| Vierhapper's aster | Aster alpinus L. var. vierhapperi (Onno) Cronq. | ASALV |
| Viguiera deltoidea | Viguiera deltoidea Gray var. genuina Blake [excluded] | VIDEG2 |
| Viguiera dentata var. dentata | Helianthus dentatus Cav. | HEDE9 |
| Viguiera parishii | Viguiera deltoidea Gray var. parishii (Greene) Vasey & Rose | VIDEP |
| Viguiera phenax | Helianthus ludens Shinners | HELU5 |
| Viguiera phenax | Viguiera ludens (Shinners) M.C. Johnston | VILU5 |
| Viguiera stenoloba var. chihuahuensis | Heliomeris tenuifolia Gray | HETE18 |
| Viguiera triloba | Zaluzania grayana Robins. & Greenm. | ZAGR |
| villalba | Condylidium iresinoides (Kunth) King & H.E. Robins. | COIR |
| villalba | Condylidium King & H.E. Robins. | CONDY2 |
| villous four-nerve daisy | Tetraneuris scaposa (DC.) Greene var. villosa (Shinners) Shinners | TESCV |
| villous woodyaster | Xylorhiza glabriuscula Nutt. var. villosa (Nutt.) A. Nels. | XYGLV |
| viper beggarticks | Bidens campylotheca Schultz-Bip. | BICA2 |
| viper beggarticks | Bidens campylotheca Schultz-Bip. ssp. campylotheca | BICAC |
| viper beggarticks | Bidens campylotheca Schultz-Bip. ssp. pentamera (Sherff) Ganders & Nagata | BICAP |
| Virgin River brittlebush | Encelia virginensis A. Nels. | ENVI |
| virgin thistle | Cirsium virginense Welsh | CIVI6 |
| Virginia dwarfdandelion | Krigia virginica (L.) Willd. | KRVI |
| Virginia goldenrod | Solidago gracillima Torr. & Gray | SOGR4 |
| Virginia sneezeweed | Helenium virginicum Blake | HEVI6 |
| Virginia thistle | Cirsium virginianum (L.) Michx. | CIVI |
| viscid candyleaf | Stevia viscida Kunth | STVI3 |
| viscid tansyaster | Rayjacksonia annua (Rydb.) R.L. Hartman & M.A. Lane | RAAN2 |
| Vreeland's erigeron | Erigeron vreelandii Greene | ERVR |
| Wahiawa Bog dubautia | Dubautia pauciflorula St. John & G.D. Carr | DUPA5 |
| Wahiawa dubautia | Dubautia syndetica G.D. Carr & D.H. Lorence | DUSY |
| Waialeale dubautia | Dubautia waialealae Rock | DUWA |
| Waianae Range dubautia | Dubautia sherffiana Fosberg | DUSH |
| Waianae Range nehe | Lipochaeta tenuifolia Gray | LITE7 |
| Waianae Range tetramolopium | Tetramolopium lepidotum (Less.) Sherff | TELE2 |
| Waianae Range tetramolopium | Tetramolopium lepidotum (Less.) Sherff ssp. arbusculum (Gray) Lowrey | TELEA |
| Waianae Range tetramolopium | Tetramolopium lepidotum (Less.) Sherff ssp. lepidotum | TELEL2 |
| Waihoi beggarticks | Bidens campylotheca Schultz-Bip. ssp. waihoiensis St. John | BICAW |
| Waimea Canyon nehe | Lipochaeta waimeaensis St. John | LIWA2 |
| wall hawkweed | Hieracium murorum L. | HIMU |
| wall-lettuce | Mycelis muralis (L.) Dumort. | MYMU |
| Walter's aster | Symphyotrichum walteri (Alexander) Nesom | SYWA |
| wand blackroot | Pterocaulon virgatum (L.) DC. | PTVI2 |
| wand blazing star | Liatris virgata Nutt. | LIVI8 |
| wand fleabane | Erigeron oxyphyllus Greene | EROX2 |
| wand goldenrod | Solidago stricta Ait. | SOST |
| wand lessingia | Lessingia virgata Gray | LEVI8 |
| wand lessingia | Lessingia virgata Gray var. glomerata (Greene) J.T. Howell | LEVIG |
| wand lessingia | Lessingia virgata Gray var. virgata | LEVIV |
| wand tarbush | Holocarpha virgata (Gray) Keck ssp. elongata Keck | HOVIE |
| wand wirelettuce | Stephanomeria virgata Benth. ssp. pleurocarpa (Greene) Gottlieb | STVIP |
| Ward's false goldenweed | Oonopsis wardii (Gray) Greene | OOWA |
| Warner Springs lessingia | Lessingia glandulifera Gray var. tomentosa (Greene) Ferris | LEGLT |
| Warnock's ragwort | Senecio warnockii Shinners | SEWA3 |
| Warnock's rockdaisy | Perityle warnockii A. Powell | PEWA10 |
| Wasatch aster | Eurybia wasatchensis (M.E. Jones) Nesom | EUWA4 |
| water ragwort | Senecio aquaticus Hill | SEAQ |
| water ragwort | Senecio hydrophilus Nutt. | SEHY2 |
| waterbuttons | Cotula L. | COTUL |
| Watson's brickellbush | Brickellia microphylla (Nutt.) Gray var. watsonii (B.L. Robins.) Welsh | BRMIW |
| Watson's false clapdaisy | Pseudoclappia watsonii A. Powell & B.L. Turner | PSWA3 |
| Watson's fleabane | Erigeron watsonii (Gray) Cronq. | ERWA5 |
| Watson's goldenbush | Ericameria watsonii (Gray) Nesom | ERWA8 |
| wavyleaf aster | Symphyotrichum undulatum (L.) Nesom | SYUN |
| wavyleaf purple coneflower | Echinacea simulata R.L. McGregor | ECSI |
| wavyleaf thistle | Cirsium undulatum (Nutt.) Spreng. | CIUN |
| wavyleaf thistle | Cirsium undulatum (Nutt.) Spreng. var. undulatum | CIUNU |
| wavyleaf thoroughwort | Chromolaena sinuata (Lam.) King & H.E. Robins. | CHSI |
| waxy coneflower | Rudbeckia glaucescens Eastw. | RUGL7 |
| waxy thoroughwort | Eupatorium glaucescens Ell. | EUGL7 |
| wayside aster | Eucephalus vialis Bradshaw | EUVI8 |
| weak groundsel | Packera debilis (Nutt.) W.A. Weber & A. L?ve | PADE22 |
| weakleaf burr ragweed | Ambrosia confertiflora DC. | AMCO3 |
| weather prophet | Dimorphotheca pluvialis (L.) Moench | DIPL4 |
| Weber's saw-wort | Saussurea weberi Hult | SAWE |
| Wedelia fruticosa | Stemmodontia calycina (L.C. Rich.) O.E. Schulz | STCA14 |
| Wedelia fruticosa | Wedelia calycina L.C. Rich. | WECA |
| Wedelia parviflora | Wedelia calycina L.C. Rich. var. parviflora (L.C. Rich.) Alain | WECAP |
| Wedelia texana | Wedelia acapulcensis Kunth var. hispida auct. non (Kunth) Strother [misapplied] | WEACH |
| Wedelia texana | Wedelia hispida auct. non Kunth [misapplied] | WEHI |
| Wedelia texana | Zexmenia hispida auct. non (Kunth) Gray ex Small [misapplied] | ZEHI2 |
| wedge beggarticks | Bidens cuneata Sherff | BICU |
| wedgeleaf | Calotis cuneifolia R. Br. | CACU22 |
| wedgeleaf fleabane | Erigeron cuneifolius DC. | ERCU6 |
| weedy dogfennel | Chamaemelum mixtum (L.) All. | CHMI5 |
| weedy dwarfdandelion | Krigia caespitosa (Raf.) Chambers | KRCA |
| weevil prairie-dandelion | Nothocalais troximoides (Gray) Greene | NOTR2 |
| Welsh's aster | Symphyotrichum welshii (Cronq.) Nesom | SYWE |
| West Indian beggarticks | Bidens cynapiifolia Kunth | BICY |
| West Indian cinchweed | Pectis linearis Llave | PELI14 |
| western aster | Symphyotrichum ascendens (Lindl.) Nesom | SYAS3 |
| western blanketflower | Gaillardia spathulata Gray | GASP |
| western bog aster | Symphyotrichum spathulatum (Lindl.) Nesom var. yosemitanum (Gray) Nesom | SYSPY |
| western coneflower | Rudbeckia occidentalis Nutt. | RUOC2 |
| western daisy | Astranthium Nutt. | ASTRA2 |
| western daisy fleabane | Erigeron bellidiastrum Nutt. | ERBE2 |
| western daisy fleabane | Erigeron bellidiastrum Nutt. var. bellidiastrum | ERBEB |
| western daisy fleabane | Erigeron bellidiastrum Nutt. var. robustus Cronq. | ERBER |
| western dwarfdandelion | Krigia occidentalis Nutt. | KROC |
| western goldentop | Euthamia occidentalis Nutt. | EUOC4 |
| western marsh cudweed | Gnaphalium palustre Nutt. | GNPA |
| western meadow aster | Symphyotrichum campestre (Nutt.) Nesom | SYCA3 |
| western meadow aster | Symphyotrichum campestre (Nutt.) Nesom var. campestre | SYCAC |
| western mountain aster | Symphyotrichum spathulatum (Lindl.) Nesom | SYSP |
| western mountain aster | Symphyotrichum spathulatum (Lindl.) Nesom var. spathulatum | SYSPS |
| western pearly everlasting | Anaphalis margaritacea (L.) Benth. | ANMA |
| western ragwort | Packera hesperia (Greene) W.A. Weber & A. L?ve | PAHE11 |
| western rattlesnakeroot | Prenanthes alata (Hook.) D. Dietr. | PRAL |
| western rosinweed | Calycadenia DC. | CALYC |
| western rough goldenrod | Solidago radula Nutt. | SORA |
| western rough goldenrod | Solidago radula Nutt. var. laeta (Greene) Fern. | SORAL |
| western rough goldenrod | Solidago radula Nutt. var. radula | SORAR |
| western rough goldenrod | Solidago radula Nutt. var. stenolepis Fern. | SORAS |
| western showy aster | Eurybia conspicua (Lindl.) Nesom | EUCO36 |
| western silver aster | Symphyotrichum sericeum (Vent.) Nesom | SYSE2 |
| western snakeroot | Ageratina occidentalis (Hook.) King & H.E. Robins. | AGOC2 |
| western sunflower | Helianthus anomalus Blake | HEAN4 |
| western yarrow | Achillea millefolium L. var. occidentalis DC. | ACMIO |
| Wheeler's skeletonweed | Chaetadelpha wheeleri Gray ex S. Wats. | CHWH |
| Wheeler's tarweed | Madia elegans D. Don ex Lindl. ssp. wheeleri (Gray) Keck | MAELW |
| Wheeler's thistle | Cirsium wheeleri (Gray) Petrak | CIWH |
| whip pussytoes | Antennaria flagellaris (Gray) Gray | ANFL2 |
| white arrowleaf aster | Symphyotrichum urophyllum (Lindl.) Nesom | SYUR |
| white crownbeard | Verbesina virginica L. | VEVI3 |
| white crownbeard | Verbesina virginica L. var. laciniata (Poir.) Gray | VEVIL |
| white crownbeard | Verbesina virginica L. var. virginica | VEVIV |
| white cudweed | Pseudognaphalium leucocephalum (Gray) A. Anderb. | PSLE4 |
| white cushion fleabane | Erigeron disparipilus Cronq. | ERDI3 |
| white doll's daisy | Boltonia asteroides (L.) L'H?r. | BOAS |
| white doll's daisy | Boltonia asteroides (L.) L'H?r. var. asteroides | BOASA |
| white doll's daisy | Boltonia asteroides (L.) L'H?r. var. latisquama (Gray) Cronq. | BOASL |
| white doll's daisy | Boltonia asteroides (L.) L'H?r. var. recognita (Fern. & Grisc.) Cronq. | BOASR |
| white easterbonnets | Antheropeas lanosum (Gray) Rydb. | ANLA7 |
| white false tickhead | Eatonella nivea (D.C. Eat.) Gray | EANI |
| white goldenrod | Solidago bicolor L. | SOBI |
| white hawkweed | Hieracium albiflorum Hook. | HIAL2 |
| white heath aster | Symphyotrichum ericoides (L.) Nesom | SYER |
| white heath aster | Symphyotrichum ericoides (L.) Nesom var. ericoides | SYERE |
| white heath aster | Symphyotrichum ericoides (L.) Nesom var. stricticaule (Torr. & Gray) Nesom | SYERS |
| White Mountain ragwort | Packera cynthioides (Greene) W.A. Weber & A. L?ve | PACY9 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom | SYLA6 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. hesperium (Gray) Nesom | SYLAH |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. hesperium (Gray) Nesom var. hesperium | SYLAH6 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. lanceolatum | SYLAL6 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. lanceolatum var. hirsuticaule (Semple & Chmielewski) Nesom | SYLAH7 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. lanceolatum var. interior (Wieg.) Nesom | SYLAI3 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. lanceolatum var. lanceolatum | SYLAL4 |
| white panicle aster | Symphyotrichum lanceolatum (Willd.) Nesom ssp. lanceolatum var. latifolium (Semple & Chmielewski) Nesom | SYLAL5 |
| white pincushion | Chaenactis artemisiifolia (Harvey & Gray ex Gray) Gray | CHAR |
| white prairie aster | Symphyotrichum falcatum (Lindl.) Nesom | SYFA |
| white prairie aster | Symphyotrichum falcatum (Lindl.) Nesom var. commutatum (Torr. & Gray) Nesom | SYFAC |
| white prairie aster | Symphyotrichum falcatum (Lindl.) Nesom var. falcatum | SYFAF |
| white rattlesnakeroot | Prenanthes alba L. | PRAL2 |
| white rocklettuce | Pinaropappus roseus (Less.) Less. | PIRO |
| white rocklettuce | Pinaropappus roseus (Less.) Less. var. foliosus (Heller) Shinners | PIROF |
| white rocklettuce | Pinaropappus roseus (Less.) Less. var. roseus | PIROR |
| white rosinweed | Silphium albiflorum Gray | SIAL |
| white sagebrush | Artemisia ludoviciana Nutt. | ARLU |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. albula (Woot.) Keck | ARLUA |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. candicans (Rydb.) Keck | ARLUC8 |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. estesii Chambers | ARLUE |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. incompta (Nutt.) Keck | ARLUI2 |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. ludoviciana | ARLUL2 |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. mexicana (Willd. ex Spreng.) Keck | ARLUM2 |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. redolens (Gray) Keck | ARLUR |
| white sagebrush | Artemisia ludoviciana Nutt. ssp. sulcata (Rydb.) Keck | ARLUS |
| white snakeroot | Ageratina altissima (L.) King & H.E. Robins. | AGAL5 |
| white snakeroot | Ageratina altissima (L.) King & H.E. Robins. var. altissima | AGALA |
| white snakeroot | Ageratina altissima (L.) King & H.E. Robins. var. angustata (Gray) Clewell & Woot. | AGALA2 |
| white snakeroot | Ageratina altissima (L.) King & H.E. Robins. var. roanensis (Small) Clewell & Woot. | AGALR |
| white sunbonnets | Chaptalia albicans (Sw.) Vent. ex Steud. | CHAL18 |
| white tackstem | Calycoseris wrightii Gray | CAWR |
| white thistle | Cirsium hookerianum Nutt. | CIHO |
| white thoroughwort | Eupatorium album L. | EUAL2 |
| white thoroughwort | Eupatorium album L. var. album | EUALA |
| white thoroughwort | Eupatorium album L. var. subvenosum Gray | EUALS |
| white wood aster | Eurybia divaricata (L.) Nesom | EUDI16 |
| white wormwood | Artemisia herba-alba Asso | ARHE10 |
| whitebuttons | Anacyclus clavatus (Desf.) Pers. | ANCL2 |
| whitecrown | Holozonia filipes (Hook. & Arn.) Greene | HOFI |
| whitedaisy tidytips | Layia glandulosa (Hook.) Hook. & Arn. | LAGL5 |
| whiteflower goldenbush | Ericameria gilmanii (Blake) Nesom | ERGI5 |
| whiteflower leafcup | Polymnia canadensis L. | POCA11 |
| whiteflower rabbitbrush | Chrysothamnus albidus (M.E. Jones ex Gray) Greene | CHAL9 |
| whiteflower tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. leucanthemifolia (Greene) Welsh | MACAL |
| whitehair goldenrod | Solidago albopilosa E.L. Braun | SOAL3 |
| whitehead mule-ears | Wyethia helenioides (DC.) Nutt. | WYHE |
| whiteleaf sunflower | Helianthus glaucophyllus D.M. Sm. | HEGL2 |
| whitemargin pussytoes | Antennaria marginata Greene | ANMA5 |
| whiteplume wirelettuce | Stephanomeria exigua Nutt. ssp. carotifera (Hoover) Gottlieb | STEXC2 |
| whiteplume wirelettuce | Stephanomeria exigua Nutt. ssp. coronaria (Greene) Gottlieb | STEXC3 |
| whiteplume wirelettuce | Stephanomeria exigua Nutt. ssp. macrocarpa Gottlieb | STEXM |
| whiteray leastdaisy | Chaetopappa bellidifolia (Gray & Engelm.) Shinners | CHBE2 |
| whiteray pygmydaisy | Pentachaeta bellidiflora Greene | PEBE |
| whitespine thistle | Cirsium clokeyi Blake | CICL2 |
| whitestem distaff thistle | Carthamus leucocaulos Sm. | CALE52 |
| whitestem goldenbush | Ericameria discoidea (Nutt.) Nesom | ERDI14 |
| whitestem goldenbush | Ericameria discoidea (Nutt.) Nesom var. discoidea | ERDID |
| whitestem goldenbush | Ericameria discoidea (Nutt.) Nesom var. linearis (Rydb.) Nesom | ERDIL |
| whitestem paperflower | Psilostrophe cooperi (Gray) Greene | PSCO2 |
| whitetop | Doellingeria Nees | DOELL2 |
| whitetop aster | Sericocarpus Greene | SERIC |
| whitewash cornflower | Centaurea dealbata Willd. [excluded] | CEDE15 |
| whiteweed | Ageratum L. | AGERA |
| Whitney's bristleweed | Hazardia whitneyi (Gray) Greene | HAWH3 |
| Whitney's bristleweed | Hazardia whitneyi (Gray) Greene var. discoidea (J.T. Howell) W.D. Clark | HAWHD2 |
| Whitney's bristleweed | Hazardia whitneyi (Gray) Greene var. whitneyi | HAWHW |
| wholeleaf goldenweed | Pyrrocoma insecticruris Henderson | PYIN2 |
| wholeleaf rosinweed | Silphium integrifolium Michx. | SIIN2 |
| wholeleaf rosinweed | Silphium integrifolium Michx. var. integrifolium | SIINI |
| wholeleaf rosinweed | Silphium integrifolium Michx. var. laeve Torr. & Gray | SIINL |
| wholeleaf rosinweed | Silphium integrifolium Michx. var. neglectum Settle & T.R. Fisher | SIINN |
| whorled rosinweed | Silphium trifoliatum L. | SITR7 |
| whorled rosinweed | Silphium trifoliatum L. var. latifolium Gray | SITRL |
| whorled rosinweed | Silphium trifoliatum L. var. trifoliatum | SITRT |
| whorled tickseed | Coreopsis verticillata L. | COVE5 |
| whorled wood aster | Oclemena acuminata (Michx.) Greene | OCAC |
| widehead groundsel | Packera eurycephala (Torr. & Gray ex Gray) W.A. Weber & A. L?ve | PAEU5 |
| widehead groundsel | Packera eurycephala (Torr. & Gray ex Gray) W.A. Weber & A. L?ve var. eurycephala | PAEUE |
| Wiebke's beggarticks | Bidens wiebkei Sherff | BIWI |
| wig knapweed | Centaurea phrygia L. | CEPH |
| wild cineraria | Cineraria saxifraga DC. | CISA4 |
| wild cosmos | Cosmos caudatus Kunth | COCA21 |
| wild quinine | Parthenium auriculatum Britt. | PAAU7 |
| wild quinine | Parthenium hispidum Raf. | PAHI8 |
| wild quinine | Parthenium integrifolium L. | PAIN3 |
| wild quinine | Parthenium integrifolium L. var. integrifolium | PAINI |
| wild quinine | Parthenium integrifolium L. var. mabryanum Mears | PAINM |
| wild sandheath | Centaurea eriophora L. | CEER |
| Willamette fleabane | Erigeron decumbens Nutt. | ERDE3 |
| Willamette fleabane | Erigeron decumbens Nutt. var. decumbens | ERDED |
| Willamette fleabane | Erigeron decumbens Nutt. var. robustior (Cronq.) Cronq. | ERDER2 |
| willow glowweed | Hesperodoria salicina (Blake) Nesom | HESA13 |
| willow ragwort | Barkleyanthus (Kunth) H.E. Robins. & Brett. | BARKL |
| willow ragwort | Barkleyanthus salicifolius (Kunth) H.E. Robins. & Brett. | BASA5 |
| willowleaf aster | Symphyotrichum praealtum (Poir.) Nesom | SYPR5 |
| willowleaf aster | Symphyotrichum praealtum (Poir.) Nesom var. angustior (Wieg.) Nesom | SYPRA |
| willowleaf aster | Symphyotrichum praealtum (Poir.) Nesom var. praealtum | SYPRP |
| willowleaf aster | Symphyotrichum praealtum (Poir.) Nesom var. subasperum (Lindl.) Nesom | SYPRS |
| willowleaf candyleaf | Stevia salicifolia Cav. | STSA |
| willowleaf lettuce | Lactuca saligna L. | LASA |
| willowleaf sunflower | Helianthus salicifolius A. Dietr. | HESA2 |
| willowleaf yellowhead | Inula salicina L. | INSA |
| winged cudweed | Pseudognaphalium viscosum (Kunth) W.A. Weber | PSVI4 |
| winged plumeless thistle | Carduus tenuiflorus W. Curtis | CATE2 |
| wingpetal | Heterosperma pinnatum Cav. | HEPI2 |
| wingstem | Verbesina alternifolia (L.) Britt. ex Kearney | VEAL |
| wingstem camphorweed | Pluchea sagittalis (Lam.) Cabrera | PLSA5 |
| Winkler's blanketflower | Gaillardia aestivalis (Walt.) H. Rock var. winkleri (Cory) B.L. Turner | GAAEW |
| Winn Falls fleabane | Erigeron scopulinus Nesom & Roth | ERSC7 |
| wirelettuce | Stephanomeria Nutt. | STEPH |
| wireweed | Rigiopappus leptocladus Gray | RILE2 |
| Wislizenus's false threadleaf | Schkuhria pinnata (Lam.) Kuntze ex Thell. var. guatemalensis (Rydb.) McVaugh | SCPIG |
| woman's tobacco | Antennaria plantaginifolia (L.) Richards. | ANPL |
| Woodhouse's bahia | Picradeniopsis woodhousei (Gray) Rydb. | PIWO |
| woodland arctic cudweed | Omalotheca sylvatica (L.) Schultz-Bip. & F.W. Schultz | OMSY |
| woodland burdock | Arctium vulgare (Hill) Evans | ARVU2 |
| woodland lettuce | Lactuca floridana (L.) Gaertn. | LAFL |
| woodland lettuce | Lactuca floridana (L.) Gaertn. var. floridana | LAFLF |
| woodland lettuce | Lactuca floridana (L.) Gaertn. var. villosa (Jacq.) Cronq. | LAFLV |
| woodland madia | Madia madioides (Nutt.) Greene | MAMA |
| woodland monolopia | Monolopia gracilens Gray | MOGR |
| woodland ragwort | Senecio sylvaticus L. | SESY |
| woodland sunflower | Helianthus divaricatus L. | HEDI2 |
| woodland tickseed | Coreopsis pulchra Boynt. | COPU9 |
| woodland tidytips | Layia gaillardioides (Hook. & Arn.) DC. | LAGA |
| woody goldenrod | Chrysoma pauciflosculosa (Michx.) Greene | CHPA18 |
| woodyaster | Xylorhiza Nutt. | XYLOR |
| woolbearing dandelion | Taraxacum eriophorum Rydb. | TAER2 |
| woolly brickellbush | Brickellia incana Gray | BRIN |
| woolly burdock | Arctium tomentosum P. Mill. | ARTO |
| woolly chaffhead | Carphephorus tomentosus (Michx.) Torr. & Gray | CATO5 |
| woolly desert marigold | Baileya pleniradiata Harvey & Gray ex Gray | BAPL3 |
| woolly desertdandelion | Malacothrix floccifera (DC.) Blake | MAFL |
| woolly distaff thistle | Carthamus lanatus L. | CALA20 |
| woolly distaff thistle | Carthamus lanatus L. ssp. creticus (L.) Holmboe | CALAC3 |
| woolly distaff thistle | Carthamus lanatus L. ssp. lanatus | CALAL10 |
| woolly easterbonnets | Antheropeas wallacei (Gray) Rydb. | ANWA |
| woolly fleabane | Erigeron lanatus Hook. | ERLA |
| woolly fruit burr ragweed | Ambrosia eriocentra (Gray) Payne | AMER |
| woolly goat chicory | Agoseris apargioides (Less.) Greene | AGAP2 |
| woolly goat chicory | Agoseris apargioides (Less.) Greene var. apargioides | AGAPA |
| woolly goat chicory | Agoseris apargioides (Less.) Greene var. eastwoodiae (Fedde) Munz | AGAPE |
| woolly goat chicory | Agoseris apargioides (Less.) Greene var. maritima (Sheldon) Q. Jones ex Cronq. | AGAPM |
| woolly goatsbeard | Tragopogon floccosus Waldst. & Kit. | TRFL15 |
| woolly groundsel | Packera cana (Hook.) W.A. Weber & A. L?ve | PACA15 |
| woolly hawkweed | Hieracium triste Willd. ex Spreng. | HITR2 |
| woolly hawkweed | Hieracium triste Willd. ex Spreng. var. fulvum Hult | HITRF |
| woolly hawkweed | Hieracium triste Willd. ex Spreng. var. triste | HITRT2 |
| woolly ironweed | Vernonia lindheimeri Gray & Engelm. | VELI3 |
| woolly marshelder | Leuciva dealbata (Gray) Rydb. | LEDE23 |
| woolly mock goldenweed | Stenotus lanuginosus (Gray) Greene | STLA7 |
| woolly mule-ears | Wyethia mollis Gray | WYMO |
| woolly paperflower | Psilostrophe tagetina (Nutt.) Greene | PSTA |
| woolly paperflower | Psilostrophe tagetina (Nutt.) Greene var. cerifera (A. Nels.) B.L. Turner | PSTAC |
| woolly paperflower | Psilostrophe tagetina (Nutt.) Greene var. tagetina | PSTAT |
| woolly pricklyleaf | Thymophylla micropoides (DC.) Strother | THMI7 |
| woolly pussytoes | Antennaria lanata (Hook.) Greene | ANLA3 |
| woolly ragwort | Packera tomentosa (Michx.) C. Jeffrey | PATO4 |
| woolly sunbonnets | Chaptalia tomentosa Vent. | CHTO |
| woolly sunflower | Eriophyllum Lag. | ERIOP2 |
| woollyhead lessingia | Lessingia hololeuca Greene | LEHO |
| woollyhead neststraw | Stylocline micropoides Gray | STMI2 |
| woollyheads | Psilocarphus Nutt. | PSILO |
| woollyleaf burr ragweed | Ambrosia grayi (A. Nels.) Shinners | AMGR5 |
| Wooton's ragwort | Senecio wootonii Greene | SEWO |
| wreath goldenrod | Solidago caesia L. | SOCA4 |
| wreathplant | Stephanomeria diegensis Gottlieb | STDI6 |
| Wright's baccharis | Baccharis wrightii Gray | BAWR |
| Wright's cudweed | Pseudognaphalium canescens (DC.) W.A. Weber | PSCA11 |
| Wright's cudweed | Pseudognaphalium canescens (DC.) W.A. Weber ssp. beneolens (A. Davids.) Kartesz | PSCAB |
| Wright's cudweed | Pseudognaphalium canescens (DC.) W.A. Weber ssp. canescens | PSCAC2 |
| Wright's cudweed | Pseudognaphalium canescens (DC.) W.A. Weber ssp. microcephalum (Nutt.) Kartesz | PSCAM |
| Wright's cudweed | Pseudognaphalium canescens (DC.) W.A. Weber ssp. thermale (E. Nels.) Kartesz | PSCAT |
| Wright's dogweed | Adenophyllum wrightii Gray | ADWR |
| Wright's dwarfdandelion | Krigia wrightii (Gray) Chambers ex Kim | KRWR |
| Wright's false threadleaf | Schkuhria anthemoidea (DC.) Coult. | SCAN |
| Wright's false threadleaf | Schkuhria anthemoidea (DC.) Coult. var. anthemoidea (DC.) Coult. [excluded] | SCANA6 |
| Wright's false threadleaf | Schkuhria anthemoidea (DC.) Coult. var. wrightii (Gray) Heiser | SCANW |
| Wright's goldenrod | Solidago wrightii Gray | SOWR |
| Wright's goldenrod | Solidago wrightii Gray var. adenophora Blake | SOWRA |
| Wright's goldenrod | Solidago wrightii Gray var. wrightii | SOWRW |
| Wright's pricklyleaf | Thymophylla tenuiloba (DC.) Small var. wrightii (Gray) Strother | THTEW |
| Wright's snakeroot | Ageratina wrightii (Gray) King & H.E. Robins. | AGWR2 |
| Wright's snakeweed | Gutierrezia wrightii Gray | GUWR |
| Wright's thimblehead | Hymenothrix wrightii Gray | HYWR |
| Wright's thistle | Cirsium wrightii Gray | CIWR |
| Wright's wirelettuce | Stephanomeria wrightii Gray | STWR2 |
| wrinkleleaf goldenrod | Solidago rugosa P. Mill. | SORU2 |
| wrinkleleaf goldenrod | Solidago rugosa P. Mill. ssp. aspera (Ait.) Cronq. | SORUA |
| wrinkleleaf goldenrod | Solidago rugosa P. Mill. ssp. rugosa | SORUR |
| wrinkleleaf goldenrod | Solidago rugosa P. Mill. ssp. rugosa var. rugosa | SORUR2 |
| wrinkleleaf goldenrod | Solidago rugosa P. Mill. ssp. rugosa var. sphagnophila Graves | SORUS |
| wrinkleleaf goldenrod | Solidago rugosa P. Mill. ssp. rugosa var. villosa (Pursh) Fern. | SORUV |
| Wyethia amplexicaulis | Espeletia amplexicaulis Nutt. | ESAM |
| Wyethia angustifolia | Wyethia angustifolia (DC.) Nutt. var. foliosa (Congd.) Hall | WYANF |
| Wyoming big sagebrush | Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young | ARTRW8 |
| Wyoming thistle | Cirsium pulcherrimum (Rydb.) K. Schum. | CIPU3 |
| Wyoming threetip sagebrush | Artemisia tripartita Rydb. ssp. rupicola Beetle | ARTRR2 |
| Wyoming Townsend daisy | Townsendia alpigena Piper | TOAL |
| Wyoming Townsend daisy | Townsendia alpigena Piper var. alpigena | TOALA |
| Wyoming Townsend daisy | Townsendia alpigena Piper var. caelilinensis (Welsh) Kartesz & Gandhi | TOALC |
| Wyoming Townsend daisy | Townsendia alpigena Piper var. minima (Eastw.) Dorn | TOALM |
| Xanthisma texanum ssp. drummondii | Xanthisma texanum DC. var. drummondii (Torr. & Gray) Gray | XATED |
| Xanthisma texanum ssp. texanum | Xanthisma texanum DC. var. orientale Semple | XATEO |
| Xanthisma texanum ssp. texanum | Xanthisma texanum DC. var. texanum | XATET2 |
| Xanthium spinosum | Acanthoxanthium spinosum (L.) Fourr. | ACSP5 |
| Xanthium spinosum | Xanthium spinosum L. var. inerme Bel. | XASPI |
| Xanthium strumarium var. canadense | Xanthium acerosum Greene | XAAC |
| Xanthium strumarium var. canadense | Xanthium californicum Greene | XACA2 |
| Xanthium strumarium var. canadense | Xanthium californicum Greene var. rotundifolium Widder | XACAR |
| Xanthium strumarium var. canadense | Xanthium campestre Greene | XACA3 |
| Xanthium strumarium var. canadense | Xanthium canadense P. Mill. | XACA4 |
| Xanthium strumarium var. canadense | Xanthium cavanillesii Schouw | XACA6 |
| Xanthium strumarium var. canadense | Xanthium cenchroides Millsp. & Sherff | XACE2 |
| Xanthium strumarium var. canadense | Xanthium commune Britt. | XACO |
| Xanthium strumarium var. canadense | Xanthium echinatum Murr. | XAEC |
| Xanthium strumarium var. canadense | Xanthium glanduliferum Greene | XAGL2 |
| Xanthium strumarium var. canadense | Xanthium italicum Moretti | XAIT |
| Xanthium strumarium var. canadense | Xanthium macounii Britt. | XAMA |
| Xanthium strumarium var. canadense | Xanthium oligacanthum Piper | XAOL |
| Xanthium strumarium var. canadense | Xanthium oviforme Wallr. | XAOV |
| Xanthium strumarium var. canadense | Xanthium pensylvanicum Wallr. | XAPE2 |
| Xanthium strumarium var. canadense | Xanthium saccharatum Wallr. | XASA3 |
| Xanthium strumarium var. canadense | Xanthium speciosum Kearney | XASP3 |
| Xanthium strumarium var. canadense | Xanthium strumarium L. ssp. italicum (Moretti) D. L?ve | XASTI |
| Xanthium strumarium var. canadense | Xanthium strumarium L. var. oviforme (Wallr.) M.E. Peck | XASTO |
| Xanthium strumarium var. canadense | Xanthium strumarium L. var. pensylvanicum (Wallr.) M.E. Peck | XASTP |
| Xanthium strumarium var. canadense | Xanthium varians Greene | XAVA |
| Xanthium strumarium var. glabratum | Xanthium americanum Walt. | XAAM2 |
| Xanthium strumarium var. glabratum | Xanthium calvum Millsp. & Sherff | XACA5 |
| Xanthium strumarium var. glabratum | Xanthium chasei Fern. | XACH |
| Xanthium strumarium var. glabratum | Xanthium chinense P. Mill. | XACH2 |
| Xanthium strumarium var. glabratum | Xanthium curvescens Millsp. & Sherff | XACU |
| Xanthium strumarium var. glabratum | Xanthium cylindraceum Millsp. & Sherff | XACY |
| Xanthium strumarium var. glabratum | Xanthium echinellum Greene | XAEC2 |
| Xanthium strumarium var. glabratum | Xanthium globosum Shull | XAGL3 |
| Xanthium strumarium var. glabratum | Xanthium inflexum Mackenzie & Bush | XAIN |
| Xanthium strumarium var. glabratum | Xanthium macrocarpum DC. var. glabratum DC. | XAMAG |
| Xanthium strumarium var. glabratum | Xanthium occidentale Bertol. | XAOC |
| Xanthium strumarium var. glabratum | Xanthium orientale L. | XAOR |
| Xanthium strumarium var. glabratum | Xanthium strumarium L. var. wootonii (Cockerell) M.E. Peck | XASTW |
| Xanthium strumarium var. glabratum | Xanthium wootonii Cockerell | XAWO |
| xanthocephalum | Xanthocephalum Willd. | XANTH6 |
| Xanthocephalum gymnospermoides | Grindelia gymnospermoides (Gray) Ruffin | GRGY |
| Xanthocephalum gymnospermoides | Gutierrezia gymnospermoides Gray | GUGY |
| Xylorhiza cognata | Aster cognatus Hall | ASCO29 |
| Xylorhiza cognata | Aster standleyi A. Davids. | ASST13 |
| Xylorhiza cognata | Machaeranthera cognata (Hall) Cronq. & Keck | MACO17 |
| Xylorhiza cognata | Xylorhiza standleyi (A. Davids.) A. Davids. | XYST2 |
| Xylorhiza confertifolia | Machaeranthera confertifolia (Cronq.) Cronq. | MACO30 |
| Xylorhiza confertifolia | Machaeranthera glabriuscula (Nutt.) Cronq. & Keck var. confertifolia Cronq. | MAGLC |
| Xylorhiza cronquistii | Machaeranthera cronquistii (Welsh & Atwood) Cronq. | MACR7 |
| Xylorhiza glabriuscula var. glabriuscula | Aster glabriuscula (Nutt.) Torr. & Gray | ASGL9 |
| Xylorhiza glabriuscula var. glabriuscula | Aster glabriuscula (Nutt.) Torr. & Gray var. parryi (Gray) Onno | ASGLP2 |
| Xylorhiza glabriuscula var. glabriuscula | Aster parryi Gray | ASPA21 |
| Xylorhiza glabriuscula var. glabriuscula | Aster xylorhiza (Nutt.) Torr. & Gray | ASXY |
| Xylorhiza glabriuscula var. glabriuscula | Machaeranthera glabriuscula (Nutt.) Cronq. & Keck | MAGL7 |
| Xylorhiza glabriuscula var. linearifolia | Machaeranthera linearifolia (T.J. Wats.) Cronq. | MALI6 |
| Xylorhiza glabriuscula var. villosa | Machaeranthera glabriuscula (Nutt.) Cronq. & Keck var. villosa (Nutt.) Cronq. & Keck | MAGLV2 |
| Xylorhiza glabriuscula var. villosa | Xylorhiza villosa Nutt. | XYVI |
| Xylorhiza orcuttii | Aster orcuttii Vasey & Rose | ASOR3 |
| Xylorhiza orcuttii | Machaeranthera orcuttii (Vasey & Rose) Cronq. & Keck | MAOR8 |
| Xylorhiza tortifolia var. imberbis | Machaeranthera tortifolia (Torr. & Gray) Cronq. & Keck var. imberbis Cronq. | MATOI |
| Xylorhiza tortifolia var. tortifolia | Aplopappus tortifolius Torr. & Gray | APTO |
| Xylorhiza tortifolia var. tortifolia | Aster abatus Blake | ASAB3 |
| Xylorhiza tortifolia var. tortifolia | Aster goodingii Onno | ASGO3 |
| Xylorhiza tortifolia var. tortifolia | Aster mohavensis Coville, non Kuntze | ASMO15 |
| Xylorhiza tortifolia var. tortifolia | Aster tortifolius (Torr. & Gray) Gray, non Michx. | ASTO7 |
| Xylorhiza tortifolia var. tortifolia | Machaeranthera tortifolia (Torr. & Gray) Cronq. & Keck | MATO4 |
| Xylorhiza tortifolia var. tortifolia | Xylorhiza lanceolata Rydb. | XYLA2 |
| Xylorhiza tortifolia var. tortifolia | Xylorhiza scopulorum A. Nels. | XYSC5 |
| Xylorhiza venusta | Aster venustus M.E. Jones | ASVE11 |
| Xylorhiza venusta | Machaeranthera venusta (M.E. Jones) Cronq. & Keck | MAVE4 |
| Xylorhiza wrightii | Aster wrightii Gray | ASWR2 |
| Xylorhiza wrightii | Machaeranthera wrightii (Gray) Cronq. & Keck | MAWR4 |
| Xylorhiza wrightii | Townsendia wrightii (Gray) Gray | TOWR |
| Xylothamia palmeri | Aster palmeri Gray, non Ericameria palmeri (Gray) Hall | ASPA19 |
| Xylothamia palmeri | Ericameria austrotexana M.C. Johnston | ERAU3 |
| Xylothamia palmeri | Isocoma palmeri (Gray) Shinners | ISPA3 |
| Xylothamia triantha | Ericameria triantha (Blake) Shinners | ERTR14 |
| Xylothamia triantha | Haplopappus trianthus Blake | HATR3 |
| yacon | Polymnia sonchifolia Poeppig & Endl. | POSO4 |
| yambush | Gundlachia corymbosa (Urban) Britt. ex Boldingh | GUCO |
| yankeeweed | Eupatorium compositifolium Walt. | EUCO7 |
| yapana | Eupatorium triplinerve Vahl | EUTR4 |
| yarrow | Achillea ageratifolia (Sibth. & Smith) Boiss. | ACAG |
| yarrow | Achillea L. | ACHIL |
| yellow aster | Eastwoodia elegans Brandeg. | EAEL |
| yellow blanketflower | Gaillardia flava Rydb. | GAFL |
| yellow creeping zinnia | Sanvitalia ocymoides DC. | SAOC3 |
| yellow crownbeard | Verbesina occidentalis (L.) Walt. | VEOC |
| yellow hawkweed | Hieracium fendleri Schultz-Bip. | HIFE |
| yellow hawkweed | Hieracium fendleri Schultz-Bip. var. discolor Gray | HIFED |
| yellow hawkweed | Hieracium fendleri Schultz-Bip. var. fendleri | HIFEF |
| yellow pincushion | Chaenactis glabriuscula DC. | CHGL |
| yellow pincushion | Chaenactis glabriuscula DC. var. glabriuscula | CHGLG2 |
| yellow pincushion | Chaenactis glabriuscula DC. var. heterocarpha (Torr. & Gray ex Gray) Hall | CHGLH |
| yellow pincushion | Chaenactis glabriuscula DC. var. lanosa (DC.) Hall | CHGLL2 |
| yellow pincushion | Chaenactis glabriuscula DC. var. megacephala Gray | CHGLM |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. | CHVI8 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. axillaris (Keck) L.C. Anders. | CHVIA4 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. lanceolatus (Nutt.) Hall & Clements | CHVIL4 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. planifolius L.C. Anders. | CHVIP3 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. puberulus (D.C. Eat.) Hall & Clements | CHVIP4 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. viscidiflorus | CHVIV2 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. viscidiflorus var. latifolius (D.C. Eat.) Greene | CHVIL10 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. viscidiflorus var. stenophyllus (Gray) Hall | CHVIS5 |
| yellow rabbitbrush | Chrysothamnus viscidiflorus (Hook.) Nutt. ssp. viscidiflorus var. viscidiflorus | CHVIV4 |
| yellow salsify | Tragopogon dubius Scop. | TRDU |
| yellow star-thistle | Centaurea solstitialis L. | CESO3 |
| yellow streamers | Viguiera triloba (Gray) J. Olsen | VITR9 |
| yellow tackstem | Calycoseris parryi Gray | CAPA7 |
| yellow thistle | Cirsium horridulum Michx. | CIHO2 |
| yellow thistle | Cirsium horridulum Michx. var. horridulum | CIHOH |
| yellow thistle | Cirsium horridulum Michx. var. vittatum (Small) R.W. Long | CIHOV |
| yellowdicks | Helenium amarum (Raf.) H. Rock | HEAM |
| yellowdicks | Helenium amarum (Raf.) H. Rock var. amarum | HEAMA |
| yellowdicks | Helenium amarum (Raf.) H. Rock var. badium (Gray ex S. Wats.) Waterfall | HEAMB2 |
| yellowdome | Trichoptilium incisum (Gray) Gray | TRIN2 |
| yellowflower tarweed | Holocarpha virgata (Gray) Keck | HOVI |
| yellowflower tarweed | Holocarpha virgata (Gray) Keck ssp. virgata | HOVIV |
| yellowhead | Inula L. | INULA |
| yellowray Fremont's-gold | Syntrichopappus fremontii Gray | SYFR |
| yellowray goldfields | Lasthenia glabrata Lindl. | LAGL4 |
| yellowray goldfields | Lasthenia glabrata Lindl. ssp. glabrata | LAGLG2 |
| yellowspine thistle | Cirsium ochrocentrum Gray | CIOC2 |
| yellowspine thistle | Cirsium ochrocentrum Gray ssp. ochrocentrum | CIOCO2 |
| yellowtops | Flaveria Juss. | FLAVE |
| yerba de cabra | Melanthera aspera (Jacq.) Steud. ex Small | MEAS3 |
| yerba de cabra | Melanthera aspera (Jacq.) Steud. ex Small var. aspera | MEASA |
| yerba de cabra | Melanthera aspera (Jacq.) Steud. ex Small var. glabriuscula (Kuntze) J.C. Parks | MEASG |
| yerba de faja | Struchium sparganophorum (L.) Kuntze | STSP7 |
| yerba de pasmo | Baccharis pteronioides DC. | BAPT |
| yerba de peo | Porophyllum leiocarpum (Urban) Rydb. | POLE9 |
| yerba de plata | Rolandra fruticosa (L.) Kuntze | ROFR |
| yerba de plata | Rolandra Rottb. | ROLAN |
| yerba de San Juan | Pectis humifusa Sw. | PEHU4 |
| yerba porosa | Porophyllum ruderale (Jacq.) Cass. | PORU6 |
| yerba porosa | Porophyllum ruderale (Jacq.) Cass. ssp. macrocephalum (DC.) R.R. Johnson | PORUM2 |
| yerba porosa | Porophyllum ruderale (Jacq.) Cass. ssp. ruderale | PORUR |
| Yosemite tarweed | Jensia yosemitana (Parry ex Gray) B.G. Baldwin | JEYO |
| Yosemite woolly sunflower | Eriophyllum nubigenum Greene ex Gray | ERNU6 |
| youngia | Youngia Cass. | YOUNG |
| Youngia japonica | Crepis japonica (L.) Benth. | CRJA4 |
| Youngia japonica | Youngia japonica (L.) DC. ssp. elstonii (Hochr.) Stebbins | YOJAE |
| Youngia japonica | Youngia thunbergiana DC. | YOTH |
| Yucatan camphorweed | Pluchea yucatanensis Nesom | PLYU |
| Yukon aster | Symphyotrichum yukonense (Cronq.) Nesom | SYYU |
| Yukon fleabane | Erigeron yukonensis Rydb. | ERYU2 |
| Yukon groundsel | Tephroseris yukonensis (Porsild) Holub | TEYU |
| Yukon hawkweed | Hieracium gracile Hook. var. yukonense Porsild | HIGRY |
| Yukon wormwood | Artemisia macrobotrys Ledeb. | ARMA20 |
| Ziegler's tansyaster | Machaeranthera canescens (Pursh) Gray ssp. canescens var. ziegleri (Munz) B.L. Turner | MACAZ2 |
| zigzag goldenrod | Solidago flexicaulis L. | SOFL2 |
| zigzag silkgrass | Pityopsis flexuosa (Nash) Small | PIFL5 |
| zinnia | Zinnia L. | ZINNI |
| Zinnia acerosa | Zinnia pumila Gray | ZIPU |
| Zinnia grandiflora | Crassina grandiflora (Nutt.) Kuntze | CRGR12 |
| Zinnia maritima var. palmeri | Zinnia palmeri Gray | ZIPA4 |
| Zinnia peruviana | Crassina multiflora (L.) Kuntze | CRMU7 |
| Zinnia peruviana | Zinnia multiflora L. | ZIMU3 |
| Zinnia peruviana | Zinnia pauciflora L. | ZIPA5 |
| Zinnia violacea | Crassina elegans (Jacq.) Kuntze | CREL6 |
| Zinnia violacea | Zinnia elegans Jacq. | ZIEL |
| Zion chickensage | Sphaeromeria ruthiae A. Holmgren, L. Shultz & Lowrey | SPRU3 |
| Zion false goldenaster | Heterotheca zionensis Semple | HEZI |
| Zion fleabane | Erigeron sionis Cronq. | ERSI6 |
| Zion goldenbush | Isocoma humilis Nesom | ISHU |
Plant List