| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| SENNA | Senna P. Mill. | senna | Fabaceae
|
| SEGI3 | Sequoia gigantea (Lindl.) Dcne. | Sequoiadendron giganteum | Taxodiaceae
|
| SESE3 | Sequoia sempervirens (Lamb. ex D. Don) Endl. | redwood | Taxodiaceae
|
| SEWE6 | Sequoia wellingtonia Seem. | Sequoiadendron giganteum | Taxodiaceae
|
| SEQUO | Sequoia Endl. | redwood | Taxodiaceae
|
| SEGI2 | Sequoiadendron giganteum (Lindl.) Buchh. | giant sequoia | Taxodiaceae
|
| SEQUO2 | Sequoiadendron Buchh. | giant sequoia | Taxodiaceae
|
| SEAT4 | Serapias atrorubens O. Hoffmann | Epipactis atrorubens | Orchidaceae
|
| SEHE6 | Serapias helleborine L. | Epipactis helleborine | Orchidaceae
|
| SERE2 | Serenoa repens (Bartr.) Small | saw palmetto | Arecaceae
|
| SESE10 | Serenoa serrulata (Michx.) Nichols. | Serenoa repens | Arecaceae
|
| SEREN | Serenoa Hook. f. | serenoa | Arecaceae
|
| SENE9 | Serianthes nelsonii Merr. | Hayun lagu | Fabaceae
|
| SERIA | Serianthes Benth. | | Fabaceae
|
| SEAC5 | Sericocarpus acutisquamosus (Nash) Small | Sericocarpus tortifolius | Asteraceae
|
| SEAS3 | Sericocarpus asteroides (L.) B.S.P. | toothed whitetop aster | Asteraceae
|
| SEBI7 | Sericocarpus bifoliatus (Walt.) Porter | Sericocarpus tortifolius | Asteraceae
|
| SECA13 | Sericocarpus californicus Dur. | Sericocarpus oregonensis var. californicus | Asteraceae
|
| SELI5 | Sericocarpus linifolius (L.) B.S.P. | narrowleaf whitetop aster | Asteraceae
|
| SEORC | Sericocarpus oregonensis Nutt. ssp. californicus (Dur.) Ferris | Sericocarpus oregonensis var. californicus | Asteraceae
|
| SEORC2 | Sericocarpus oregonensis Nutt. var. californicus (Dur.) Nesom | Oregon whitetop aster | Asteraceae
|
| SEORO2 | Sericocarpus oregonensis Nutt. var. oregonensis | Oregon whitetop aster | Asteraceae
|
| SEOR6 | Sericocarpus oregonensis Nutt. | Oregon whitetop aster | Asteraceae
|
| SERI4 | Sericocarpus rigidus Lindl. | Columbian whitetop aster | Asteraceae
|
| SETO5 | Sericocarpus tomentellus Greene | Eucephalus tomentellus | Asteraceae
|
| SETO7 | Sericocarpus tortifolius (Michx.) Nees | Dixie whitetop aster | Asteraceae
|
| SERIC | Sericocarpus Greene | whitetop aster | Asteraceae
|
| SEDI11 | Sericotheca discolor (Pursh) Rydb. | Holodiscus discolor | Rosaceae
|
| SEOP | Serinia oppositifolia (Raf.) Kuntze | Krigia caespitosa | Asteraceae
|
| SEARL | Seriphidium arbusculum (Nutt.) W.A. Weber ssp. longilobum (Osterhout) W.A. Weber | Artemisia arbuscula ssp. longiloba | Asteraceae
|
| SEAR9 | Seriphidium arbusculum (Nutt.) W.A. Weber | Artemisia arbuscula ssp. arbuscula | Asteraceae
|
| SECAB | Seriphidium canum (Pursh) W.A. Weber ssp. bolanderi (Gray) W.A. Weber | Artemisia cana ssp. bolanderi | Asteraceae
|
| SECAV | Seriphidium canum (Pursh) W.A. Weber ssp. viscidulum (Osterhout) W.A. Weber | Artemisia cana ssp. viscidula | Asteraceae
|
| SECA9 | Seriphidium canum (Pursh) W.A. Weber | Artemisia cana ssp. cana | Asteraceae
|
| SENO | Seriphidium novum (A. Nels.) W.A. Weber | Artemisia nova | Asteraceae
|
| SEPY | Seriphidium pygmaeum (Gray) W.A. Weber | Artemisia pygmaea | Asteraceae
|
| SERI6 | Seriphidium rigidum (Nutt.) W.A. Weber | Artemisia rigida | Asteraceae
|
| SERO4 | Seriphidium rothrockii (Gray) W.A. Weber | Artemisia rothrockii | Asteraceae
|
| SETRP | Seriphidium tridentatum (Nutt.) W.A. Weber ssp. parishii (Gray) W.A. Weber | Artemisia tridentata ssp. parishii | Asteraceae
|
| SETRV | Seriphidium tridentatum (Nutt.) W.A. Weber ssp. vaseyanum (Rydb.) W.A. Weber | Artemisia tridentata ssp. vaseyana | Asteraceae
|
| SETRW | Seriphidium tridentatum (Nutt.) W.A. Weber ssp. wyomingense (Beetle & Young) W.A. Weber | Artemisia tridentata ssp. wyomingensis | Asteraceae
|
| SETR4 | Seriphidium tridentatum (Nutt.) W.A. Weber | Artemisia tridentata ssp. tridentata | Asteraceae
|
| SETR6 | Seriphidium tripartitum (Rydb.) W.A. Weber | Artemisia tripartita ssp. tripartita | Asteraceae
|
| SEVA | Seriphidium vaseyanum (Rydb.) W.A. Weber | Artemisia tridentata ssp. vaseyana | Asteraceae
|
| SEFO2 | Serissa foetida (L. f.) Lam. | snowrose | Rubiaceae
|
| SEJA2 | Serissa japonica (Thunb.) Thunb. | Serissa foetida | Rubiaceae
|
| SERIS | Serissa Commerson ex A. Juss. | snowrose | Rubiaceae
|
| SEBR4 | Serjania brachycarpa Gray | littlefruit slipplejack | Sapindaceae
|
| SEDI7 | Serjania diversifolia (Jacq.) Radlk. | fowlsfoot | Sapindaceae
|
| SEIN5 | Serjania incisa Torr. | slashleaf slipplejack | Sapindaceae
|
| SEPO4 | Serjania polyphylla (L.) Radlk. | basketwood | Sapindaceae
|
| SERJA | Serjania P. Mill. | serjania | Sapindaceae
|
| SEAR12 | Serratula arvensis L. | Cirsium arvense | Asteraceae
|
| SETI2 | Serratula tinctoria L. | Dyer's plumeless saw-wort | Asteraceae
|
| SERRA | Serratula L. | plumeless saw-wort | Asteraceae
|
| SEAL10 | Sesamum alatum Thonn. | sesamum | Pedaliaceae
|
| SEIN3 | Sesamum indicum L. | Sesamum orientale | Pedaliaceae
|
| SEOR4 | Sesamum orientale L. | sesame | Pedaliaceae
|
| SERA6 | Sesamum radiatum Schumacher | sesamum | Pedaliaceae
|
| SESAM | Sesamum L. | sesame | Pedaliaceae
|
| SEBI8 | Sesban bispinosus (Jacq.) Rydb. | Sesbania bispinosa | Fabaceae
|
| SEEM2 | Sesban emerus (Aubl.) Britt. & Wilson | Sesbania emerus | Fabaceae
|
| SEEX3 | Sesban exaltatus (Raf.) Rydb. | Sesbania herbacea | Fabaceae
|
| SEAC7 | Sesbania aculeata Poiret | Sesbania bispinosa | Fabaceae
|
| SEAR10 | Sesbania arborea O.& I. Deg. | Sesbania tomentosa | Fabaceae
|
| SEBI3 | Sesbania bispinosa (Jacq.) W. Wight | dunchi fiber | Fabaceae
|
| SECA23 | Sesbania cannabina Poir. | sesbania | Fabaceae
|
| SEDR | Sesbania drummondii (Rydb.) Cory | poisonbean | Fabaceae
|
| SEEM | Sesbania emerus (Aubl.) Urban | danglepod | Fabaceae
|
| SEEX | Sesbania exaltata (Raf.) Rydb. ex A.W. Hill | Sesbania herbacea | Fabaceae
|
| SEGR5 | Sesbania grandiflora (L.) Poir. | vegetable hummingbird | Fabaceae
|
| SEHA8 | Sesbania hawaiiensis O.& I. Deg. | Sesbania tomentosa | Fabaceae
|
| SEHE8 | Sesbania herbacea (P. Mill.) McVaugh | bigpod sesbania | Fabaceae
|
| SEHO4 | Sesbania hobdyi O.& I. Deg. | Sesbania tomentosa | Fabaceae
|
| SEMA9 | Sesbania macrocarpa Muhl. ex Raf. | Sesbania herbacea | Fabaceae
|
| SEMA81 | Sesbania marginata Benth. | Sesbania virgata | Fabaceae
|
| SEPL6 | Sesbania platycarpa Pers. | Glottidium vesicarium | Fabaceae
|
| SEPU7 | Sesbania punicea (Cav.) Benth. | rattlebox | Fabaceae
|
| SESE7 | Sesbania sericea (Willd.) Link | papagayo | Fabaceae
|
| SESE8 | Sesbania sesban (L.) Merr. | Egyptian riverhemp | Fabaceae
|
| SETOM | Sesbania tomentosa Hook. & Arn. var. molokaiensis O. Deg. & Sherff | Sesbania tomentosa | Fabaceae
|
| SETO3 | Sesbania tomentosa Hook. & Arn. | Oahu riverhemp | Fabaceae
|
| SETR10 | Sesbania tripetii (Poit.) hort. ex Hubb. | Sesbania punicea | Fabaceae
|
| SEVE | Sesbania vesicaria (Jacq.) Ell. | Glottidium vesicarium | Fabaceae
|
| SEVI7 | Sesbania virgata (Cav.) Poir. | wand riverhemp | Fabaceae
|
| SESBA | Sesbania Scop. | riverhemp | Fabaceae
|
| SELI2 | Seseli libanotis (L.) W.D.J. Koch | mooncarrot | Apiaceae
|
| SESEL | Seseli L. | seseli | Apiaceae
|
| SEDA | Sesleria dactyloides Nutt. | Buchloe dactyloides | Poaceae
|
| SECR3 | Sesuvium crithmoides Welw. | tropical seapurslane | Aizoaceae
|
| SEER3 | Sesuvium erectum Correll | Sesuvium verrucosum | Aizoaceae
|
| SEMA3 | Sesuvium maritimum (Walt.) B.S.P. | slender seapurslane | Aizoaceae
|
| SEMI7 | Sesuvium microphyllum Willd. | | Aizoaceae
|
| SEPO2 | Sesuvium portulacastrum (L.) L. | shoreline seapurslane | Aizoaceae
|
| SESE5 | Sesuvium sessile Pers. | western seapurslane | Aizoaceae
|
| SETR3 | Sesuvium trianthemoides Correll | Texas seapurslane | Aizoaceae
|
| SEVE2 | Sesuvium verrucosum Raf. | verrucose seapurslane | Aizoaceae
|
| SESUV | Sesuvium L. | seapurslane | Aizoaceae
|
| SEAD | Setaria adhaerens (Forsk.) Chiov. | burr bristlegrass | Poaceae
|
| SEAR7 | Setaria arizonica Rominger | Arizona bristlegrass | Poaceae
|
| SEBA | Setaria barbata (Lam.) Kunth | East Indian bristlegrass | Poaceae
|