| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| SELYL | Senecio lynceus Greene var. leucoreus (Greenm.) Blake | Packera multilobata | Asteraceae
|
| SELY2 | Senecio lynceus Greene | Packera multilobata | Asteraceae
|
| SELY | Senecio lyonii Gray | island senecio | Asteraceae
|
| SEMA12 | Senecio macdougalii Heller | Senecio eremophilus var. macdougalii | Asteraceae
|
| SEMA | Senecio macounii Greene | Packera macounii | Asteraceae
|
| SEMA15 | Senecio madagascariensis Poir. | Madagascar ragwort | Asteraceae
|
| SEMA16 | Senecio malmstenii Blake ex Tidestrom | Packera malmstenii | Asteraceae
|
| SEMA20 | Senecio mandraliscae (Tineo) Jacobsen | blue finger | Asteraceae
|
| SEMA8 | Senecio manitobensis Greenm. | Packera tridenticulata | Asteraceae
|
| SEME | Senecio megacephalus Nutt. | rocky ragwort | Asteraceae
|
| SEME5 | Senecio memmingeri Britt. | Packera millefolia | Asteraceae
|
| SEME7 | Senecio metcalfei Greene | Packera neomexicana var. metcalfei | Asteraceae
|
| SEMI | Senecio mikanioides Otto ex Walp. | Delairea odorata | Asteraceae
|
| SEMI2 | Senecio millefolium Torr. & Gray | Packera millefolia | Asteraceae
|
| SEMI3 | Senecio millelobatus Rydb. | Packera millelobata | Asteraceae
|
| SEMI4 | Senecio minimus Poir. | Erechtites minima | Asteraceae
|
| SEMO3 | Senecio mohavensis Gray | Mojave ragwort | Asteraceae
|
| SEMO8 | Senecio molinarius Greenm. | Packera werneriifolia | Asteraceae
|
| SEMO9 | Senecio monoensis Greene | Senecio flaccidus var. monoensis | Asteraceae
|
| SEMO10 | Senecio moresbiensis (Calder & Taylor) G.W. Douglas & G. Ruyle-Douglas | cleftleaf ragwort | Asteraceae
|
| SEMU6 | Senecio muehlenbergii Schultz-Bip. | Arnoglossum muehlenbergii | Asteraceae
|
| SEMU7 | Senecio muirii Greenm. | Packera werneriifolia | Asteraceae
|
| SEMU2 | Senecio multicapitatus Greenm. ex Rydb. | Senecio spartioides var. multicapitatus | Asteraceae
|
| SEMUH | Senecio multidentatus Schultz-Bip. ex Hemsl. var. huachucanus (Gray) T.M. Barkl. | Huachuca Mountain ragwort | Asteraceae
|
| SEMU9 | Senecio multidentatus Schultz-Bip. ex Hemsl. | Huachuca Mountain ragwort | Asteraceae
|
| SEMU3 | Senecio multilobatus Torr. & Gray ex Gray | Packera multilobata | Asteraceae
|
| SEMU12 | Senecio musiniensis Welsh | Musinea ragwort | Asteraceae
|
| SEMU8 | Senecio mutabilis Greene | Packera neomexicana var. mutabilis | Asteraceae
|
| SENEG2 | Senecio neomexicanus Gray var. griffithsii Greenm. | Packera neomexicana var. neomexicana | Asteraceae
|
| SENEM | Senecio neomexicanus Gray var. metcalfei (Greene) T.M. Barkl. | Packera neomexicana var. metcalfei | Asteraceae
|
| SENEM2 | Senecio neomexicanus Gray var. mutabilis (Greene) T.M. Barkl. | Packera neomexicana var. mutabilis | Asteraceae
|
| SENET | Senecio neomexicanus Gray var. toumeyi (Greene) T.M. Barkl. | Packera neomexicana var. toumeyi | Asteraceae
|
| SENE4 | Senecio neomexicanus Gray | Packera neomexicana var. neomexicana | Asteraceae
|
| SENE6 | Senecio neowebsteri Blake | Olympic Mountain ragwort | Asteraceae
|
| SEOBE | Senecio obovatus Muhl. ex Willd. var. elliottii (Torr. & Gray) Fern. | Packera obovata | Asteraceae
|
| SEOBR2 | Senecio obovatus Muhl. ex Willd. var. rotundus Britt. | Packera obovata | Asteraceae
|
| SEOB2 | Senecio obovatus Muhl. ex Willd. | Packera obovata | Asteraceae
|
| SEOG | Senecio ogotorukensis Packer | Packera ogotorukensis | Asteraceae
|
| SEOO | Senecio oodes Rydb. | Packera streptanthifolia | Asteraceae
|
| SEOR7 | Senecio oresbius Greenm. | Packera neomexicana var. neomexicana | Asteraceae
|
| SEPA12 | Senecio palustris (L.) Hook. | Senecio congestus | Asteraceae
|
| SEPA13 | Senecio pammelii Greenm. | Packera streptanthifolia | Asteraceae
|
| SEPA2 | Senecio parryi Gray | mountain ragwort | Asteraceae
|
| SEPA3 | Senecio pattersonensis Hoover | Patterson's senecio | Asteraceae
|
| SEPAF | Senecio pauciflorus Pursh var. fallax (Greenm.) Greenm. | Packera indecora | Asteraceae
|
| SEPAJ | Senecio pauciflorus Pursh var. jucundulus Jepson | Packera pseudaurea var. pseudaurea | Asteraceae
|
| SEPA4 | Senecio pauciflorus Pursh | Packera pauciflora | Asteraceae
|
| SEPAB | Senecio pauperculus Michx. var. balsamitae (Muhl. ex Willd.) Fern. | Packera paupercula | Asteraceae
|
| SEPAC | Senecio pauperculus Michx. var. crawfordii (Britt.) T.M. Barkl. | Packera paupercula | Asteraceae
|
| SEPAF2 | Senecio pauperculus Michx. var. firmifolius (Greenm.) Greenm. | Packera paupercula | Asteraceae
|
| SEPAN2 | Senecio pauperculus Michx. var. neoscoticus Fern. | Packera paupercula | Asteraceae
|
| SEPAP | Senecio pauperculus Michx. var. praelongus (Greenm.) House | Packera paupercula | Asteraceae
|
| SEPAT | Senecio pauperculus Michx. var. thompsoniensis (Greenm.) Boivin | Packera paupercula | Asteraceae
|
| SEPA5 | Senecio pauperculus Michx. | Packera paupercula | Asteraceae
|
| SEPE5 | Senecio pereziifolius Rydb. | Senecio hydrophiloides | Asteraceae
|
| SEPL | Senecio plattensis Nutt. | Packera plattensis | Asteraceae
|
| SEPL5 | Senecio platylobus Rydb. | Packera streptanthifolia | Asteraceae
|
| SEPO | Senecio porteri Greene | Packera porteri | Asteraceae
|
| SEPSF2 | Senecio pseudaureus Rydb. ssp. flavulus (Greene) G.W. Douglas & G. Ruyle-Douglas | Packera pseudaurea var. flavula | Asteraceae
|
| SEPSS2 | Senecio pseudaureus Rydb. ssp. semicordatus (Mackenzie & Bush) G.W. Douglas & G. Ruyle-Douglas | Packera pseudaurea var. semicordata | Asteraceae
|
| SEPSF | Senecio pseudaureus Rydb. var. flavulus (Greene) Greenm. | Packera pseudaurea var. flavula | Asteraceae
|
| SEPSS | Senecio pseudaureus Rydb. var. semicordatus (Mackenzie & Bush) T.M. Barkl. | Packera pseudaurea var. semicordata | Asteraceae
|
| SEPS2 | Senecio pseudaureus Rydb. | Packera pseudaurea var. pseudaurea | Asteraceae
|
| SEPS | Senecio pseudoarnica Less. | seaside ragwort | Asteraceae
|
| SEPS3 | Senecio pseudotomentosus Mackenzie & Bush | Packera plattensis | Asteraceae
|
| SEPU3 | Senecio pudicus Greene | bashful ragwort | Asteraceae
|
| SEPU9 | Senecio purshianus Nutt. | Packera cana | Asteraceae
|
| SEQU2 | Senecio quaerens Greene | Packera quaerens | Asteraceae
|
| SEQU | Senecio quercetorum Greene | Packera quercetorum | Asteraceae
|
| SERA | Senecio rapifolius Nutt. | openwoods ragwort | Asteraceae
|
| SERE5 | Senecio resedifolius Less. | Packera cymbalaria | Asteraceae
|
| SERI2 | Senecio riddellii Torr. & Gray | Riddell's ragwort | Asteraceae
|
| SERO6 | Senecio robbinsii Oakes ex Rusby | Packera schweinitziana | Asteraceae
|
| SERO5 | Senecio rotundus (Britt.) Small | Packera obovata | Asteraceae
|
| SERU7 | Senecio rubricaulis Greene | Packera streptanthifolia | Asteraceae
|
| SERU6 | Senecio rugelia Gray | Rugelia nudicaulis | Asteraceae
|
| SERU5 | Senecio rupestris Waldst. & Kit. | rock ragwort | Asteraceae
|
| SESA3 | Senecio sacramentanus Woot. & Standl. | Sacramento ragwort | Asteraceae
|
| SESA4 | Senecio salignus DC. | Barkleyanthus salicifolius | Asteraceae
|
| SESA5 | Senecio sandvicensis auct. non Less. | Senecio hydrophilus | Asteraceae
|
| SESA6 | Senecio sanguisorboides Rydb. | Packera sanguisorboides | Asteraceae
|
| SESAT | Senecio saxosus Klatt var. toiyabensis Greenm. | Packera werneriifolia | Asteraceae
|
| SESA7 | Senecio saxosus Klatt | Packera werneriifolia | Asteraceae
|
| SESC4 | Senecio schweinitzianus Nutt. | Packera schweinitziana | Asteraceae
|
| SESC | Senecio scorzonella Greene | Sierra ragwort | Asteraceae
|
| SESC6 | Senecio scribneri Rydb. | Senecio integerrimus var. scribneri | Asteraceae
|
| SESE11 | Senecio seemanii auct. non Schultz-Bip. ex Seem. | Roldana hartwegii | Asteraceae
|
| SESE15 | Senecio semicordatus Mackenzie & Bush | Packera pseudaurea var. semicordata | Asteraceae
|
| SESEA | Senecio serra Hook. var. admirabilis (Greene) A. Nels. | tall ragwort | Asteraceae
|
| SESEA2 | Senecio serra Hook. var. altior Jepson | Senecio serra var. serra | Asteraceae
|
| SESEI | Senecio serra Hook. var. integriusculus Gray | Senecio serra var. serra | Asteraceae
|
| SESES | Senecio serra Hook. var. serra | tall ragwort | Asteraceae
|
| SESE2 | Senecio serra Hook. | tall ragwort | Asteraceae
|
| SESM3 | Senecio smallii Britt. | Packera anonyma | Asteraceae
|
| SESO | Senecio soldanella Gray | Colorado ragwort | Asteraceae
|
| SESPF | Senecio spartioides Torr. & Gray var. fremontii (Torr. & Gray) Greenm. ex L.O. Williams | Senecio riddellii | Asteraceae
|
| SESPG | Senecio spartioides Torr. & Gray var. granularis Maguire & A. Holmgren ex Cronq. | Senecio spartioides var. spartioides | Asteraceae
|
| SESPM | Senecio spartioides Torr. & Gray var. multicapitatus (Greenm. ex Rydb.) Welsh | broomlike ragwort | Asteraceae
|
| SESPP3 | Senecio spartioides Torr. & Gray var. parksii (Cory) Shinners | Senecio riddellii | Asteraceae
|
| SESPS2 | Senecio spartioides Torr. & Gray var. spartioides | broomlike ragwort | Asteraceae
|
| SESP3 | Senecio spartioides Torr. & Gray | broomlike ragwort | Asteraceae
|