| Symphyotrichum purpurascens (Sch. Bip.) G.L. Nesom, 2018 |
| Symphyotrichum schaffneri (Sch. Bip. ex S.D. Sundb. & A.G. Jones) G.L. Nesom, 1994 |
| Symphyotrichum spathulatum (Lindl.) G.L. Nesom, 1994 |
| Symphyotrichum squamatum (Spreng.) G.L. Nesom, 1995 |
| Symphyotrichum subulatum (Michx.) G.L. Nesom, 1995 |
| Symphyotrichum trilineatum (Sch. Bip. ex Klatt) G.L. Nesom, 1995 |
| Symphyotrichum turneri (S.D. Sundb. & A.G. Jones) G.L. Nesom, 2018 |
| Syncephalantha Bartl., 1836 |
| Syncephalantha decipiens Bartl., 1836 |
| Syncephalantha macrophylla Klatt, 1889 |
| Syncephalantha sanguinea Klatt, 1889 |
| Synchaeta Kirp., 1950 |
| Synedrella Gaertn., 1791 |
| Synedrella nodiflora (L.) Gaertn., 1791 |
| Synedrella vialis (Less.) A. Gray, 1882 |
| Syntrichopappus A. Gray, 1857 |
| Syntrichopappus fremontii A. Gray, 1857 |
| Tageteae Cass., 1819 |
| Tagetes L., 1753 |
| Tagetes alamensis Rydb., 1915 |