| Sigesbeckia andersoniae B.L. Turner, 1978 |
| Sigesbeckia blakei (McVaugh & Lask.) B.L. Turner, 1978 |
| Sigesbeckia cordifolia Kunth, 1818 |
| Sigesbeckia hartmannii B.L. Turner, 1978 |
| Sigesbeckia jorullensis Kunth, 1818 |
| Sigesbeckia orientalis L., 1753 |
| Sigesbeckia pringlei D.L. Schulz, 1988 |
| Sigesbeckia repens B.L. Rob. & Greenm., 1895 |
| Silphium L., 1753 |
| Silphium arborescens Mill., 1768 |
| Silphium trilobatum L., 1759 |
| Silybum Adans.,1763 |
| Silybum marianum (L.) Gaertn., 1791 |
| Simsia Pers., 1807 |
| Simsia adenophora (Greenm.) S.F. Blake, 1913 |
| Simsia amplexicaulis (Cav.) Pers., 1807 |
| Simsia annectens S.F. Blake, 1917 |
| Simsia annectens var. annectens S.F. Blake, 1917 |
| Simsia annectens var. grayi (Sch. Bip. ex S.F. Blake) D.M. Spooner, 1990 |
| Simsia auriculata DC., 1836 |