| Spartina patens var. juncea (Michx.) Hitchc., 1906 |
| Spartina patens var. monogyna (M.A. Curtis) Fernald, 1947 |
| Spartina pittieri Hack., 1902 |
| Spartina platensis Mez ex St.-Yves, 1932 |
| Spartina polystachya (Michx.) P. Beauv., 1812 |
| Spartina pubera Hassk., 1844 |
| Spartina pumila Roth, 1806 |
| Spartina spartinae (Trin.) Merr. ex Hitchc., 1913 |
| Spartina spartinae (Trin.) Merr., 1902 |
| Spelta Wolf, 1776 |
| Spermachiton Llanos, 1851 |
| Sphaerium Kuntze, 1891 |
| Sphaerium lacryma (L.) Kuntze, 1891 |
| Sphaerocarpa Hitchc. & Chase, 1910 |
| Sphenopholis Scribn., 1906 |
| Sphenopholis annua (Suksd.) A. Heller, 1910 |
| Sphenopholis hallii (Scribn.) Scribn., 1906 |
| Sphenopholis interrupta (Buckley) Scribn., 1906 |
| Sphenopholis interrupta subsp. californica (Vasey) Scribn., 1906 |
| Sphenopholis interrupta subsp. interrupta (Buckley) Scribn., 1906 |