| Aristida orizabensis E. Fourn., 1886 |
| Aristida orizabensis var. pseudospadicea (F.T. Hubb.) Henrard, 1928 |
| Aristida pallens Pursh, 1814 |
| Aristida palmeri Vasey, 1883 |
| Aristida pansa Wooton & Standl., 1913 |
| Aristida pansa f. contracta Allred & Valdés-Reyna, 1997 |
| Aristida pansa f. dissita (I.M. Johnst.) Allred & Valdés-Reyna, 1997 |
| Aristida pansa f. pansa Wooton & Standl., 1913 |
| Aristida pansa var. dissita (I.M. Johnst.) Beetle, 1974 |
| Aristida pansa var. pansa Wooton & Standl., 1913 |
| Aristida parishii Hitchc., 1912 |
| Aristida peninsularis Hitchc., 1924 |
| Aristida peruviana Beetle, 1975 |
| Aristida petersonii Allred & Valdés-Reyna, 1995 |
| Aristida pseudospadicea F.T. Hubb., 1913 |
| Aristida purpurascens Poir., 1810 |
| Aristida purpurascens var. alabamensis Trin. & Rupr., 1842 |
| Aristida purpurascens var. glaucissima Kearney ex Scribn. & Ball, 1901 |
| Aristida purpurascens var. minor Vasey, 1892 |
| Aristida purpurascens var. tenuispica (Hitchc.) Allred, 1986 |