| Senna pentagonia var. pentagonia (Mill.) H.S. Irwin & Barneby, 1982 |
| Senna peralteana (Kunth) H.S. Irwin & Barneby, 1982 |
| Senna pilifera (Vogel) H.S. Irwin & Barneby, 1982 |
| Senna pilifera var. subglabra (S. Moore) H.S. Irwin & Barneby, 1982 |
| Senna pilosior (B.L. Rob. ex J.F. Macbr.) H.S. Irwin & Barneby, 1979 |
| Senna polyantha (Collad.) H.S. Irwin & Barneby, 1982 |
| Senna polyphylla (Jacq.) H.S. Irwin & Barneby, 1982 |
| Senna pumilio (A. Gray) H.S. Irwin & Barneby, 1979 |
| Senna purpusii (Brandegee) H.S. Irwin & Barneby, 1982 |
| Senna quinquangulata (Rich.) H.S. Irwin & Barneby, 1982 |
| Senna quinquangulata var. quinquangulata (Rich.) H.S. Irwin & Barneby, 1982 |
| Senna racemosa (Mill.) H.S. Irwin & Barneby, 1982 |
| Senna racemosa var. coalcomanica H.S. Irwin & Barneby, 1982 |
| Senna racemosa var. liebmannii (Benth.) H.S. Irwin & Barneby, 1982 |
| Senna racemosa var. moctezumae H.S. Irwin & Barneby, 1982 |
| Senna racemosa var. racemosa (Mill.) H.S. Irwin & Barneby, 1982 |
| Senna racemosa var. sororia H.S. Irwin & Barneby, 1982 |
| Senna reticulata (Willd.) H.S. Irwin & Barneby, 1982 |
| Senna ripleyana (H.S. Irwin & Barneby) H.S. Irwin & Barneby, 1979 |
| Senna roemeriana (Scheele) H.S. Irwin & Barneby, 1982 |