| Herbertia drummondii (Graham) Small, 1937 |
| Hydastylus Salisb. ex E.P. Bicknell, 1900 |
| Hydastylus cernuus E.P. Bicknell, 1900 |
| Hydastylus longipes E.P. Bicknell, 1900 |
| Hydastylus parvus E.P. Bicknell, 1900 |
| Hydastylus schaffneri (S. Watson) E.P. Bicknell, 1900 |
| Hydastylus serrulatus E.P. Bicknell, 1900 |
| Hydastylus subcernuus E.P. Bicknell, 1900 |
| Hydastylus translucens E.P. Bicknell, 1900 |
| Hydrotaenia Lindl., 1838 |
| Hydrotaenia ehrenbergii Schltdl., 1844 |
| Hydrotaenia meleagris Lindl., 1838 |
| Hydrotaenia vanhouttei (Roezl ex G. Nicholson) Baker, 1892 |
| Iridaceae Juss., 1789 |
| Irideae Kitt., 1840 |
| Iridoideae Eaton, 1836 |
| Iris L., 1753 |
| Iris missouriensis Nutt., 1834 |
| Iris pseudacorus L., 1753 |
| Iris versicolor L., 1753 |