Index of plants by genus
| Species | Common Name | Family |
| Ulmus americana | American Elm | Ulmaceae |
| Ulmus rubra | Slippery Elm | Ulmaceae |
| Ulmus thomasii | Rock Elm | Ulmaceae |
| Ulota crispa | Curled Leaf Moss | Orthotrichaceae |
| Umbilicaria spp. | Rock Tripe | Umbilicariaceae |
| Urtica dioica | Stinging Nettle | Urticaceae |
| Utricularia cornuta | Horned Bladderwort | Lentibulariaceae |
| Utricularia intermedia | Flat-leaved Bladderwort | Lentibulariaceae |
| Utricularia purpurea | Purple Bladderwort | Lentibulariaceae |
| Utricularia resupinata | Reclined Bladderwort | Lentibulariaceae |
| Utricularia subulata | Slender Bladderwort | Lentibulariaceae |
| Utricularia vulgaris ssp. macrorhiza | Common Bladderwort | Lentibulariaceae |
| Uvularia grandiflora | Large-flowered Bellwort | Liliaceae |
| Uvularia perfoliata | Perfoliate Bellwort | Liliaceae |
| Uvularia sessilifolia | Sessile Bellwort | Liliaceae |
© 2004 Michael Hough