| Jack-in-the-pulpit, Small | Arisaema triphyllum subsp. pusillum |
| Jack-in-the-pulpit, Swamp | Arisaema triphyllum subsp. triphyllum |
| Jetbead | Rhodotypos scandens |
| Jewel-weed, Pale | Impatiens pallida |
| Jewel-weed, Spotted | Impatiens capensis |
| Jimsonweed | Datura stramonium |
| Joe-pye-weed, Hollow-stem | Eutrochium fistulosum |
| Joe-pye-weed, Purple-node | Eutrochium purpureum var. purpureum |
| Joe-pye-weed, Three-nerved | Eutrochium dubium |
| Jointweed, Eastern | Polygonum articulatum |