| Family | Scientific Name | Common Name | Habitat | Distribution | Image |
|---|---|---|---|---|---|
| Apocynaceae | Asclepias verticillata | Whorled Milkweed | Barrens, thin soils of rock outcrops (especially mafic or calcareous rocks), prairies, open woodlands, longleaf pine sandhills, pine flatwoods, road and powerline rights-of-way. | E. MA west to ND and MB, south to s. FL, TX, NM, and AZ. |  |
| Apocynaceae | Asclepias subverticillata | Horsetail Milkweed, Poison Milkweed | Prairies, disturbed areas. | Native from w. KS, s. WY, s. ID south to w. TX, NM, AZ, and s. Mexico; reported scattered occurrences eastwards of that area are either definitely introductions as waifs (MO), possibly so (nc. TX, se. TX, s. TX), or possibly misidentifications. |  |