| 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. Massachusetts west to North Dakota and Manitoba, south to s. Florida, Texas, New Mexico, and Arizona. |  (c) Stuart, Will |
| Apocynaceae | Asclepias subverticillata | Horsetail Milkweed, Poison Milkweed | Tallgrass or mixed grass prairies, pastures, disturbed areas. | Native from w. Kansas, s. Wyoming, s. Idaho south to w. Texas, New Mexico, Arizona, and s. Mexico; reported scattered occurrences eastwards of that area are either definitely introductions as waifs (Missouri), possibly so (nc. Texas, se. Texas, s. Texas), or possibly misidentifications. |  (c) Cressler, Alan M. |