Northern Prairie Wildlife Research Center
One of our smallest milkweeds, plains milkweed occurs mostly in the southern half of North Dakota, with most records from southwest of the Missouri River. Elsewhere, the plant ranges from northeastern Montana southward across the Great Plains to the trans-Pecos region of Texas, at elevations up to 5,500 ft.
Plains milkweed is perennial from a taproot or slender rhizome. Plants are usually about 8 to 10 inches tall. Stems may be simple or branched near the base or below ground. Leaves usually alternate in a tight spiral up the stems. Leaves are about 1 1/2 inches long and only about 1/16 inch wide. Groups of 4-20 flowers about 1/4 inch long arise from peduncles on the leaf axils. Flowers are usually white, but may be tinged with rose or yellow-green on the upper surfaces. The smooth pods (follicles) are about 2 inches long and 1/4 inch wide and are filled with oval seeds bearing whitish hairs about one inch long.
Look for plains milkweed in early July on native prairie pastures lightly or moderately grazed by cattle. Domestic livestock has been poisoned by milkweeds, but all milkweeds are distasteful to livestock, and losses occur only when animals are forced to eat these plants. Many milkweeds are used for fiber, medicines, gums, and foods, but I could find no references to economic uses of plains milkweed.
Most of the roughly 2,400 species in the milkweed family (Asclepiadaceae after Asklepios, the Greek god of medicine) is found in Africa and tropical America. There are about 100 species of Asclepias; most are found in the Americas. The specific name pumila means "dwarf" in botanical Latin.
After its initial discovery by the renowned Harvard professor Asa Gray (1810-1888), plains milkweed was described for science in 1898 by Anna Murray Vail (1863-1955), librarian at the New York Botanical Garden and authority on legumes and milkweeds.