Northern Prairie Wildlife Research Center
A plant of northern and eastern North Dakota, ovalleaf milkweed is uncommon west of the Missouri River. Elsewhere, the species can be found in Canada just north of the Great Lakes, Illinois, and westward through South Dakota into low elevations of Wyoming.
Ovalleaf milkweed is perennial from a slender rhizome (lateral underground stem). Plants are about 10-20 inches tall and covered with silky hairs. The oval leaves are mostly opposite each other and about 2-3 inches long. Stems are mostly solitary or paired. Each stem usually produces 1-3 clusters of 5-20 greenish-white flowers about 3/16 inch wide. Flowers are on stalks (peduncles) about an inch long. The fuzzy follicles (pods) stand erect at maturity and are pointed at both ends, about 2 1/2 inches long, and 1/2 inch thick. Seeds bear a tuft of long tan hairs.
Look for ovalleaf milkweed from June through July in low areas around wetlands and at the bases of hills in native prairie. Domestic livestock have been poisoned by certain species of milkweeds, but all milkweeds seem distasteful to them, and losses occur only when animals are forced to eat the plants. Nevertheless, more ovalleaf milkweed seems to occur where grazing pressure is light. Lightly grazed pastures have more vegetation to slow runoff and increase soil moisture. Many milkweeds are used for fiber, medicines, gums, and foods, but I could find no references to economic uses of ovalleaf milkweed.
Most of the roughly 2,400 species in the milkweed family (Asclepiadaceae after Asklepios, the Greek god of medicine) are found in Africa and tropical America. There are about 100 species of Asclepias worldwide and most are found in the Americas. North Dakota has nine species. The specific epithet ovalifolia means "oval-leaved" in botanical Latin. Ovalleaf milkweed was first described for science in the late 1800's by Belgian botanist Joseph Decaisne (1807-1882), Director of the Jardin des Plantes, Paris.