Sullivants Milkweed (Asclepias sullivantii), Smooth Milkweed or Prairie Milkweed is a rough, weedy perennial which commonly occurs in moist prairies areas including river bottomland and moist meadowland. It typically grows 2-4 feet tall on stout, upright stems with broad-oblong, medium green leaves with pinkish-red midribs. Rounded clusters (umbels to 3 inches across) of pinkish-white to pinkish-purple, star-like flowers appear mostly in the upper leaf axils over a long bloom period from late spring well into summer. Stems and leaves exude a milky sap when cut or bruised. Flowers give way to smooth seed pods (2-4 inch long) which split open when ripe releasing their numerous silky-tailed seeds for dispersal by the wind. During dry weather, some of the lower leaves may turn yellow and fall off the plant. This also happens when the seedpods develop, which is quite normal. Active growth occurs during the late spring and early summer.
Easily grown in average, medium to wet soils in full sun. Easily grown from seed, and may self-seed in the landscape if seed pods are not removed prior to splitting open. Once established, it is best to leave plants undisturbed because they develop deep taproots which make transplanting difficult.
Habitats include black soil prairies, cemetery prairies, prairie remnants along railroads, moist meadows along rivers or near woodlands, thickets, and roadside ditches. Prairie Milkweed is an indicator plant of average to high quality prairies.