Common milkweed is a sturdy, upright, perennial plant with broad leaves, milky sap, and clusters of pink or lilac flowers. Blooms May–August. Flowers are pink to lilac, very fragrant, borne in clusters terminally and along the stems, arising from leaf axils. Leaves are broadly elliptical, rounded at the base, to 6 inches long, with fine hairs underneath, on distinct leaf stalks. Fruit are large seedpods (follicles), elongated and covered with slender warty projections. When dry, these split to release hundreds of seeds, each attached to a “parachute” of white, silky, flossy hairs that can carry them on the wind.
Similar species: There are 17 species in the genus Asclepias in Missouri. The one most similar to common milkweed is purple milkweed, but its flowers are darker and more purplish, and its pods lack slender warty projections.