Prairie Milkweed (Asclepias Sullivantii)

Features and Characteristics

Asclepias sullivantii, commonly called smooth milkweed, Sullivant’s milkweed or prairie milkweed, is a rough, weedy perennial which is very similar to common milkweed (Asclepias syriaca) except smooth milkweed has (a) smooth (glabrous) stems, leaves and seed pods, (b) leaves with a significant upward sweep and distinctive reddish midveins and (c) larger flowers. It is a Missouri native plant which commonly occurs in moist prairies areas including river bottomland and moist meadowland mostly north of the Missouri River. It typically grows 2-4′ tall (less frequently to 5′) on stout, upright stems with broad-oblong, medium green leaves (to 8″ long) with pinkish-red midribs. Rounded clusters (umbels to 3″ 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″ long) which split open when ripe releasing their numerous silky-tailed seeds for dispersal by the wind. Seed pods are valued in dried flower arrangements. Flowers are a nectar source for many butterflies and leaves are a food source for monarch butterfly larvae (caterpillars).

Genus name honors the Greek god Asklepios the god of medicine.

Specific epithet honors 19th century American botanist William Starling Sullivant.