common milkweed

Scientific name: Asclepias syriaca. Verified common names: common milkweed, silkweed. Family: Asclepiadaceae (many modern treatments place Asclepias in Apocynaceae, subfamily Asclepiadoideae). Genus: Asclepias. Taxonomic placement in the milkweed group (Asclepiadoideae) is well established.

A clumping, perennial herbaceous plant with one or more erect, unbranched stems arising from a fleshy rootstock. Stems and all tissues exude a milky latex when broken. The plant typically reaches about 1–4 feet tall. Flowers are borne in dense, spherical umbels that are generally pink to purplish-pink; individual flowers show a characteristic milkweed structure with reflexed petals and a central corona composed of hoods and horns (often described as 5 reflexed petals surrounding a complex corona). Leaves are opposite, simple, broadly ovate to elliptic, with entire margins and a distinct midrib; foliage may be somewhat fuzzy or hairy, especially on stems and petioles. Distinctive identifying features include the globose clusters of pink flowers, coarse rough seed pods (follicles) that form after flowering, silky floss attached to flat seeds, and the milky sap. Seasonal variation: plants typically flower in summer, followed by the development of spiny-textured seed pods that split to release silky-seeded follicles in late summer to fall; aboveground parts die back in winter.

Common milkweed is typically found in open, sunny settings such as fields, roadsides, meadows, prairies, and disturbed ground. It often tolerates a range of soils but generally prefers well-drained sites and moderate moisture; it can persist in dry to mesic conditions. The species is distributed widely across much of eastern and central North America and is documented in the listed states (AL, AR, CT, DE, GA and 33 more), commonly occupying landscapes from agricultural edges to wild prairies.

Flowers provide nectar to a variety of pollinators, including bees, butterflies, and wasps; Asclepias species employ a specialized pollination mechanism in which pollinia attach to visiting insects. Common milkweed is a well-documented larval host for monarch butterflies, whose caterpillars feed on the leaves and sequester plant toxins. Seeds are wind-dispersed by silky floss.

Common milkweed is generally widespread and not considered globally threatened. Fascinating adaptations include its milky, toxic latex that deters many herbivores and its pollinia-based pollination system. Monarch butterfly declines have increased conservation interest in milkweeds because they are key larval host plants.