Asclepias syriaca, commonly called common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed, is a species of flowering plant. It is in the genus Asclepias, the milkweeds.
Common milkweed is a perennial herb growing up to 2.6 m tall from a rhizome. All parts of common milkweed plants produce white latex when broken. The leaves are opposite or sometimes whorled; simple, broad ovate-lanceolate; up to 25 cm long and 12 cm broad, usually with undulate margins and reddish main veins. They have very shortpetioles and velvety undersides.
The fragrant, nectariferous flowers occur in umbellate cymes. Individual flowers are about 1 cm in diameter, each with five cornate hoods and five pollinia. The seeds, each with long, white flossy hairs, occur in large follicles.