Asclepias quadrifolia is a species of milkweed commonly called fourleaf milkweed or whorled milkweed. The plant occurs in the eastern United States and Canada.
Fourleaf milkweed is a perennial herb from a fleshy rhizome. The plant is small and slender compared to other milkweeds at only 45 cm tall. Leaves usually elliptic to ovate, opposite in arrangement but clustered to form a false whorl, 2.5-12.0 cm long, 1-6 cm wide. Pale pink to white flowers are borne in rounded, usually pendulous clusters from the leaf axils and terminus. The fruit is a follicle or pod which is very slender, 3.2 to 5.6 inches long, 1/4 to 1/3 thick, lacking tubercles, minutely hairy to glabrous; seeds broadly oval, to 1/3 inch long, tufted with white to tan hairs at tips.
Unlike more commonly known species such as common milkweed or butterflyweed, fourleaf milkweed is a woodland denizen. It usually occurs in dry, rocky open forest. It is frequently found on upland slopes.
Insects that take nectar from the plant include bumblebees and other bees, wasps, ants, flies, and butterflies. The caterpillars of the Monarch butterfly feed on the foliage.
Most Asclepias are toxic if consumed in large quantities due to cardiac glycoside content.
Fourleaf milkweed is rare in cultivation.