Asclepias eriocarpa is an erect perennial herb which is usually coated in a thick layer of white hairs. The leaves are lance-shaped to oval, rippled, and arranged oppositely in pairs or in whorls of 3 or 4. The inflorescence is a large umbel-like cluster of flowers. Each flower is white to cream and usually tinted with bright pink. It has a central array of rounded hoods and a corolla reflexed against the stalk. The fruit is a large, woolly follicle.
Native to California and adjacent parts of Nevada and Baja California, where it grows in many habitat types, especially dry areas.
Asclepias eriocarpa is a specific monarch butterfly food and habitat plant. It is one of the most poisonous milkweeds. Natural History July/August 2015 calls it the most poisonous, but most sources put it below A. lancifolia.
The plant was used as a source of fiber and medicine by several California Indian groups, including the Ohlone and Luiseño.