Asclepias is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans and many other species, primarily due to the presence of cardenolides. However, as with many such plants, some species feed upon them or from them. The most notable of them is the monarch butterfly, which uses and requires certain milkweeds as host plants for their larvae.

Latex is an emulsion of polymer microparticles in water. Latices are found in nature, but synthetic latices are common as well.