This genus contains about 140 species with a milky sap that consists of a type of latex which is slightly toxic in some species. They are native to Eastern North America. Carl Linnaeus named the genus after the Greek god of healing, Asclepius.

As the name implies, several species of Asclepias are the main food supply for butterflies, specifically for the monarch butterfly. It is thought that the recent decline in monarch populations can be related to the decrease in areas where milkweed grows naturally.