[Wikipedia] Native to American Tropics, Cultivation, Distribution: It is native to the American tropics and has a pantropical distribution as an introduced species. It is grown as an ornamental garden plant and as a food source for some butterflies, however it may be harmful to the migration patterns of monarch butterflies when used in gardens outside of its native tropical range. Cultivation There are a number of different cultivars with improved flower colors and shorter habit; some have bright red, yellow or orange colored flowers. Asclepias curassavica is sometimes used in butterfly gardens (see above for concerns for monarchs) or as a cut flower. However, when the stems or leaves are broken, a poisonous milky sap exudes which can cause eye injury. (link added by Mary Ann Machi)