According to APG II, the Asclepiadaceae is a former plant family now treated as a subfamily (subfamily Asclepiadoideae) in the Apocynaceae (Bruyns 2000). They form a group of perennial herbs, twining shrubs, lianas or rarely trees but notably also contain a significant number of leafless stem succulents. The name comes from the type genus Asclepias (milkweeds). There are 348 genera, with about 2,900 species. They are mainly located in the tropics to subtropics, especially in Africa and South America. Many new hybrids have been formed due to the unique fertilization method of the flowers.