As of January 2018 APG IV places Family Apocyanceae in Order Gentianales, and Sub-family Asclepiadoideae within Apocynaceae. Our plant, with its drooping leaves and beautiful flowers, lines trails and adorns dry slopes and is related to Milkweed. For more on this, go to these links: Wikipedia on Apocynaceae, and Wikipedia on Asclepiadoideae.