H. retusa hails from India and the Eastern Himalayas.  It's name, "retusa", refers to the unique shape of the leaf, and it's unusual among Hoyas in being a true epiphyte, growing attached to trees and rocks in its native environment.  This Hoya enjoys drying out a bit between waterings, so never let its soil stay wet, and a couple of hours of full sun daily will help encourage its lovely blossoms to form.  This rare species is a great example of the amazing diversity of Hoyas!