- Periwinkle (Vinca spp.) and Madagascar periwinkle (Catharanthus spp.) are both members of the Apocynaceae family. Madagascar periwinkle was formerly classified as a Vinca species (Vinca rosa) but is now classified as a separate species. The two are similar in appearance and are both commonly referred to as "myrtle."
- Lesser periwinkle is commonly cultivated for use as ornamental ground cover, though it is considered an invasive weed in some areas of North America and Australia. Madagascar periwinkle is also commonly used as an ornamental plant but thrives only in a subtropical environment where temperatures do not fall below 41ºF (5ºC).
- Both species produce alkaloids that have been studied and used as a treatment for treatment of a wide variety of conditions, including diabetes, cancer, hypertension (high blood pressure), and stroke.
- The use of periwinkle as a dietary supplement is not recommended, because it contains vinca alkaloids, which may cause damage to the liver, kidneys, and nerves, as well as death.