"Periwinkle" sounds cuter than the genus name "Vinca," but this plant with starry blue flowers plays many diverse roles on our planet and not all can be considered friendly. The two principal types of Vinca plants—Vinca minor and Vinca major—offer low-growing evergreen ground cover and provide drugs for chemotherapy. But without cultivation, these hardy vines can choke out native species.
Those plants in the Vinca genus are tough evergreen vines. The genus name Vinca comes from the Latin verb meaning "wrap," "bind" or "fetter," referring to the flexible stems. As the vines grow, they develop roots at the leaf nodes to hold tight to the ground. Both Vinca major and Vinca minor are popular and easy-to-grow ground cover that spreads quickly and requires little maintenance.
But be warned! Not every plant called periwinkle is a Vinca, a word that is also used as a common name for plants that are not from this genus. For example, Catharanthus roseus is called both Annual Vinca and Madagascar Periwinkle. An excellent, drought-resistant plant, it is not even vaguely related to the Vinca species.
Common periwinkle _(_Vinca minor) wins many popularity contests when it comes to evergreen ground covers. Its training stems quickly spread to cover a bed or even field, rooting regularly along the way. The vine is so prolific that it can mound to six feet tall.
In spring and summer, lovely lavender-blue flowers an inch across appear in the axils of the the smooth, evergreen leaves. They light up your yard like little blue stars throughout the summer and bloom well in both shade or partial shade. You can even grow them in sunny spots.
Common periwinkle is amazingly hardy in cold climates, one of the reasons for its popularity. It thrives in U.S. Department of Agriculture (USDA) plant hardiness zones three through nine. You can find cultivars with variegated leaves and a variety of blossom colors.
The bigger-leafed version of common periwinkle is greater periwinkle _(_Vinca major). It is also an evergreen, prostrate mat-forming perennial, and like common periwinkle, it has long trailing stems that root along the way. The leaves grow up to three inches long, twice the size of common periwinkle leaves. The pretty blue flowers are also slightly bigger, at 1 1/2 inches across.
Greater periwinkle foliage can grow to 18 inches tall. Once it is established, the plant spreads aggressively and indefinitely. Much less cold-hardy than common periwinkle, greater periwinkle is only hardy to USDA zone seven.
Some Vinca-genus plants contain alkaloids that are used to make chemotherapy agents. Both vincamine and vinorelbine come from common periwinkle. They are used to treat types of lung cancer.
Both types of Vinca are considered invasive species. Common periwinkle is more of a threat, given its more extensive reach. It regularly escapes cultivation and invades shady wild areas, especially in the eastern U.S. It often escapes from overgrown gardens and moves into nearby forests. Given its vigor and dense matting, common periwinkle shuts out native herbaceous and woody plant species.
Greater periwinkle has been identified as an invasive plant along the west coast and scattered areas throughout the southeast. It has been found in Yosemite National Park as well as Sequoia and Redwoods National Parks in California.