Perennial periwinkle, also known as “Vinca” or “Vinca minor” is a semi-evergreen groundcover that prefers to grow in shady spots. It survives periods of drought better than many shade loving groundcovers. It is one of the few plants that can be tucked close to evergreens and thrive. Periwinkle has glossy leaves and a treasured pure blue flower in spring. If the foliage turns yellow, it is a sign of too much sun, not enough moisture, or a lack of iron. While the leaves and flowers are toxic if ingested, scientists have used components of the plant to help treat cancer.