Periwinkle (Vinca Minor, Vinca Major)
Periwinkle comes in both small-leafed and large-leafed varieties. It blooms mostly in the spring with blue or purple flowers. Throughout the summer it will bloom sporadically.
This is a fast-growing perennial vine that makes a superb evergreen groundcover. A bed beneath a tree is an ideal location for periwinkle, though it will happily spread in a sunny place as well. Keep in mind that it can become invasive.