The blue, funnel-shaped flowers are 1 to 2 inches in diameter. They are borne in abundance in early spring and sporadically throughout the summer. Large periwinkle spreads rapidly and will mound up to 2 feet. Non-flowering stems root at the tips where they touch the ground. The trailing, arching stems that root where they touch the soil make these evergreen plants useful as groundcovers, for erosion control on banks, or for cascading from window boxes or planters.
Periwinkle grows well under trees and shrubs, on shaded slopes or on the north side of buildings.
Spring-flowering bulbs interplanted with periwinkle will lend color and interest to the groundcover planting. Daffodils are particularly well-suited since they bloom with periwinkle and do not require frequent division. The foliage color is richer green in partial shade, but more flowers are produced in the sun. Rooted cuttings or established plants are normally spaced from 12 to 18 inches apart. At a 6-inch spacing periwinkle will completely cover an area in one year.