Periwinkle is also called vinca or myrtle. Of the 12 species of periwinkle, two are popular groundcovers. All species have opposite leaves and single flowers. The perennial periwinkle should not be confused with the bedding plant, Madagascar periwinkle (Catharanthus roseus).
Periwinkle (Vinca minor) is an excellent evergreen groundcover with dark green foliage. Oblong to ovate leaves are opposite, simple, ½ to 2 inches long, glossy, with a short petiole. They exude a milky juice when broken. Flowers are purple, blue or white depending on the cultivar. Plants bloom in March or April and sometimes again in the fall. Vinca minor grows about 6 inches tall, spreading in all directions by sending out long trailing and rooting shoots, which make new plants.
Vinca major or large periwinkle is a larger, more aggressive species than V. minor. Leaves are up to 3 inches long. 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.
Periwinkle prefers shade but will grow well in full sun. 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. Plant whenever the soil is workable and provide sufficient water, especially when planting in summer. Weeding and mulching are required on a regular basis until the groundcover fills in the planted area. Periwinkle prefers moist, well-drained soil, abundantly supplied with organic matter, but it is tolerant of a wide variety of soil conditions. Fertilize only when necessary, preferably in the spring with a complete fertilizer such as 10-10-10 at a rate of 6 to 8 pounds per 1,000 square feet. Occasionally shear plants close to the ground to encourage new growth. Propagate by taking tip cuttings of non-flowering stems in late spring or divide throughout the season.
Cultivars of Periwinkle
- ‘Alba’ has white flowers.
- ‘Atropurpurea’ has purple flowers.
- ‘Bowles Variety’ has blue flowers and grows vigorously in clumps.
- ‘Variegata’ has blue flowers and leaves variegated with rich yellow.
- ‘Flore Pleno’ has double, purple flowers.
- ‘Alboplena’ bears white, double flowers.
- ‘Jekyll’s White’ has single, pure white flowers and is more floriferous than ‘Alba.’
- ‘Sterling Silver’ bears dark blue flowers and foliage with white margins.
Cultivars of Large Periwinkle
- ‘Alba’ has white flowers.
- ‘Pubescens’ bears more pubescent leaves than the species and red-purple flowers with narrow petals.
- ‘Reticulata’ has foliage netted with yellow lines.
- ‘Variegata’ has creamy white blotches on the leaves. Flowers are blue and plants are sometimes known as ‘Elegantissima.’
Periwinkle is susceptible to dieback (plants wilt and “die back” to the ground), caused by fungal diseases. Cankers, which are sunken, wound-like lesions, may be visible on the stem near the ground-line. Fungal leaf spots occasionally occur and look like brown circular-to-oval spots on the leaves. Infected leaves should be sheared off and discarded. To reduce fungal infection, avoid overhead irrigation. Chemical control is seldom necessary.