Two plants are known by the common name vinca. The name is just about the only thing the plants have in common: One is a perennial ground cover for shade and the other is a mounding annual for sun. Despite the confusing name, it's not hard to tell the two plants apart.
Annual vincas (Catharanthus roseus) are heat-loving, annual bedding plants for full sun. There are many different types or "series" of vinca available, in heights from 6 to 18 inches. Most annual vincas are white or shades of pink or lilac; there are no true blue or yellow varieties available.
Annual Vinca Culture
Grow annual vincas in full sun or very light shade, as they will not flower well without at least six hours of direct sunlight. Space the plants 8 to 10 inches apart and feed them lightly when you first install them. They'll need supplemental watering for the first two or three weeks, but once established, vincas are drought-tolerant and need watering only during extended dry spells. The plants are self-cleaning and don't need deadheading. Annual vincas are sensitive to cold and will be ruined by even a light frost.
Periwinkle or creeping myrtle (Vinca minor) is a 6-inch, creeping perennial ground cover for partial to full shade. This fine-textured evergreen spreads at a medium rate and is often used under shrubs and trees, as it doesn't climb up into the larger plants like ivy will. Periwinkle has a big flush of blue, purple or white flowers in spring, followed by sporadic flowering throughout the rest of the season. Both white-and-green and yellow-and-green variegated cultivars are available. Vinca minor is hardy to U.S. Department of Agriculture plant zone 4.
Periwinkle's big cousin (Vinca major) is known as bigleaf or greater periwinkle. It grows up to 12 inches high, with larger leaves and flowers, and while it also spreads, it makes a more mounding or undulating ground cover than V. minor. Bigleaf periwinkle is most commonly seen in the South, as it's hardy only to zone 6, where it may suffer die-back during harsh winters. The variegated forms of bigleaf periwinkle are also sold in individual pots as trailing plants for large, mixed container gardens.
Perennial Vinca Culture
Both "Vinca minor" and "V. major" need the same growing conditions. Plant them in partial to full shade in moist, well-drained soil in areas where they can spread out. They're good choices for under-planting shrubs and trees, as a lawn substitute in shady spots and for controlling erosion on slopes. If they suffer leaf burn during the winter, give them a haircut with your mower set on its highest setting.