The common name “periwinkle” leads to frequent confusion because it refers to two completely different garden plants. One is a true perennial that reliably returns year after year, and the other is a tropical plant cultivated as an annual in most temperate climates. Understanding the botanical distinctions between these two plants is necessary for successful gardening.
The Groundcover Periwinkle
The true perennial periwinkle belongs to the Vinca genus, most commonly Vinca minor, often called Lesser Periwinkle or Creeping Myrtle. This plant functions as a hardy, evergreen groundcover, with long, trailing stems that root as they spread across the soil. It is known for its dense mat of small, dark green, glossy leaves that persist through the winter in USDA Hardiness Zones 4 through 9.
Its five-petaled flowers are smaller than its annual counterpart, typically appearing in shades of blue, lavender, or white. The main bloom occurs reliably in early spring, with sporadic flowering throughout the summer. Native to Europe, this perennial tolerates cooler temperatures and is often planted in shaded or partially shaded locations.
The Bedding Periwinkle
The plant grown as an annual is Catharanthus roseus, commonly known as Madagascar Periwinkle or Annual Vinca. Unlike the trailing Vinca, this species has an upright, bushy growth habit, typically reaching heights of six to eighteen inches. It features glossy, dark green leaves and produces abundant, phlox-like flowers from early summer until the first hard frost.
This species is technically a tender perennial, hardy only in tropical regions (USDA Zones 10 and 11). Gardeners in cooler climates treat it as an annual because it is intolerant of frost. Catharanthus roseus is prized for its heat and drought tolerance, making it a popular choice for continuous color in summer conditions. Modern cultivars offer a wide spectrum of flower colors, including pink, rose, red, and white, often with a contrasting eye.
Choosing the Right Plant for Your Garden
The perennial Vinca minor is the appropriate selection for a permanent, low-maintenance groundcover in shady or partially shaded areas. Its trailing growth habit holds soil on slopes and effectively covers large sections of ground.
In contrast, the annual Catharanthus roseus is best suited for sunny flower beds, mass plantings, or containers where continuous, vibrant color is desired. This bedding plant requires full sun to thrive and produce its heavy floral display. When shopping, gardeners can easily distinguish the two by their form: look for the low, vining habit of the perennial Vinca or the taller, more compact, bushy structure of the annual Catharanthus.