Common periwinkle or myrtle (Vinca minor) is hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 4 through 8. The low-growing groundcover features oval-shaped glossy green leaves and blue-purple flowers with five petals apiece. Vinca is generally not fussy about light exposure and while optimal flower production takes place in full sun, the plants will grow and flower in light shade. The plants are often used successfully in dry, partially shaded conditions.
Vinca is an evergreen, vining plant that grows 3 to 6 inches tall, with a spread of 6 to 18 inches. The species' blue-purple flowers bloom in spring, generally in May through June, depending on climate zone and conditions. In protected parts of the garden, vinca may be among the first plants to bloom after the winter. The leaves are small and densely clustered and the stems will root readily at leaf nodes, allowing for a rapid spread. Because it forms a mat of foliage, vinca can act as a green mulch, helping retain soil moisture.
Vinca's shade-tolerant disposition makes it a good choice for difficult locations under trees. It is also a good groundcover in areas trouble by browsing deer, as it is less attractive to the animals than many other plants. Vinca spreads readily and naturalizes, making it suitable for erosion control. It is a good weed suppressor and remains evergreen, offering four seasons of garden interest. It is a good backdrop for spring bulbs like daffodils (Narcissus spp.) or tulips (Tulipa spp.) and after the blooms have faded, the vinca foliage hides the dying leaves of those plants.
Plant breeders have developed a number of vinca varieties. "Honeydew" (Vinca minor "Honeydew") is hardy in USDA zones 4 through 8 and features golden-green leaves. A variegated form, "Alba Variegata" (Vinca minor "Alba Variegata"), hardy in USDA zones 4 through 8, sports green leaves edged in cream. Developed in the first part of the twentieth century, "Bowles White" (Vinca minor "Bowles White"), also hardy in USDA zones 4 through 8, bears large white flowers. "Bowles Blue" (Vinca minor "Bowles Blue"), hardy in the same zones, has identical large flowers that are more blue than purple in color.
Use vinca carefully around children and pets, as all parts of the plant can cause gastric distress if ingested. Vinca, which was first brought to the U.S. from Europe in the eighteenth century for use as an ornamental plant, is often vigorous to the point of invasiveness. It is reportedly invasive in many states in the eastern half of the country, as well as Texas, Washington, Oregon and California. Consider alternatives like bigroot geranium (Geranium macrorrhizum), hardy in USDA zones 4 through 8; or bunchberry (Cornus canadensis), hardy in USDA zones 2 through 7.