Saturday, August 8, 2009

Vinca Covers Ground

A walk along an urban trail is an education in diversity. You'll pass people of many nationalities and dress with one thing in common - they need exercise outdoors. You may notice that the plant world along the way is also inhabited by species from far away places.

Vinca, an evergreen ground cover vine that now inhabits much of North America, is actually native to parts of Europe, North Africa and western Asia. The name was probably derived from a Latin word meaning "to bind." Certainly, as a ground cover, it is very effective for erosion control. In addition, David MacKenzie in Perennial Ground Covers says the tough runners used to be twisted together to form rope.

The trailing, vine-like plant is in the Dogbane family, along with Bluestar (Amsonia spp.), Asiatic Jasmine (Trachelospermum asiaticum), Confederate Jasmine (T. jasminoides) and Mandevilla. Mature height as a ground cover is usually from 8" to 18". The runners root as they go. Flowers may be blue, white or burgundy, depending upon the cultivar. Vinca prefers moist soil in partial shade to full shade, but will also tolerate sun and drought. It is deer resistant.

Two species of Vinca are commonly available: Vinca major and Vinca minor.

Vinca major is so named because the flowers and leaves are larger and the runners longer than Vinca minor. Its common name is Bigleaf Periwinkle. Leaves are oval, green or variegated, 1" wide and approximately 2" long. Simple flowers are up to 2" diameter. It is reliably hardy in USDA climate zones 6 through 9. Recommended soil pH is 5.6 to 7.8. In addition to its effectiveness as a ground cover, it is a fine subject for hanging baskets. Plant 8" to 12"

Vinca minor is commonly known as dwarf periwinkle, creeping myrtle, or death myrtle. V. minor does contain toxic substances, but MacKenzie says that "during the Middle Ages, the heads of criminals who were to be executed were adorned with stems of V. minor, hence the Italian name Fiore di morte (flower of death)." Foliage is about 3/4" wide and 1" long. Mature height is less than V. major; about 4". Evergreen foliage is deep green and shiny. It is fine for erosion control in medium-sized areas provided that water does not flow with such force that the plants are dislodged before established. Vinca minor is hardy in USDA climate zones 4 through 8. Recommended soil pH is 6.1 to 7.8. Plant 6" to 12" apart.

Vinca does well in shallow soil, even where tree roots make it impossible to cultivate. But if possible, prepare the planting bed by cultivating at least 4" deep, removing all traces of weeds. Composted manure may be incorporated into the soil. Fertilizer may be used. If you choose to do so, incorporate 10-10-10 fertilizer at a rate of no more 2 lbs. per 100 square feet into the top 4" of soil. Avoid synthetic fertilizers contacting any part of your plants.

Vinca can be planted any time you have a shovel handy, even bare root plants. It is very tough. Nevertheless, you should water occasionally until the plants become established to avoid drought stress. Maintenance is minimal. Vinca has few pest and disease problems, and tolerates poor soil.

Because it is so common, some folks think that Vinca is over-used, even invasive. But I don't agree; I'm all about diversity. It does what a ground cover is supposed to do; it covers ground. Vinca is popular because it is effective, attractive, and requires little or no maintenance.

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