Vinca

Vinca (from Latin vincire "to bind, fetter") is a genus of five species in the family Apocynaceae, native to Europe, northwest Africa and southwest Asia. The common name, shared with the related genus Catharanthus, is Periwinkle.

They are subshrubs or herbaceous, and have slender trailing stems 1-2 m (3-6 feet) long but not growing more than 20-70 cm (8-30 inches) above ground; the stems frequently take root where they touch the ground, enabling the plant to spread widely. The leaves are opposite, simple broad lanceolate to ovate, 1-9 cm (0.25-3.5 inches) long and 0.5-6 cm (0.25-2.25 inches) broad; they are evergreen in four species, but deciduous in the herbaceous V. herbacea, which dies back to the root system in winter.

The flowers, produced through most of the year, are salverform (like those of Phlox), simple, 2.5-7 cm (1-3 inches) broad, with five usually violet (occasionally white) petals joined together at the base to form a tube. The fruit consists of a group of divergent follicles; a dry fruit which is dehiscent along one rupture site in order to release seeds.

Cultivation and uses
Two species, the Small Periwinkle V. minor and the Large Periwinkle V. major, are very popular ornamental plants in gardens, grown for dense evergreen ground cover and their delicate violet flowers. V. major has broader leaves with a hairy margin and larger flowers, is less cold hardy, and has twice as many chromosomes as V. minor. A variegated selection of V. major is commonly cultivated. Both species are considered invasive weeds in parts of the United States and Australia. They do not respond to common herbicides and require hormone based sprays to control.

Medical uses
This plant was formerly used in homeopathy for catarrh, dyspepsia but due to the nature and effects of the alkaloids vincamine, isovincamine and vincamidine, it is rarely used. This plant also contains tannin. All parts of the periwinkles may cause stomach distress if ingested.

The chemotherapy drugs vincristine and vinblastine are derived from this plant.