Madagascar Periwinkle - Definition and Overview

Madagascar Periwinkle (Catharanthus) is a genus of eight species of herbaceous perennial plants, seven endemic to the island of Madagascar, the eighth, C. pusillus, from Sri Lanka. They were formerly included in the related genus Vinca. One species, C. roseus, has been widely cultivated and introduced, becoming an invasive species in some areas. The name Catharanthus derives from the Greek meaning "pure flower".

The leaves are simple, opposite, rich glossy green, ovate to oblong and up to 5 cm long. The 2.5-5 cm broad flowers are salverform (like those of phlox), simple, with five usually pink, red or white petals, sometimes with "eyes" of contrasting colour at their centres.

Uses and cultivation

Illustration of foliage and flowers

C. roseus has gained interest from the pharmaceutical industry; the alkaloids vincristine and vinblastine) from its sap have been shown to be an effective treatment for leukaemia. Although the sap is poisonous if ingested, some 70 useful alkaloids have been identified from it. In Madagascar, extracts have been used for hundreds of years in herbal medicine for the treatment of diabetes, as hemostatics and tranquilizers, to lower blood pressure, and as disinfectants. The extracts are not without their side effects, however, which include hair loss.

Appreciated for its hardiness in dry and nutritionally deficient conditions, Catharanthus is an undemanding plant popular in subtropical gardens where temperatures never fall below 5°C. It is noted for its long flowering period, throughout the year in tropical conditions, and from spring to late autumn in warm temperate climates. Full sun and well-drained soil are preferred, the plants being sensitive to excessive moisture (which may cause fungus or leaf blight to develop). Growth is moderate to slow, but a lack of natural predators ensures it is unimpeded. Early cultivars were low and creeping; modern cultivars may reach a height and spread of 30 cm. Mauve, peach, scarlet and reddish-orange flowered cultivars have also been developed.

Madagascar Periwinkles are self-propagating from seed; the seeds require a period of total darkness to germinate. Cuttings from mature plants will also root readily.

External link

• 2002: Year of the Vinca (http://www.colostate.edu/Depts/CoopExt/4DMG/Whats/vinca2.htm)
• List of Catharanthus species and varieties (http://www.plantamed.com.br/GEN/Catharanthus.htm)