COMMON NAME: Madagascar periwinkle, Vinca, Begraafplaas blom
REASON FOR INTRODUCTION IN SOUTH AFRICA: Ornamental
INVASIVE STATUS IN SOUTH AFRICA: NEMBA Category 1b
DESCRIPTION: It is an erect, perennial herb up to one metre high, with a woody base. The leaves are bright green and glossy, with attractive pink or white flowers in the axils, although modern cultivars are available in a variety of colours and colour combinations. Each flower has 5 petals that fuse to form a tube at the base. Plants flower throughout the year, and are followed by green, cylindrical fruit that resemble unopened flower buds.
Flowers of Catharanthus roseus are pollinated by butterflies and moths. This species is self-compatible, though self-pollination under normal conditions may be relatively uncommon. Seeds are dispersed by ants, wind and water
THE PROBLEM: In Knysna this plant has colonised vast areas after the fire of 2017, especially vacant stands, along road verges and public areas. In KwaZulu-Natal, Limpopo and Gauteng Provinces, Madagascar periwinkle is capable of colonising virtually any area within a wide range of ecological conditions. It is recorded to invade riverbanks, rocky outcrops, roadsides, urban areas, open spaces in dry savannah, as well as plantations, forests and coastal scrub margins. The plants reproduce from seed, which may be dispersed by wind and animals, or be transported to new areas in water and garden waste. The stems and leaves of the plant contain a milky sap, and the entire plant is toxic.
CONTROL: Infestations can be removed by hand-pulling. Gloves should be worn to protect the skin from the latex, and all seeds must first be removed from the plants to prevent them from germinating in the disturbed soil. The collected seeds must be destroyed, preferably by burning. Although no herbicide has been registered for use specifically on Madagascar periwinkle, herbicides designed for broad-leafed plants may be used. Follow-up treatments are recommended for both mechanical and chemical control, to ensure there is no re-colonisation from roots or seeds. As with most invasive alien plants, the only long-term, sustainable solution is biological control. Unfortunately, no potential agents have been identified for use. In the meantime, gardeners and landowners are strongly urged to remove these plants from their property, and to replace them with indigenous plants.