Madagascar periwinkle, scientifically known as Catharantus roseus, is a perennial plant species belonging to the family Apocynaceae. This species is a native to Madagascar and India but is widely distributed throughout many tropical regions. It can tolerate drought when it is already established and prefers full sun or partial shade. Commonly grown as a garden plant, the Madagascar periwinkle is also known by other names, such as old maid, cayenne jasmine, and rose periwinkle. There is sometimes confusion regarding the official name of the species because it was once referred to as Vinca rosea.
The flowers of this species have five petals, and their colors vary between pink, red, and white. Its leaves are arranged opposite each other on moderately firm stems and measure about 2 to 3 inches (5 to 8 cm) in length. As an annual plant, the Madagascar periwinkle can grow up to 3 feet (about 0.9 m) in height and just about the same in width.
This tropical plant is commonly found in gardens because of its distinctive appearance. With its long blooming period and dark glossy leaves, the Madagascar periwinkle is often regarded as an excellent ground cover plant. The leaves tend to curl under heat, but they quickly unfurl once dew falls on them or the temperature drops. Numerous cultivars are grown for their wide variance in flower color and cold tolerance. One example is the peppermint cooler, which is more tolerant of cold than the original plant and sprouts white flowers with a red center.
Propagation of the Madagascar periwinkle is usually done by sowing its seeds but can also be done by planting cuttings taken from the mature plant. In loose soil, the seeds easily grow and may become invasive if not maintained by pulling unwanted seedlings. Transplanting is relatively easy and best done during early evening because the cooler temperature prevents seedlings from wilting.
The Madagascar periwinkle has caught the attention of the pharmaceutical industry because the vinblastine and vincristine alkaloids from its sap are considered an effective cure for lymphoma and leukemia by some researchers. These two alkaloids were discovered to be active anti-cancer agents and significant for chemotherapy. For hundreds of years, extracts from this plant have been used in herbal medicine to treat diabetes, lower blood pressure and act as tranquilizer. The extracts, however, are found to cause side effects such as hair loss. It is also toxic to livestock, especially if ingested in large amounts.