Although related to the common periwinkle (Vinca), the 8 annuals and perennials of this genus are far less hardy and will not tolerate frost. All species are native to Madagascar, and they are busy plants with simple elliptical leaves on semi-succulent stems. Flat 5-petalled flowers, mainly in pink and mauve shades, appear at the stem tip and leaf axils. Though considered a weed in the tropics and subtropics, the widely cultivated species Catharanthus roseus is a perennial often grown as a greenhouse plant or as a summer bedder in temperate gardens. Although highly toxic in its natural form, this species is the source of the drugs known as vinca alkaloids that are used to treat Hodgkin's disease and lymphocytic leukemia.
CULTIVATION
These plants are very easily grown in part-shade, and can withstand strong sunlight. They are drought tolerant, but flower more heavily with summer moisture. Water moderately in the growing season. Gently pinch back to encourage bushiness. In cool climates with winter frost, bring indoors or discard and replace in spring. Propagate from seed or half-hardened summer cuttings.
Top Tip
Tip prune Cathranthus species to maintain their fullness, but don't get too enthusiastic-over-pruning can discourage flowering. A bit of liquid fertilizer once a month is also recommended.
CULTIVATION
These plants are very easily grown in part-shade, and can withstand strong sunlight. They are drought tolerant, but flower more heavily with summer moisture. Water moderately in the growing season. Gently pinch back to encourage bushiness. In cool climates with winter frost, bring indoors or discard and replace in spring. Propagate from seed or half-hardened summer cuttings.
Top Tip
Tip prune Cathranthus species to maintain their fullness, but don't get too enthusiastic-over-pruning can discourage flowering. A bit of liquid fertilizer once a month is also recommended.
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