Madagascar Periwinkle (Catharanthus roseus) — identification, habitat & look-alikes

Madagascar periwinkle is a flowering plant from Madagascar that keeps blooming through summer heat. All parts are poisonous if eaten, though some of its compounds are used in two cancer drugs. In U.S. garden centers, it is sold as annual vinca.

Appearance

Growth form: A tender evergreen perennial usually grown as an annual. Garden plants are 6 in to 1.5 ft (15–45 cm) tall and 8 in to 1 ft (20–30 cm) wide.
Leaves: Glossy, oval leaves grow in opposite pairs along the stems.
Flowers: Flat, five-petaled flowers about 1–3 in (2.5–7.5 cm) across in white, rose-pink, lavender, purple, or white with a contrasting eye.
Flowering time: Blooms from summer until frost, even in intense heat.
Fruit: Produces slender paired pods that hold many seeds.

Look-alikes

Common periwinkleVinca minor

Annual vinca is upright with flowers that often have a contrasting eye. Common periwinkle is a trailing groundcover with smaller blue or purple flowers that blooms mostly in spring.

Garden impatiensImpatiens walleriana

Annual vinca has smooth-edged leaves in opposite pairs. Garden impatiens has toothed leaves arranged alternately and a little spur behind each flower.

Where it lives

Typical habitats: Flower beds
Containers
Sunny borders
Range: Native to eastern and southern Madagascar. In the US it is widely planted as a summer annual, survives as a perennial in 10–11, and has escaped cultivation in parts of southern California.
Preferred conditions: Likes full sun to part shade and well-drained soil. It tolerates heat and drought well but can't take frost.
Flowering: Flowers Jul–Sep
Flowers Jul–Sep

Life cycle

Seed dispersal: Seeds are spread by ants, water, wind, and dumped yard waste, which helps it pop up outside gardens.

Name and classification

About the name: The older scientific name Vinca rosea explains the garden name “vinca.” It belongs to a different from common periwinkle (Vinca minor). Two varieties have also been named within this species.
Varieties and forms: Garden vary in flower color and plant shape.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed
Status: In California, its spread outside gardens is monitored.

Culture and stories

Culture and stories: Researchers looking for a diabetes remedy in the 1950s found compounds now used in cancer treatment.

15 sources