Perfect for a garden site where irrigation doesn't reach and the soil isn't the most fertile, Vinca rosea is not shy about flowering during the heat of summer. Its flowers resemble those of the impatiens, an annual that needs huge amounts of water and shady conditions look its best. Vinca rosea is killed by winter frost, so is grown in summer. It will remain as a shrub-like perennial in U.S. Department of Agriculture hardiness zones 10 and warmer.
Native to Madagascar, this plant naturally grows in the sunny, open scrubland or at the edges of forests.
Common English names for Vinca rosea are Madagascar periwinkle and vinca. Botanically, it is known today as Catharanthus roseus and is a member of the dogbane family, Apocynaceae.
In tropical, frost-free settings, Vinca rosea becomes a partially woody-stemmed sub-shrub, growing 3 feet tall and 4 feet wide. Usually it is grown as a summer bedding annual where it grows to modest proportions, anywhere from 12 to 24 inches tall and wide before being killed by fall frosts. Its leaves are emerald green and glossy and the stem tips bear cheerful, five-petaled blossoms in clusters. Flower colors range from white to pink and fuchsia as well as bi-colored types with a contrasting color in the center "eye" of the blossom.
Plant breeders developed many varieties of this plant, broadening the range of flower colors as well as creating some that are more prostrate and sprawling in growth habit. Collections of varieties with similar features, such as resistance to fungal rot or an increased tolerance to humidity, are grouped into series. Some series are named: Pacifica, Cora, Mediterranean, Pretty or Cooler. Each series includes a wide array of different flower color choices, too.
Fast-growing in hot temperatures and tolerant of nutrient-poor and sandy soils, it produces large numbers of seeds and may sprout unwanted seedlings across the garden. In subtropical regions where natural frosts do not kill plants, gardens may become filled with Vinca rosea. The white sap oozes out of broken stems and can cause allergic skin reactions in some people. Consumption of the leaves and stems will cause severe stomach pain.