If you search for resilient flowering plants that tolerate sun, heat, drought and salt-spray, periwinkle flower should be on the top of the list. More widely called Madagascar periwinkle, the five-petaled flowers continue until frost or you pull out the plant. This plant usually grows to a mature height of 8 to 30 inches with a spread of 15 to 30 inches.
Madagascar periwinkle belongs to the botanical genus, or group, called Apocynaceae, commonly called the dogbane family. The species name is Catharanthus roseus, formerly called Vinca rosea which is a botanical name now abandoned by gardeners and taxonomists alike.
Madagascar periwinkle grows naturally in open, sunny bushland or on the forest edges on the African island of Madagascar.
Dark glossy green leaves shaped like elongated ovals cover the green to tan stems as long as temperatures remain above freezing. Stem tips bear repeated flushes of five-petaled flowers with rounded to wedge-shaped petals. The blossoms range in color from fuchsia and pink to pure white as well as new varieties with blood red tones. Some selections bear bicolored flowers with petals one color surrounding a central eye of a contrasting hue.
In cold winter areas, Madagascar periwinkle grows as an annual flower, gracing garden beds, hanging baskets and containers. Visually it resembles impatiens, and is the perfect substitute for them in hot, sunny areas, especially in sandy or fast-draining soils where impatiens perish. Varieties in the Nirvana or Cora Series of Madagascar periwinkle demonstrate excellent tolerance to oppressive humidity or frequent summer-occurring thunderstorm regions.
Where frosts never occur, Madagascar periwinkle becomes a shrub-like plant with woody lower stems. Flowering indefinitely, it adds color and mounding forms to building foundation beds or tropical rockeries where bright sunlight, dry soils or reflective heat from concrete and asphalt dominates.
The milky sap in the stems of Madagascar periwinkle contains alkaloids which may cause irritation on the skin of some people. No parts of the plant should be eaten or chewed.
In frost-free climates, this plant species often flowers year round, producing seeds and increasing their numbers in areas with moist, sandy soils. It looks pretty when in flower, but becomes weedy, sprouting up in waste sites and roadsides where other native grasses or wildflowers fail to prosper.
Gardeners also casually call the Madagascar periwinkle "vinca," adding confusion in conversations when also talking about the vining periwinkle (Vinca minor and Vinca major). The vine periwinkle species also belong in the dogbane plant family, Apocynaceae. All of these plants bear five-petaled flowers, a primarily difference being Madagascar periwinkle blossom colors range from white to pink and red, while the vining periwinkles produces blue to blue-violet flowers.