Vinca: A Case of Mistaken Identity

Vinca represents a good example of why botanical (scientific) names are important.. Known variously as vinca, periwinkle, and Madagascar periwinkle, summer-flowering vinca (Catharanthus roseus) is easily confused with Vinca minor and Vinca major. All of them are members of the Apocynaceae or dogbane family. However, Catharanthus likes the exact opposite conditions of its cousins, which are also called vinca; it prefers sunny, hot conditions and blooms all summer until frost. Vinca minor is an evergreen vining ground cover for shade that flowers in spring and is propagated from cuttings, not seed. Vinca major (vinca vine), is a trailing vine with soft green leaves variegated whitish-yellow; it is popular for use in containers, window boxes and hanging baskets.

The confusion can be blamed on botanists who first observed Catharanthus and noticed that its flower closely resembled that of Vinca minor. Consequently, they first named it Vinca rosea. By the time botanists realized the differences between the plants, the name vinca had become too common to change. The botanical genus name for the summer flowering vinca, however, underwent a few changes from Lochnera to Ammocallis until it was finally classified as Catharanthus. The specific epithet, roseus, which means rose-colored, changed only from the feminine rosea to the masculine roseus to match the gender of the Latin name of the genus.

All vinca flowers are single and most modern varieties have overlapping petals. The species, Catharanthus roseus, is rosy pink with a small mauve “eye” at the center; there is also a white form. Thanks to extensive breeding, the color range of vinca now includes pink, deep rose, red, scarlet, white with red eye, lavender blue with white eye, peach, apricot, orchid, raspberry, burgundy and many other shades. Vinca usually grows 8 to 18 inches tall with a one-foot spread, although there are trailing types that spread to two feet.

Vinca has been cultivated for centur ies in Europe, India, China and America . In Europe and elsewhere, it was used, along with its cousins Vinca minor and Vinca major, to treat all kinds of diseases, from coughs and sore throats to eye and lung infections. Perhaps most interesting was its folk use in treating diabetes. In the 20th century, researchers discovered the plant contains dozens of alkaloids: some of them lower blood sugar levels (providing folk remedies with scientific verification) and blood pressure. In the 1950’s, scientists discovered two alkaloids (vincristine and vinblastine) that are the source of some of the most effective cancer-fighting drugs still used today.

As far back as the 1920’s, hybridizers worked with selections of the species, Catharanthus roseus, to come up with improved plants but through the 1980’s, the popularity of vinca as a bedding plant was limited because commercial varieties had a narrow color range. Plus, seed germination was poor. In the background, however, improved cultivars were pending. In 1976, an interspecific breeding program was started at the University of Connecticut aimed at developing new colors, plant habits, freedom of bloom and improved garden performance in vinca.

In 1988, two new cultivars with improved germination rates and colors were introduced: ‘Grape Cooler’ (lavender-pink with rose eye) and ‘Peppermint Cooler’ (white with red eye). In 1991, the first of UConn’s new varieties (‘Pretty in White’ and ‘Parasol’) became available. Both earned the coveted All-America Selection award. The same year, Waller Genetics, in California, introduced the new ‘Tropicana’ series from the Connecticut breeding program. The plants had new colors with larger flowers and overlapping petals. They were followed in 1993 by the ‘Pacifica’ series which included the first red-flowered vinca. In subsequent years, additional color breakthroughs came as commercial breeders began to use more of the interspecies cultivars. Bodger Seeds introduced the ‘Heatwave’ series including new flower colors and PanAmerican Seed introduced the first F1 hybrid vinca, ‘Blue Pearl.’ New and improved varieties appear frequently now, including carpet-type plants with trailing habits. Recent All-American Selections include ‘Pacifica Burgundy Halo’ (2007), ‘First Kiss Blueberry’ (2005) and ‘Jaio Dark Red’ (2003).

Vinca is heat-loving and drought tolerant. Although it prefers full sun, it can tolerate light shade and should be grown in soil of average fertility. Rich soil leads to poor flower production. Plant established plants only after the soil (and weather) has warmed significantly. In Missouri, it is wise to wait until May to plant vinca. Pinching the plant shortly after it is established will help to promote bushiness but is not an absolute necessity for an attractive floral display. Vinca are drought tolerant and suffer if too much water is applied. In many cases, vinca needs little, if any, extra water than that supplied by nature. Mulch the soil around the plants to help conserve soil moisture and to deter weeds. A layer of mulch, such as bark chips, also helps minimize splashing during rainy weather; the latter can transfer fungal spores from soil to leaves.

Problematic diseases of vinca include root rot, Botrytis, Alternaria leaf spot and aerial Phytophthora. In all cases ,proper watering will help to prevent them from becoming a problem. This includes applying water in such a way as to keep the foliage as dry as possible and not over-water. Aerial Phytophthora is probably the most harmful fungus to vinca and the best technique for preventing the disease is to water with drip irrigation and apply fungicides when warranted. Insects seldom bother vinca, although one might occasionally find aphids on the plants. Larger pests such as rabbits and deer avoid vinca. Therefore, vinca is highly recommended for summer color where deer damage is a problem.

Vinca is effective as an annual plant in either a bed or border. Carpet beds of vinca are attractive, or it can be used to edge a border of annual or perennial flowers. Even its most vibrant flower colors tend to be soft in hue, so they never overpower other flowers. The appealing central eye on each bloom adds a bright, cheery note to any garden. When not in bloom (which is seldom), the plants offer a neat, green edge around the perimeter of a garden or along a walk or driveway. Planted as a ground cover, they fill in empty spaces within a border nicely.

Additionally, vinca is an excellent plant for containers. Their short, yet graceful stature and season-long bloom period allows for the creation of beautiful combinations in pots or baskets. Consider mixing vinca with blue or red salvias, geraniums, zinnias (especially Zinnia angustifolia), French marigolds or petunias. Edge a large container of coreopsis or daylily (especially ’Stella d’Oro’) with white-, apricot-, or cherry-flowered vinca. Blend a series of vinca colors in one pot and edge the planting with some sweet alyssum. Fill a hanging basket with trailing vincas in shades of white, apricot, pink or rose.

As we enter into an era where summers appear to be warmer and warmer, our search for the ideal flowering annual must take into account heat tolerance. Vinca approaches that desirable trait about as closely as any other annual and is (relatively) maintenance-free as well. Now available in a wide array of colors, serious gardeners should consider planting some this spring for a season of pleasing floral display with minimal care.

Credit: National Garden Bureau

David Trinklein
Assoc. Prof. Plant Sciences