Introduction
Commonly known as Vinca or Periwinkle, Catharanthus roseus (not to be confused with the genus of European groundcovers which have the botanical name Vinca, and similar flowers), is the summer mainstay of the regional horticultural industry, with millions of plants produced each season to meet local requirements.
Originating from Madagascar, these plants have evolved over millions of years in geographic, climatic, and botanical isolation. They belong to the Family Apocynaceae and are known for their ruggedness, adaptability, and will to survive, especially in the Gulf region.
The Beauty of Vinca
Vinca, or Catharanthus, is an annual or very short/ medium-lived solitary perennial that thrives on neglect and high temperatures. It produces flowers in shades of red from purple to white (including some new recent "blue" cultivars). The original form of the plant has off-pink flowers with sharply tapered petals and is extraordinarily hardy and drought-tolerant.
Uses of Vinca
The sheer ruggedness and adaptability of Catharanthus have made it almost legendary in the Gulf where it's widely used in open and municipal spaces throughout the region. Once planted, they survive with minimal water, fertilizer, and maintenance, yet you can be assured of a profusion of color lasting the entire season. In the UAE, Catharanthus/ Vinca is one of the few seasonal plants that can survive through the hottest months of summer. It has a moderate to high salt tolerance and can endure high humidity levels with very few side effects from fungi.
Propagation and Pests
Catharanthus tolerates temperatures between 13 and 50 degrees Celsius. Seed germinates within 14 days and should be lightly covered with soil to aid germination. Plants can also be propagated from softwood cuttings in early spring. However, be aware that second and subsequent generations grown from collected seed will not look like the parent plants. These seedlings are most likely to produce leggy, weak plants with insipid small or variable-shaped flowers. Plant spacing in an open bed (at the time of planting) should be between 15 and 20cm center to center, do not plant the seedlings too deeply into the soil as this can result in stem rot.
Common garden pests on Catharanthus include Aphids, Thrips, and Mealy bugs. Damage from these pests can be remedied by the application of a contact or systemic insecticide applied directly to the plant. For a light infestation of Aphids or Mealy bugs, a weak solution of domestic dishwashing liquid in water (1 ml in 1 liter of water) can be applied.
Vinca plants are also very susceptible to Nematodes, this is why either soil sterilization methods should be employed in subsequent plantings or the application of a suitable watered-in Nemacide should be applied to the planting bed between planting seasons.
The soil-born fungus Phytophthora, and also affect the performance of these plants, especially when they are still small resulting in root and stem infections and rot, this situation can be remedied by employing soil sterilization techniques before planting and not encouraging the germination of fungal spores (especially in summer), by not watering in the late afternoon.
Medicinal Value
Catharanthus plants produce more than 95 different alkaloids, including one specific to the plant called catheranthine. Traditionally, extracts from the plant were used in folk medicine to treat both diabetes and rheumatism. Modern medicine has identified several more specific alkaloids which are currently used in medications to treat various cancers and melanomas, Hodgkin’s disease, and Hodgkin’s lymphoma. However, other alkaloids in the plant can be toxic if not fatal if ingested. Therefore, any remedies should only be applied by a trained medical professional.
Conclusion
In South Africa, Catharanthus is colloquially known as a “grave-yard plant” due to its ability to survive with the bare minimum of care once planted and still produce a good and sustained supply of flowers. Modern hybrids of the original plant are bred for their color as well as compact growth form. The color range of the original drab pink wildflower has been expanded to dark maroon red, red, bright hot pink, cerise pink, clear rose, salmon, and pure white, including now a range of "blue" cultivars. These are a popular choice for mass displays, border plants, container planters, and hanging baskets.
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