The clear crisp flowers and glossy green leaves of annual vinca are so perfect; you may be tempted to rub them to see if they are real.
The plants are grown for its attractive glossy, green foliage, as well as its flowers.
Vinca plants are subshrubs or herbs, and have slender trailing stems 1 to 2 m (3 to 6 feet) long but not growing more than 20 to 70 cm (8 to 30 inches) above ground; the stems frequently take root where they touch the ground, enabling the plant to spread widely. The leaves are opposite, simple broad lanceolate to ovate, 1 to 9 cm (0.25 to 3.5 inches) long and 0.5 to 6 cm (0.25 to 2.25 inches) broad.
The flowers, produced through most of the year, are salverform (like those of Phlox), simple, 2.5 to 7 cm (1 to 3 inches) broad, with five petals joined together at the base to form a tube. The fruit consists of a pair of divergent follicles; a dry fruit which is dehiscent along one rupture site in order to release seeds.
Annual vinca plants are of the genus Catharanthus, a member of the Apocynaceae family. This is a case where paying attention to the Latin name is helpful: you must distinguish the annual vinca flower from the perennial vinca minor vine, which forms a dense mat and can be invasive.
Water the vinca only when the surrounding soil becomes completely dry. Provide water to the plants only during the morning to allow time for drops of moisture to dry before nightfall. Vinca grows well in any type of soil but sandy loamy, light well-drained soil is preferred. Vinca grows best in full sunlight but partial sunlight is also suited to them.
Fertilize the plants once a month with a 10-10-10 nitrogen, phosphorous, potassium water-soluble fertilizer. Mix 1 teaspoon of fertilizer with 1 gallon of water, or according to the instructions on the package. Apply the fertilizer in place of a watering.
Special features: The low care nature of vinca plants helps them succeed in window boxes and other garden containers.
Ornamental use: Vinca is commonly used for boundaries or as a hedging plant, and to cover ground.
Medicinal use: Lowering blood pressure, lowering sugar levels for diabetics, treatment for coughs, colds, sore throat, treating eye and lung infections.
Note: Use only after consulting the specialist.