ANNUAL VINCA

Commercial Greenhouse Production

Scientific Name: Catharanthus roseus

Common Name: Madagascar Periwinkle, Vinca

Family: Apocynaceae

Dr. J. Raymond Kessler, Jr.

Auburn University

Uses

Annual vinca is one of the best bedding plants for dry, warm locations in full sun. In the southeast, it tolerates the hot, humid summers and still remains attractive into the fall. Many greenhouse growers consider vinca a difficult crop to grow. This is because it is very sensitive to overwatering, high fertility, and cool growing conditions. The best quality vinca is usually grown late in the spring season and in greenhouses where high temperatures and high light can be maintained.

Breeding

Vinca is usually grown as a bedding or pot plant. Some excellent breeding has resulted in large-flowered cultivars with pink, lavender, white, and bicolor flowers. Vinca series include Cooler, Little, Pacifica, Pretty, and Tropicana.

Germination

Purchase refined seed that have been cleaned and graded by size or weight. Seed pretreated with a fungicide as a preventive measure against damping-off disease is also available. Seed are usually sown in 405 or 512 plug trays, and a light seed covering can be applied as fine vermiculite to hold moisture next to the seed. Many growers avoid any nutrient charge in the plug medium. The germinating medium should have a 5.5-5.8 pH with the soluble salts <0.75 mmhos/cm (2:1 extract). Avoid ammonium levels greater than 10 ppm and keep the phosphorus level on the low side. Darkness is recommended during germination or light for less than 12 hours per day. Continuous light has been found to reduce germination percentages. Germinate vinca very warm for the first 3-5 days, 78-80F and 95-100% RH up until the radical emerges, then drop the temperature to 75-78F and 75-80% RH until the cotyledons unfold. Some growers will start at 90-95F for the first three days, then drop down to 78-80F. Bottom heat greatly benefits seed germination and early growth. It is critical to reduce to moisture when the radical emerges. Keep the germinating medium moist but not saturated. If an early crops is required, supplemental light from HID lamps (300 ft.ca.) can be benefitial, even in the south. Complete germination generally requires 7-15 days depending on the cultivar and environment. Begin fertilizing seedlings at 50-75 ppm N using calcium/potassium nitrate when the cotyledons unfold. Apply a protective fungicide for Thielaviopsis, Pythium, and Rhizoctonia once a full stand is achieved. Seedlings are ready to transplant from plugs when four mature leaves are present or about 5-6 weeks from sowing.

Growing-On

Temperature: Reduce temperature to 68-72F at night and 80-85F during the day, night temperatures below 65F causes foliar yellowing, stunted growth, and poor quality. This frequently necessitates establishing a separate greenhouse or greenhouse section with temperature control for growing vinca. Low temperature is the major cause of poor Vinca crops.

Photoperiod: None has been demonstrated.

Light: Give Vinca as much light as possible!

Growing medium: Light, well-drained, peat-lite medium with a pH of 5.5-6.0. pH above 6.5 causes iron deficiency. Be aware of water alkalinity for Vinca. Allow the medium to dry between waterings but do not allow Vinca to wilt. Fertilize at 100-150 ppm N using a fertilizer about equal in nitrogen and potassium, but low in phosphorus. EC should not exceed 1.0 mmhos/cm. Supplemental magnesium sulfate should be applied at 16 oz. / 100 gal. once per month. Avoid fertilizers high in ammoniacal fertilizer forms.

Growth Retardant: Daminozide at 2500 ppm (B-Nine) is particularly effective during stage 3. A-Rest (16-33 ppm) and Bonzi (10-15 ppm) are also registered for Vinca but may cause foliar damage if applied incorrectly.

Supplemental Light and Carbon Dioxide: Supplemental light from HID lamps benefits growth at 400 ft.ca. during the plug stage (begin stage 2).

Common Problems

Physiological: Cool temperatures and overwatering are the most common problems both in the greenhouse and in the landscape. Trickle or drip rather than overhead irrigation is best for watering Vinca in the landscape.

Pests: Very few except occasional thrips or aphids.

Diseases: Thielaviopsis, Pythium, and Rhizoctonia are most prevalent when the plant is under stress, usually cool temperatures. Pythium causes black lesions on the roots and the medium has a musty smell. Thielaviopsis produces similar lesions on the roots without a disagreeable smell and causes older leaves to yellow and fall off.

Scheduling

Requires 5-7 weeks in plugs depending on the cultivar and climate, followed by 5-7 weeks in finishing flats or 9-11 weeks in 4" pots. Ten-inch hanging baskets with five plugs per container will finish in about 11-13 weeks from transplanting, again depending on the environment and time of year.