A native plant of Madagascar, vinca (Catharanthus roseus) produces rounded, five-petalled flowers in colors of pink, purple, white and red. The bright blooms appear repeatedly throughout the growing season, standing out against the plant's dark green, shiny oval leaves. Plant vinca, also known as Madagascar periwinkle, in mixed flower beds, planters and hanging baskets for season-long color.
Although vinca grows as a perennial only in U.S. Department of Agriculture plant hardiness zones 9b through 11, gardeners in colder zones grow this herbaceous bloomer as an annual. Vinca grows best in full sunlight but tolerates some shade during the hottest part of the day. It prefers fast-draining soils with average fertility and has a tolerance for dry, rocky soils with poor fertility. Soil pH has no bearing on a vinca plant's growth as it grows just as well in acidic, neutral and alkaline soils. Its mature spread ranges from 8 to 24 inches, depending upon the specific variety, so read the plant label before planting to space vinca correctly.
Water and Fertilizer
Soggy, constantly moist soil harms vinca plants; supplemental watering requires strict monitoring to ensure healthy growth. In general, vinca plants require water when the top 2 inches of soil are dry. Water during the early morning hours, moistening the soil to a depth of 8 to 10 inches. This practice allows wet foliage time to dry before nightfall and encourages deep rooting. A 10-10-10 nitrogen, phosphorous, potassium fertilizer mixed at a rate of 1 tablespoon per gallon of water every four weeks provides these bloomers with adequate nutrients. Apply 1/4-gallon fertilizer solution per 2 1/2 square feet of soil to maintain the proper rate.
Novice and expert gardeners alike enjoy the low-maintenance needs of the vinca plant. The flowers fall from the plants after they fade, negating the need for deadheading. Occasionally, a stem may turn yellow or die back and require removal with a quick clip of pruning shears, but otherwise, the plant requires little pruning. Spread a 1-inch-deep layer of mulch around vinca after planting to reduce weed growth throughout the season. Keep the mulch 2 to 4 inches away from the plant's stems to prevent mold or rot from forming.
Fungal diseases such as powdery mildew, root rot and fusarium wilt attack vinca plants when the soil remains wet for prolonged periods of time. These diseases attack the roots and stems of the plant, killing the tissue and causing it to turn black and mushy. The most effective control for these diseases is prevention. Maintain proper watering practices, allowing the soil to dry out between watering and the leaves to dry off before nightfall. Proper plant spacing allows adequate air circulation, which helps with drying soil and foliage. Remove diseased plants as soon as they appear to prevent the disease's spread.