Vinca (Catharanthus) plants light up a flowerbed with their upturned, open blossoms in bright shades of red, pink, apricot and lavender. The annual variety of vinca grows between 8 and 18 inches in favorable conditions. It produces abundant blossoms all summer long, often blooming until the first frost. The clear blossoms contrast with the background, glossy foliage. These easy flowers enhance flowerbeds and borders along sidewalks and driveways. They also create colorful container plants on patios and porches.
Test the soil in your yard. Vincas flourish in slightly acidic soils, preferring a pH balance around 6.0 to 6.5. Purchase any recommended soil additives according to the results of your soil test. The vegetative particles in compost and aged manure adequately lower the pH level of neutral soils.
Plant your vinca plants outdoors after the final frost in the spring. Select small, upright seedlings from a nursery or garden center. Purchase at least a few of these annuals to plant in bunches to make a statement in your yard.
Prepare the planting site in a sunny location of your landscape. These plants prefer full sunlight in cooler climates but thrive with a little filtered shade during the day in hot, southern climates. Use a shovel to turn the soil in your selected planting site. Loosen about the top 6 inches of soil, breaking apart any hard dirt clumps. Add your soil amendments, compost or manure and work in well with your shovel.
Plant your seedlings in the prepared soil on a cloudy, calm day. Place the plants about 8 to 12 inches apart to allow adequate airflow around the foliage. Dig each hole a little wider than the width of each plant's root ball. Set the root balls in the holes and backfill with your soil, keeping the surface of your plants' root balls even with the surrounding surface. Press down the soil over the roots. Soak the soil near the roots with water.
Place a layer of mulch around the bases of your new plants to help retain moisture and to reduce weeds. Spread between 1 and 2 inches of shredded bark or course sawdust over the soil. Do not mound the mulch around the stems of your vinca plants. Allow about an inch of space between the stems and the mulch.
Water your vincas when the soil near the roots becomes dry. These flowers require minimal amounts of supplemental water and can suffer in wet, boggy conditions. Don't prune these low-maintenance flowers that maintain their compact form. Allow blossoms to remain on the plants until they drop.
Fertilize your vinca flowers every month to ensure adequate amounts of nutrients. Use a liquid fertilizer or granules formulated for use on flowering plants. Mix and apply your fertilizer according to the instructions on the container.