Clear flower colors and glossy green leaves make vinca indispensable for season-long interest in the garden and in containers. Add practically no maintenance to these drought tolerant plants and you have a winning combination. Native to Madagascar, vinca acts as an annual in most regions of North America. It blooms beautifully from the first warm days of late spring to the first frost in fall.
Look for plants with bright green foliage. Avoid any with yellowed leaves on the upper or lower parts of the plant; they indicate potential problems with root rot. Pass up leggy plants in favor of more compact, well-branched specimens.
Most vinca will be in flower when you buy them, so you can select by color. If you find plants in bud, look at the variety name. Variety names are usually, but not always, a good indication of the plant's bloom color.
Plant vinca in full sun. Plant only when the temperatures have warmed up in late spring. If you set the plants out too early, you risk losing them or having poor growth and few flowers. The deep green, glossy foliage of vinca forms an attractive edging even when the plants are not in bloom.
Prepare the soil. Vinca needs a soil that drains well, but not one that is particularly rich or fertile. Dig the bed to a depth of about 8 inches and incorporate a one-inch layer of compost or dried manure before planting. If you plant in an existing flower border, the amendments you originally added there should suffice. Good drainage is a must…. vinca will not tolerate wet feet at any time.
Transplant. Pick a cloudy, calm day to transplant. Use a trowel to dig a hole, pop the plant out of its pot, and set it in the ground at the same level (not deeper) it was growing in the pot. Firm the soil around the root ball. Space plants 8 to 12 inches apart for a border edging, 6 to 8 inches apart to quickly cover an area as a ground cover. Be careful, though, with close spacing because lack of air circulation creates the potential for problems later on. When you finish setting all the plants, water well.
GROWING IN THE GARDEN
Use vinca to edge a border of annual or perennial flowers, to weave color through a bed, or in container gardens. Even the most vibrant flower colors tend to be soft in hue so they never overpower other flowers. The appealing central eye on each bloom adds a bright, cheery note to any garden. When not in bloom (which is seldom) the plants offer a neat, green edge around the perimeter of a garden or along a walk or driveway. Planted as a ground cover, they fill in empty spaces within a border.
Mulch the soil around the plants, not only to help the soil conserve moisture and to deter weeds but also to protect the plants during inordinately rainy weather. A layer of mulch, such as bark chips, helps minimize splashing, which can transfer fungal spores from soil to leaves.
Fertilize monthly with a granular fertilizer such as Espoma Plant Tone or water soluble such as Miracle Grow Bloom Booster. Water infrequently, if at all once the plants have become established in the garden.
In the midst of a hot summer drought, the leaves may curl up during the day. Don't worry. They will unfurl when evening arrives with its touch of dew.
You do not need to groom vinca by removing spent blooms; they drop off. Plants stay neat looking all season.
PRETTY IN CONTAINERS
Being drought tolerant, vincas do particularly well in containers, where the soil can dry out quickly. That is not the main reason to use them, however. Their medium height and all-season bloom help you create beautiful combinations and pots of color. Mix them with blue or red salvias, geraniums, zinnias (especially Z. angustifolia), French marigolds, or petunias. Edge a large container of coreopsis or daylilies (particularly Hemerocallis 'Stella d'Oro') with white-, apricot-, or cherry-flowered vinca. Blend a series of vinca colors in one pot and edge the planting with some sweet alyssum. Fill a hanging basket with trailing vincas in shades of white, apricot, pink, or rose.
Planting. Select a container with drainage holes in the bottom or sides so the soil does not become waterlogged. Use a packaged potting mix or a soilless mix; do not use garden soil. Garden soil often contains weed seeds and is quite heavy when wet. If you plan to move the container around or you plant a window box for a sill or deck railing, consider using a soilless mix, which is lightweight. If you want to skip fertilizing the plants during the season, incorporate a controlled-release fertilizer in the mix before planting, though not really necessary with vinca.
Before unpotting the plants, set them on top of the mix in the container and rearrange them until you like the design. Then, unpot and place the plants in the mix at the same level they were growing originally. Water the planting well.
Check the soil in the containers frequently in very hot weather and water as needed. You can wait to water vinca until the leaves just begin to wilt, but if you plant them with other flowers and vines, figure to water before they reach that stage.
Fertilize monthly with a water-soluble plant food, if you did not use a controlled-release fertilizer at planting time.
DISEASES AND PESTS
Water correctly to prevent most of the fungal diseases that can cause problems for vinca: Root rot, botrytis, alternaria leaf spot, and aerial phytophthora. The latter is the most common fungus you may find in the garden. Direct water from the hose onto the soil or mulch, not on the plants themselves. Overhead watering splashes the fungal spores onto the leaves and stems. Because vinca is very drought tolerant, you can water infrequently. In fact, unless you encounter a severe drought, you may not need to provide extra water after the plants get established in the garden.
Pests seldom bother vinca, although you may occasionally find aphids on the plants. Wash them off with hard spray of water from the garden hose. Larger pests such as rabbits and deer avoid eating vinca. In deer infested areas, vincas are highly recommended plants that will provide summer color.
Judy Sedbrook - Denver County Cooperative Extension Master Gardener