If you want a pop of color that lasts from spring all the way to the fall, annual vinca (Catharanthus roseus) is the plant for you. Another name for vinca is periwinkle, but don't let the name fool you. These vibrant flowers come in red, apricot, purple, pink and other hues. Some varieties even produce flowers with one color petal and a different color center for a two-toned effect. Do be careful, however, if you live in a warm climate. While vinca grows as an annual in most of the United States, it's a perennial in the plant hardiness zones 10 and 11. When growing in this region, confine your vinca to a pot or plant it in an area where you won't mind it coming back. Vincas tolerate dry conditions and are resistant to deer and bunnies, so you won't have to worry about the local wildlife munching on your garden plants.
Vincas don't like cold weather, so wait to plant yours until on or after May 1. It's tempting to rush these charmers into the ground, so you can enjoy them, but one cold night is all it takes to damage the plants. When you do plant them, choose a location where they can enjoy full sun to part shade. Vincas are fans of acidic soil, and their ideal soil pH level is around 5.5. Vincas survive droughts well but don't like wet soil, so give them a home in loamy or sandy soil that drains well. Space your plants 10 to 12 inches apart to promote airflow and minimize the risk of fungus. Mulch the plants lightly if desired.
Once they're planted, vincas need very little attention from you. They love hot, humid weather and are fairly self-sufficient. Water the plants only when the top inch of soil is dry. Container plants will need water more often than those planted in beds, but it's important to avoid over-watering both. Vinca typically needs no fertilization. If, however, you know your soil is nutritionally lacking, you can apply a general purpose 10-10-10 fertilizer early in the spring. You'll only need 1/4 cup of fertilizer for every 100 square feet of soil, so use lightly.
Unless it falls victim to over-watering, vinca is typically free of disease and insect problems. If you or rainfall water the plant too much, it could develop stem and leaf rots or fungi. You can generally avoid all of these issues by pointing your hose at the soil when watering the plants rather than dowsing the leaves and flowers. Proper spacing promotes airflow and allows plants to dry more quickly when they do get wet. If a plant suffers from rot, remove it from the planting bed, so the problem doesn't spread.
The likelihood of vinca disease is small, but you can further reduce the risk by planting disease-resistant cultivars like "Cora" and "Nirvana." If your plants do fall victim to disease, plant them elsewhere in the next growing season. You can replant vincas in the same area after skipping one season. Slugs and snails sometimes enjoy a taste of vinca. If you see them on your plants, simply remove them by hand.