Butterfly Pea

Butterfly pea (Clitoria ternatea) is a trailing vine in the bean family, grown for its sky-blue flowers. It is believed to come from tropical Africa and Asia, and it is now widespread in the tropics.

The plant can grow rapidly to about 15 feet (4.6 m) tall and can be trained to climb an arbor or trellis. It is perennial in the tropics, but in temperate areas it is usually grown as an annual. The flowers can be used to tint foods and drinks blue, and the dried flowers are a popular natural food coloring.

Sowing. Seeds have a thick seed coat, so soak them in warm water for 24 hours before planting. Start them indoors six to eight weeks before the last frost date for your USDA growing zone. You can also sow seeds directly outdoors after the last frost, spacing them 6 to 8 inches (15 to 20 cm) apart.

Germination. Seeds usually sprout within 14 to 21 days.

Site. Choose a spot in full sun, with at least six to eight hours of sun a day. The plant does well in well-drained, fertile soil that is dry to slightly moist.

Watering. The plant has a reputation for drought tolerance, but it does best with consistent watering.

Support. The vines can reach 3 to 4 feet (about 90 to 120 cm) in length, so a trellis helps keep the plant tidy. Without support it climbs weakly and can spread as a ground cover.

Butterfly pea is susceptible to spider mites, whiteflies, anthracnose and bacterial soft rot.

The flowers bloom from June through August, and the plant can bloom from summer into fall. Pick flowers early in the morning after the dew has dried for use as natural food coloring. The flattened pods are said to be edible when they are immature.