Centrosema virginianum aka Butterfly Pea

Centrosema virginianum is a perennial vine in the pea family. Gardeners call it butterfly pea or spurred butterfly pea. Its native range spans the central and eastern United States. It extends south through tropical and subtropical parts of the Americas. It grows in dry woods, thickets, pastures, and disturbed ground. In North Carolina, it grows in pine woods and coastal uplands.

Garden references place its height near 3.3 feet [1 metre]. Slender stems range from 1–5.2 feet [0.3–1.6 metres] long. In Puerto Rico, stems can reach 20–23 feet [6–7 metres]. Those longer vines may have somewhat woody stems. The thin, green stems bend easily and lack tendrils. They climb by winding around nearby plants or supports. Without support, the vine spreads across the ground. Its green, compound leaves grow in an alternate pattern. Each leaf has three narrow leaflets with smooth edges. The plant sheds its leaves.

The flowers appear through summer, though tropical plants can bloom year-round. Violet blooms have a white mark at the centre. Pink flowers also occur. Each bloom measures about 0.125 feet [0.038 metres] across. Flowers grow alone or in groups of two to four. The largest petal has a curved, scooped form. The blooms face upside down and last only half a day. New flowers open each day during the bloom season. Bees provide most pollination, and butterflies also visit the flowers. Flat pods split when ripe and throw out their seeds.

This vine grows best in full sun with good drainage. It also tolerates partial shade, but not deep shade. Sandy or loamy soil suits it, including poor soil. It accepts dry or moist ground and withstands drought. It grows in acid, neutral, and alkaline soils. NC State lists it for USDA zones 5b–9b. Its growth rate is moderate, and it needs little upkeep. Gardeners can raise new plants from seed. NC State reports no known diseases or insect pests. Wet soil and salt spray do not suit it.

The vine works as ground cover or in borders. It also suits naturalized areas and butterfly gardens. Its roots help hold soil and limit erosion. Root bacteria fix nitrogen, which can also benefit nearby plants. Growers use it as green manure and livestock forage. It hosts Northern cloudywing and Long-tailed skipper butterfly larvae. Plants For A Future lists no known edible uses. That source lists no known medicinal uses, despite reported traditional use. The references report no known hazards; this does not establish food safety.