Mucuna pruriens aka Cow Itch

Mucuna pruriens is a climbing plant in the bean family, Fabaceae. Common names include velvet bean, cowitch, and cowage. Its native range spans the tropical and subtropical Old World. This includes tropical parts of Africa and Asia. It has spread into the American tropics and parts of Australia. Growers raise it across warm regions for soil cover and forage.

Its lifespan and form vary with growing conditions. It can grow as an annual, short-lived perennial, or climbing shrub. Slender stems become partly woody and twine around nearby plants. Without support, they trail across the ground. North Carolina Extension gives garden heights of 3–8 feet [0.91–2.44 metres]. It lists a spread of 1–3 feet [0.30–0.91 metres]. Useful Tropical Plants reports stems reaching 3–20 feet [1–6 metres]. Some plants climb into the tops of tall trees. The green, compound leaves grow in an alternate pattern. They have a thin, papery feel and bear hairs.

The fruits are legumes, with green or brown pods. Their soft-looking coat hides hairs that cause intense itching. Reddish-orange hairs break free and can cling to clothes. Even dry hairs can still irritate skin. Contact may cause red skin, small bumps, or hives. Hairs in the eyes can cause serious harm. The seeds also contain substances toxic to people and non-ruminant animals. These include L-DOPA and hallucinogenic compounds. Some communities eat seeds and young pods after special preparation. Such food use does not mean raw seeds are safe.

Velvet bean grows fast in heat and humid air. It needs frost-free conditions and grows well in full sun. It also accepts some shade. Moist, well-drained soil rich in organic matter suits it. It grows in sand, loam, clay, and rocky soils. It accepts a broad soil pH range. Established plants can withstand drought. Young growth can suffer severe damage at 41°F [5°C]. Growers can raise new plants from seed.

As a summer cover crop, its dense growth helps suppress weeds. It fixes nitrogen and can improve soil fertility. It may also help suppress some root-knot nematodes. Cutting the crop at flowering avoids later contact with hairy pods. The vine hosts velvetbean caterpillars and kudzu bugs. Both pests can also harm soybean crops. Its seeds supply L-DOPA for pharmaceutical use. The plant also has a long history in traditional medicine.