Centrosema pubescens aka Mexican Butterfly Pea

Centrosema pubescens is a climber that lives for years. It belongs to the pea family, Fabaceae. Its names include centro and butterfly pea. It is native from Mexico into tropical America. It grows best in warm, wet parts of the tropics. Growers use it for pasture, green manure, and ground cover. It has also spread from farms and gardens into the wild.

This evergreen plant has soft stems and a deep taproot. Its stems trail on soil or twine through nearby plants. PFAF gives its height and spread as about 1.6 feet [0.5 metres]. Field reports note thick ground cover 1.1–1.5 feet [0.35–0.45 metres] deep. Vines can reach 6.6 feet [2 metres] with tall pasture plants for support. These sizes depend on how much support the stems find. Growth starts at a slow pace but becomes strong later. Thick cover can take four to eight months to form. By their second year, plants have a firm hold.

Centro grows in sandy, loamy, and clay soils, even poor ones. The soil can be slightly acid, neutral, or slightly alkaline. It grows in sun, light shade, or deep shade. Once rooted well, plants can survive shade that blocks 80 percent of light. It prefers moist to wet soil but copes with waterlogged ground. It does best with at least 1,500 millimetres of rain each year. Some plants in pasture survive on just 800 millimetres. It can stand three to four dry months, but not long droughts. Growth suffers below 15°C. PFAF lists USDA zones 10–12.

Farmers grow centro beneath plantation crops and in mixed pasture. It fixes nitrogen and adds plant matter as green manure. Growers in Java and Peninsular Malaysia have used it since the nineteenth century. Its use now spans much of the wet tropics. It can keep growing as plantation trees close their leaf canopy. Hard seed coats can delay sprouting. Scarification, which breaks the seed coat, can help seeds sprout. A hot-water treatment can also help.

Its strong growth poses a serious weed risk. Plants make many seeds that can sprout and escape planted sites. They form thick mats and climb trees on disturbed ground. This growth can smother other plants and stop native plants from regrowing. Plants now grow wild by roads, along rivers, and in coconut plantations. Both reference sites report no known hazards. PFAF lists no known food or medicinal uses. This does not mean the plant is safe to eat.