Strophostyles helvola

Strophostyles helvola, the trailing wild bean or amberique bean, is an annual to short-lived perennial herbaceous vine in the legume family (Fabaceae) native to eastern Canada and the eastern United States, reaching the Great Plains in the west. The slender stems trail or twine to 3 meters or more and are lightly pubescent throughout. Leaves are alternate and pinnately trifoliolate; each leaflet is ovate to lanceolate and often shallowly to deeply three-lobed, giving a characteristic fiddle-like or rabbit-ear silhouette. The papilionaceous flowers are borne in short, head-like clusters on long axillary peduncles raised above the foliage; each flower is pink to rose-purple, fading to a creamy yellow with age, and has a gradually inward-curving keel petal - a diagnostic feature for the genus. The fruit is a slender, cylindrical pod up to 10 centimeters long that twists open explosively at maturity to fling the shiny black, hairy-coated seeds; the seed-coat hairs allow flotation and water dispersal in the species' frequent dune and riverbank habitats. The plant pioneers disturbed sandy ground, dunes, riverbanks, and old fields and tolerates dry or moist conditions.