Round-leaf cassia

Chamaecrista rotundifolia, the round-leaf cassia, is a short-lived perennial or sometimes annual herb to subshrub in the Fabaceae (subfamily Caesalpinioideae) native to tropical and subtropical America from the southern United States through Central and South America and the Caribbean. It is widely cultivated and naturalized as a pasture legume and cover crop in tropical Africa, Asia, and Australia. Plants are prostrate to ascending, 20 to 80 centimetres long, with slender, often reddish, finely pubescent stems. The alternate, pinnate leaves bear a single pair of broadly obovate to nearly circular leaflets 1 to 3 centimetres long with an asymmetric base, sensitive to touch and to nightfall. The bright yellow, slightly asymmetric flowers are solitary or paired in the upper axils, with five spreading petals and ten unequal stamens. The fruit is a flat, linear pod 2 to 5 centimetres long that dehisces elastically to disperse small dark seeds.