American sicklepod

Senna obtusifolia, commonly called American sicklepod or Chinese senna, is an annual herb or short-lived subshrub of the legume family (Fabaceae) reaching 0.5–2 m in height. The pinnate leaves bear three pairs of obovate, blunt-tipped leaflets 2–6 cm long that fold together at night. Bright yellow, five-petalled flowers about 1–1.5 cm across are borne singly or in pairs in the leaf axils. The fruit is a long, slender, sharply curved pod 10–20 cm long — the sickle shape that gives the species its name — splitting at maturity to release numerous shiny, rhomboidal brown seeds. Native to the Americas, the plant has become widely naturalised in Africa, Asia and Oceania, often regarded as a troublesome weed in pastures and arable land up to about 1100 m elevation.