Woolly rattlepod

Crotalaria incana, the woolly rattlepod or shake-shake, is a softly hairy annual or short-lived perennial herb in the legume family (Fabaceae). The species is pantropical in distribution, naturalised across the Americas, Africa, Asia, and Australia, and grows mainly in disturbed ground in seasonally dry tropical regions. Plants reach 0.6 to 1.5 meters in height, with grey-pubescent stems and trifoliolate leaves whose obovate leaflets are 2 to 5 centimeters long and conspicuously hairy beneath. The yellow papilionaceous flowers, sometimes streaked or veined with brown or purple, are borne in terminal racemes. After fertilisation the calyx persists around an inflated, oblong pod 2.5 to 4 centimeters long that turns black when ripe; the loose seeds rattle inside the dry pod, giving rise to the common names. The whole plant contains pyrrolizidine alkaloids, principally monocrotaline, that are hepatotoxic and pulmonary-toxic to livestock and humans, and the species is regarded as a contaminant of cereal crops and pastures.