This annual is scattered widely across eastern states and Central America, but probably just adventive in northern states. In Ky. it has sometimes been misidentified as C. purshii DC., which occurs further south (M). Plants contain unusual pyrrolidizie alkaloids, which are lethally toxic to livestock but have been used for narcotic and medicinal purposes (Moerman 2009, Roeder et al. 2015). These alkaloids (monocrotaline, spectabiline) may be known only from the genus Crotolaria.