Crotalaria rotundifolia

Crotalaria rotundifolia is a low-growing herbaceous legume native to the southeastern United States and the Caribbean, found in sandy, well-drained soils of pine flatwoods and open disturbed areas. It bears rounded leaves as its name indicates, along with yellow papilionoid flowers that develop into inflated pods that rattle when dry — a trait common to the genus rattlepod. The plant is adapted to fire-maintained ecosystems and poor, acidic soils.