This annual is widespread from eastern states to tropical America, but largely restricted to open or disturbed ground on dry acid soils. Several Ky. colls. have been referred to var. setigera Fern. & Grisc., including some from BULL, ESTI, LETC, MCRA, METC and WAYN (B, Anderson 1947); see also M. However, that largely midwestern taxon has not been recognized in recent treatments. See references in W for justification of the recent revival of this genus and of its priority over Diodia of Small.