This annual is widespread across warmer southeastern regions on seasonally dry to damp sites with varied substrates. It is sometimes hard to distinguish from purpurea, and has been treated as a variety in Tenn. (Robinson 1960). However, typical fasciculata may generally differ in several characters that deserve further attention (F). It differs from purpurea and allies in its vegetative form (W): stems appearing copiously leafy because of the well-developed fascicles of axillary leaves (versus not copiously leafy, the axillary fascicles absent or poorly developed). Although pubescence varies in both species, typical fasciculata has denser hairs on stems, and D. Estes (pers. comm.) has shown that in Tenn. and Ky. it has a distinctive line of hairs along each midrib of calyx teeth.