This short-lived perennial or annual occurs in riparian vegetation and wetlands from the southeastern states to South America (K, W, Y); there may be significant variation (2n = 32 and 48). In the Ohio River watershed, it occurs mostly on bottomland along the largest rivers, especially the Ohio Rv. upstream to se. Ohio and w. W.Va. (K). Its range is similar to that of decurrens, but leptocarpa tends to be more restricted to persistently open areas along the banks of larger rivers, sloughs and other shorelines, "often on logs or tree bases in deep swamps" (W). It is less widespread into headwaters and ditches than decurrens. However, both species often do occur together.