This is not easily distinguished from typical muhlenbergii, and it has also been confused with aggregata. Colls. that have been named var. enervis in Ky. have been tentatively assigned here to either of those two species. MacKenzie (1940) considered these plants a species (= C. plana MacKenzie) typical of calcareous soils, but F noted typical muhlenbergii "passing insensibly into the relatively unimportant var. enervis." FNA 23 indicates that the perigynia (2.7-3.1 mm versus 3-4.2 mm) and scales (2-2.5 mm versus 2.5-3.6) are relatively short and veinless adaxially (versus often veined in typical plants). The illustration in FNA suggests a more open spike, with typical muhlenbergii more congested (somewhat resembling cephalophora). Var. enervis may be typical of richer soils, sometimes appearing in pastures and lawns, as does aggregata.