This ranges across east-central states, with a concentration in Appalachian regions (FNA 25, K); closely related plants in East Asia are now considered to be a distinct species (curviaristata). M. tenuiflora is most similar to sobolifera, and there may be intermediates (e.g. the coll. from HEND at EKY). In general, tenuifolia is restricted to more or less acid sandy soils; sobolifera is most abundant on calcareous soils but also occurs on moderately base-rich inclusions within non-calcareous landscapes. Distinction of tenuiflora from some other species can be difficult. Some possible transitions to sobolifera within southern Appalachian regions have been named var. variabilis (Scribn.) R.W. Pohl; these have sheaths and stems virtually glabrous, and lemmas with awns only 0-4 mm long (Cr, J). Distinction of tenuiflora from sylvatica can also be difficult; the detailed keys of FNA 25 and W are useful. Colls. from GARR and JESS match tenuiflora in their relatively short abruptly tapering glumes, but sylvatica in other characters. Note also that M. tenuiflora has sometimes been confused in name with M. tenuifolia (Kunth) Trin., which is a western species; see switched maps in FNA 25 (1st printing).