This species is a high polyploid (2n = 120-170) that is sometimes difficult to distinguish from the more widespread pubiflorum (FNA 25). Both have southeastern ranges, but pubiflorum extends further inland, and occurs on relatively fertile soils. P. floridanum differs in its rhizomatous habit with erect culms, 8-21 dm tall (versus stoloniferous, 3-13 dm tall); its spikelets are strictly glabrous (versus often hairy), usually larger (2.9-4.3 x 1.9-3.1 mm versus 2.5-3.6 x 1.3-2.4 mm), more or less suborbicular (versus elliptic to obovate), with upper florets often golden-brown (versus just pale to tan). Var. floridanum itself is relatively hairy, and generally associated with acid soils (including pinewoods further south). It appears to be rare in Ky. (F). A related species, P. bifidum (Bertoloni) Nash, is known mostly from longleaf pine savannas but extends north to sandy soils of se. Mo. and w. Tenn.