This taxon occurs in the lower Mississippi Valley. Distinction from septentrionalis is tentative in some colls. from Ky. It may be better treated as var. arkansanas (Fern.) Steyermark & Kucera; both taxa are probably tetraploids with 2n = 40 (FNA 24). The only clear difference is that in arkansana lemmas are hispidulous (hairs ca. 0.1 mm long) versus scabrous (ca. 0.05 mm). Panicles and spikelets may be smaller on average but there is much overlap.