This tall grass, (4)8-14(17) dm, occurs mostly in thin woods or full sun on wet acid soils from the mid-Atlantic coastal plain to the Appalachian Plateaus (FNA 24). Within Calamagrostis, the name C. coarctata (Torr.) Eat. had priority, but a proposal for conservation of cinnoides was pending (FNA 24; W). However, the new genus Greeneochloa has been recently defined for this species, based largely on DNA data, by Peterson et al. (2019), who differentiated it from Calamagrostis in "having hairy ovaries, extravaginal shoot innovations, flat leaf blades, and panicles contracted usually with ascending tightly appressed or slightly spreading branches." There is only one other species currently recognized: G. tweedyi (Scribn.) P.M. Peterson, Soreng, Romasch. & Barberá, which occurs in Oregon, Washington and Montana. G. coarctata differs from native Calamagrostis in southeastern states (excluding Ammophila) as follows (W): awns attached on the upper 2/5 of the lemmas, 0.5-2 mm long, straight (versus on lower half of lemmas, 0.9-6 mm, straight or bent). But is this new genus reasonable, and should Ammophila also be recognized?