This is widely scattered across eastern states, but concentrated on relatively infertile acid soils of the southeastern Coastal Plain; more interior populations are generally disjunct (K; Thomas 2017). In Ky. and Tenn., longifolia occurs mostly on hydroxeric streamhead flats and meadows of the southern Cumberland Plateau. It is reasonably treated as a distinct species (see also W), but it has often been treated as a variety of rigidulum (e.g. FNA 25). These species and others in Panicum section Agrostoides have recently been transferred to the genus Coleataenia (Weakley et al. 2011; and their citations). Although this genus is a reasonable segregate, the whole process of dismantling Panicum has further to go. Confusion could result from adopting partial changes for Ky. until the process is completed.