This occurs mostly in mid-Atlantic states, northeastern states and adjacent Canada, especially in dry sandy woodland and grassland (R.J. LeBlond in W); it has recently been confirtmed in Mo., where it is locally common in "remnants of the once extensive sand prairie communities in southeastern Missouri" (Thomas 2015, 2017). A few Ky. colls. have been referred to Panicum tsugetorum Nash (with longer spikelets), which is combined in recent treatments. The species has often been confused with meridionale, acuminatum, lindheimeri and other close relatives. It has been recently treated as a largely northeastern subspecies of acuminatum (FNA 25). But, as in commsonianum and ovale, columbianum differs from acuminatum (and villosissimum) in its lower and basal sheaths possessing a double vestiture of relatively long (0.3-3.7 mm) and short (0.1-0.4 mm) hairs or just short hairs (versus hairs mostly 0.4-3.8 mm); see also Hitchcock & Chase (1950), Y and W. Also, columbianum (as in its close southern relative D. portoricense) has distinctive "crisp-puberulent:" internodes (W). The columbianum complex (perhaps including commsonianumm and meriodonale) may be allied with D. leucothrix (Nash) Freckman and other southern taxa in a broadly defined Ensifolia clade, based on analysis of DNA (Majure et al. 2003). However, morphology of the columbianum complex generally suggests affiliation with the acuminatum complex; it is possible that hybridization has been involved in the phylogeny.