This is a widespread northeastern species of mesic to subxeric woods, with much variation that deserves further study. Although generally distinct (2n = 28), perigynium shape and leaf width can be variable enough to confuse differences from other species (e.g. using the key in FNA 23), and some colls. should be rechecked. Several colls. from the Bluegrass or adjacent hills (BATH, FAYE, JESS, GARR & OLDH at KY, etc.), and perhaps elsewhere (CLAY, HARD & LAUR at KNK or DOV), have relatively narrow leaves. Some robust colls. from Appalachian regions are provisionally treated here as amplisquama; see notes under that name.