This variable species is widely scattered across eastern North America, but strongly concentrated in Atlantic states and the Great Lakes region (F, K). In Ky. it is largely restricted to wet acid soils on the southern Appalachian Plateau and on the Mississippi Embayment. Also expected in Ky. is a related species, J. brachycephalus (Engelm.) Buchenau (= J. canadensis var. brachycephalus Engelm.); 2n = 80 in both taxa (FNA 22). This may be particularly close to subcaudatus (see below), and a deeper review of colls. in the canadensis group is needed to check identifications. J. brachycephalus occurs mostly in northeastern states and adjacent Canada, but there are scattered records south to Ga., Ala. and Okl. (K, W). Unlike canadensis, it occurs mostly on calcareous soils.