This shrub occurs mostly in dry woods of Ozarkian and Appalachian regions, but the range is fragmented and disjunct populations are scattered across southeastern states (K). T. prinophyllum may be expected in w. Ky., since it is known from s. Ill. (ML), but some reports from c. Tenn. have been erroneous (K, Ch). There has been some confusion with periclymenoides, which may hybridize, and with canescens, which Gm reported from GRNP but probably based on prinophyllum. In Ky., prinophyllum flowers mostly in May. Both canescens and prinophyllum may be part of a distinct clade with densely pubescent bud-scales (versus glabrous or sparsely pubescent) and with flowers emerging before or with the leaves (versus before, with or after leaves). However, these characters are not clear-cut and hybridization may complicate the situation.