This widespread northern species can be confused with typical virginicus without flowers or fruits, through it is often distinctly tuberous (versus rarely so in virginicus); see F, Y, W. Extensive hybridization is known where ranges overlap (Cr; Henderson 1962, Thomas 2017). For Ky. the only definite record is a coll. of B from ROWA (US). There is also a somewhat immature coll. from KENT (KNK) that may be uniflorus (BT), and an apparent hybrid with virginicus from EDMO (US).