Abstract
Trillium sulcatum, a new species with two petal color forms, was first circumscribed by Barksdale as a variety in 1938, but without a Latin diagnosis. It superficially resembles the mainly northernT. erectum and appears to be closely related to the primarily midwesternT. flexipes. Its distinguishing features are ringent flowers, short sepals, and long pedicels; additional characters are presented in a chart contrasting it with species with which it has been confused. Distribution suggesting relictual significance is documented. Except that intermediates withT. flexipes are occasional,T. sulcatum maintains its distinctiveness throughout its southern Appalachian range.