This southern Appalachian species occurs mostly west of the Blue Ridge. In Ky., many plants appear transitional to the more northeastern erectum, and current reassmment using DNA data indicates little distinction across the range (A. Floden, pers. comm.). The combination T. erectum var. sulcatum Barksdale is available if desired. However, other authors have insisted that these two taxa should be treated as separate species (Patrick 1984; FNA 26; W); 2n = 10 in both (as in all Trillium), but chromosomes differ in morphology (Hill 2005). T. sulcatum is distinguished by its cup-shaped flowers, with "petals carried somewhat forward to recurved-spreading in distal half, ovate to broadly ovate-overlapping" (versus "spreading, carried in same plane as sepals or ascending, slightly lanceolate, ovate-lanceolate, or occasionally ovate"); it has larger stamens (15-18 mm long versus 5-15 mm) and ovaries (14-18 mm long versus 5-10 mm); its smell is "faintly musty, like fresh fungus" (versus "fetid, like a wet dog"); pedicels are relatively long and often flexed or declined (versus erect). Flowers are usually maroon (petals) and purple (sepals); a few paler colls. Are referable to forma albolutescens Patrick (e.g. from CART and HARL at KY). Without flowers, leaves may be tentatively distinguished by their "obovate to broadly elliptic shape" (versus "broadly rhombic to ovate-rhombic").