This is known mostly in or near the southern Appalachians, but there are disjunct populations in southeastern states from e. Ark. to n. Fla. (PL). There has been confusion with Z. aurea (and perhaps with Thaspium trifoliatum in name); see W for a detailed key. No verified colls. of Z. trifoliata from Ky. have been located (M), but there have been some authoritative reports (e.g. Gl, Cr), and it is known from adjacent counties of w. Va.