This is known mostly in or near the southern Appalachians, but there are disjunct populations in southeastern states as far south as n. Fla. (K, W). There has been confusion with Z. aurea and with Thaspium trifoliatum in name; see W for a detailed key. No verified colls. of Z. trifoliata from Ky. have been located despite several colls. initially identified as this species (M). Some misidentified colls. have continued to be listed on SERNEC in 2025. However, there have been a few supposedly authoritative reports of Z. trifoliata (e.g. Gl and Cr but not F), and the species is known from adjacent counties of w. Va.