In its broad sense, this species occurs locally in or near several southern Appalachian regions (from Ky. and Va. to Ala. and S.C.), mostly on streambanks and seeping slopes and especially near cliffs (FNA 3, W). In Ky. it occurs only under sandstone cliffs at the western edge of the Appalachian Plateaus, and further west at a few disjunct sites along the "Pottsville Escarpment" of the Shawnee Hills. Most or all colls. mapped here match the description of T. mirabile Small, but that taxon does not seem to be clearly distinct from plants that have been named clavatum in Ky. Typical clavatum, sensu stricto, may be restricted to more eastern regions, where it often occurs on open slopes, rather than just under cliffs. The recorded range of mirabile is largely restricted to the Cumberland Plateau, with a concentration in nw. Ala. (FNA 3, K). It has been distinguished mostly by its shorter achenes (ca. 2.5-4 mm long versus 3-5 mm), which are about equal to the longer stipe (ca. 2.5-3.5 mm versus ca. 1-3 mm) and have a straight upper margin (versus concave). But the achene character is often mixed or intermediate within populations. It is reported that mirabile also tends to have shorter stamen filaments (2-3 mm versus 2.5-4 mm). Walck (2000) found that a population in POWE has the same chromosome as reported for clavatum; 2n = 14. Variety status, at most, may be reasonable instead of species. In FNA 3 (1997), M. Park & D. Festerling stated: "Thalictrum mirabile is very similar to T . clavatum. Field studies are in progress to clarify the status of this species." However, no such studies have been published so far.