This species is endemic to e. Ky., where it has been found at about 90-140 sites under sandstone cliffs of the Red Rv. Gorge, in three counties (MENI, POWE, WOLF) at the edge of the Appalachian Plateaus (Braun 1942, Campbell et al. 1989, White & Drozda 2006, USFWS 2016). Although soils under these cliffs are derived largely from infertile acid sands, relatively high nutrient levels can occur locally due to evaporative processes and due to imported deposition from aerial or zoological sources (Walck et al. 1996; Francis 1998). Only about 10 sites have excellent quality (A in Natural Heritage terms). Some populations have been eliminated or much reduced by excessive recreational disturbance. It has recently become delisted as a Federally Threatened Species, but it remains truly rare in global terms and it would continue to be threatened without careful monitoring and management (USFWS 2016). S. albopilosa is a tetraploid (2n = 36) that probably diverged from typical flexicaulis, sensu lato, which has diploids and tetraploids (Cook & Semple 2008). Phylogenetic analysis has been complicated by variation within flexicaulis; using RAPD bands Esselman (1996, Figure 26) indicated that albopilosa is closest to an "Indian Creek" sample of flexicaulis, but not to the main cluster of samples (which were closer to caesia). Morphological analysis needs to be combined more with molecular analysis; superficially, albopilosa appears closer to flexicaulus sensu stricto than to the "Appalachian variant" (S. latifolia L.), S. albopilosa differs from flexicaulis sensu lato as follows (Braun 1942, Esselman 1996; FNA 20, W): larger leaf blades 2-6 cm long (versus 8-20 cm); stems densley villous with spreading white hairs (versus glabrous to moderately hairy, the hairs not especially long or white); leaves relatively thin and translucent; most lower leaves usually retained on flowering stems (versus lost).