This was recognized as a species by Sm and F but it has been largely overlooked for 50 years. Its stoloniferous habit, small basal leaves, and pubescence patterns (with mostly eciliate paleae) are generally distinctive (Campbell & Seymour 2013). R. tenax occurs mostly on the Interior Low Plateaus, also on the southern Cumberland Plateau, southern Ridge & Valley, and locally central Gulf Coastal Plain; it grows typically in dry rocky glades and open woodlands on base-rich soils. Some colls. come from roadsides on sandy uplands of the Cumberland Plateau, where there appears to be hybridization with typical fulgida, but these populations are probably somewhat adventive and promoted by imported limestone gravel; similar adventive plants may exist in Mo. (Ladd & Thomas 2015). There may be also some intergradation with deamii, speciosa and truncata; see notes under those species.