This widespread North American species is close to anthelatus, interior, dichotomus, secundus and other taxa; there are frequent difficulties in identification and some indications of hybridization. But R.E. Brooks (FNA 22) valiently maintained these all as species, in contrast to Cr. J. tenuis and anthelatus are distinguished from others of this group in Ky. by their longer whitish membraceous auricles (ca. 1-4+ mm versus < 1 mm), but no other clearly defined differences are known. There may still be much variation to explore within tenuis; reportedly 2n = 30-84 versus just 80 in most others (or often 84 in dudleyi). Diversity of inflorescence branching patterns, in particular, deserves deeper analysis for potential diagnostic use.