This largely southeastern taxon is centered in Appalachian regions, in contrast to typical laeve, which is largely midwestern. The only clear difference in concinnum from typical laeve is its narrower, less clasping leaves, but it has been considered a distinct species in some treatments (F, Cr, W). There may be intergradation in Ky., as reported by B. Across its whole range (which remains poorly documented), concinnum may prove to be a miscellaneous group of narrow-leaved variants adapted to local conditions, especially on non-calcareous or highly leached soils. Relatively extensive and distinctive populations in Ky. are documented only on rocky sandstone banks of the Rockcastle, Cumberland and Big South Fork Rivers.