Mapping here is highly provisional; further review of the loomisii - incanum - pycnanthemoides group is needed. In calyx and pubescence patterns, loomisii appears somewhat intermediate between incanum and pynanthemoides, but Chambers (1993) and others have indicated that it is a distinct but cryptic diploid (2n = 38) species with a southeastern range east of the Mississippi Rv. (and mostly east of albescens). The best supposedly diagnostic character remains somewhat obscure: compared to pycnanthemoides, loomisii tends to have smaller seeds with a smoother surface (F, Cr, W).