Northern Prairie Wildlife Research Center
References:
Henderson, N. C. 1962. A taxonomic revision of the genus Lycopus. Amer.
Midl. Naturalist 68:95-138.
Hermann, F. J. 1936. Diagnostic characteristics in Lycopus. Rhodora 38:
373-375.
| Lead | Characteristic | Go To |
| 1 | Calyx lobes slender, firm, sharply pointed, 1-3 mm long, surpassing the nutlets. | Lead 2 |
| 1 | Calyx lobes broad, triangular to ovate, soft, obtuse to bluntly acute, 0.5-1 mm long, shorter than to about equaling the nutlets. | L. uniflorus |
| 2 | Nutlets rounded apically on the outer margin, mostly 1-1.5 mm long; leaves short-petioled to subsessile, the blades irregularly incised-toothed to subpinnatifid. | L. americanus |
| 2 | Nutlets truncate apically on the outer margin, mostly 1.5-2 mm long; leaves sessile, the blades rather regularly and coarsely serrate. | L. asper |