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Key to Lycopus

Lamiaceae

Lycopus

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1 Calyx lobes acute at the apex, shorter than or equaling the nutlets.
  2 Plant without tubers; leaf base tapered to a long, winged petiole; corolla lobes 4, erect; leaf teeth (6-) avg. 8.6 (-11) per side
  2 Plant usually with tubers; leaf base subsessile or tapered to a short, winged petiole; corolla lobes 4 or 5, all or some spreading; leaf teeth (2-) avg. 5.0 (-7) per side.
    3 Corolla lobes 4, one erect and three spreading; nutlet tubercles well-developed, deeply toothed; leaf teeth (2-) avg. 4.5 (-6) per side; [Fall-line Sandhills of NC and SC]
    3 Corolla lobes 5, spreading; nutlet tubercles weakly developed, undulate; leaf teeth (4-) avg. 5.4 (-7) per side; [Mountains, upper Piedmont, and VA Coastal Plain]
1 Calyx lobes acuminate to subulate-tipped, much exceeding the nutlets.
      4 Nutlet tubercles not developed or only weakly so.
        5 Calyx 2.0-3.3 mm long; stems and branches glabrous to sparsely pubescent with hairs < 0.5 mm long; leaf teeth sharply acute to short-acuminate
        5 Calyx 3.0-4.5 mm long; stems and branches densely to sparsely pubescent with hairs 0.5-1.6 mm long; leaf teeth blunt to acute
      4 Nutlet tubercles well developed (appearing as 4-5 knuckle-like knobs.
          6 Leaves evidently petiolate, the petioles narrowly winged; collectively widespread in our region].
             7 Calyx lobes subulate, apex acute; leaves pubescent with short eglandular, and also densely distributed short stipitate-glandular trichomes, especially distal vegetative parts; [West Gulf Coastal Plain]
             7 Calyx lobes triangular, attenuate to acute apex; leaves glabrous, glabrate, canescent or pubescent, sometimes densely so throughout; [widespread in our region]
          6 Leaves sessile or subsessile; [mainly Coastal Plain, scattered and disjunct inland].
               8 Leaves ovate to lanceolate, usually rounded at the base, scarcely reduced upward on the stem, occasionally glandular pubescent
               8 Leaves lanceolate to linear, cuneate at the base, upper leaves conspicuously narrower (and often also shorter) than the lower leaves, typically glandular pubescent