Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Key to Mentha

Lamiaceae

Mentha

Copy permalink to share

1 Flowers in axillary verticils subtended by ordinary foliage leaves, and separated by internodes of ordinary length.
  2 Calyx glabrous throughout, or pubescent toward the tips only; calyx 2-3.5 mm long; plants usually sterile; fresh plant usually with spearmint odor or flavor
  2 Calyx pubescent throughout its length; calyx 1.5-2.5 mm long; plants usually fertile; fresh plant usually with a rather unpleasant odor or flavor.
    3 Leaves subtending the inflorescence mostly broadly rounded at the base; leaves of the inflorescence relatively narrow; [exotic]
    3 Leaves subtending the inflorescence mostly cuneate at the base; leaves of the inflorescence relatively broad; [native, though often in weedy situations]
1 Flowers in terminal spikes or heads, the subtending leaves absent or distinctly smaller than the foliage leaves.
      4 Inflorescence a terminal globose to ovoid head of 1-3 verticils.
          6 Bracteal leaves much longer than the flowers, resembling the foliage leaves, but smaller or narrower
          6 Bracteal leaves linear to lanceolate, little surpassing the flowers.
             7 Calyx tube glabrous; leaves glabrous, or with scattered hairs on the lower surface.
               8 Petioles of the main leaves 4-15 mm long; spikes stout; plants sterile; fresh plant with peppermint odor or flavor
               8 Petioles of the main leaves 0-3 mm long; spikes slender; plants fertile; fresh plant with spearmint odor or flavor
             7 Calyx tube pubescent; leaves moderately to densely hairy on the lower surface.
                   10 Hairs of the leaf undersurface unbranched; leaves widest near the middle, slightly rugose; fertile anthers 0.28-0.38 mm long; fresh plant with musty flavor or odor
                   10 Hairs of the leaf undersurface dendritic; leaves oblong lanceolate, widest toward the base, conspicuously rugose; fertile anthers 0.38-0.52 mm long; fresh plant with spearmint odor or flavor
                 9 Leaves oblong to ovate, 1-3× as long as wide.
                     11 Leaves generally 1-2× as long as wide, ovate-orbicular, broadly rounded to subcordate at the base, obtuse at the apex; leaf serrations rounded and often turned downward (thus appearing crenate); leaf surface strongly rugose, with scattered dendritic hairs below; fresh plant with sickly or sweet flavor or odor
                     11 Leaves generally 1-3× as long as wide, ovate to oblong, broadly cuneate to rounded at the base, acute at the apex; leaf serrations sharp; leaf surface moderately rugose; fresh plant with spearmint odor.
                       12 Leaves generally oblong, with nearly parallel sides and a broadly rounded base; flowers consistently with 4 fertile anthers
                       12 Leaves generally ovate, infrequently oblong; flowers typically with all or mostly sterile anthers