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Wisconsin Plant of the Week

Pycnanthemum virginianum (L.) T.Durand & B.D.Jacks.ex B.L.Rob. & Fern.

Lamiaceae (Mint Family)

Common Name:

mountain mint


Mountain mint is a native perennial of sunny plant communities.  It grows in dry to wet prairies and calcareous fens, usually among taller grasses, so that walking through a field one usually notices the minty odor of crushed plants before seeing them. Mountain mint tolerates disturbance and is one of the last natives to remain after weedy species invade.  It spreads by seed and rhizomes.

Plants are from 1 to 3 feet tall with a flat-topped flower arrangement that blooms from July through September.  Small white flowers are crowded into dense heads.  The flower petals are about 1 mm long.

The leaves are simple, narrowly lance-shaped, smooth and arranged opposite each other on the stem.  Lower leaves may be up to 6 cm long; leaves in the flower clusters are more closely spaced and shorter.  The stem is square with hairs only along the angled edges.

Typical characters of the mint family are aromatic oils, a square stem, opposite leaves and flowers with 4 stamens -- 2 pairs of different lengths. Note: not all mints have an odor or a square stem, and square stems occur in other species too. The mint family is most similar to  the verbena family -- but itís easier to learn the individual species than to see the small floral features that distinguish these two groups.

Mountain mint leaves can be used for a tea and the flowers attract butterflies.

  • Origin of the name: Pycnanthemum, Gr., puknos, thick or dense; anthemis, Gr., flowery, refers to the dense flower heads; virginianum, L. from Virginia
  • Range:  ME to ND, s. to OK, GA
  • WI Range:  Statewide
  • Common associates: Switchgrass, bluejoint, blazingstar, winged loosestrife
  • Wetland Indicator Status: FACW+
  • Coefficient of Conservatism: C = 5 (S&W), C = 5 (MI)
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