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These are mostly very aromatic plants, a pleasure to crush in the field and scenting even a herbarium case. The corollas are white, generally dotted or tinged with a pink or purple shade.

1. Main stem (except sometimes at nodes) pubescent only on the angles or glabrous; leaves all or mostly not over 7 mm wide (rarely to 13 mm); outermost bracts of heads pubescent (if at all) only on lower surface and margins.

2. Calyx lobes with distinct subulate tip glabrate at least on upper side; stem glabrous.

P. tenuifolium

2. Calyx lobes with tip not subulate but densely white-pubescent; stem pubescent on angles with spreading and/or incurved hairs.

P. virginianum

1. Main stem pubescent on all sides; leaves often over 7 mm wide; outermost bracts of heads finely pubescent on both surfaces (only on lower surface in P. muticum).

3. Leaf blades on distinct petioles at least 2.5 mm long; inflorescence somewhat open, the branches evident.

P. incanum

3. Leaf blades sessile or essentially so; inflorescence dense and head-like.

4. Principal leaves less than 3 times as long as broad; outermost bracts of heads glabrous on upper surface.

P. muticum

4. Principal leaves over 3 times as long as broad; outermost bracts of heads pubescent on both surfaces.

5. Leaves pubescent beneath on surface as well as veins; involucral bracts merely acute.

P. pilosum

5. Leaves pubescent beneath only on main veins; involucral bracts shortly acuminate.

P. verticillatum

All species found in Pycnanthemum

Pycnanthemum incanumHOARY MOUNTAIN MINT 
Pycnanthemum pilosumHAIRY MOUNTAIN MINT 
Pycnanthemum tenuifoliumSLENDER MOUNTAIN MINT 
Pycnanthemum verticillatumWHORLED MOUNTAIN MINT 
Pycnanthemum virginianumCOMMON MOUNTAIN MINT 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 28, 2017. http://michiganflora.net/genus.aspx?id=Pycnanthemum.