Pycnanthemum tenuifolium

slender mountain-mint, narrowleaf mountainmint, slender mountainmint, slender mountain mint, common horsemint
Family

Lamiaceae

Leaf Arrangement

opposite

Leaf Attachment

sessile

Leaf Type

simple

Leaf Shape

linear, elliptic

Growth Form

forb

Flower Color

blue, pink, purple, white

Flower Month

May - October

Height (meters)

0.4 - 1.2

Milky Sap

No

Armed/Unarmed

Unarmed

Origin

native

Lifespan

perennial

Growing Season

Warm season


Wetland Class

FACW

Prairie Coefficient of Conservatism

7

Field Characters

Pycnanthemum tenuifolium can be confused with Houstonia nigricans which has narrow leaves, 4-angled stems, and small white flowers. They can be distinguished by their flowers which are terminated by four small retangular lobes in H. nigricans and a two lipped corolla in P. tenuifolium. Another species of Pycnanthemum, P. albescens, has leaves that are 1 1/2" long by 1/2 " wide (nearest the middle). The terminal one-half to two-thirds of each margin has six to eight widely spaced shallow teeth. The upper leaf surfaces of lower leaves are dull olive green and the lower surfaces are greenish gray. The upper leaves and inflorescence bracts are conspicuously whitened with a dense but thin coating of grayish-white hair.

Cultural Information

May be propagated by cuttings and division. Seeds need no treatment but are slow to germinate. Steffen (1979) recommeds cold/dry stratification which may speed germination. Dried heads can be clipped into paper bags and shaken to remove seed. Seeds average approximately 6,400,000 seeds/lb.

Animal Use

Not considered to be valuable as forage for livestock, although they are rated as good deer-food plants and as good seed producers for wildlife. They also attract pollinators.

Natural History

Where the common name "mountain mint" comes from is not clear as this species ranges throughout the central intermountain area of the United States. The leaves of mountain mint were used by prairie Acadians to make tea.

Habitat

Grassy moist open woods, bogs, savannahs, old fields, meadows, marshes, upland woods, dry soil in prairies, pastures, and roadsides.