Pycnanthemum tenuifolium Schrad. - Slender Mountain Mint

Pycnanthemum tenuifolium plant

Family - Lamiaceae

Stems - To +80cm tall, erect, herbaceous, multiple or single from base, branching, 4-angled, glabrous, from thin rhizomes.

Leaves - Opposite, sessile, entire, linear, acute, to 5.5cm long, 2-4mm broad, glabrous, dark green above, lighter green below, punctate.

Pycnanthemum tenuifolium leaves

Inflorescence - Compact corymbose arrangement of glomerules. Glomerules +/-7mm broad, 4mm tall(long), with an involucre of attenuate pubescent bracts. Bracts 3-4mm long, 2mm broad, with densely ciliate margins, reduced inward. Flowers sessile.

Flowers - Corolla white to pinkish, bilabiate. Corolla tube to -5mm long, pubescent externally near apex. Upper lip single-lobed. Lobe to 2.6mm long, 1.4mm broad, emarginate, pubescent internally and externally. Lower lip 3-lobed, with faint pinkish spotting. Central lobe longer than lateral lobes, to 2.5mm long, 1.2mm broad, pubescent internally and externally. Stamens 4, didynamous, adnate at apex of corolla tube. Filaments to 1.9mm long, white, glabrous. Anthers pale lilac, .4mm broad. Style white, to 6mm long, glabrous, long exserted, tuberculate and expanded just above ovary. Stigma 2-lobed. Ovary 4-parted, green, glabrous. Calyx tube 2.7mm long, lanate, 4-lobed. Lobes equal, acute, to 1.1mm long, short pubescent to glabrous externally, glabrous internally. Nutlets dark brown at maturity, to 1mm long.

Pycnanthemum tenuifolium flower

Flowering - June - September.

Habitat - Dry rocky open woods, prairies, wet thickets, meadows, streambanks, roadsides, railroads.

Origin - Native to U.S.

Other info. - This species is common throughout the entire state of Missouri.
This member of the mint family is easy to recognize because of its thin dense leaves and its dense small flower clusters (glomerules). Insects like to visit the plant to retrieve nectar. The leaves and stem have a strong minty odor and the plant can be brewed as a tea.

Photographs taken in St Clair County, MO., 6-25-04.


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