Lycopus americanus Muhl.

Lycopus americanus plant

Family - Lamiaceae

Stems - To 1m tall, erect, branching, 4-angled, herbaceous, from fibrous roots and horizontal rhizomes, glabrous except for tufts of hairs at nodes in leaf axils, with rounded angles, hollow, with single vertical groove on each flat side of the stem.

Leaves - Opposite, decussate, sessile or short-petiolate, pinnately lobed below, becoming nearly entire near tip of stem, to +/-12cm long, 7cm broad, glabrous or sometimes scabrous near base of blade, opposite leaves connected by a thin hairy strip of tissue which encircles the stem.

Lycopus americanus leafFresh leaf.

Pressed leaves.

Inflorescence - Verticillasters in the upper 2/3 of the stem. Each cluster of a leaf axil with +/-20 flowers. Flowers sessile.

Lycopus americanus inflorescenceA good view of the verticillasters.

Flowers - Corolla whitish, to 3mm long, glabrous externally, with dense tufts of hairs near apex of tube internally, subequally 4-lobed. The lobes rounded, -1mm long. Stamens 2, exserted, adnate at apex of corolla tube. Filaments to 2mm long, white, glabrous. Anthers pale yellow or with a purplish tinge, .4mm broad. Style exserted, to 3mm long, white, glabrous, expanded slightly at base. Stigma 2-lobed, often with a purplish tinge. Ovary 4-lobed. The lobes deep purple with whitish glands at apex. Calyx green, glabrous, the tube to 1mm long, 5-lobed (weakly bilabiate). Lobes acuminate, to 1.3mm long, the lower 4 with minute teeth on their margins. The single upper lobe (tooth) shallowly notched at the apex.

Lycopus americanus flowerFlower close-up.

Flowering - June - October.

Habitat - Moist to wet locations.

Origin - Native to U.S.

Other info. - This is a common plant along pond, lake, and stream margins. The plant typically has green stems but if grown in harsh conditions the stems will become reddish-brown. Although this plant is in the mint family it has no minty odor. The leaves and small white clusters of flowers make this species easy to ID in the field.

Photographs taken at the Kansas City Zoo, 7-15-99, in Van Buren, MO., 6-16-01, and in Pictured Rocks National Seashore, MI., 7-21-02.


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