Lycopus americanus is a perennial herb 30-90 cm tall, stems 4-sided, colonial from long rhizomes, stems 4-angled.
Leaves opposite, short-stalked, blade lance-shaped, 3-8 cm long, 2-4 cm wide (Radford et al. 1968), mostly pointed at both ends, margin with large, irregular, often blunt-tipped teeth, teeth larger toward leaf base, sometimes lobed at base, surface sprinkled with tiny dots (glandular-punctate), hairy only on vein axils below.
Flowers white, tiny, tubular, hairy inside, petal lobes 4, to 0.3 cm long; calyx 0.3 cm, lobes 5, linear, stamens white to slightly purple, longer than corolla; stigma 2-lobed, often slightly purple, ovary purple, 4-parted (Yatskievych 2006); flowers embedded in small bracts, in tight axillary clusters that surround stem; blooms June-Sept.
Fruit dry, 4 nutlets surrounded by old calyx, each wedge-shaped, one side flat, other side rounded, top oblique; fruits Oct.
Wetland status: OBL.
Frequency in NYC: Occasional.
Habitat: Open or part-shaded wet soil, ditches, swamp forests, pond edges, wet roadsides.