Teucrium canadense is a perennial herb, colonial from shallow rhizomes, stems mostly unbranched, but often in large stands (Hilty 2006), to 1 m tall, finely hairy, solitary, 4-sided, hollow.
Leaves opposite, stalks hairy, to 1.5 cm long, blade 5-12 cm long, hairy below, lance-shaped to oblong, base blunt, surface often puckered by deeply impressed veins, margin toothed (Yatskievych 2006).
Flowers purplish, bilaterally symmetrical, tubular, to 1.8 cm long, very irregularly 2-lipped, appearing 1-lipped due to very enlarged lower lip, acting as a landing site for insect visitors, upper lip 2-lobed, appearing lateral as part of lower lip; stamens 4, of two lengths, arching upward from petal tube; inflorescence a crowded spike, 5-20 cm long with narrow bracts, at top of stem, blooms June- Aug. Pollinated by several bees, infrequently by hummingbirds (Hilty 2006).
Fruit dry, of four small nutlets.
Wetland status: FACW-.
Frequency in NYC: Infrequent.
Habitat: Wet shade, swamp edges. Soil pH 4.5-8, tolerant of anaerobic soils, moderately tolerant of shade, intolerant of salt and drought (USDA 2006).
Notes: Winter plant with raceme of bell-shaped, 2-lipped, 5-lobed calyx remains, and large, dry opposite leaves (Levine 1995). Plants apparently very bitter and not eaten by mammals (Hilty 2006). Although Teucrium has been used medicinally, the aromatic, bitter furano neo-clerodane diterpenoids in Teucrium may cause liver damage (Sundaresan et al. 2006).