Prunella vulgaris is a perennial herb, to 50 cm prostrate to suberect from creeping rhizome, tufted, stems sparsely or not branched, square, two side grooved, angles rounded.
Leaves opposite , stalk 1-3 cm long, slightly winged, blade narrowly elliptic, to 9 cm long, 4 cm wide, lower leaves broadest, base of blade tapering to stalk, margin entire or vaguely toothed.
Flowers purple, bilaterally symmetrical, petal tube 2-lipped, upper lip helmet-shaped (galeate), mostly unlobed, lower lip 3-lobed, shorter than upper lip; stamens 4, filament tips ca 2-toothed; calyx 0.7-1 cm long, green-purple, hairy, 2-lipped, 5-lobed, upper lip shallowly 3-toothed, lobes pointed; flowers interspersed with hairy, broad-based bracts to about 1 cm long and wide; inflorescence a spike 2-5 cm long, 2 cm wide, at ends of stems; blooming and fruiting June-Nov., found blooming Aug. 13 in wet woods.
Fruit dry, small, nut-like, surface smooth.
Wetland status: FACU+.
Frequency in NYC: Occasional.
Origin: Native and European varieties very similar, the native variety P. v. var. lanceolata has mid-stem leaves about a third as wide as long, the European P. v. var. vulgaris has wider leaves, about a half as wide as long.
Habitat: Wooded or open, disturbed areas, trail margins. Euopean variety mostly in diturbed sites, soil pH 5.4-8 (USDA, NRCS 2009).