Plants 1-4 dm, ±erect, rhizomatous but without stolons; stems ±villous all around, varying to subglabrous; lvs wavy-toothed or subentire, the basal ones commonly soon deciduous, the lower cauline mostly 3-7 נ1-3 cm, elliptic to obovate and tapering to a narrow or petiolar base, the upper generally broad-based and sessile, passing into the obovate bracts of the usually somewhat arachnoid-villous infl, this thyrsoid-spicate, its well developed bracts often suffused with blue; verticils 6-many-fld; cor bright blue (pink or white), 12-20 mm, the upper lip very short and minutely 2-toothed, the lower lip 5-8 mm; stamens exserted; filaments hairy; 2n=32. Native of Eurasia, escaped into lawns, gardens, and roadsides in our range. Apr.-June. Hybridizes with no. 2 [Ajuga reptans L.].
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.