Fernald (Rhodora 23: 289. 1921) separated the large-flowered form of this species from the small-flowered one. Most of our reports for the species were made before the separation was made. These reports show the species to be all over the state. However, my specimens and observations of recent years show that the large-flowered form is rare in the state. Habitat the same as that of the variety [parviflora]. In lawns, gardens, waste places, and moist, open woodland along streams, and along roadsides. It is an obnoxious weed wherever found. It prefers the open and is generally found with bluegrass and herbs, and not in leaf mold in woods.
General: Introduced perennial, with a creeping habit; stems lax, 10-40 cm long, scabrous, with downward-pointing hairs to nearly glabrous, commonly pilose at the nodes; stoloniferous and rhizomatous; aromatic scent noticeable when plant is stepped on or mown. Leaves: Cauline, opposite, simple, rounded-cordate to kidney- shaped, 1-3 cm long, glabrous or hirsute, margins strongly crenate; petioles shorter to longer than the length of the blade. Flowers: Inflorescence a dense verticil, appearing spike-like, the lowest whorl of flowers often interrupted; flowers subtended by spine-tipped leafy bracts; calyx 9-15 mm long, the tube about equaling the spine-tipped teeth, hirsute to nearly glabrous; corolla scarcely surpassing the calyx, blue to purplish pink; stamens nearly equaling the upper lip of the corolla; stamens 4; flowers April- October. Fruits: Nutlets 4. Ecology: Moist woods, thickets, disturbed sites, lawns; 2100 m (7000 ft); Coconino County; widely distributed throughout North America. Notes: Native of Eurasia and escaped from cultivation. This plant tends to be quite weedy. Editor: Springer et al. 2008
Fibrous-rooted perennial from slender stolons or superficial rhizomes, the stems lax, 1-4 dm, retrorsely scabrous (or hirsute) to subglabrous, pilose at the nodes; lvs all about alike, petiolate, the blade glabrous or hirsute, rotund-cordate to cordate-reniform, strongly crenate, 1-3 cm; fls short-pedicellate; cal narrow, 5-6 mm, hirtellous-scabrous, the upper teeth the longer; cor blue-violet, purple-maculate, 13-23 mm, or in pistillate plants only 8-15 mm, the anthers then minute and included in the cor-tube; 2n=18, 36. Moist woods and various disturbed habitats; native of Eurasia, now found throughout our range. Apr.-June. (Nepeta h.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.