Stems slender, procumbent or ascending, rooting at the nodes below, the tips at least erect and simple or branched, 3 to 20 inches high, pubescent or nearly smooth and four-angled. Leaves ovate, oblong or oblong-lanceolate, blunt or somewhat pointed at the apex, usually narrowed at the base, entire or with a few teeth, 1 to 4 inches long, the lower leaves usually shorter. Flowers in dense terminal spikes which are one-half to 1 inch long, becoming 2 to 4 inches long in fruit. Calyx oblong, green or sometimes purplish, recticulate-veined, deeply two-lipped, closed in fruit, upper lip nearly truncate with three low teeth, lower lip two-cleft with lanceolate teeth. Corolla violet, purple or lilac, sometimes white, one-third to one-half of an inch long, the top of the flower strongly two-lipped, the upper lip entire and arched, the lower lip three-lobed and spreading or drooping; the four stamens ascending under the upper lip of the corolla.
Memoir 15 N. Y. State Museum
Plate 187 self-heal; heal-all - Prunella vulgaris