Stolons ascending, rooting at nodes. Stems 15-30 cm or more, young parts sparsely villous to puberulent, glabrescent, base sometimes purplish. Petiole of basal leaves ca. 3 × as long as blade, mid cauline petioles 1.2-2.5 cm; leaf blade of basal leaves smaller, mid cauline blade cordate, 2-4.2 × 1.9-3.8 cm, villous, abaxially purplish, margin coarsely crenate, apex needlelike-acute. Verticillasters 6-9-flowered; bracts and bracteoles linear, ca. 4 mm, ciliate. Calyx tubular to campanulate, slightly curved, 1-1.2 cm, villous, puberulent; teeth narrowly triangular, 4-5 mm, apex spinescent-aristate, ciliate. Corolla reddish to purplish, tubular-campanulate, 2-2.4 cm, sparsely villous; tube gradually dilated ascending, to 6 mm wide at throat; upper lip straight, broadly ovate, apex emarginate; lower lip obliquely spreading, middle lobe flabellate, apex emarginate; lateral lobes ovate. Nutlets basally slightly triquetrous, with impressed dots. Fl. Apr-May, fr. May-Jun.