Plants perennial. Rhizomes woody. Stems purple-red, numerous, much branched, 0.7-1.5(-2) m tall, glabrous. Petiole of stem leaves 2-5 cm; leaf blade circular to ovate-orbicular, 6-10 × 4-6 cm, palmatipartite, sparsely villous, abaxially glandular, base broadly cuneate to shallowly cordate; lobes ± broadly cuneate, pinnately divided into broadly lanceolate, apically obtuse segments. Verticillasters 15-20-flowered, to 2 cm in diam., in widely spaced spikes 10-30 cm; floral leaves narrowly rhombic, 3-partite, base cuneate; bracts spiny, spreading or reflexed, 4-6 cm. Flowers sessile. Calyx campanulate, slightly saccate toward apex, appressed fine puberulent, gray-green at apex, veins slightly elevated, tube ca. 6 mm; teeth triangular, spinescent; anterior teeth spreading, ca. 5 mm, narrow; posterior teeth equal, ca. 3 mm. Corolla reddish, ca. 1 cm, villous; tube ca. 6 mm, obliquely villous annulate inside, dilated beyond annulus; upper lip obovate, concave, curved forward; lower lip with ovate lobes, middle lobe larger. Nutlets gray-brown, triquetrous, oblong, ca. 2 mm, base cuneate, apex truncate, puberulent. Fl. Jul-Aug, fr. Aug-Sep.
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