水苏 shui su

Stachys aspera Michaux var. chinensis (Bunge ex Bentham) Maximowicz f. glabrata Nakai; S. aspera var. japonica (Miquel) Maximowicz; S. baicalensis Fischer ex Bentham var. japonica V. Komarov; S. japonica f. glabrata Matsumura & Kudo; S. riederi Chamisso var. japonica (Miquel) H. Hara.

Herbs perennial, rhizomatous. Stems unbranched, ascending, 20-80 cm, glabrous, angles and nodes minutely hispid. Petiole conspicuous, 0.3-1.7 cm; leaf blade broadly oblong-lanceolate, 5-10 × 1-2.3 cm, glabrous, abaxially gray-green, base rounded to shallowly cordate, margin crenate-serrate, apex acute. Spikes 5-13 cm; verticillasters 6-8-flowered, lower widely spaced; floral leaves sessile, lanceolate, margin subentire, lower ones longer than verticillasters, upper shorter; bracteoles spiny, ca. 1 mm, glabrous. Pedicel ca. 1 mm. Calyx campanulate, to 7.5 mm, glandular puberulent, veins pilose, rarely appressed-puberulent or subglabrous, obscurely 10-veined; teeth equal, triangular-lanceolate, spinescent, ciliate, sparsely puberulent inside. Corolla reddish or reddish purple, ca. 1.2 cm; tube ca. 6 mm, ± included, saccate, glabrous, throat scaly-puberulent below lower lip; limb puberulent outside, glabrous inside; upper lip straight, obovate, ca. 4 × 2.5 mm; lower lip spreading, ca. 7 × 6 mm; middle lobe subcircular, emarginate; lateral lobes ovate. Filaments slightly dilated at apex, puberulent. Style slightly longer than stamens. Nutlets brown, ovoid, glabrous. Fl. May-Jul, fr. Aug-Sep.

Wet areas in ravines, riverbanks; 0-2300 m. Anhui, Fujian, Hebei, Henan, Jiangsu, Jiangxi, Liaoning, Nei Mongol, Shandong, Zhejiang [Japan, Russia].

Used medicinally for tonsillitis, sore throat, and dysentery.