Description from Flora of China
Plectranthus serra Maximowicz, Melanges Biol. Bull. Phys.-Math. Acad. Imp. Sci. Saint Petersbourg 9: 428. 1875.
Herbs perennial. Stems erect, to 1.5(-2) m tall, ± glabrescent basally, densely retrorse pubescent, much branched at apex. Petiole 0.5-3.5 cm, broadly winged at apex, densely pubescent; leaf blade ovate to ovate-lanceolate, 3.5-10 × 1.5-4.5 cm, thin papery, adaxially dark green, abaxially greenish, ± glabrescent, sparsely yellowish glandular, base cuneate, margin coarsely incurved serrate, apex ± acuminate; lateral veins 4- or 5-paired, elevated. Panicles loose, 10-20 cm, terminal; cymes 5- to many flowered, pedunculate; floral leaves short petiolate, lanceolate to linear-lanceolate; bracteoles 1-3 mm, pubescent. Calyx campanulate, ca. 1.5 mm, densely whitish pubescent outside, glandular; teeth erect, narrowly triangular, subequal, ca. 0.8 mm; fruiting calyx dilated, broadly campanulate, base ± urceolate, ca. 3 mm, conspicuously veined. Corolla purple, to 6 mm, puberulent outside; tube ca. 3 mm. Stamens included. Style included. Nutlets broadly ovoid, ca. 1.5 mm, apex whitish barbate. Fl. Aug-Oct, fr. Sep-Oct.
Hills, riverbanks, streamsides, thickets, forests, sandy areas; 100-1200 m. Anhui, Gansu, Guangdong, Guangxi, Guizhou, Heilongjiang, Henan, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Shaanxi, Shanxi, Sichuan, Taiwan, Zhejiang [Korea, Russia].