Description from Flora of China
Herbs, (13-)30-60 cm tall; stems, leaf blades, bracts, and calyces setiferous. Stems erect, basally subterete, channeled, usually branched at or above middle. Leaves opposite, rarely alternate, sessile, linear-lanceolate, 2-3 cm X 3-4 mm, margin entire and subrevolute, midrib abaxially bulging. Bracts shorter or rarely as long as corolla. Flowers borne above middle of stem. Calyx 7-15 X 4-6 mm, densely hispid, apex constricted, slightly curved; lobes reduced to 3 mucros. Corolla yellow, purple-red, or white with purple lobes, 1.5-4 cm; lower lip lobes 3, orbicular; upper lip lobes 2, orbicular. Anterior stamens ca. 1 cm; posterior stamens 6-7 mm; filaments all woolly. Ovary glabrous. Stigma linear-elliptic, ca. 3 X 1 mm, hairy. Capsule ovoid, ca. 8 X 4 mm, apex mucronate. Seeds yellow, small, spirally striate. Fl. and fr. Jul-Oct.
Dry grassy slopes, grassland, fields, forests, wastelands, rice fields; near sea level to 1500 m. Anhui, Fujian, Guangdong, Guangxi, Hainan, Hunan, Jiangsu, Jiangxi, Sichuan, Xizang, Yunnan [Cambodia, India, Indonesia, Japan, Korea, Laos, Malaysia, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam; N Australia, Oceania].