Description from Flora of China
Herbs annual, 20-50 cm tall. Stems erect, stout, much branched, strigose. Leaves alternate or subopposite; petiole 2-5 cm; leaf blade 3-9 × 2-4 cm, pubescent or strigose, base rounded or truncate, decurrent to petiole, margin undulate, apex acute; lateral veins 5-7 pairs. Cymes solitary, scorpioid, 5-15 cm, ebracteate. Flowers sessile, crowded. Calyx lobes lanceolate, 1.5-2 mm, strigose. Corolla light blue or blue-purple, salverform, 3-4 mm, base ca. 1 mm wide; throat contracted to ca. 0.5 mm; limb 2-2.5 mm wide; lobes rotund, ca. 1 mm wide, margin crispate. Anthers narrowly ovate, ca. 0.5 mm, inserted ca. 1 mm above base. Ovary glabrous. Style ca. 0.5 mm; stigma conical, pubescent. Fruit ribbed, 3-3.5 mm, glabrous or nearly so, deeply 2-cleft into mericarps each divided into 2 1-seeded pyrenes; mericarps longitudinally ribbed. Fl. and fr. Apr-Oct. 2n = 22, 24, 44, 64.
Hills, river banks, open waste places; 0-700 m. Widely scattered. Fujian, Hainan, Nanhai Zhudao, Taiwan, SW Yunnan [Cambodia, India, Indonesia, Japan (Ryukyu Islands), Laos, Malaysia, Myanmar, Thailand, Vietnam; Africa, North America, Pacific Islands, South America]