Description from Flora of China
Herbs, annual, decumbent or suberect, to 80 cm or longer; stems flattened to subterete, hispidulous or scaberulous and hirsute. Petiole 5-10 mm, hispidulous to pilosulous; leaf blade drying membranous to thickly papery, ovate, elliptic, or lanceolate, 1-5 × 0.5-3.5 cm, both surfaces scaberulous to glabrescent, base acute to cuneate, apex acute to obtuse; stipule sheaths 1-3 mm, pilose to pilosulous, with 3-11 setae 2-4 mm. Inflorescences ca. 1 cm in diam. (not including leaflike bracts or subtending leaves). Calyx with ovary portion obovoid, 1-1.5 mm, densely papillose or hispidulous to smooth; lobes 6, lanceolate or narrowly lanceolate, 1.5-3.5 mm, glabrescent, margins ciliate, apex acute. Corolla white, glabrous inside and outside; tube 3-8 mm; lobes 6, 1-3 mm. Fruit with mericarps 3, ellipsoid to obovoid, laterally somewhat dorsiventrally flattened, 2-3 mm, dorsally papillose to subsmooth, ventrally with 2 broad parallel grooves along length of face. Fl. and fr. Feb-Sep.
This species was reported as naturalized in Taiwan by Ou (Bull. Exp. Forest Natl. Chung Hsing Univ. 8: 11-30. 1987, article not seen, cited by Wu et al., Taiwania 49: 16-31. 2004) and later by Wu et al. (loc. cit.) but not by other contemporaneous authors (e.g., Chaw & Peng, J. Taiwan Mus. 40: 71-83. 1987). It was not cited at all by H. Y. Liu and T. Y. A. Yang (Fl. Taiwan, ed. 2, 4: 245-340. 1998).
Wastelands; ca. 300 m. Naturalized in Guangdong and Taiwan [native to South America; adventive and naturalized occasionally throughout Old World tropics].