Description from Flora of China
Stem erect, green or somewhat tinged purple, 30-100 cm tall, terete or obtusely angulate, much branched, glabrous or slightly pubescent. Petiole 1-8 cm, glabrous, 2-armed at base; leaf blade ovate-rhombic or ovate-lanceolate, 3-12 × 1-6 cm, glabrous or slightly pubescent along veins when young, base cuneate, margin entire, apex obtuse, with a mucro. Complex thyrsoid structures terminal or axillary, 8-25 cm; terminal spike usually with all male flowers at or toward apex. Bracts becoming very sharply spiny in proximal part of spike. Tepals green, transparent at margin and with green or purple median band, apex acute, with a mucro; male flowers oblong, 2-2.5 mm; female flowers oblong-spatulate, ca. 1.5 mm. Filaments nearly as long as or slightly shorter than perianth. Stigmas 3(or 2). Utricles included in perianth, oblong, 1-1.2 mm, circumscissile slightly below middle. Seeds brownish black, subglobose, ca. 1 mm in diam. Fl. and fr. Jul-Nov. 2n = 34, 68.
Waste places, gardens. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [probably native to neotropics, now cosmopolitan in warm-temperate and tropical regions].