2. Ageratum conyzoides Linnaeus, Sp. Pl. 2: 839. 1753.
藿香蓟 huo xiang ji
Herbs, annual, 50-100 cm tall, sometimes less than 10 cm, with inconspicuous main root. Stems robust, ca. 4 cm in diam. at base, simple or branched from middle, stems and branches reddish, or green toward apex, white powdery puberulent or densely spreading long tomentose. Leaves often with axillary abortive buds; petiole 1-3 cm, densely white spreading villous; median leaves ovate, elliptic, or oblong, 3-8 × 2-5 cm; upper leaves gradually smaller, oblong, sometimes all leaves small, ca. 1 × 0.6 cm, both surfaces sparsely white puberulent and yellow gland-dotted, basally 3-veined or obscurely 5-veined, base obtuse or broadly cuneate, margin crenate-serrate, apex acute. Capitula small, 4-14, in dense terminal corymbs; peduncle 0.5-1.5 cm, powdery puberulent; involucre campanulate or hemispheric, ca. 5 mm in diam.; phyllaries 2-seriate, oblong or lanceolate-oblong, 3-4 mm, glabrous, margin lacerate; corollas 1.5-2.5 mm, glabrous or apically powdery puberulent; limb purplish, 5-lobed. Achenes black, 5-angled, 1.2-1.7 mm, sparsely white setuliferous; pappus scales 5 or awned, 1.5-3 mm. Fl. and fr. year-round. 2n = 20, 38, 40.
Valleys, forests, forest margins on slopes, riversides, grasslands, field margins. Cultivated and naturalized in Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Jiangsu, Jiangxi, Nanhai Zhudao, Shaanxi, Sichuan, Taiwan, Yunnan; only cultivated in Hebei and Zhejiang [native to tropical America; widespread weed throughout Africa, India, Nepal, and SE Asia].
Ageratum conyzoides is used medicinally in China to treat a variety of conditions, including common colds, headaches, boils, eczema, bleeding wounds, and burns.