1. Ageratina adenophora (Sprengel) R. M. King & H. Robinson, Phytologia. 19: 211. 1970.
破坏草 po huai cao
Eupatorium adenophorum Sprengel, Syst. Veg., ed. 16, 3: 420. 1826, based on E. glandulosum Kunth in Humboldt et al., Nov. Gen. Sp. 4, ed. f°: 96. 1818, not Michaux (1803).
Shrubs or perennial herbs, 30-90(-200) cm tall. Stems erect; branches opposite, obliquely ascending, white or ferruginous puberulent, upper part and peduncles more densely so, glabrescent or glabrous in lower part by anthesis. Leaves opposite, long petiolate; blade abaxially pale, adaxially green, ovate, triangular-ovate, or rhombic-ovate, 3.5-7.5 × 1.5-3 cm, thin, both surfaces sparsely puberulent, more densely so abaxially and on veins, basally 3-veined, base truncate or slightly cordate, margin coarsely crenate, apex acute. Synflorescences terminal, corymbose or compound-corymbose, to 12 cm in diam. Capitula numerous, 2-4 cm, 40-50-flowered; involucre broadly campanulate, ca. 3 × 4 mm; phyllaries 2-seriate, linear or linear-lanceolate, 3.5-5 mm, apex acute or acuminate; receptacle convex to conical; corollas purplish, tubular, ca. 3.5 mm. Achenes black-brown, narrowly elliptic, 1-1.5 mm, 5-angled, without hairs and glands; pappus setae 10, basally connate, white, fine, equal to corolla. Fl. and fr. Apr-Oct. 2n = 51.
Wet places or roadsides on slopes, forest margins; 900-2200 m. Introduced and naturalized in Guangxi, Guizhou, Nanhai Zhudao, and Yunnan [native to Mexico; pantropical and pansubtropical invasive weed in Cambodia, India, Laos, Myanmar, Nepal, Indonesia, Philippines, Thailand, Vietnam; S Africa, America, Atlantic islands (Canary Islands), Australia, Pacific islands].
Ageratina adenophora was introduced into China in the middle of the 19th century. It is poisonous; oxen and horses have become ill and have sometimes died from consuming it.