Eupatorium odoratum L.
life form: herb, plant
description: Perennial coarse herbs to 2 m tall; stems terete, striate, crisp-puberulous. Leaves opposite, median ones larger, ovate to subdelotoid, 7-15×3.5-8 cm, apex acute to acuminate, base obtuse to very broadly cuneate or truncate, sometimes decurrent, lower surface glandular punctate, 3-nerved, margins sparsely dentate, sometimes entire apically, petiole 1-2.5 cm long; upper leaves gradually smaller near inflorescence. Inflorescence loose corymbs, heads ca. 10 mm long, 4.5-5 mm wide, peduncle 8-16 mm long, densely pubescent; involucre cylindric, ca. 7 mm long; bracts ca. 30, 3-4 seriate, trinerved, outer ones ovate to ovate oblong, inner ones narrowly oblong, apex acute, base obtuse, sparsely pubescent. Florets ca. 30. Achenes black, ca. 4-4.5 mm long, 5-angular, pubescent on ribs.
origin: Native of tropical America
Summary: A fast-growing perennial herbs native to South America and Central America. It has been introduced and has become an aggressive invasive weed in much of tropical Asia, Africa, and the Pacific. Siam weed forms dense stands, which prevent establishment of other species, both due to competition and allelopathic effects. It is also a problem in agricultural land and commercial plantations.
Habitat: agricultural areas, disturbed areas
occurance: established and expanding
introduction types: intentional
pathways of introduction types: by agricultural interests, introduced for medicinal purposes
vector of introduction types: anthropogenic vectors
impact types: competition, economic, environmental
eradication methods: poison, mechanical