Ageratina Spach
Perennial herbs, subshrubs or shrubs. Lvs usually opposite, rarely alternate, petiolate, simple, entire to serrate or lobed. Infl. a lax or dense corymb. Involucral bracts in 1-2-(3) rows, usually subequal, with membranous margins. Receptacle convex; scales 0, but sometimes minute hairs present. Corolla tubular. Style usually with a distinctly swollen basal node. Achenes ellipsoid-cylindric, usually 5-angled, glabrous, hairy, or glandular; pappus of scabrid hairs, easily deciduous, with acute apical cells.
Key
230 spp., America. Naturalised spp. 2.
Ageratina is one of the genera recently resurrected as a segregate from Eupatorium, and is distinguished by a well defined set of microcharacters [King, R. M. and Robinson, H., Phytologia 19 : 201-229 (1970)].
