Description: Perennial herbs or undershrubs.
Leaves cauline, opposite, toothed, petiolate.
Inflorescence terminal, heads in dense panicles; heads campanulate; involucral bracts herbaceous with scarious margins, hardly imbricate, 1- or 2-seriate; receptacle naked, pitted, flat or slightly convex. Ray florets absent. Disc florets numerous, bisexual, tubular, 4- or 5-toothed; corolla lobes papillose inside. Anthers obtuse at the base, with short apical appendage. Style base glabrous; branches filiform, obtuse, papillose outside.
Achenes slender, ± terete, 5-angled; carpodium with distinct upper rim present; pappus of 5–40 barbellate to plumose bristles which are fragile and fall easily, in 1–3 series.
Distribution and occurrence: World: c. 230 species, North & South America. Australia: 3 species (naturalized), Qld, N.S.W., S.A.
Text by M. F. Porteners
Taxon concept:
| | Key to the species | |
| 1 | Stems, leaves and inflorescence branches glandular-hairy; leaves triangular to rhombic, almost as broad as long | Ageratina adenophora |
| Stems, leaves and inflorescence branches hairy but not glandular-hairy; leaves lanceolate to narrow-ovate, much longer than broad | Ageratina riparia |
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