From Ageratum, the name of a related genus often used in horticulture.
Perennial herbs, shrubs or small trees, often glandular-hairy. Stems erect or ascending, branched. Leaves along stems, opposite, rarely alternate, simple, margins toothed, petiolate. Capitula diskoid, terminal, in dense panicles, with stalks. Involucral bracts in 1 or 2 rows, slightly overlapping, equal. Receptacle flat or convex. Florets bisexual, tubular, white, pink or pale mauve. Achenes 5-angled, hairy or glandular. Pappus of many barbed or feathery bristles, deciduous.
Three species have become naturalised in Australia and are declared noxious weeds.
Weakly 5-angled achenes; glandular-hairy herbs or subshrubs; leaves simple, toothed.
About 290 species from N, S and C America.
Source: (2002). Asteraceae. In: . Horticultural Flora of South-eastern Australia. Volume 4. Flowering plants. Dicotyledons. Part 3. The identification of garden and cultivated plants. University of New South Wales Press.