Ageratum L.

Greek a — not, geras — old, as the flowers last for a long time.

Annual or perennial herbs. Stems often spreading and rooting at nodes. Leaves along stems, opposite or sometimes alternate, entire or toothed. Capitula diskoid, small, in tassel-like clusters. Involucral bracts in 1 or 2 overlapping rows, more or less equal. Receptacle with or without scales, conical. Florets all bisexual, tubular. Achenes 4- or 5-ribbed, glabrous or with short hairs on ribs. Pappus a crown, of 5 or 6 scales or short bristles, or absent.

Small capitula in tassel-like clusters; glandular dots on leaf undersides; florets all tubular, mostly blue, pink or white.

44 species from C and S America and the W Indies.

Johnson (1971).

Source: Jeanes, J. (2002). Asteraceae. In: Spencer, R.. 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.

Hero image
kingdom Plantae
phylum   Tracheophyta
class    Magnoliopsida
superorder     Asteranae
order      Asterales
family       Asteraceae
Higher taxa
Subordinate taxa
species         Ageratum houstonianum Mill.