Taxonomy

Chromolaena odorata (L.) R.M.King & H.Rob., Phytologia 20(3): 204. 1970.

Common synonyms

Eupatorium odoratum L., Syst. Nat., ed. 10. 2: 1205. 1759.

Common name

Siam weed, archangel, bitterbush, butterfly weed, Christmas bush, chromolaena, devil weed, hagonoy, jack in the bush

Description

Propagule or dispersal unit is the fruit with pappus. Fertile part 3-5 mm long, 0.2-0.8 mm wide, in side view widest in upper part (obovoid), +/- straight, the upper (apical) end narrowing, in cross-section angular (prismatic), basal scar (carpopodium) pronounced and well-differentiated, central or off to the side (oblique) or at least asymmetric, beak (=thinner sterile stalk between seed and pappus) absent, wings absent, fruit surface black, smooth (except at cellular level), with no hairs (glabrous), rarely simple straight hairs, thickened margin absent, longitudinal ribs present, 4-5, their surfaces smooth, with simple straight hairs.

Pappus type bristles / hairs, pappus elements all +/- similar, up to 3-5 mm long, in one row, pappus elements numerous, persistent, the individual bristles rough / serrated (barbellate), +/- equal width along length, brown.

Ecology

Perennial herb to slightly bushy or somewhat climbing, forming dense thickets, fruits wind-dispersed. Humid tropics and inter-tropical zone at low to medium elevations. Found on cultivated or abandoned fields, in clearings, wastelands, and along trails, roads and fences.

Native range

Mexico, Central America, Carribean, South America except Chile.

Introduced range

Widespread in tropical areas of Africa, Asia, Australia, and the Pacific.

Weed status within Australia

NAQS target species; NSW Class 1 State Prohibited Weed; Qld Restricted Invasive Plant Cat. 3; NT Category C; WA Declared Pest – s12 (C1 Prohibited).

Past interceptions (Australia): origins

India, Bangladesh, Thailand.

Past interceptions (Australia): commodities

Containers, dried spice leaves, new vehicles.