Ageratum conyzoides L. subsp. conyzoides

Johnson, M.F. (1971) Annals of the Missouri Botanical Garden 58: 26 (1971).

Goat Weed; Billygoat Plant; Billygoat Weed; Blue Top; Whiteweed

Usually flowers and fruits as a shrub about 1 m tall but also flowers when smaller.

Leaves variable in size, about 3-7.5 x 1.5-4.5 cm. White or silver hairs visible on both the upper and lower surfaces of the leaf blade, petioles and twigs. Pale yellowish glands visible on the underside of the younger leaves. Lower leaves opposite, upper leaves sometimes alternate. Petiole grooved on the upper surface.

Each flower head consisting of 60-75 flowers. Calyx lobes ending in long filiform tips. Corolla tube green at the base, white about the middle and pale purple at the apex. Anthers closely packed, fused, apiculate or mucronate at the apex, filaments free. Pollen white. Style arms or stigmas long and filiform. Ovary black.

Fruits about 1.5-2 mm long, hairy and marked with four or five longitudinal ribs. Calyx lobes persisting at the apex as plumes about 2-3 mm long.

Cotyledons wider than long, about 3.5 x 5 mm. Stem hairs between the cotyledons and first pair of leaves multicellular, mainly tortuous. At the tenth leaf stage: stem hairs multicellular, mainly straight and erect. Leaf margin toothed except for the basal section. Seed germination time 6 to 12 days.

An introduced weed originally from tropical America, now naturalised in WA, NT, CYP, NEQ, CEQ and southwards to south-eastern Queensland and north-eastern New South Wales. Altitudinal range from near sea level to 1200 m. Grows in disturbed areas in rain forest.

The crushed leaves of this plant are sometimes used in folk medicine to treat cuts, abrasions and burns. Ming (1999).

This species has been used medicinally in Malaysia and Indonesia. Cribb (1981).

Ageratum conyzoides L., Species Plantarum 2: 839 (1753), Type: Habitat in America.