Erigeron canadensis L.

Linnaeus, C. von (1753) Species Plantarum: 863. Type: Habitat in Canada, Virginia, nunc in Europa australi.

Fleabane; Hogweed; Canadian Flea Bane; Butterweed; Horseweed

Usually flowers and fruits as a shrub about 1-2 m tall but occasionally flowers when smaller.

Leaf blades variable in size and shape, about 2-10 x 0.3-0.8 cm, hairy on both the upper and lower surfaces. Teeth sparse, about 7 or 8 on each side of the leaf blade. Stems or twigs hairy and longitudinally ribbed.

Flower heads less than 5 mm diam. at anthesis consisting entirely of disk florets subtended by an involucre of persistent bracts. Flowers in the outer ring are female with hermaphrodite flowers located towards the centre of the head.

Achenes about 4 mm long with persistent pappus attached at the apex. Pappus bristles microscopically barbed or toothed. Embryo straight, cotyledons about as wide as the radicle.

Cotyledons elliptic, ovate to broadly spathulate, about 3-4 x 2-3 mm. First pair of leaves ovate on comparatively long slender petioles. Apex rounded and apiculate, base attenuate. Both the upper and lower surfaces sparsely clothed in pale hairs. At the tenth leaf stage: leaves spathulate, base of petiole clasping the stem. All plant parts clothed in erect white hairs. Seed germination time 23 to 37 days.

An introduced species originally from North America, now naturalised in NEQ, CEQ and southwards as far as Victoria and Tasmania. Altitudinal range in NEQ not known but collected in the 750-1150 m range. Usually grows as a weed of agricultural land but also found in disturbed areas and along roads in rain forest.

Conyza canadensis (L.) Cronquist, Bulletin of the Torrey Botanical Club 70 : 632 (1943).