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Conyza canadensis

Family

Asteraceae

Botanical Name

Conyza canadensis (L.) Cronquist

Cronquist, A.J. (1943) Bulletin of the Torrey Botanical Club 70: 632. Type: ?.

Synonyms

Erigeron canadensis L., Species Plantarum: 863(1753), Type: ?.

Common name

Fleabane; Hogweed; Canadian Flea Bane; Butterweed; Horseweed

Weed

*

Stem

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

Leaves

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.

Flowers

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.

Fruit

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.

Seedlings

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.

Distribution and Ecology

An introduced species originally from North America, now naturalized in NEQ and southwards as far as south-eastern Queensland. 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.

NEQ

X

Herb (herbaceous or woody, under 1 m tall)

X

Shrub (woody or herbaceous, 1-6 m tall)

X

RFK Code

3381