Conyza sumatrensis (Retz.) E. H. Walker
Conyza albida Willd. ex Sprengel, Conyza altissima Bonnet, Conyza nandina Bonnet
fleabane, tall fleabane, broad-leaved fleabane, white horseweed, Sumatran fleabane, Guernsey fleabane
North America, sub-tropical South America
It is an erect, annual (living 1 season only) that is 1 to 2 metres tall with basal leaves in a rosette formation. The rosette formation being particularly evident at the juvenile stage. The plant develops from the middle of the rosette and arises from a central stem branching towards the top of the plant.
Widespread throughout Australia, adapted to most soil types, particularly disturbed or neglected areas. It is most prevalent in Summer through Autumn.
Stems and Leaves:
An erect plant growing to 1 to 2 metres in height. It has a central stem branching towards the top of the plant below the inflorescence (flowerheads). The stems are very leafy and softly hairy. The leaves are grey/green in colour they are 4-10cm long and 5-12mm wide. The basal leaves form a rosette and are lanceolate with toothed edges. As you move up the stem the leaves are then alternate, these leaves being lanceolate (tapering from a rounded base toward an apex) to linear with the margin entire. The leaves are covered in small, white hairs.
Flowers and Fruit:
Each "flower" is in fact a group of small flowers callet florets. The "flowers" are arranged in groups that form a pyramid like shape. Each "flower" is broad-campanulate (bell-shaped) and is 4-6mm long and 6-10mm wide. The involucral bracts (outer covering) are hirsute (hairy), greenish white in colour with the inner surface when reflexed being a reddish brown colour. The florets are cream coloured and less than 1mm long. The fruit is 3mm in length, ovoid and sparsely hairy. It is single seeded with a straw coloured pappus that has minutely barbed bristles. Flowering occurs chiefly from December to August.
An erect stem with branching only towards the top of the plant and branching just below the inflorescence (flowerhead). All the florets are no longer than 1mm long. The bracts around the "flower" do not have any hairs at the apex. It has hairy leaves and red/brown bracts. The pappus is straw coloured. The receptacle (extended tip of the stalk that the flowerhead grows out of) is usually roughly pitted.
Conyza sumatrensis can easily be confused with Conyza canadensis and Conyza bonariensis which are also weeds. Conyza canadensis is distinguished by glabrous (hair free) or almost glabrous bracts which lack an apical (at top) red dot but have a brownish inner surface. Grows to 1.5m high. Conyza bonariensis has densely hairy bracts, is especially hairy on the stems and around the leaf axils, and grows to 1m. Conyza sumatrensis also has hairy bracts but there are no long hairs near the apex of the bracts. Also inner surface of bracts reddish brown and grows to 2m.
Other plants easily confused with this plant
Sources & References
Carolin R, Tindale MD (1993) 'Flora of the Sydney region.' (Reed: Chatswood, Australia)
Cunningham GM, Mulham PL, Leigh JH (1981) 'Plants of Western New South Wales.' (NSW Government Printing Office: Australia)
Hanks M, Rose L (2001) 'A growers guide to pests, weeds and diseases.' ( Murdoch Books: Sydney, Australia)
Jessop J (1981) 'Flora of Central Australia.' (AH &AW Reed Pty Ltd: Sydney, Australia)
Kleinschmidt HE, Johnson RW (1987) 'Weeds of Queensland.' (QLD Department of Primary Industries: Brisbane, Australia)
Muenscher WC (1955) 'Weeds.' 2nd edn. (The Macmillan Company: New York,USA)
Pacific island ecosystems at risk (2004) www.hear.org
Prepared by Kylie Pethybridge, 2005
Checked by Carole Campbell, 2005
Updated by Justin KY Chu, July 2005
Checked by Dr Peter Michael, July 2005
Revised by IEWF, March 2006