flaxleaf fleabane

Conyza bonariensis
Herb
Alternate
Simple
Yellow
Cream
Green

A short-lived herbaceous plant developing a basal rosette of leaves at first. Its upright branched stems are densely hairy and usually grow up to 1 m tall. Its lower leaves (4-10 cm long) are elongated in shape with bluntly toothed to deeply lobed margins. Its smaller upper leaves are usually long and narrow with finely toothed or entire margins. Its small flower-heads (6-12 mm across) do not have any obvious 'petals' and turn whitish and fluffy as they mature. Its small 'seeds' (1.5-2 mm long) are topped with a tuft of whitish-coloured hairs about 3 mm long.

Common names 
Also known as: Argentine fleabane, asthma weed, conyza, flax-leaf fleabane, flaxleaf fleabane, flax-leaved fleabane, flax-leaved horseweed, fleabane, hairy fleabane, hairy horseweed, horse-weed, horseweed, little horseweed,
Family 
Asteraceae
Deciduous 
No
Flowering time 
year round
Native/Exotic 
Exotic
Origin 
This species is widespread throughout the tropical regions of the world (i.e. pan-tropical). Its exact origin is somewhat obscure, but it probably originated in tropical America.
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

Widely naturalised and very common in south-eastern Queensland. Widely naturalised other parts of Australia (i.e. New South Wales, the ACT, Victoria, Tasmania, South Australia, the Northern Territory, many parts of Western Australia, and other parts of Queensland). Also naturalised on Lord Howe Island, Norfolk Island, Christmas Island and in the Cocos Islands.

Habitat 

A very common weed of crops, fallows, pastures, roadsides, disturbed sites, waste areas, gardens, lawns, footpaths, parks, coastal environs, riparian vegetation, forest and wetland margins, and disturbed woodlands.

Habit 

A short-lived (i.e. annual or biennial) herbaceous plant developing a basal rosette of leaves at first. It later produces a single upright (i.e. erect) stem with several branches relatively close to the ground. Plants grow up to 1.5 m tall, but are usually less than 1 m in height.

Impact and control methods 
Stem and leaves 

The stems are densely covered in hairs (i.e. hirsute) that give them a greyish appearance. The larger rosette leaves are borne on stalks (i.e. petioles) to 4 cm long. These leaves (4-10 cm long and 1-2 cm wide) are narrowly egg-shaped in outline (i.e. ovate), narrowly oval (i.e. elliptic) or elongated (i.e. lanceolate) with bluntly toothed (i.e. crenate) to deeply lobed (i.e. pinnatifid) margins. Leaves that are produced along the stems are alternately arranged and have shorter stalks, while those towards the tops of the branches are stalkless (i.e. sessile). These uppermost leaves (3-6 cm long and 2-10 mm wide) are smaller and usually more elongated in shape (i.e. linear) with entire margins. All of the greyish-green leaves are hairy (i.e. pubescent) and they are often also somewhat twisted or curled.

Flowers and fruits 

The small flower-heads (i.e. capitula) are borne in leafy clusters towards the tips of the branches (i.e. in racemes or racemose panicles). These flower-heads (6-12 mm across and 5-6 mm long) do not have any obvious 'petals' (i.e. ray florets). They have numerous tiny cream or yellowish coloured flowers (i.e. tubular or disc florets) that are surrounded by a few rows of green bracts (i.e. an involucre). These bracts (5-6 mm long) are long and narrow (i.e. linear or lanceolate), often with purplish-tinged tips. Flowering occurs throughout the year, but mainly from spring through to autumn. As the 'seeds' (i.e. achenes or cypselae) mature, the flower-heads become fluffy, globular in shape, and turn whitish in colour. These tiny oblong 'seeds' (1.5-2 mm long and about 0.5 mm wide) are topped with a tuft (i.e. pappus) of whitish-coloured hairs about 3 mm long.

Reproduction and dispersal 

Flaxleaf fleabane (Conyza bonariensis) reproduces only by seed, which are easily blown and dispersed by the wind. Seeds may also be spread by machinery, water, vehicles, animals, and in clothing and contaminated agricultural produce.

Similar species 

There are several other fleabanes (Conyza spp.) present in the region, the most common being tall fleabane (Conyza sumatrensis ), Canadian fleabane (Conyza canadensis var. pusilla) and Chilean fleabane (Conyza primulifolia). These species can be distinguished from flaxleaf fleabane (Conyza bonariensis) by the following differences: flaxleaf fleabane (Conyza bonariensis ) is a moderately-sized plant, usually less than 1 m in height, with toothed and curled leaves. Its flower-heads are relatively large (6-12 mm across and 5-6 mm long) and when mature they turn whitish in colour.tall fleabane (Conyza sumatrensis) is a relatively large plant and grows up to 2 m tall, with toothed leaves. Its flower-heads are relatively small (5-10 mm across and 4-6 mm long ) and off-white when mature (i.e. they often have a slight brownish or yellowish tinge).Canadian fleabane (Conyza canadensis var. pusilla) is a moderately-sized plant, usually about 1 m in height, with toothless leaves. Its flower-heads are noticeably smaller (3-5 mm across and 3-4 mm long) and off-white when mature (i.e. they often have a slight brownish or yellowish tinge).Chilean fleabane (Conyza primulifolia) is a relatively small plant, usually less than 80 cm in height. Its flower-heads are noticeably larger (15-20 mm across and 8-12 mm long) but are produced in small clusters.