Praxelis (Praxelis clematidea)

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Impact

Praxelis is an invader of both disturbed and relatively undisturbed ecosystems, praxelis could threaten, and significantly increase the costs of managing, such crops as bananas, other fruits and sugar cane. It could infest pastoral grasslands and conservation areas, particularly open eucalypt woodlands.

Distribution

Praxelis is a native of South America (southern Brazil, Venezuela, Bolivia, northern Argentina). 

Praxelis was first recorded in Tully and Innisfail, Queensland, in 1993 but was probably present there for about 20 years before being positively identified. It is spreading extremely quickly and effectively throughout northern and eastern Queensland.

Spread

Praxelis mainly spreads by seeds. It can produce large numbers of seeds in as little as three or four months after germinating. The seeds possess a ‘pappus’, a tuft of barbed bristles that can help them spread by wind or water, or by attaching themselves to animal fur and feathers, clothing or machinery. Long distance dispersal is mainly attributed to seed attached to vehicles or carried as accidental contaminants of building supplies and landscaping materials. Praxelis is also capable of vegetative growth, in which roots and new plantlets form along branches in contact with the soil. 

Description

Praxelis is an annual or short-lived perennial herb growing 0.2–1.0 m tall. Its leaves are arranged in opposite pairs along the brittle cylindrical stems, which are covered in short soft hairs.

The leaves are tear-shaped or 'rhomboid', with a conspicuously toothed margin containing between five and eight teeth. When crushed, they emit a pungent odour similar to cat’s urine.

The flowers, which are clusters of numerous (30–50) lilac or bluish coloured ‘florets’, are 7–10 mm long and occur in groups at the ends of stems. The florets are set into a cone shaped receptacle – this is a key distinguishing feature of this species. 

The seeds are black and about 2.5–3.0 mm long. They bear a pale tuft of finely barbed bristles, 3–4 mm long.

Habitat

Praxelis is particularly suited to disturbed areas such as roadsides, railway lines and fencelines, and rapidly colonises bare earth following fire. Able to survive on a range of soil types, it invades crops, grasslands and, particularly, over-grazed pastures. It can become the dominant herbaceous plant in open eucalypt woodlands, and grows vigorously along riverbanks. It tolerates partial shade to full sun but does not cope well under heavy shade.

Acknowledgements

CRC for Australian Weed Management: Barbara Waterhouse (AQIS/Weeds CRC), Rachel McFadyen (Weeds CRC), Ailsa Holland (Queensland Herbarium) and John Thorp (National Weeds Management Facilitator).

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Control

Because there are relatively few praxelis infestations, and it can potentially be eradicated before it becomes established, any new outbreaks should be reported immediately to your local council weed officer. Do not try to control praxelis without expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem.

Herbicide options

Contact your local council weeds officer for control advice for Praxelis (Praxelis clematidea).

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Legal requirements

Praxelis (Praxelis clematidea) is not declared in NSW under the Noxious Weeds Act 1993.

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Reviewed 2014