Praxelis (Praxelis clematidea)

Praxelis is a herb up to 1 m tall with lilac flowers. It competes with other plants including pasture, crop and native plants.

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How does this weed affect you?

Praxelis:

• invades disturbed and relatively undisturbed ecosystems
• competes with native plants, particularly in open eucalypt woodlands
• invades crops such as bananas and sugar cane, increasing management costs
• competes with pastures
• is a weed in commercial nurseries.

Livestock poisoning

Praxelis contains pyrrolizidine alkaloids which are poisonous to herbivores.

What does it look like?

Praxelis is an upright annual or short-lived perennial herb 0.2–1 m tall.

Leaves are:

• diamond or oval-shaped, pointed at the tips and tapered at the base
• 2.5–6 cm long and 1–4 cm wide
• sharply toothed along the edges with 5–8 teeth on each side
• pungent when crushed, smelling like cat’s urine
• hairy, especially on the underside
• on stalks 3–20 mm long
• in opposite pairs along the stem.

Flowerheads are:

• purple, lilac or bluish
• 7–10 mm long and 4–5 mm wide
• made up of fine tubular florets[WG2] 
• in clusters at the ends of the branches
• mostly present from January to May (but may be present year-round).

Seeds are:

• black with a pale tuft of 15–40 white finely-barbed bristles (a pappus), 3–4 mm long
• about 2.5–3 mm long
• produced in large numbers.

Stems are:

• covered in soft downy hairs
• brittle
• cylindrical or angular.

Similar looking plants

Praxelis looks similar to:

• Blue goat weed (Ageratum houstonianum), which has much finer teeth along the leaf edges. It also has broad or heart shaped leaf bases and sticky bracts on the flowerheads.
• Goat weed (Ageratum conyzoides) which has less sharply toothed leaves that are more rounded at the tip. The base of the leaves is broad to heart shaped.
• Siam weed (Chromolaena odorata), Its leaves have prominent veins, and the plant becomes a taller, woody shrub.

Where is it found?

Praxelis has never been found in NSW. It is present in Queensland and was first recorded in Tully and Innisfail in 1993. It is likely to have been present there for about 20 years before positive identification. It is spreading very quickly throughout northern and eastern Queensland.

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

What type of environment does it grow in?

Praxelis grows in tropical and subtropical environments. Plants can grow on a wide variety of different soil types. They tolerate partial shade to full sun. Praxelis often grows in disturbed areas such as roadsides, railway lines, along fence lines and quickly takes over bare earth following a fire. It is also found in crops, grasslands, open eucalypt woodlands, and areas along riverbanks.

How does it spread?

By seed

Praxelis mainly spreads by seeds. Plants can start producing seeds within 3–4 months of germination. The number of seeds per plant varies but can be up to 1400 seeds per plant. Most long-distance spread is by seeds attaching to animals, clothing, machinery or carried in contaminated building supplies and landscaping materials. Seeds also spread by wind and water.

By plant parts

New plants grow from branches in contact with the soil.

References

CRC, Cooperative Research Centre for Australian Weed Management (2003). Weed Management Guide, Praxelis (Praxelis clematidea). CRC

Intanon, S., Wiengmoon, B., & Mallory-Smith, C. A. (2020). Seed morphology and allelopathy of invasive Praxelis clematidea. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, 48(1), 261-272.

McKenzie, R. (2012). Australia's poisonous plants, fungi and cyanobacteria: a guide to species of medical and veterinary importance. CSIRO.

Identic and Lucid (2016). Weeds of Australia, Biosecurity Queensland edition Fact sheet: Praxelis clematidea (Griseb.). Retrieved 5 May 2021 from: https://keyserver.lucidcentral.org/weeds/data/media/Html/praxelis_clematidea.htm

More information

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Control

Successful weed control relies on follow-up after the initial efforts. This means looking for and killing regrowth or new plants. Using a combination of control methods is usually more successful.

Physical control 

Seedlings can be hand weeded before they flower.  

Disposal

Contact your local council for advice about disposing of this weed.

Chemical control

Spot spraying

Spray actively growing plants. Apply to all foliage to the point of visible wetness.

Splatter gun

Splatter-guns use small amounts of concentrated herbicide. They spray large droplets that limit spray drift. They are useful for very dense infestations of weeds that are difficult to reach.

Weed wipers

Wipers or wands apply herbicide directly onto leaves. This can better target the chemical and minimise damage to other species.

Herbicide options

See Using herbicides for more information.

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PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L (Various products)
Rate: 500 mL to 1 L per 100 L water
Comments: Spot spray
Withholding period: Do not graze failed crops and treated pastures or cut for stock feed for 7 days after application. See label for further information.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 300 to 600 mL per 100 L water
Comments: Spot spray
Withholding period: Do not graze failed crops and treated pastures or cut for stock food for 7 days after application. See label for more information.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 50 parts water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 9 parts water
Comments: Splatter gun
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 20 parts water
Comments: Wipe onto leaves
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 - 20 g per 100 L water plus surfactant
Comments: Spot spray
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High

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PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 g per 1 L of water plus surfactant
Comments: Wipe onto leaves
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

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Reviewed 2024