This document was originally published on the website of the CRC for Australian Weed Management, which was wound up in 2008. To preserve the technical information it contains, the department is republishing this document. Due to limitations in the CRC’s production process, however, its content may not be accessible for all users. Please contact the department’s Weed Management Unit if you require more assistance. alert list for environmental weeds Praxelis – Praxelis clematidea G Current Praxelis (Praxelis clematidea) The problem Praxelis is on the Alert List for Environmental Weeds, a list of 28 non- native plants that threaten biodiversity and cause other environmental damage. Although only in the early stages of Praxelis establishment, these weeds have the potential to seriously degrade Australia’s ecosystems. – Praxelis clematidea 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 effect- ively throughout northern and eastern Praxelis can invade both disturbed and undisturbed ecosystems including grasslands, woodlands and Queensland – an isolated infestation conservation areas. recently found in Gympie is some 1200 km Photo: AQIS by road south of the nearest infestation in Townsville. Its leaves are arranged in opposite pairs Key points An invader of both disturbed and along the brittle cylindrical stems, which • Prevention is the most cost-effective form relatively undisturbed ecosystems, praxelis are covered in short soft hairs. The leaves of weed control. Keep uninfested areas free could threaten, and significantly increase are tear-shaped or ‘ovate’ to diamond- of praxelis. the costs of managing, such crops as shaped or ‘rhomboid’, with a conspicu- bananas, other fruits and sugar cane. ously toothed margin containing between • Praxelis spreads into new areas very quickly. It could infest pastoral grasslands and five and eight teeth. When crushed, they Seed dispersal is aided by machinery and vehicles. conservation areas, particularly open emit a pungent odour similar to cat’s urine. • Disturbed areas such as roadsides, fencelines, eucalypt woodlands. Praxelis is easily railway lines, run-down pastures and plantations The flowers, which are clusters of mistaken for two species of Ageratum, are all at risk from infestation. numerous (30–50) lilac or bluish coloured less serious weeds found in similar regions. • Contact your state or territory weed manage- ‘florets’, are 7–10 mm long and occur in ment agency or local council if you find praxelis, There is some evidence that it may groups at the ends of stems. The florets especially any infestations outside its known be poisonous to stock and humans are set into a highly conical (ie cone- distribution. Any new information on its presence if ingested. shaped) receptacle – this is a key is extremely important. distinguishing feature of this species. • Do not attempt control on your own. The weed The seeds are black and about 2.5– Praxelis is an annual or short-lived 3.0 mm long. They bear a pale tuft of perennial herb growing 0.2–1.0 m tall. finely barbed bristles, 3–4 mm long. 2 Growth calendar Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flowering Seed formation Seed drop Germination General pattern of growth Growth pattern in suitable conditions In tropical and subtropical regions praxelis mainly flowers during the wetter months between November and May. However, a few flowers may be present on some plants year round. Seeds are formed and drop from the plant very quickly, mainly throughout summer Praxelis leaves are tear-shaped or ‘ovate’ and autumn. Most germination occurs following rainfall, but it can occur year round to diamond-shaped or ‘rhomboid’, with under suitable conditions (eg in gardens, irrigated pasture). a conspicuously toothed margin containing between five and eight teeth. Photo: John Swarbrick How it spreads Infestations have been recorded along the coast of northern Queensland from annual rainfall in the range 500–700 mm. Praxelis mainly spreads by seeds. It can Townsville to Cairns, and on the Atherton In these drier areas praxelis behaves produce large numbers of seeds in as little Tablelands at Kuranda, Mareeba, more like an annual, setting seed and as three or four months after germinating. Herberton and Malanda. Other scattered dying off until the next rainy season, The seeds possess a ‘pappus’, a tuft of infestations exist in remote parts of Cape when germination takes place. It will barbed bristles that can help them spread York Peninsula and the Torres Strait probably only exist in cultivated areas by wind or water, or by attaching them- islands, originating from seeds in building or along waterways in areas where selves to animal fur and feathers, clothing and landscaping materials brought in from annual rainfall is less than 500 mm. or machinery. Long distance dispersal is infested regions. In 2002 an infestation – Praxelis clematidea mainly attributed to seed attached to was discovered just north of Gympie, Why we need to be ‘alert’ vehicles or carried as accidental contam- some 1200 km by road from Townsville to praxelis inants of building supplies and landscap- and only 160 km north of Brisbane. Praxelis ing materials. Praxelis is also capable of Praxelis is capable of quickly spreading large distances. Because it was not vegetative growth, in which roots and Where it grows new plantlets form along branches in positively identified early, and is contact with the soil. A native of South America (southern extremely similar to two less serious Brazil, Venezuela, Bolivia, northern weeds (Ageratum species), it has been Praxelis is thought to have first entered Argentina), praxelis invades a range allowed to spread virtually unimpeded Australia in a batch of contaminated seed of habitats. It is particularly suited to during its first 20 years in Australia. from Brazil between 1965 and 1975. It disturbed areas such as roadsides, railway In that time it could easily have spread is believed to have been part of the same lines and fencelines, and rapidly colonises into new areas where it may not yet seed batch that also included Siam weed, bare earth following fire. Able to survive have been identified, as shown by the Chromolaena odorata – a closely related on a range of soil types, it invades crops, discovery of an infestation in Gympie species also on the Alert List for grasslands and, particularly, over-grazed in 2002. Environmental Weeds – because the two pastures. It can become the dominant species were first found growing in very It is a close relative of Siam weed, herbaceous plant in open eucalypt close association in the Tully region. Chromolaena odorata, which is regarded woodlands, and grows vigorously along Although it was recognised by landholders as one of the worst weeds of the riverbanks. It tolerates partial shade to in the area as a weed, it was not formally tropics. These two plants share similar full sun but does not cope well under identified as praxelis until 1993 during characteristics (eg rapid growth and heavy shade. the initial investigations into the Siam early seed production, high numbers weed infestation (for more information Praxelis is well established in areas that of easily dispersed seeds, adaptability on Siam weed, see the companion have more than 900 mm annual rainfall to wide range of climates and habitats). guide in this series). and is expected to survive in areas with Weed Management Guide • Praxelis – Praxelis clematidea 3 Praxelis is also showing its weedy Early detection and eradication are also import conditions database potential in Hong Kong and mainland important to prevent infestations of <www.aqis.gov.au/icon>. Also, take China, where it appears set to become praxelis. Small infestations can be easily care when travelling overseas that you a significant weed of dryland agriculture. eradicated if they are detected early but do not choose souvenirs made from or It can survive some exposure to frost an ongoing commitment is needed to containing seeds, or bring back seeds and in China it grows above the frost ensure new infestations do not establish. attached to hiking or camping equipment. line as an annual. Report any breaches of quarantine you Quarantine to prevent further see to AQIS. What to do about it introductions Raising community awareness Quarantine laws require that before the Prevention is better than Australian Quarantine and Inspection Because there is a high probability that the cure Service (AQIS) could consider applications praxelis exists outside known to import praxelis, a comprehensive weed infestations, it is extremely important As with all weed management, risk assessment would need to be that the general public be made aware prevention is better and more cost- conducted by Plant Biosecurity Australia. of the potential impacts of praxelis and effective than control. The annual cost Considering its potential impacts on how to identify it and distinguish it of weeds to agriculture in Australia, agriculture and the environment, it is from similar weeds (see box on p.5). in terms of decreased productivity and unlikely that permission to import this Assistance from landholders, natural management costs, is conservatively plant would be granted. resource managers and interested estimated at $4 billion. Environmental community groups will be vital in impacts are also significant and lead to Do not buy seeds via the internet or from compiling up-to-date maps of known a loss of biodiversity. To limit escalation mail order catalogues unless you check infestations, alerting authorities to new of these impacts, it is vital to prevent with quarantine first and can be sure infestations and helping to prevent the further introduction of new weed that they are free of weeds like praxelis. spread of praxelis. species, such as praxelis, into uninfested Call 1800 803 006 or see the Australian natural ecosystems.