Praxelis (Praxelis clematidea)

Present distribution

Scientific name:	Praxelis clematidea R.M. King & H. Rob
Common name(s):	praxelis

This weed is not known to be naturalised in Victoria

Habitat:

Roadsides, railway lines, disturbed areas, urban wasteland, beneath fences, rural paths; altitude 0-700 m in Hong Kong, 0-800 m in Queensland; 350 – 3050 m in South America (Veldkamp 1999). Survives a wide range of soil types. Invades grasslands and particularly over-grazed pastures. Found in open eucalypt woodlands and grows vigorously along riverbanks. Can survive some exposure to frost. (CRC for Australian Weed Management 2003).

Potential distribution

Potential distribution produced from CLIMATE modelling refined by applying suitable landuse and vegetation type overlays with CMA boundaries

Map Overlays Used

Land Use:
Broadacre cropping, Forest private / public plantation, Pasture dryland / irrigation

Broad vegetation types
Coastal grassy woodland; riverine grassy woodland

Colours indicate possibility of Praxelis clematidea infesting these areas.

In the non-coloured areas the plant is unlikely to establish as the climate, soil or landuse is not presently suitable.

map showing the potential distribution of praxelis

Red= Very high	Orange = Medium
Yellow = High	Green = Likely

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	“Annual or short-lived perennial herb” (Waterhouse, 2003). “It can grow up to c. 1.2m tall but most plants are c. 40-80cm” (Csurhes, 1998). They have brittle stems (CRC Weed Management, 2003). Infestations of Praxelis would not impede pedestrian access as the plants would be easily pushed aside or crushed underfoot.	L	MH
2. Reduce tourism?	“When crushed they [the leaves] emit a pungent odour similar to cat’s urine” (CRC Weed Management, 2003). “Unpleasant-smelling, softly-hairy herb, 20-80cm tall…The flower colour is light violet…but can appear blue to purple” (Corlett & Shaw, 1995). “Forms monospecific stands, excluding other vegetation” (PIER, 2005). Flowering generally occurs from November to May but some flowers may appear at any time of the year (CRC Weed management, 2003). The brightly coloured flowers could be obvious to most visitors for much of the year and the smell would be off-putting to many people, but the presence of this weed would be unlikely to inhibit activity.	ML	MH
3. Injurious to people?	“Anecdotal reports suggest that it may be poisonous to…humans if ingested” (Veldkamp, 1999) but there was no further record of the plant’s ability to injure people (CRC Weed Management, 2003). However, it is unlikely to be ingested.	ML	MH
4. Damage to cultural sites?	The brightly coloured flowers could have a moderate visual effect for much of the year (see description from Q. 2).	ML	MH
Abiotic
5. Impact flow?	“Grows vigorously along riverbanks” (CRC Weed Management, 2003), but there is no evidence that it invades the water.	L	M
6. Impact water quality?	See Q. 5.	L	M
7. Increase soil erosion?	“Can become the dominant herbaceous plant in open eucalypt woodlands.” In drier areas Praxelis dies off until the next rainy season and also “grows vigorously along riverbanks” (CRC Weed Management, 2003). There is the potential for large areas of soil to become bare when Praxelis dies off and with heavy rain and/or flooding of waterways, large scale soil movement is likely with major offsite implications.	H	M
8. Reduce biomass?	As this plant can “become the dominant herbaceous plant in open eucalypt woodlands” and can seasonally die off in drier areas (CRC Weed Management, 2003), biomass may be slightly decreased where there was once a more permanent herbaceous cover.	MH	M
9. Change fire regime?	This species is not noted for changes to fire regime. As an herbaceous annual or short-lived perennial that can invade grasslands (CRC Weed Management, 2003), it may reduce fuel load and flammability, thereby reducing the frequency and/or intensity of fires in these communities. Elsewhere, where it replaces similar vegetation it is likely to have little effect.	ML	M
Community Habitat
10. Impact on composition (a) high value EVC	Climate modelling shows that this species is not likely to occur as an invasive plant in Victoria.	L	H
(b) medium value EVC	Climate modelling shows that this species is not likely to occur as an invasive plant in Victoria.	L	H
(c) low value EVC	Climate modelling shows that this species is not likely to occur as an invasive plant in Victoria.	L	H
11. Impact on structure?	Its ability to “become the dominant herbaceous plant in open eucalypt woodlands” (CRC Weed Management, 2003) could have a major effect on ground level vegetation.	MH	M
12. Effect on threatened flora?	Climate modelling shows that this species is not likely to occur as an invasive plant in Victoria.	L	H
Fauna
13. Effect on threatened fauna?	Climate modelling shows that this species is not likely to occur as an invasive plant in Victoria.	L	H
14. Effect on non-threatened fauna?	“It can become the dominant herbaceous plant in open eucalypt woodlands” (CRC Weed Management, 2003). It is “not eaten by stock” (Pollock et al, 2004) and if this is true for other fauna it may reduce access to food, forcing them to seek food elsewhere.	MH	M
15. Benefits fauna?	“There is some evidence that it may be poisonous to stock…if ingested” (CRC Weed Management, 2003), so it is unlikely to provide a food source for fauna and as an “annual or short-lived perennial herb” (Waterhouse, 2003) to 40-80cm (Csurhes, 1998), would not provide much shelter either.	H	M
16. Injurious to fauna?	“There is some evidence that it may be poisonous to stock…if ingested” (CRC Weed Management, 2003), so it may be poisonous to fauna when present.	MH	M
Pest Animal
17. Food source to pests?	Toxicity (CRC Weed Management, 2003) probably precludes this plant from being a food source to pests.	L	MH
18. Provides harbour?	As an “annual or short-lived perennial herb” (Waterhouse, 2003) to 40-80cm (Csurhes, 1998), this plant would not offer much shelter.	L	MH
Agriculture
19. Impact yield?	“Forms monospecific stands, excluding other vegetation” (PIER, 2005), “not eaten by stock” (Pollock et al, 2004). “An abundant weed of…pastures…it encroaches upon sugarcane plantations and other cultivated areas (Waterhouse, 2003). “In Hong Kong and mainland China…it appears set to become a significant weed of dryland agriculture…There is some evidence that it may be poisonous to stock…if ingested” (CRC Weed Management, 2003). Large infestations may significantly reduce the carrying capacity of pasture by forming poisonous monocultures and may reduce crop yields by encroachment.	MH	H
20. Impact quality?	It is postulated that it was introduced to north Queensland as “a contaminant of pasture seeds imported from Brazil” (Waterhouse, 2003) and this suggests that it would be unlikely to be identified as reducing the quality of pasture seed crops. Whilst it invades other crops (CRC Weed Management, 2003) its bright flower colour (Corlett & Shaw, 1995) would make an infestation obvious and able to be avoided during harvest.	L	MH
21. Affect land value?	Reduced productivity may affect land value, see Q. 19, but probably not by more than 10%	MH	MH
22. Change land use?	Increased costs of harvest (see Q. 23) and reduced quality of produce (see Q. 20) may make stocking and/or cropping less viable on infested land.	MH	MH
23. Increase harvest costs?	“Could threaten, and significantly increase the costs of managing, such crops as bananas, other fruits and sugar cane’ (CRC Weed Management, 2003).	H	M
24. Disease host/vector?	Not noted as a disease host or vector in CRC Weed Management, 2003.	L	M

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	“Most germination occurs following rainfall, but it can occur year round under suitable conditions (eg in gardens, irrigated pasture)” (CRC Weed Management, 2003).	H	M
2. Establishment requirements?	“Able to invade the understorey of relatively undisturbed woodlands” (Waterhouse, 2003). Tolerates part shade to full sun but does not cope well under heavy shade (CRC Weed Management, 2003). Can establish under moderate canopy cover.	MH	H
3. How much disturbance is required?	“Able to invade the understorey of relatively undisturbed woodlands.” Also invades roadsides, streambanks, pastures, sugarcane etc., (Waterhouse, 2003).	MH	H
Growth/Competitive
4. Life form?	“Annual or short-lived perennial herb” (Waterhouse, 2003).	L	H
5. Allelopathic properties?	None found	L	L
6. Tolerates herb pressure?	“Not eaten by stock” (Pollock et al, 2004)	H	MH
7. Normal growth rate?	“It can grow up to c. 1.2m tall but most plants are c. 40-80cm” (Csurhes, 1998), which is an average height for an annual or short-lived perennial.	MH	MH
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Frost resistance (Waterhouse, 2003). Rapidly colonises bare earth after fire (CRC Weed Management, 2003) although this is probably by seed. “Woody rhizome protects from fire” (anon, 2004). Not noted as growing in permanently wet conditions, although it does “grow vigorously along riverbanks” which is the type of environment it would likely be found in “areas where annual rainfall is less than 500mm” (CRC Weed Management, 2003), suggesting low drought tolerance. Exhibits some frost and fire resistance, but not waterlogging or drought.	ML	M
Reproduction
9. Reproductive system	“Mainly spreads by seeds…Roots and new plantlets form along branches in contact with soil” (CRC Weed Management, 2003).	H	M
10. Number of propagules produced?	“Can produce large numbers of seeds.” Each infloresence has 30 - 50 florets. Sixteen florets appear on one stem, with 5 flowering stems on one plant, as pictured in CRC Weed Management (2003). 50 x 16 x 5 = 4000.	H	M
11. Propagule longevity?	No data found	M	L
12. Reproductive period?	“Forms monospecific stands, excluding other vegetation (PIER, 2005).	H	MH
13. Time to reproductive maturity?	Already flowering in its first season (Veldkamp, 1999).	H	H
Dispersal
14. Number of mechanisms?	Airborne seed dispersal seems to be effective over short distances (Waterhouse, 2003). Pappus assists dispersal also by water, or by attaching to fur or feathers (CRC Weed Management, 2003).	MH	MH
15. How far do they disperse?	As this plant “grows vigorously along riverbanks” and its seed can be dispersed by water (CRC Weed Management, 2003), many propagules would be likely to reach 200-1000m but few will disperse greater than 1km. “Airborne seed dispersal seems to be effective over short distances” (Waterhouse, 2003).	MH	MH

References

Anon 2004, COOKShire, Queensland Government, Australia, viewed: 09/01/2006, http://www.cook.qld.gov.au/council/publications/COOKSC-Pest Management Plan.pdf.

Corlett RT and Shaw JC 1995, ‘Praxelis clematidea: yesterday South America, today Hong Kong, tomorrow the world?’ Memoirs of the Hong Kong Natural History Society vol. 20, p. 235-236

CRC Weed Management 2003, Weed Management Guide: Praxelis- Praxelis clematidea, CRC Weed Management, Australia.

Csurhes S & Edwards R 1998, Potential Environmental Weeds in Australia, Candidate Species for Preventative Control, Biodiversity Group, Environment Australia, Canberra, ACT.

Pacific Island Ecosystems at Risk (PIER), 2005, Hawaiian Ecosystems at Risk project (HEAR), US Geological Survey, USA, Viewed: 12/10/2005, www.hear.org/pier/species/praxelis_clematidea.htm.

Pollock S, Holland A, Smith W 2004, New alien weed for Queensland: Praxelis. Queensland Herbarium alert sheet, Environmental Protection Agency, Queensland.

Veldkamp, JF 1999, ‘Eupatorium catarium, a New Name for Eupatorium clematideum Griseb., non Shc.Bip. (Compositae), a South American species Naturalised and Spreading in SE Asia and Queensland, Australia,’ Gardens’ Bulletin Singapore, Vol. 51, p. 119-124.

Waterhouse, B.M 2003. Know your enemy: recent records of potentially serious weeds in northern Australia, Papua New Guinea and Papua (Indonesia). Telopea 10(1): 483

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