Acacia paradoxa_C122-06
Photo courtesy UC Davis Weeds of California

Acacia paradoxa Risk Assessment

Common names: kangaroothorn

Acacia paradoxa -- California

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Created by: Elizabeth D. Brusati
Created on: Monday, Jan 25th, 2016
Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
January 25, 2016
Evaluation Time (hrs): 
Not Recorded
Evaluation Status: 
Completed
Plant Information
Plant: 
Acacia paradoxa
Plant Material: 
If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how: 
Regional Information
Region Name: 
California
Climate Matching Map
These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.
Link to Climate Matching Map: 
Climate Matching Maps PDF: 
Invasive History and Climate Matching
1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Present in 11 California counties. Naturalized in South Africa. Also naturalized in Australia outside its native range there. No other locations listed by USDA GRIN.
Reference(s): 
2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
Naturalized in 11 counties in California and in South Africa.
Reference(s): 
3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
Invasive in Tasmania and Western Australia but might really be native to SW Western Australia.(Native to southern and eastern Australia.) Also becoming a problem in the Cape region of South Africa, although populations are small and not spreading much. Forms locally dense stands.
Reference(s): 
4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
3
Confidence Level: 
High
Answer / Justification: 
Considered an environmental weed in Tasmania and Western Australia (although may be native to SW Western Australia). Also becoming a problem in the Cape region of South Africa, although populations are small and not spreading much. Forms locally dense stands. Large portions of these areas match California, according to Cal-IPC's climate map, so yes.
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Acacia dealbata and A. melanoxylon are listed on Cal-IPC Inventory as invasive in California.
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
The Australian native and naturalized locations are clustered in areas that mostly match California, according to Cal-IPC's climate map. Map of Australian locations: http://avh.ala.org.au/occurrences/search?taxa=acacia+paradox#tab_mapView. (No entry in GBIF for this species or its synonyms.)
Reference(s): 
Impact on Native Plants and Animals
7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Can become dominant in some areas of Australia because thorny stems prevent grazing by livestock. In South Africa, at a local has formed thick stands of up to 20 plants per square m.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Listed as a "fire risky" plant to avoid in landscaping in Australia, but no information on whether it changes fire regimes.
Reference(s): 
9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Can be a problem in grazing areas in Australia because livestock will not graze the thorny stems and therefore the plant becomes dominant. As a tall woody species, its spines could also be a health hazard to humans or animals.
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
In South Africa, at a local scale it has formed thick stands of up to 20 plants per square m. Has formed dense stands in Australia. Answering yes based on thick stands and the fact that it's a fairly tall, woody species with spines.
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Weeds of California mentions that black acacia produces suckers but does not mention this method of reproduction for Acacia paradoxa.
Reference(s): 
12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
No indication that it would be capable of this.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Yes
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Mean firm seed production per plant for A. paradoxa calculated at 58.
Reference(s): 
15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Seeds are hard coated and require degradation or scarification to germinate.
Reference(s): 
16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Produces seed at an early age.
Reference(s): 
17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Flowers for 3 months. Flowers February - April in California so I am extrapolating that to seed production.
Reference(s): 
Dispersal
18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Pods and seeds not typically used by native wildlife. (However, in Australia, most species of acacia are bird or ant-dispersed.)
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Can be dispersed long distances by water.
Reference(s): 
20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Can be dispersed by human activities.
Reference(s): 
Evaluation Notes

Queensland factsheet:http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Acacia_paradoxa.htm

Reviewed by Steve Schoenig, CA Dept. of Fish and Wildlife and CA Dept. of Agriculture (retired) and Eric Wrubel, National Park Service

Total PRE Score

  • < 13 : accept (low risk of invasiveness)
  • 13 - 15 : evaluate further
  • > 15 : reject (high risk of invasiveness)

PRE Score: 
19
Number of questions answered: 
20
Screener Confidence (%): 
84.0
PRE Content Access and Privacy
Organization: 
California Invasive Plant Council (Cal-IPC)
Evaluation visibility: 
Public - accessible to all site users

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