Photo credit: Ron Vanderhoff

Acacia saligna Risk Assessment

Synonyms: Acacia cyanophylla, Acacia bracteata, Acacia lindleyi, Mimosa saligna, Racosperma salignum

Common names: Orange wattle

Acacia saligna -- California

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Evaluation Summary
This is a shrubby tree native to Australia. It has been noted as invasive in areas with a similar climate to the study area, California. It is known to outcompete native species, spread vegetatively and produce an abundance of seed, though there was not a good source of information about seed dispersal. The species is fairly well documented and there was adequate information available based on its history of invading native vegetation in South Africa.
General Evaluation Information
Date of Evaluation: 
January 12, 2020
Evaluation Time (hrs): 
3 Hours
Evaluation Status: 
Submitted
Plant Information
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: 
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.
Climate Matching Maps PDF: 
AttachmentSize
PDF icon Matching_Results.pdf515.31 KB
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: 
Naturalized where it is not native in Africa, Australia and the United States (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 where it is not native in Africa, Australia and the United States (USDA GRIN). Naturalized in Southeastern Australia, South Africa, southern Europe, and the west coast of the United States in similar climates (GBIF). Naturalized in the southwestern Cape Province, South Africa (Milton & Hall 1981). The species occurs in 7 counties in coastal and southern California, the region of interest. (Calflora)
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: 
Very High
Answer / Justification: 
The species is invasive in Cyprus, Israel and South Africa. (GISD) The species has been noted to be invasive in the southwestern Cape of South Africa. (Holmes et al. 1987)
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: 
Very High
Answer / Justification: 
The species is invasive in Cyprus, Israel and South Africa, all of which are a similar climate to the study area, California, USA. (GISD) The species has been noted to be invasive in the southwestern Cape of South Africa, which is similar in climate. (Holmes et al. 1987; Holmes & Cowling 1997)
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 paradoxica is on the California noxious weed list (CDFA). 3 other Acacias are on the California Invasive Plant Council Inventory as of this writing (January 2020) (Cal-IPC, 2020)
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: 
Yes, the balance of occurrences are in areas matching the climate in the study region. The following areas match the climate of the region of concern: west coast of the US (7 counties in California, USA), central Mexico; southern Europe and the Mediterranean; very northern Africa (Mediterranean); the middle East (Israel, Palestine); South Africa (Cape and eastern region); Western Australia and southeastern Australia. (GBIF) The following areas where the plant occurs do not match the climate of the study region: Pakistan, Ethiopia, Sweden, the North Island of New Zealand, and the occurrences in South America. (GBIF)
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: 
Medium
Answer / Justification: 
Noted to produce "dense shade" in long-invaded areas in South Africa.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
After fire a "dense sward of Acacia seedlings is usually the result," outcompeting the native fynbos species after fire. The species may also resprout after fire.
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: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Not listed as a health risk to humans or animals. (Canada BIF, FDA) Examined as feed for goats, found to be not a candidate as a whole food source. (Degen et al. 1997)
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: 
Medium
Answer / Justification: 
Areas in the Cape Peninsula in South Africa were noted to have >80% canopy cover of the species (notably high for a Mediterranean ecosystem).
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Noted to spread by both "root suckers and seed." (Flora of Australia) Can resprout from underground tissue post-fire. (Holmes & Cowling, 1997)
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: 
Very Low
Answer / Justification: 
The species occurs on upland sites and the species wasn't noted to spread beyond immediately from the vegetative reproduction. (Holmes & Cowling 1997)
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: 
Noted to reproduce by seed.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Seeds falling within seed traps below the canopy were noted to catch 5,443 seeds per meter square per year.
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: 
Medium
Answer / Justification: 
Germination without treatment is shown to be <25%. (Table 7, Milton & Hall)
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: 
Points: 
Confidence Level: 
Very Low
Answer / Justification: 
I could not locate this informatoin.
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: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Flowers "July-November" in Australia (Flora of Australia online) Flowers March, April, May (3 months) in California (Calflora) "Pod and seed fall: The pods and seeds of Acacia longifolia and A. saligna fall over a six week period, three to four months after the fall of withered flowers." This observation from South Africa. (Milton & Moll 2008)
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: 
Low
Answer / Justification: 
Even though it was noted in a species summary in GISD as being dispersed by birds, the original reference cited shows only: water, mammals and ants as dispersal agents (Appendix 6). (Henderson 1998). No distance or other information was found, and no specific adaptations for long-distance dispersal were noted. "The seeds of these species have small grey-white funicles (Fig. 16), unlikely to attract frugivorous dispersers, and are not presented to potential dispersers while on the tree, the pods being both deciduous and dehiscent." (Milton & Moll 2008)
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
No
Points: 
0
Confidence Level: 
Low
Answer / Justification: 
There are no specific adaptations to disperse via these methods. See image, GRIN. Literature indicates that this species does occur on some water courses and may have spread downstream to other locations but this seems not special to this species in any way.
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: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
No specific adaptations for this. This species is not in wildflower packets. It is used for stock fodder and grown in plantations in many areas. I did not find any specific information about mode of spread from the intentional introductions.
Reference(s): 
Invasive Species Specialist Group (2017).  GISD.
Evaluation Notes
Notes: 
Total PRE Score

  • < 13 : Low Potential Risk
  • 13 - 15 : Moderate Potential Risk
  • > 15 : High Potential Risk

PRE Score: 
17
Number of questions answered: 
19
Screener Confidence (%): 
69.0
PRE Content Access and Privacy
Evaluation visibility: 
Private - accessible only to organization members

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