Genista linifolia Risk Assessment

Common names: Mediterranean broom

Genista linifolia -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
January 27, 2016
Evaluation Time (hrs): 
Not Recorded
Evaluation Status: 
Completed
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: 
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: 
Australia, New Zealand, Morocco (however, USDA lists Morocco as part of the native range).
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 4 California counties.
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: 
Noxious weed in Victoria, Australia, where it is a prohibited species in some areas. Found predominantly on roadsides and fencelines where it spreads into grazing areas. Can invade grasslands, forests, heathland, and riparian areas. Also very invasive on Santa Catalina Island and spreading at Franklin Canyon in Santa Monica Mtns and in the Ojai area, California. (Personal communication from Irina Irvine, National Park Service).
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: 
Listed as a noxious weed in Victoria, Australia (Prohibited weed in one region, Controlled weed in others). Found predominantly on roadsides and fencelines where it spreads into grazing areas. Invades grasslands, forests, heathland, and riparian areas. Has the ability to crowd out smaller species. No maps available on GBIF or the Australian Herbarium. Locations in Noxious Weeds of Australia book overlap with areas that match California.
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: 
Yes, Genista monspessulana invasive in California (and other places).
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: 
Native to the Mediterranean (France, Spain, Canary Islands) and invasive in Victoria.
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: 
Very High
Answer / Justification: 
Forms dense thickets in Australia. Has the ability to crowd out smaller species.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Low
Answer / Justification: 
Regenerates prolifically after fire from seedbank. Other brooms promote fire, no specific information on this species.
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: 
Thought to be toxic but is little grazed and not a problem in this regard. Invades grazing lands, forms dense clumps that reduce grazing (Parsons and Cuthbertson). Seeds are poisonous to humans (Weeds of Australia).
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: 
Forms dense clumps which reduce grazing. Can grow up to 3m tall. Noxious Weeds of Australia specifically says it forms impenetrable thickets and has a photo of one.
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: 
No mention of coppicing or sprouting.
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: 
Medium
Answer / Justification: 
No information but seems unlikely for a woody shrub.
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: 
Reproduces 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: 
2000 flowers per plant, producing up to 4000 seeds.
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: 
The seeds have a hard seed coat that requires heat or some form of superficial cutting, abrasion or incision to break dormancy and stimulate germination.
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: 
High
Answer / Justification: 
Flowers at two years old.
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: 
High
Answer / Justification: 
Flowers Feb - Aug in California. In Australia, flowers in the spring and seeds are released in spring and summer. Seeds Oct-Feb in Australia.
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: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Can be dispersed by animals. Parsons and Cuthbertson say that spread occurs when seeds contaminate vehicles, produce or mud, and does not mention animal dispersal. Not sure how common animals are for dispersal.
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: 
Medium
Answer / Justification: 
Can be dispersed by water. Seeds are a silky pod with two or three seeds. Water not mentioned by Parsons and Cuthbertson so rating my confidence lower.
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: 
Seeds spread by vehicles and mud.
Reference(s): 
Evaluation Notes

A Plant Assessment Form was completed for the Cal-IPC Inventory, but the species wasn't added because of uncertainty about impacts, specifically whether the impacts would be similar to French broom. Most of the information in the PAF was based on extrapolation from French Broom. The PAF was never finalized.

Direct link to Australia websites:

Queensland - http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-060...

Victoria -  http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/weeds...

PRE reviewed by Irina Irvine, Santa Monica Mountains National Recreation Area.

Total PRE Score

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

PRE Score: 
21
Number of questions answered: 
20
Screener Confidence (%): 
82.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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