Senecio linearifolius_Ron Vanderhoff
Photo: Ron Vanderhoff

Senecio linearifolius Risk Assessment

Common names: fireweed groundsel

Senecio linearifolius -- California

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Created by: Elizabeth D. Brusati
Created on: Monday, Mar 21st, 2016
Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
March 21, 2016
Evaluation Time (hrs): 
Not Recorded
Evaluation Status: 
Completed
Plant Information
Plant: 
Senecio linearifolius
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: 
North Island of New Zealand and two counties in California. There is also one location in GBIF from Chile.
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: 
Present in two counties in California. Seasonal wetland, sandy soils, drainage areas, disturbed areas.
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: 
Based upon my observations at these two locations I can rather confidently say that the species can overtop and smother native vegetation. At least at these two sites the species has developed thick, nearly impenetrable stands, crowding and shading much of the native vegetation. In some patches the invasion is now approaching a monoculture. - Ron Vanderhoff, Orange County CNPS
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: 
Based upon my observations at these two locations I can rather confidently say that the species can overtop and smother native vegetation. At least at these two sites the species has developed thick, nearly impenetrable stands, crowding and shading much of the native vegetation. In some patches the invasion is now approaching a monoculture. - Ron Vanderhoff, Orange County CNPS
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: 
Senecio jacobaea (tansy ragwort) is invasive in California (Limited rating on Cal-IPC Inventory) because it can crowd out desirable forage species and displace native plants in disturbed areas. Cape-ivy (Delairea odorata, formerly Senecio mikanioides) is a highly invasive plant in California (High on Cal-IPC Inventory) because it creates dense infestations in coastal areas.
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: 
Very High
Answer / Justification: 
I am basing this answer mostly on the native range in Australia since there are very few naturalized locations. Most Australian locations are on the coast of New South Wales, Victoria, and Tasmania. These areas match California. GBIF map: http://www.gbif.org/species/3108807
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: 
There are five populations in California and I have detailed knowledge of two of these populations, including California's original infestation near the UC Irvine campus from 1998. Based upon my observations at these two locations I can rather confidently say that the species can overtop and smother native vegetation. At least at these two sites the species has developed thick, nearly impenetrable stands, crowding and shading much of the native vegetation. In some patches the invasion is now approaching a monoculture. - Ron Vanderhoff, Orange County CNPS
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Very Low
Answer / Justification: 
No information is available.
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: 
Very Low
Answer / Justification: 
No information is available.
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: 
My personal observations at two of the five California colonies would rather strongly indicate that this plant does produce impentratable thickets. In the coastal sage scrub areas where I have observed this plant (including the UC Irvine land of the original 1998 CA record) it is pushing out native vegetation. In some patches it is creating a near monoculture of dense chest high thick herbaceous growth that can hardly be penetrated. - Ron Vanderhoff, Orange County CNPS
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Seems unlikely for a woody subshrub.
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: 
Seems unlikely for a woody subshrub.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Produces fruits.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Points: 
Confidence Level: 
Very Low
Answer / Justification: 
No information
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: 
Points: 
Confidence Level: 
Answer / Justification: 
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: 
Answer / Justification: 
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 May - October in California.
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: 
There is no evidence on dispersal of S. linearifolius by mammals or birds.
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: 
Dispersal by wind is most likely since the fruit has a pappus. Note from Ron Vanderhoff: I do not have a reference study to support this, but it would be strongly assumed that this species would be wind dispersed, and likely at long distances. The architecture of the seed, like almost all Senecios, is built for wind transport. It has long pappus bristles of 5-8 mm and a very light seed. Virtually all species of the genus Senecio share an airborne seed dispersal quality.
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: 
Low
Answer / Justification: 
There is no evidence for dispersal by contaminated seed, equipment, vehicles or clothing.
Reference(s): 
Evaluation Notes

Cannot find information on even basic biology of this species. A literature search brought up only four articles. Australian plant websites had only maps.

Jepson Flora: http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=82562

The plants in California are S. linearifolius var. linearifolius.

Reviewed and observations added by Ron Vanderhoff, Orange County CNPS. Also reviewed by Mona Robison.

Total PRE Score

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

PRE Score: 
16
Number of questions answered: 
17
Screener Confidence (%): 
68.2
PRE Content Access and Privacy
Organization: 
California Invasive Plant Council (Cal-IPC)
Evaluation visibility: 
Public - accessible to all site users

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