Gunnera tinctoria_Richard Spellenberg
Photo by Richard Spellenberg

Gunnera tinctoria Risk Assessment

Common names: Chilean gunnera

Gunnera tinctoria -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
June 29, 2016
Evaluation Time (hrs): 
2 Hours
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: 
Naturalized in the Azores, New Zealand, United Kingdom, Ireland, France and California.
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: 
The Azores and some of the locations in New Zealand are similar to California and it is naturalized in California.
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: 
Invasive in Ireland, the United Kingdom and New Zealand. In New Zealand it is included in the National Pest Plant Accord list and particularly a problem on the North Island. In Britain, the species is listed on Schedule 9 of the amended Wildlife and Countryside Act 1981 (WCA 1981), because of its documented negative effects on plant diversity. In Britain, it grows in riparian areas and on coastal cliffs down to the high tide mark, indicating a tolerance to salt spray. Gunnera also has severe ecological impacts on Sao Miguel Island in the Azores. It can alter the soil seed bank of native communities, change soil biochemistry, and homogenize the seed flora by increasing the relative abundance of weeds and rushes. Gunnera is the only genus of angiosperm that is known to form an intracellular symbiosis with nitrogen-fixing cyanobacteria.
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: 
Of the regions listed in Q3, the Azores and New Zealand are similar to California.
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
The only other species listed in Randall 2012 is G. manicata and it is only cited as naturalized rather than invasive.
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Britain and Ireland do not match California, nor does the area in northern France where it is naturalized. Part of its native range in South America, the Azores, and part of New Zealand do match. It's a split but I don't think it fits the definition of predominantly.
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: 
Invasive in Ireland, the United Kingdom and New Zealand. In New Zealand it is included in the National Pest Plant Accord list and particularly a problem on the North Island. In Britain, the species is listed on Schedule 9 of the amended Wildlife and Countryside Act 1981 (WCA 1981), because of its documented negative effects on plant diversity. Also has severe ecological impacts on Sao Miguel Island in the Azores. It can alter the soil seed bank of native communities, change soil biochemistry, and homogenize the seed flora by increasing the relative abundance of weeds and rushes. Gunnera is the only genus of angiosperm that is known to form an intracellular symbiosis with nitrogen-fixing cyanobacteria.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
No mention of this in the thorough review by Gioria and Osborne 2013.
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 High
Answer / Justification: 
The species is edible and it has been reported to have medicinal properties (but may also contain neurotoxins). The areas it invades seem to be focused on riparian areas rather than grazing areas.
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: 
This is a very large herbaceous plant that grows 8 ft tall with leaves that are 4-8 ft across on 6 ft tall stalks with stiff hairs. Plants have multiple stalks. Given its size and the fact that it can create dense infestations, "impenetrable" stands seem likely.
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Can spread clonally through a horizontal rhizome system. Rhizomes have been recorded growing an average 15 cm per year.
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: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Once established at a site, vegetative spread and dispersal of plant fragments appear to be the most important factors for the persistence of the species. Eradication by mechanical removal has proved effective only where the entire rhizome system was removed together with standing biomass, to prevent any re-sprouting.
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: 
Produces large numbers of seeds.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Estimates of seed production quoted in Gioria and Osborne 2013 include 750,000/plant in Ireland and 250,000/plant in New Zealand. Almost all fresh seeds collected from an invasive population in Ireland germinated. Seeds from a native population in Chile had a 77% germination rate.
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: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Seeds are not dormant at maturity and do not have any cold stratification requirements. Germination can occur throughout the year except in winter (results from Ireland).
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: 
No
Points: 
0
Confidence Level: 
Very High
Answer / Justification: 
Begins producing seed at about 5 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: 
Medium
Answer / Justification: 
In California, it flowers from July to October according to the Jepson eFlora. One record from the Bay Area in Calflora indicates it flowering in early May. In Britain, Ireland, and the Azores, flowers and fruits appear from April to Oct, and in South America from Oct to February. In the Azores, flowers develop in Feb-March, pollination occurs in April, seeds start forming in May, and fruits mature between July and October.
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: 
Very High
Answer / Justification: 
Seeds are thought to be dispersed mostly by birds and water. In Scotland, starlings, redwings, and thrushes have been seen eating and dispersing the fruits.
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: 
Seeds are thought to be dispersed mostly by birds and water. This species often grows along streams.
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: 
High
Answer / Justification: 
This does not seem to be a major form of dispersal.
Reference(s): 
Evaluation Notes

USDA GRIN: https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?id=400231;

GBIF: http://www.gbif.org/species/2984306;

Jepson: http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=27405

Reviewed by Tim Hyland, California State Parks, and Ron Vanderhoff, California Native Plant Society - Orange County.

Comment by Ron Vanderhoff: Given the climate match statistics and the known habitat and ecology of the species this would seem to be a regional concern. Establishment of the species South of the Bay Area may be unlikely. 

Total PRE Score

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

PRE Score: 
18
Number of questions answered: 
20
Screener Confidence (%): 
92.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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