Helianthus tuberosus_Nick Kurzenko
Photo by Nick Kurzenko

Helianthus tuberosus Risk Assessment

Common names: Jerusalem artichoke

Helianthus tuberosus -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
June 29, 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: 
Naturalized in the Azores, much of Europe, parts of Asia, Australia, New Zealand, Argentina, Uruguay. (Native to eastern and central United States.)
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: 
High
Answer / Justification: 
Of the areas listed by USDA GRIN, the following match California: Italy, France, Spain, Croatia, the Azores. The Jepson Manual does not list it as naturalized in California (it doesn't list this species at all) and there are only two points in Calflora, from 1969 and 1995, so it does not appear to be naturalized here. This species was placed on the Cal-IPC watchlist based on our article (Brusati et al 2014) finding it to be invasive in other Mediterranean regions and naturalized in California but the naturalization may have been an exaggeration.
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 Romania. Included in study on the phenotype plasticity and functional traits in invasive plants there. One of the five most widespread species invading river floodplains in Central Europe. Listed as a major invader in Mediterranean France, defined as being widespread and having a significant ecological impact.
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 major invader in Mediterranean France, defined as being widespread and having a significant ecological impact.
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: 
Medium
Answer / Justification: 
Several other species of Helianthus are listed in Randall 2012 but most are only indicated as naturalized. Several species are listed on the DAISIE invasives website for Europe but without much information. Helianthus ciliaris is listed by Randall as invasive in several areas, including California, where it is an A-rated noxious weed due to impacts in agricultural fields.
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: 
High
Answer / Justification: 
This is a widespread species that grows in much of North America and Europe, as well as scattered locations in other parts of the world.
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: 
Listed as a major invader in Mediterranean France, defined as being widespread and having a significant ecological impact based on field observations. The reference did not give details (it's just a list of species) but I am making the assumption than if it's considered a major invader, it must be displacing native plants.
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.
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: 
High
Answer / Justification: 
Grown as a food crop and was eaten by Native Americans. The tubers are edible. Sold as sunchokes (this species is not actually related to artichokes, despite the name). Also eaten by snails in the Czech Republic. It was introduced into Europe partly as a food for pigs.
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
No
Points: 
0
Confidence Level: 
Answer / Justification: 
This is a sunflower that grows 10 ft tall. However, I don't have information on dense infestations or imprenetrable thickets.
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: 
Reproduces from tubers.
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: 
This does not seem likely given its biology.
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, produces many seeds.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Could not find specific numbers but based on it being a form a sunflower I would assume yes. "Results showed that the seed fertilities of five collected varieties ranged from 2.4 % to 14.7 % and the number of seed produced by one plant ranged from 88 to 1058." http://agris.fao.org/agris-search/search.do?recordID=KR9036226
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: 
Medium
Answer / Justification: 
I would guess yes but couldn't find specific information. "Results showed that the seed fertilities of five collected varieties ranged from 2.4 % to 14.7 % and the number of seed produced by one plant ranged from 88 to 1058." http://agris.fao.org/agris-search/search.do?recordID=KR9036226
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: 
Medium
Answer / Justification: 
It's a large, fast-growing, perennial herb, i.e. a sunflower. I am guessing yes.
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: 
Very High
Answer / Justification: 
In Britain, it flowers in October and seeds ripen in November. In its native range in North America, it flowers in August to 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: 
The seeds are attractive to birds.
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: 
High
Answer / Justification: 
Birds seem to be the main form of seed dispersal.
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: 
As it's a native sunflower in North America, it could be included in wildflower packets but I do not have information on this and it has not really naturalized in California. In other places, it seems to have spread from plantings.
Reference(s): 
Evaluation Notes
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: 
20
Screener Confidence (%): 
76.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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