Nardus stricta_James Lindsey Wikimedia
Photo by James Lindsey

Nardus stricta Risk Assessment

Common names: matgrass

Nardus stricta -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
August 22, 2016
Evaluation Time (hrs): 
3 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: 
High
Answer / Justification: 
Nardus stricta is naturalized in Michigan, New York, New Hampshire, Massachusetts, Oregon, Idaho and New Zealand. It is not yet reported in 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: 
High
Answer / Justification: 
Nardus stricta is naturalized in Michigan, New York, New Hampshire, Massachusetts, Oregon, Idaho and New Zealand. It is not yet reported in California. The naturalized distribution matches California in Oregon, Idaho and parts of New Zealand.
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: 
N. stricta is considered invasive in New Zealand. It is also a noxious weed in Oregon and Idaho.
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: 
N. stricta is considered invasive in New Zealand and some of the locations there match California's climate.
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: 
Very High
Answer / Justification: 
Nardus is a monotypic genus.
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: 
Although there are areas where N. stricta occurs which match California, it is also found in much colder regions.
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: 
Once established it can exclude smaller species due to its growth form, which allows the plant to suppress surrounding vegetation. Its potential to dominate extensive areas is well known from Europe.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
There is no information on whether Nardus promotes or changes fire regime. Due to its low stature and habitat preference it would not be likely to do so.
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: 
N. stricta is able to invade grazing systems because it is less palatable than other grasses. It is also able to reproduce and spread by apomictic seed production.
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: 
High
Answer / Justification: 
Nardus stricta is a wiry, 10 - 40 (-60) cm tall and densely tufted perennial tussock grass with tillers closely packed on laterally branching rhizomes. Since it is low-growing it would not impede movement of animals, livestock or humans.
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: 
It reproduces mostly through transport of tufts in mud clinging to the hooves of grazing animals. Nardus can also regenerate from detached pieces of rhizome, but does not form stolons.
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: 
High
Answer / Justification: 
It reproduces mostly through transport of tufts in mud clinging to the hooves of grazing animals.
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: 
Tiny spikelets can produce 1000 seeds during each blooming.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Tiny spikelets can produce 1000 seeds during each blooming.
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: 
High
Answer / Justification: 
In a study of N. stricta germination, tests of different treatments showed germination percentages from 31 to 90%.
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: 
0
Confidence Level: 
Answer / Justification: 
The studies available do not indicate how long it takes Nardus to reach reproductive maturity. In the available seed study researchers collected mature plants from the field and used those to compare seed production.
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: 
Nardus flowers from June until August.
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: 
High
Answer / Justification: 
N. stricta is most likely to invade low stature vegetation on acid soils, e.g. cushion communities or ephemeral wetlands, and invasion is probably assisted by grazing (Kissling 2004). It reproduces mostly through transport of tufts in mud clinging to the hooves of grazing animals. Seed dispersal on and in the wool of sheep, as reported for a range of other plant species could be an effective mode of transport for Nardus seeds in New Zealand (Kissling 2005).
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: 
Medium
Answer / Justification: 
N. stricta is mainly dispersed by cattle or contaminated seed.
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: 
Medium
Answer / Justification: 
It is hypothesized that N. stricta was first introduced into New Zealand in mixtures of European pasture grasses, which were imported to provide forage for dairy cattle.
Reference(s): 
Evaluation Notes

Invasive Plant Atlas: http://www.invasiveplantatlas.org/subject.html?sub=6076

Reviewed by Chris McDonald.

 

Total PRE Score

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

PRE Score: 
17
Number of questions answered: 
19
Screener Confidence (%): 
75.8
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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