Paspalum vaginatum_Ron Vanderhoff
Photo by Ron Vanderhoff

Paspalum vaginatum Risk Assessment

Common names: seashore paspalum

Paspalum vaginatum -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
August 26, 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: 
Naturalized in California. Present in 6 counties according to Calflora. Also naturalized in Europe, northern Africa, the Azores, New Zealand, Hawaii and Fiji.
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: 
Naturalized in California. Present in 6 counties according to Calflora. Also naturalized in Europe, northern Africa, the Azores, New Zealand, Hawaii and Fiji. Occurs in climates which match California in Europe.
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: 
Paspalum vaginatum is known from warm temperate, tropical, and subtropical regions around the world, and is widely regarded as an invasive species; In southern California, rapidly expanding populations and the formation of dense monocultures of P. vaginatum pose a serious threat to the structure, function, and native species composition of estuarine wetlands. In the coastal lowland wetlands of the Hawaiian Islands, P. vaginatum is highly invasive in brackish wetlands (Riefner 2010).
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: 
P. vaginatum is invading estuarine and other saline wetlands in southern California (Riefner 2010). In the coastal lowland wetlands of the Hawaiian Islands, P. vaginatum is highly invasive in brackish wetlands. It is also considered invasive in New Zealand and Spain, and it matches the California climate in Spain.
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: 
High
Answer / Justification: 
P. urvillei invades and establishes in highly disturbed natural ecosystems where it grows in dense stands, displacing indigenous vegetation and altering the lower strata. It is listed as invasive in China, Japan, parts of Africa, United States, Puerto Rico and Australia (CABI Invasive Species Compendium). There are many points in GBIF, including areas of Australia with climate similar to California.
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: 
While P. vaginatum is widespread, most of the recorded locations in GBIF do not match California's climate.
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: 
In coastal habitats it can spread at 1-2 m per year and become dominant over native vegetation. In New Zealand it is of concern having invaded the nesting areas of the endangered New Zealand fairy tern (Sterna nereis), threatening a range of uncommon or endangered plant species, and possibly affecting fish breeding. It is also regarded as a threat to native vegetation in California (Riefner and Columbus 2008).
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 P. vaginatum promotes or changes fire regimes. Since it is a small stature perennial grass of coastal wetlands it is not likely to promote fire.
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: 
Medium
Answer / Justification: 
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: 
Since plants are only 10-50 cm tall they are unlikely to produce impenetrable thickets or block movement.
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 is established vegetatively using sod, containerized material, stolons, and rhizomes.
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 is established vegetatively using sod, containerized material, stolons, and rhizomes. Short rhizomes and elongated stolons are apparently the primary mechanisms for expanding stands of seashore paspalum (Lonard 2015).
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Seashore paspalum naturally produces some seed, but it has some dormancy and viability is low.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Seashore paspalum produces seed, but they are rarely viable.
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: 
In a study of a seeded Paspalum vaginatum cultivar, seed germination was improved to 80% using different combinations of light and temperature. Without special treatments the germination of the seed lot used was 5%. This germination information, however, is not likely to apply to wild plants, unless the seeded cultivar escapes into the wild.
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: 
Although seed viability is low, when it is produced it would likely occur within 3 years of clonal establishment.
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: 
P. vaginatum Flowers and fruits from June to September.
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: 
Outside of cultivation, vegetative reproduction of P. vaginatum would be possible through animal grazing and other natural physical regimes that would disturb and transport rhizomes and stolons.
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: 
High
Answer / Justification: 
Paspalum vaginatum is apparently dispersed primarily by water when pieces of stolon or rhizome are carried often long distances by streams. These vegetative fragments root easily, forming new plants that start new infestations.
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: 
High
Answer / Justification: 
P. vaginatum may have been spread vegetatively by animals, carried by mechanized landscape equipment to new sites, or rhizome and stolon fragments may have been dispersed by water during storm events from turf plantings in the uplands into urban drainages and then downstream to native wetland communities.
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: 
18
Number of questions answered: 
20
Screener Confidence (%): 
73.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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