Pennisetum villosum_C203-12
Photo: UC Davis Weeds of California

Pennisetum villosum Risk Assessment

Common names: feathertop

Pennisetum villosum -- California

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Created by: Kristina Wolf
Created on: Wednesday, Apr 13th, 2016
Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
April 13, 2016
Evaluation Time (hrs): 
2 Hours
Evaluation Status: 
Completed
Plant Information
Plant: 
Pennisetum villosum
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: 
High
Answer / Justification: 
Naturalised in New Zealand, North and South America, Asia, South Africa, Italy and the Azores (Weeds Australia - Weed Identification). Widely naturalised in southern and eastern Australia. It is most widespread and common in southern Queensland, New South Wales, Victoria, Tasmania, south-eastern South Australia and in the coastal districts of south-western and western Western Australia. Also present in northern Queensland, and in other parts of South Australia and Western Australia. It was also naturalised in the ACT, but has not been collected there for more than 30 years. Naturalised overseas in some parts of the USA (i.e. California, Colorado, Texas, Georgia and Michigan) and in Hawaii (Weeds of Australia Biosecurity Queensland Edition).
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: 
Naturalised in New Zealand, North and South America, Asia, South Africa, Italy and the Azores (Weeds Australia - Weed Identification). Widely naturalised in southern and eastern Australia. It is most widespread and common in southern Queensland, New South Wales, Victoria, Tasmania, south-eastern South Australia and in the coastal districts of south-western and western Western Australia. Also present in northern Queensland, and in other parts of South Australia and Western Australia. It was also naturalised in the ACT, but has not been collected there for more than 30 years. Naturalised overseas in some parts of the USA (i.e. California, Colorado, Texas, Georgia and Michigan) and in Hawaii (Weeds of Australia Biosecurity Queensland Edition). Many of these climates overlap substantially with California's climate zones (Cal-IPC global map of climate areas matching 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: 
High
Answer / Justification: 
Feathertop is regarded as an environmental weed in Victoria, New South Wales, Tasmania and South Australia (Weeds of Australia Biosecurity Queensland Edition).
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: 
Feathertop is regarded as an environmental weed in Victoria, New South Wales, Tasmania and South Australia (Weeds of Australia Biosecurity Queensland Edition). Many of these climates overlap substantially with California's climate zones (Cal-IPC global map of climate areas matching California).
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: 
P. setaceum is invasive in California and is present in CA, OR, AZ, NM, and CO (Cal-IPC; Weed control in natural areas in the Western United States). P. clandestinum, P. macrourum, P. pedicellatum, P. polystachion, P. polystachyon are listed as noxious weeds in California (USDA-NRCS PLANTS). P. ciliare is also invasive in AZ and is present in California, P. setaceum is invasive and widespread in CA, and P. clandestinum is widespread and invasive in CA (Invasive Species List and Scorecards for California). Many of these climates overlap substantially with California's climate zones (Cal-IPC global map of climate areas matching California).
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: 
Found throughout Mediterranean region, present in California, and worldwide (GBIF). Many of these climates overlap substantially with California's climate zones (Cal-IPC global map of climate areas matching California).
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: 
Medium
Answer / Justification: 
A weed of remnant grassy native vegetation in farming areas, where it can suppress native groundcover species (Eurobodalla Shire Council Weeds). May crowd out native vegetation if planted near open country and directly competes with natural vegetation (SAN DIEGO COUNTY INVASIVE ORNAMENTAL PLANT GUIDE).
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: 
Recover quickly after fire and may increase in density after a burn (PIER WRA). Adapted to fire (CDFA). Fire-promoting grass that recovers quickly after fire (PlantPono). However, a weed risk assessment also notes that while it may promote fire, it would not likely do so anymore than any other grass it replaces, and as such does not represent a change to fire regimes or promotion of fire (Victorian Invasive Plants).
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: 
Medium
Answer / Justification: 
Mature plants are unpalatable to stock, so the plant can become more common in over-grazed pasture (Eurobodalla Shire Council Weeds), thereby impacting grazing systems by potentially reducing carrying capacity. Produces large dense clumps, which over time tend to dominate infested pastures and reduce the available grazing area. Chokes out useful grasses and ‘being unpalatable reduces carrying capacity’. Because not specified, a moderate level of impact is assumed (Victorian Invasive Plants).
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: 
Medium
Answer / Justification: 
A tufted grass, usually around 30-50cm high with very distinctive white fluffy seed heads (Eurobodalla Shire Council Weeds). Tufted rhizomatous perennial grass to 90 cm high (Weeds Australia - Weed Identification). Mat-forming, in dense large tussocks; dense clumps can be formed that tend to dominate infested pasture (PIER WRA).
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: 
Individual clumps gradually expand by underground rhizomes (Eurobodalla Shire Council Weeds). Spread by rhizomes and seed (Weeds Australia - Weed Identification).
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: 
Root segments easily spread by grading and can produce new plants (PIER WRA). Rhizome fragments can generate new plants (CDFA).
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: 
Spread by rhizomes and seed (Weeds Australia - Weed Identification). Feathertop ornamental grass is a ready self-seeder, so grow it in an area where it can spread, or you will need to cut off the flowers before the seeds ripen in the fall (Outside Pride).
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Points: 
Confidence Level: 
Low
Answer / Justification: 
Feathertop ornamental grass produces nodding silver panicles in great profusion from late summer through early fall. The flowers look like clouds that are floating about, catching the breeze and waving about (Outside Pride). A heavy self-seeder (SAN DIEGO COUNTY INVASIVE ORNAMENTAL PLANT GUIDE). An exhaustive Google/Google Scholar search did not reveal any quantitative information about seed production, and this defaults to a "no" answer.
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: 
Medium
Answer / Justification: 
Although a prolific seeder, seedling establishment is usually poor, with plants growing best in sandy soils (PIER WRA). An exhaustive Google/Google Scholar search did not reveal any additional information about germination, but this seems unlikely given poor seedling establishment, and defaults to a "no" answer.
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: 
1-2 years (PIER WRA).
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: 
High
Answer / Justification: 
Blooms June - August (Calflora; Jepson)
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: 
The seed is spread along roads in mud on machinery and vehicles, and can adhere to animals and clothing (Eurobodalla Shire Council Weeds). Spread by water, wind, animals (external), machinery, contaminated soil or dumped garden waste. Is a contaminant in wool. Some seed held within involucral bristles can adhere to wool and fur. [produce contaminant of wool products] (PIER WRA).
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: 
Wind and water may also spread seed (Eurobodalla Shire Council Weeds). Feathertop ornamental grass produces nodding silver panicles in great profusion from late summer through early fall. The flowers look like clouds that are floating about, catching the breeze and waving about (Outside Pride). In Australia, the main infestations in the North West Weeds County Council area are located in the Delungra and Inverell areas. Lesser infestations occur in the towns of Barraba, Bingara. Infestations are also present in the Horton and McIntyre Rivers. More and more plants are showing up throughout the NWWCC district, obviously being transported by wind, stock and motor vehicles. Spread by water, wind, animals (external), machinery, contaminated soil or dumped garden waste (PIER WRA). Seeds spread far by the wind (PlantPono).
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: 
The seed is spread along roads in mud on machinery and vehicles. The seed heads may be picked for dried flower arrangements, then discarded. The plant is sometimes sold as a garden ornamental (Eurobodalla Shire Council Weeds). In Australia, the main infestations in the North West Weeds County Council area are located in the Delungra and Inverell areas. Lesser infestations occur in the towns of Barraba, Bingara. Infestations are also present in the Horton and McIntyre Rivers. More and more plants are showing up throughout the NWWCC district, obviously being transported by wind, stock and motor vehicles. Spread by water, wind, animals (external), machinery, contaminated soil or dumped garden waste (PIER WRA).
Reference(s): 
Evaluation Notes

Websites consulted for this screen included:
Tropicos: http://www.tropicos.org/Name/25514699;
GBIF: http://www.gbif.org/species/2706154;
Weeds of Australia: http://keyserver.lucidcentral.org/weeds/data/media/Html/cenchrus_longise...
Eurobodalla Shire Council: http://www.esc.nsw.gov.au/living-in/about/our-natural-environment/introd...
CalFlora: http://www.calflora.org/cgi-bin/species_query.cgi?where-taxon=Pennisetum...
Jepson: http://herbaria4.herb.berkeley.edu/eflora_display.php?tid=36829;
ICE UC Davis (congeners): http://ice.ucdavis.edu/invasives/home/species?order=field_common_name_va...
CABI: http://www.cabi.org/isc/datasheet/116203;
Eurobodalla Council Shire: http://www.esc.nsw.gov.au/living-in/about/our-natural-environment/introd...
Australian Weeds: http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&state=&s=&ib...
Outside Pride: http://www.outsidepride.com/seed/ornamental-grass/pennisetum/feathertop-...
UC WRIC (congener): http://wric.ucdavis.edu/information/natural%20areas/wr_P/Pennisetum_seta...
PIER: http://www.hear.org/pier/wra/pacific/pennisetum_villosum_htmlwra.htm;
PIER WRA: http://www.hear.org/pier/wra/pacific/pennisetum_villosum_htmlwra.htm;
CDFA: https://www.cdfa.ca.gov/plant/ipc/encycloweedia/weedinfo/pennisetum.htm;
SAN DIEGO COUNTY INVASIVE ORNAMENTAL PLANT GUIDE: http://www.asla-sandiego.org/aslasdwp/wp-content/uploads/2014/10/Most_In...
PlantPono: http://plantpono.org/inv-plant.php?id=4;
Victoria Invasive Plants WRA: http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/impact_feath...

Total PRE Score

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

PRE Score: 
21
Number of questions answered: 
19
Screener Confidence (%): 
75.8
PRE Content Access and Privacy
Organization: 
California Invasive Plant Council (Cal-IPC)
Evaluation visibility: 
Public - accessible to all site users

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