Plant Assessment Form

Acroptilon repens

Synonyms: Centaurea repens

Common Names: Russian knapweed, hardheads, creeping knapweed, mountain bluet, Turkestan thistle

Evaluated on: 7/20/04

List committee review date: 27/08/2004

Re-evaluation date:

Evaluator(s)

Rob Wilson, Weed Ecology/Cropping Systems Farm Advisor
UCCE Cooperative Extension
707 Nevada St. Susanville, CA 96130
530-251-8132
rgwilson@ucdavis.edu
Joseph M. DiTomaso/ Cooperative Extension Specialist
University of California
Weed Science Program, Robbins Hall, Davis, CA 95616
530-754-8715
ditomaso@vegmail.ucdavis.edu

List commitee members

Peter Warner
Cynthia Roye
Alison Stanton
Jake Sigg
John Randall
Joe DiTomaso

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Other Published Material
Impact?
Four-part score BABD Total Score
B
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels B. Moderate Reviewed Scientific Publication
1.4 ?Impact on genetic integrity D. None Anecdotal
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
14 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Reviewed Scientific Publication
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded C. Already invaded Observational
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Observational
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? B Other Published Material
Identify ecosystem processes impacted:

Very little information is available regarding Russian knapweed's affects on abiotic ecosystem processes. Since russian knapweed produces a deep, extensive root system, the plant likely has significant effects on soil moisture levels especially at deeper depths compared to native grassland ecotypes. The plant commonly forms monoculture stands and may influence soil erosion and soil infiltration rates compared to native ecotypes. Russian knapweed is also commonly found in saline/sodic soils and may change soluble salt distributions in the soil profile. Some evidence suggests that it leads to the accumulation of high levels of zinc in the soil surface which can alter the ability for more desirable plants to develop.


Sources of information:

Bottoms, R., C.J.Nelson, T.D. Whitson,and J.H. Coutts. 1999.Factors being considered that make russian knapweed a highly competitive plant. Proc. Western Soc. Weed Sci. 52:73


Question 1.2 Impact on plant community composition,
structure, and interactions?
A Reviewed Scientific Publication
Identify type of impact or alteration:

Russian knapweed will commonly form monoculture stands especially in disturbed areas. In open areas, Russian knapweed often spreads aggressively covering over 12m2 within a two year period. Russian knapweed stands are also very persistent with documented infestations dominating a site for >75 years. Russian knapweed is a strong competitor. It can grow in saline/sodic conditions and effectively competes for soil moisture and nutrients with several native plants. Russian knapweed's deep root system allows the plant to mine deep soil moisture that most native grasses and shrub cannot obtain. Russian knapweed is allelopathic and inhibits the growth of several plants. Russian knapweed is also unpalatable to most grazers and tends to dominate rangeland and grazed areas.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Beck, K.G. 2004. Russian Knapweed. Colorado State University Cooperative Extension Fact Sheet. no. 3.111. http://www.ext.colostate.edu
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 1.3 Impact on higher trophic levels? B Reviewed Scientific Publication
Identify type of impact or alteration:

Russian knapweed is generally avoided by grazing animals due to it's bitter taste. Prolonged consumption of Russian knapweed is toxic to horses. Russian knapweed is grazed by bighorn sheep in British Columbia. Birds and rodents eat the seed. The BLM estimates an annual loss of 55% in livestock carrying capacity.


Sources of information:

Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Beck, K.G. 2004. Russian Knapweed. Colorado State University Cooperative Extension Fact Sheet. no. 3.111. http://www.ext.colostate.edu
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 1.4 Impact on genetic integrity? D Anecdotal

The author was not able to find any native plants that might hybridize with Russian knapweed. No plants native to CA are in the Acroptilon or Centaurea genus.


Sources of information:

The Jepson manual. higher plants of California/ James C. Hickman, editor. 1993. Univesity of California Press.


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Reviewed Scientific Publication
Describe role of disturbance:

Russian knapweed typically invades disturbed, open sites such as roadsides, riverbanks, irrigation ditches, pasture, waste places, and cropland. Russian knapweed does not readily establish/thrive in healthy, natural habitats because it's sensitive to shading and aggressive competition with other plants. Occasionally, Russian knapweed is found growing in healthy native plant communities, especially in ecotypes that lack aggressive plant competition or areas that border sites with recent natural or anthropogenic disturbance. Once established in disturbed areas, Russian knapweed commonly spreads into greasewood habitats in NE California.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Beck, K.G. 2004. Russian Knapweed. Colorado State University Cooperative Extension Fact Sheet. no. 3.111. http://www.ext.colostate.edu
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.
Personal Observations by Rob Wilson.


Question 2.2 Local rate of spread with no management? A Reviewed Scientific Publication
Describe rate of spread:

The local spread rate of Russian knapweed varies quite a bit from location to location depending on soil type, soil moisture, disturbance, and the existing plant community. Under favorable conditions, Russian knapweed will spread quite rapidly extending radially in all directions (creeping roots) over 12m2 during a two year period. Tom Whitson claimed an 11% average increase in Russian knapweed populations in Wyoming. The BLM estimates an average annual rate of spread of 8% in the northwestern US.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 2.3 Recent trend in total area infested within state? B Other Published Material
Describe trend:

Russian knapweed infestations have been documented throughout most of California (32 counties). Russian knapweed invades a wide range of ecosystems, plant communties, and soils, but Russian knapweed's rate of spread in California is quite dependent on location and land-use. Russian knapweed is most invasive on open, distrurbed sites. It will grow on several soil types, but it spreads and thrives best in arid areas with clay soil. It reproduces primarily by root and tends spread at alarming rates following soil disturbance. Russian knapweed populations located in poor growing conditions have remained static with minimal spread, while other infestations growing under optimal conditions have spread at alarming rates. The rating given in this section is based on the author's estimate of average spread throughout the state.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 2.4 Innate reproductive potential? A Reviewed Scientific Publication
Describe key reproductive characteristics:

Russian knapweed reproduces by adventitious buds on horizontally spreading roots and by seed. Local infestations increase primarily by shoots arising from the root system. A singe knapweed plant can produce 1,200 seeds per year. Seed viability data differs from 2-3 years up to 9 years under dry storage. Fragmented roots quickly grow into new plants.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 2.5 Potential for human-caused dispersal? B Reviewed Scientific Publication
Identify dispersal mechanisms:

Russian knapweed commonly infests cropland and can be found as a contaminant (seeds and propagules) in hay, straw, and fill dirt. Plants often grow in roadsides, ditches, and parking areas and are spread along transportation corridors.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 2.6 Potential for natural long-distance dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Plants generally spread over short distances via root to form dense patches, but plants growing near waterways can easily spread over long distances via propagules and seed washing downstream. However, the plant does not generally grow near water sources. Seasonal high water flow or floods often spread plants over large distances. Seeds may occasionally be spread by rodents and birds.


Sources of information:

Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 2.7 Other regions invaded? C Observational
Identify other regions:

Russian knapweed is wide spread in the western United States and is currently found in at least 412 counties in 21 states.


Sources of information:

Observations by Rob Wilson, Peter Warner, Joe DiTomaso, John Randall, Jake Sigg.


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Observational

Russian knapweed has wide ecological amplitude and is found in several ecological types. First introduced in California between 1910-1914.


Sources of information:

Carpenter, Alan and Murry, Thomas. 1998. Acroptilon repens. Element Stewardship abstract. The Nature Conservancy. http://tncweeds.ucdavis.edu/esadocs/acrorepe.html
Zouhar, Kristin L. 2001. Acroptilon repens. In: Fire Effects Information System, [Online]. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. http://www.fs.fed.us/dtabase/feis
Whitson, Tom. 1999. Russian Knapweed. In: Sheley, Roger; Petroff, Janet., eds. Biology and Management of Noxious Rangeland Weeds. Corvallis, OR: Oregon State University Press: 315-322.


Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

More common in northern California, but not widespread at the present time.


Sources of information:

Wilson, R. and DiTomaso, J.M. - observational


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere Yes
Resprouts readily when cut, grazed, or burned Yes
Total points: 11
Total unknowns: 0
Total score: A?

Related traits:

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrubD, < 5%
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grasslandD, < 5%
Great Basin grasslandD, < 5%
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forestD, < 5%
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)D, < 5%
Woodlandcismontane woodland
piñon and juniper woodlandD, < 5%
Sonoran thorn woodland
Forestbroadleaved upland forestD, < 5%
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forestD, < 5%
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): A
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • CA Floristic Province
  • Cascade Range
  • Central West
  • Desert Province
  • Mojave Desert
  • Sonoran Desert
  • Great Basin Province
  • Great Valley
  • Modoc Plateau
  • Northwest
  • Sierra Nevada
  • Sierra Nevada East
  • Southwest