Plant Assessment Form

Cirsium arvense

Common Names: Canada thistle

Evaluated on: 5/23/03

List committee review date: 06/06/2003

Re-evaluation date:

Evaluator(s)

Joe DiTomaso
UC Davis
Weed Science Program, Robbins Hall, Univ. California, Davis CA 95616
530-754-8715
DiTomaso@vegmail.ucdavis.edu

List commitee members

Joe DiTomaso
Peter Warner
Alison Stanton
Carla Bossard
Cynthia Roye
Jake Sigg
Doug Johnson
Brianna Richardson

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 C Observational
Impact?
Four-part score CABC Total Score
B
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels B. Moderate Other Published Material
1.4 ?Impact on genetic integrity C. Minor/Low Anecdotal
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Other Published Material
Invasiveness?
Total Points
16 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded A. Invades 3 or more ecological types Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Other Published Material
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
C. 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? C Observational
Identify ecosystem processes impacted:

Unknown. Probably minor.


Sources of information:

DiTomaso-Observational


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

Can form dense monotypic stands. Control of Canada thistle increased plant diversity and species richness. Changes structure and composition of some habitats.


Sources of information:

Krueger-Mangold, J. 2002. Weed Technology 16:457-463; Stachion, W.J. and R.J. Zimdahl. 1980. Weed Science 28:83-86; Nuzzo. V. 1977. Canada thistle. Element Stewardship Abstract. TNC


Question 1.3 Impact on higher trophic levels? B Other Published Material
Identify type of impact or alteration:

Suggested to impact waterfowl habitat in riparian areas. Reduces forage for animals. Spines can cause mechanical injury.


Sources of information:

Question 1.4 Impact on genetic integrity? C Anecdotal

No evidence, but likely Related to numerous thistles in the genus Cirsium. No know evidence of pollen swamping but certainly possible.


Sources of information:

Unknown


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Other Published Material
Describe role of disturbance:

Very common in disturbed areas, but can invaded undisturbed sites as well.


Sources of information:

Beck, K.G. 1996. Canada thistle. Range #3108. Natural Resource Series. Colorado State Univ.


Question 2.2 Local rate of spread with no management? A Other Published Material
Describe rate of spread:

Extensive horizontal root system spreads up to several meters per year.


Sources of information:

Question 2.3 Recent trend in total area infested within state? B Observational
Describe trend:

Some control effort in northern part of state has held it in check. Likely to be spreading but only slowly.


Sources of information:

DiTomaso- Observational


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

Dioecious species. Both sexes in clones must be within 200 ft to cross. Produces up to 64,000 seeds/sq m. Seeds viable in soil to 20 years. Roots brittle and fragment easily.


Sources of information:

Donald, W.W. 1994. The biology of Canada thistle. Rev. Weed Sci. 6:77-101; Beck, K.G. 1996. Canada thistle. Range #3108. Natural Resource Series. Colorado State Univ.; Nuzzo. V. 1977. Canada thistle. Element Stewardship Abstract. TNC; DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print)


Question 2.5 Potential for human-caused dispersal? B Other Published Material
Identify dispersal mechanisms:

Some long distance dispersal in contaminated agricultural seeds. Also in hay and in cattle and horse droppings. Also transported by water.


Sources of information:

Nuzzo. V. 1977. Canada thistle. Element Stewardship Abstract. TNC


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

90% of seed land within 10 m of parent plant and only 0.2% were found 1 km from parent plant.


Sources of information:

Nuzzo. V. 1977. Canada thistle. Element Stewardship Abstract. TNC; Bakker, D. 1960. In J.L. Harper. Biology of Weeds. Blackwell Scientific Publ., Oxford, Enland


Question 2.7 Other regions invaded? A Other Published Material
Identify other regions:

Weedy throughout much of the world, including US, Australia and many other countries. Invades prairies and grassland in the midwest, but not really in California. Much more widespread in toehr intermountain states. In other states it is found in forests, meadows, prairies, grasslands, riparian areas, sand dunes, shores of lakes and streams, swamps. Currently not in all these sites in California.


Sources of information:

Nuzzo. V. 1977. Canada thistle. Element Stewardship Abstract. TNC; DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print); Parsons, W.T. and E.G. Cuthbertson. 1992. Noxious Weeds of Australia. Inkata Press, Sydney; Morishita, D.W. 1999. Canada thistle. In, Biology and Management of Noxious Rangeland Weeds. Oregon St. Univ. Press, Corvallis.


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Other Published Material

Invades low-lying, moist soils typical of riparian areas. Common agricultural weed and alos on streambanks. Introduced to North America in the early 17th century.


Sources of information:

Krueger-Mangold, J. 2002. Weed Technology 16:457-463; Stachion, W.J. and R.J. Zimdahl. 1980. Weed Science 28:83-86; Bayer, D. 2000. Cirsium arvense. In, Invasive Plants of Californias Wildlands. CalEPPC. UC Press, Berkeley; Nuzzo. V. 1977. Canada thistle. Element Stewardship Abstract. TNC; DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print)


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

Throughout California, except deserts. More dense in Northern California


Sources of information:

DiTomaso-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 Yes
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination No
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 scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparralD, < 5%
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
valley and foothill grasslandC, 5% - 20%
Great Basin grassland
vernal poolD, < 5%
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swampD, < 5%
Riparian and Bottomland habitatriparian forestD, < 5%
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodlandD, < 5%
Forestbroadleaved upland forestD, < 5%
North Coast coniferous forestD, < 5%
closed cone coniferous forestD, < 5%
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): C

Infested Jepson Regions

Click here for a map of Jepson regions

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