Plant Assessment Form

Carduus tenuiflorus

Common Names: slenderflower thistle; Italian thistle; multiheaded thistle; seaside thistle; shore thistle; winged plumeless thistle

Evaluated on: 3/28/05

List committee review date: 08/07/2005

Re-evaluation date:

Evaluator(s)

Elizabeth Brusati
Cal-IPC
1442-A Walnut St. #462, Berkeley, CA 94709
510-843-3902
edbrusati@cal-ipc.org
Joseph DiTomaso
University of California-Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu

List commitee members

Carla Bossard
John Randall
Carri Pirosko
Dan Gluesenkamp
Gina Skurka
Brianna Richardson

General Comments

This species is very similar to Carduus pycnocephalus (according to the Jepson Manual, they may be the same species).

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes D Observational
Impact?
Four-part score DCBD Total Score
C
1.2 ?Impact on plant community C. Minor Other Published Material
1.3 ?Impact on higher trophic levels B. Moderate Other Published Material
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment C. Minor Other Published Material
Invasiveness?
Total Points
8 Total Score C
2.2 ?Local rate of spread with no management C. Stable Observational
2.3 ?Recent trend in total area infested within state C. Stable Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Other Published Material
2.5 ?Potential for human-caused dispersal C. Low Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Other Published Material
2.7 ?Other regions invaded C. Already invaded 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)
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? D Observational
Identify ecosystem processes impacted:

No known impacts.


Sources of information:

Carla Bossard, St. Mary's College, and Dan Gluesenkamp, Audubon Canyon Ranch, pers. obs.


Question 1.2 Impact on plant community composition,
structure, and interactions?
C Other Published Material
Identify type of impact or alteration:

Not often encountered in wildlands in California. May replace species that are better wildlife and livestock forage (1).


Sources of information:

1. Roche C. 1992. Slender Thistle, Italian Thistle, Plumeless Thistle. Weeds Pacific Northwest Extension Publication, PNW 431.


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

Reduces value of forage for wildlife and livestock. Dense stands can restrict grazing. Restricts recreational activities.


Sources of information:

1. Roche C. 1992. Slender Thistle, Italian Thistle, Plumeless Thistle. Weeds Pacific Northwest Extension Publication, PNW 431.


Question 1.4 Impact on genetic integrity? D Other Published Material

None No native California Carduus species.


Sources of information:

Hickman. 1993. The Jepson Manual.


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
C Observational
Describe role of disturbance:

Typically inhabit disturbed open sites, roadsides, pastures, annual grasslands, and waste areas. Does not compete well in sites with established vegetation.


Sources of information:

DiTomaso, J.M., and E. Healy. in prep. Weeds of California and Other Western States.


Question 2.2 Local rate of spread with no management? C Observational
Describe rate of spread:

Rarely managed in wildland areas and has not spread much except year to year variation.


Sources of information:

DiTomaso, observational.


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

May not be a distinct species from Carduus pycnocephalus. If it is, then it is much less common and invasive.


Sources of information:

DiTomaso and Healy. 2006. Weeds of California. UC DANR Publ. #3488.


Question 2.4 Innate reproductive potential? B Other Published Material
Describe key reproductive characteristics:

DiTomaso and Healy. 2006. Weeds of California. UC DANR Publ. #3488.


Sources of information:

Seeds can disperse with human activities.


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

Seeds can disperse with human activities.


Sources of information:

DiTomaso, J.M., and E. Healy. in prep. Weeds of California and Other Western States.


Question 2.6 Potential for natural long-distance dispersal? C Other Published Material
Identify dispersal mechanisms:

Seeds can be dispersed with wind, water, birds,and small mammals.


Sources of information:

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

State-listed noxious weed in Oregon and Washington, where it primarily occurs in mixed stands on annual rangelands with Italian thistle (1). Also in Texas, Pennsylvania, and New Jersey (2).


Sources of information:

1. Roche C. 1992. Slender Thistle, Italian Thistle, Plumeless Thistle. Weeds Pacific Northwest Extension Publication, PNW 431.
2. DiTomaso, J.M., and E. Healy. in prep. Weeds of California and Other Western States.


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

Present in North Coast, North Coast Ranges, Sierra Nevada foothills, Central Coast, San Francisco Bay region, South Coast Ranges, Southwestern region, to 1000m. Colonizes disturbed sites and annual grasslands (1). Can grow in mixed stands with Italian thistle (C. pycnocephalus) (2).


Sources of information:

1. DiTomaso, J.M., and E. Healy. in prep. Weeds of California and Other Western States.
2. Roche C. 1992. Slender Thistle, Italian Thistle, Plumeless Thistle. Weeds Pacific Northwest Extension Publication, PNW 431
Dan Gluesenkamp, Audubon Canyon Ranch, pers. obs.


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

Not nearly as commonly encountered as Carduus pycnocephalus.


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 No
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 No
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes No
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned No
Total points: 4
Total unknowns: 0
Total score: B?

Related traits:

Seed production low because of effect of biocontrol agent, Rhinocyllus conicus.

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 scrubD, < 5%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
valley and foothill grasslandD, < 5%
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodlandD, < 5%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

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