Plant Assessment Form

Carduus nutans

Common Names: musk thistle; giant plumeless thistle; nodding (plumeless) thistle;

Evaluated on: 2/3/05

List committee review date: 08/07/2005

Re-evaluation date:


Elizabeth Brusati, project manager
California Invasive Plant Council
1442 Walnut St. #462, Berkeley, CA 94709
Joseph DiTomaso
University of California-Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616

List committee members

Carla Bossard
John Randall
Carri Pirosko
Dan Gluesenkamp
Gina Skurka
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. Minor Reviewed Scientific Publication
Four-part score CABD Total Score
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels B. Moderate Anecdotal
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Total Points
13 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Observational
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 C. Low Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Other Published Material
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? C Reviewed Scientific Publication
Identify ecosystem processes impacted:

May deplete soil nitrogen. C. nutans severely reduced the ability of Trifolium repens to fix nitrogen, and this inhibition lasted four months after C. nutans died. Effects were strongest in the summer, when nitrogen fixation would normally be highest, suggesting that patch effects created by thistles have the potential to greatly alter input of soil nitrogen for other native legume species (1).

Sources of information:

1. Wardle, D.A., K. S. Nicholson, M. Ahmed, and A. Rahman. 1994. Interference effects of the invasive plant Carduus nutans L. against the nitrogen fixation ability of Trifolium repens L. Plant and Soil. 163:287-297

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

Forms dense stands. Inhibits growth of other plants through possible allelopathy. Formed stands up to 150, 000 plants/ha in Canada (1). Flowering C. nutans strongly inhibited T. repens root growth, nodulation, and acetylene reduction. This appeared to be due to decomposition of rosette leaves. Experiments suggest that decomposing rosette leaves have a strong potential to inhibit T. repens nitrogen fixation (2). Bioassay experiments found that C. nutans inhibited germination of pasture plants, but C. nutans seedlings were not affected by their own species (3). Can colonize burned sites before other species and may prevent reestablishment of native plant community (4).
Host plant for introduced weevil Rhynocilus conicus, which attacks native thistles, thereby reducing populations of the native plants (Gluesenkamp and Randall).
Dan Gluesenkamp, Audubon Canyon Ranch, and John Randall, The Nature Conservancy, pers. obs.

Sources of information:

1. Desrochers, A. M., J. F. Bain, and S. I. Warwick. 1988. The biology of Canadian weeds. 89. Carduus nutans L. and Carduus acanthoides L. Canadian Journal of Plant Sciences. 68: 1053-1068.
2. Wardle et al. 1994.
3. Wardle, D. A., M. Ahmed, K. S. Nicholson. 1991. Allelopathic influence of nodding thistle (Carduus nutans L.) seeds on germination and radicle growth of pasture plants. New Zealand Journal of Agricultural Research. 34:185-191
4. Floyd-Hanna, L., W. Romme, D. Kendall, A. Loy, and M. Colyer. 1993. Succession and biological invasion at Mesa Verde NP. Park Science. vol:16-18

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

Spiny nature of plants prevent livestock foraging and likely have the same effect on wildlife.

Sources of information:

Question 1.4 Impact on genetic integrity? D Other Published Material

None No native Carduus spp.

Sources of information:

Hickman. 1993. The Jepson Manual.

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

Prefers disturbed habitats.

Sources of information:

1. DiTomaso and Healy Weeds of California and Other Western States. in prep.
2. Stuckey, R. L., and J. L. Forsyth. 1971. Distribution of naturalized Carduus nutans (Compositae) mapped in relation to geology in northwestern Ohio. Ohio Journal of Science. 71:1-15.
3. Floyd-Hanna, L., W. Romme, D. Kendall, A. Loy, and M. Colyer. 1993. Succession and biological invasion at Mesa Verde NP. Park Science. vol:16-18
4. Wardle, D. A., K. S. Nicholson, M. Ahmed, and A. Rahman. 1995. Influence of pasture forage species on seedling emergence, growth, and development of Carduus nutans. Journal of Applied Ecology. 32:225-233

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

Slowly expanding in Siskiyou, Sierra, Nevada, and Placer Counties.

Sources of information:

1. E-mail from Carri Pirosko, California Dept. of Food and Agriculture, 4/7/05
2. Stuckey and Forsyth. 1971.

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

Slowly expanding, although CDFA has been able to reduce the rate of expansion. Much larger problem in other states that do not have an active control program for this species.

Sources of information:

1. E-mail from Carri Pirosko, California Dept. of Food and Agriculture, 4/7/05

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

Biennial or occasionally winter annual. Primarily outcrossing but can be selfing (1). Reproduces by seed. First flowerheads can produce 1500 seeds/head, but late flowerheads produce many fewer seeds, to 25 seeds/head (1). Seeds generally germinate 2-4 weeks after dispersal. Seeds rarely persist in soil seedbank for more than a few years. A seedbank study of soil in a permanent pasture suggested that seeds did not persist longer than three years because of germination (2).

Sources of information:

1. Desrochers et al. 1988
2. DiTomaso and Healy in prep

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

Can disperse through human activities, but this method is probably uncommon for long distance transport.

Sources of information:

1. DiTomaso and Healy in prep.

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

Seeds fall near parent plant (1,2) and disperse to greater distances with wind, water, birds, and small mammals (3).

Sources of information:

1. DiTomaso and Healy. in prep
2. Smith, L. M. II, and L. T. Kok. 1984. Dispersal of musk thistle (Carduus nutans) seeds. Weed Science. 32:120-125

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

Native to Europe, Siberia, Asia minor, and North Africa. Naturalized in North and South America, Australia, and New Zealand (1). Present in all contiguous U.S. states except possibly Florida, Maine, and Vermont (2, 3). Habitats in other states similar to those invaded in California.

Sources of information:

1. Popay, A. I., and R. W. Medd. year. The biology of Australian weeds 21. Carduus nutans L. ssp nutans. journal vol page
2. DiTomaso and Healy in prep.
3. Dunn, P.H. 1976. Distribution of Carduus nutans, C. acanthoides, C. pycnocephalus, and C. crispus, in the United States. Weed Science. 24:518-524

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

Occurs in Klamath Ranges, Cascade Range (central and south Siskiyou, north Shasta counties), northern Sierra Nevada (south and east Plumas, east Sierra, central and east Nevada counties), Modoc Plateau (Modoc, north and south Lassen counties) to 1200m. Previous infestations now eradicated occurred in the South Coast and Mojave Desert (1). Invades range, pasture, ditch banks, forested areas in new plantations (outshaded when trees grow), and sage scrub.

Sources of information:

1. DiTomaso and Healy. in prep.
2. E-mail from Carri Pirosko, California Dept. of Food and Agriculture, 4/7/05

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

Because of control program by CDFA, musk thistle is not widely distributed in 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 No
Viable seed produced with both self-pollination and cross-pollination Yes
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 Yes
Total points: 7
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
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
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 forest
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
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): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest
  • Modoc Plateau
  • Mojave Desert