Plant Assessment Form

Cynara cardunculus

Common Names: artichoke thistle; cardoon; wild artichoke

Evaluated on: 8/12/04

List committee review date: 11/02/2005

Re-evaluation date:

Evaluator(s)

Scott Steinmaus Associate Professor
Cal Poly SLO
1 Grand Avenue Biological Sciences Department, Cal Poly State University, San Luis Obispo, CA 93407
805-756-5142
ssteinma@calpoly.edu

List commitee members

Carla Bossard
John Randall
Cynthia Roye
Jake Sigg
Peter Warner

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 4 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Reviewed Scientific Publication
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 Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
12 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Reviewed Scientific Publication
2.3 ?Recent trend in total area infested within state C. Stable Reviewed Scientific Publication
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 Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Reviewed Scientific Publication
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Reviewed Scientific Publication

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 Reviewed Scientific Publication
Identify ecosystem processes impacted:

Outcompetes native vegetation for light, water, and nutrients. No evidence of soil chemistry alteration because displaced species are able to recolonize following artichoke removal. Large arching leaves together with a large aggressive tap root system preemptively intercept resources necessary for the growth of other species. .


Sources of information:

Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;
Pepper A. and M Kelly. 1994. Portrait of an invader. The ecology and management of the wild artichoke Cynara cardunculus. Cal EPPC News Winter pg. 4-6.


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

Artichoke thistle can create a monoculture leading to the the decline of, for example, broom baccharis (Baccharis sarothroides). Artichoke thistle is a threat to the endangered San Diego thornmint. Usually displaces annual exotic grasses, which may be facilitated by fire. Seriously threatens grassland ecosystems and may affect coastal sage scrub and riparian habitat in southern California. In San Diego's Los Penasquitos Canyon, artichoke thistle invades open forb covered canyon bottomlands. It can also invade riparian woodlands under willow (Salix spp.), mulefat (Baccharis glutinosa) and sycamore (Platanus racemosa). Artichoke thistle can reach stands of 22,000 plants per acre. Forms a basal rosette of leaves up to six feet in diameter. Reduces available habitat for grassland dependent species; displaces natives. There may be some alleopathic mechanism to neighbor plant suppression. When leaves die and fall to the ground they do not readily decompose, thus providing another barrier to competing species.


Sources of information:

Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;
The Nature Conservancy Wildland weed Management and Research 1998-1999 Weed Survey by Trish Smith;
Pepper A. and M Kelly. 1994. Portrait of an invader. The ecology and management of the wild artichoke Cynara cardunculus. Cal EPPC News Winter pg. 4-6.


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

Artichoke thistle is a moderate threat to the Threatened species, California gnatcatcher and Coastal cactus wren. By displacing natives and annual grasses, it reduces the forage value for both livestock and wildlife. It is not used by birds for nesting or predative activities. Alters breeding success for threatened species by displacing native plants. The heavily armoured thistle flowerhead hinders herbivory, hower, the seedlings may be subject to rabbit herbivory and the seeds may provide a food source for birds.


Sources of information:

The Nature Conservancy Wildland weed Management and Research 1998-1999 Weed Survey by Trish Smith;
Pepper A. and M Kelly. 1994. Portrait of an invader. The ecology and management of the wild artichoke Cynara cardunculus. Cal EPPC News Winter pg. 4-6.


Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

Artichoke thistle is a progenator of the commercially cultivated, spineless globe artichoke (Cynara scolymus) while some taxonomists consider globe artichoke and artichoke thistle to be the same species because a few spiny wild types will appear within a population of globe artichoke seedlings. There are not any closely related California natives. Cultivated globe artichoke and artichoke thistle readily hybridize. The globe artichoke can revert back to the wild "thistle' state if allowed to grow from seed.


Sources of information:

Thomsen, C.D. , G. Barbe, W. Williams, and M. George. 1986. Escaped artichokes are troublesome pests. California Agriculture pg 7-9;
Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;
Artichoke thistle Anonymous http://agric.wa.gov.au/agency/pubns/infonote/infonotes/AOO687.html


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

Seems to require disturbance and most commonly heavily grazed areas. It has been observed to occasionally colonize riparian woodlands and natural openings in chaparral and costal sage scrub.. Artichoke thistle's appearance in California rangelands is linked to its introduction for ornamental and culinary purposes. It is found primarily on distrubed grasslands or abandoned agricultural fields especially those areas subjected to overgrazing practices. . It occurrence along fire maintenance roads is linked to equipement carrying seeds; grazing and fire create openings for new artichoke thistle establishment; fire prone plant communities (grasslands and sage scrub) also tend to exist in climates that are conducive for artichoke thistle growth.


Sources of information:

The Nature Conservancy Wildland weed Management and Research 1998-1999 Weed Survey by Trish Smith;
Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;


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

Spread appeared to be rapid from the late 1800's into the 1930s. Control efforts in northern California (Benecia) have stabilized and even reduced its spread. Most artichoke thistle seeds (achenes) fall very near the parent plant and can disperse 70 feet by wind when attached to a pappus. Seeds can spread further with water, mud, soil movement, animals and human activities. Dispersal by root fragments is important only following mechanical disturbance. Seedlings appear to survive best when adult rosettes are removed but seedling emergence is not influenced by prescence or absence of adult rosettes. The seeds (achenes) are relatively large (6-8 mm long) so will typically not disperse far from the mother plant. A feathery pappus (25-40 mm long) is attached to the seeds while in the flower, which can facilitate long distance dispersal by wind. However, the pappus usually breaks off soon after exiting the flower.


Sources of information:

Thomsen, C.D. , G. Barbe, W. Williams, and M. George. 1986. Escaped artichokes are troublesome pests. California Agriculture March-April 1986 ppg 7-9;
Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;
The Nature Conservancy Wildland weed Management and Research 1998-1999 Weed Survey by Trish Smith;
Artichoke thistle Anonymous http://agric.wa.gov.au/agency/pubns/infonote/infonotes/AOO687.html;
Marushia, R. and J.S. Holt. 2003. Patterns of seedling establishment in artichoke thistle, Cynara cardunculus. Proceedings to Cal EPPC 2003 Symposim pg 59.


Question 2.3 Recent trend in total area infested within state? C Reviewed Scientific Publication
Describe trend:

Infests about 150,000 acres statewide. Contra Costa, Solano, and Orange counties have 95% of the infested acreage. Santa Barabara and San Diego counties have some locally dense stands. California townships of past or present infestation are focused primarily in coastal area of southern California (Orange and San Diego Counties), the eastbay of the San Francisco bay area, and along the rangelands of the central coast. It has been reported that 70, 000 acres focused on the hillsides of Benecia have been infested but have been reduced due to substantial control efforts. In Irvine, 2000 acres are currently infested with another 6000 acres at risk of future invasion. In the 3500 acre Los Penasquitos Canyon Preserve in San Diego one 14 acre site was heavily infested and dense patches exist throughout the preserve. Populations of this plant are either large or they are small. Rarely do you see huge expanses of land covered with species because control measures are instigated soon after these are spotted. Poor grazing practices and soil disturbance on coastal range south of the San Francisco Bay Area will invite new invasions by artichoke thistle.


Sources of information:

Thomsen, C.D. , G. Barbe, W. Williams, and M. George. 1986. Escaped artichokes are troublesome pests. California Agriculture March-April 1986 ppg 7-9; Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley; The Nature Conservancy Wildland weed Management and Research 1998-1999 Weed Survey by Trish Smith;


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

Artichoke thistle seeds are dormant affording them discontinuous germination. The seeds germinate in a variety of habitats and at various times of year. The plant resprouts from perennial roots each year. Seeds survive for at about 5 years under field conditions. One year plants can flower but usually 2 year or older plants flower. Plants can survive for many years. Plants can produce sufficient seed to attain densities of 20,000 plants per acre. Artichoke thistle reproduces and spreads primarly by seed. In San Diego, one mature plant produces more than a dozen flowerheads with as amany as 200 seeds per head.


Sources of information:

Thomsen, C.D. , G. Barbe, W. Williams, and M. George. 1986. Escaped artichokes are troublesome pests. California Agriculture March-April 1986 ppg 7-9;
Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;
Artichoke thistle Anonymous http://agric.wa.gov.au/agency/pubns/infonote/infonotes/AOO687.html


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

Is used for ornamental purposes and indiscriminant disposal of flowers could facilitate its spread. It appears to grow and progress along roadways. Populations move along roadways either because seeds are blown as vehicles pass or the seeds are caught up in tires. Vegetative parts not likely except following mechanical operations, and then only for a short distance.


Sources of information:

Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;


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

Long range dispersal likely if seeds were blown by strong winds. Perhaps seeds could be transport great distances along irrigation canals or along roadway corridors.


Sources of information:

Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;


Question 2.7 Other regions invaded? C Reviewed Scientific Publication
Identify other regions:

Proclaimed a noxious weed throughout Victoria and Queensland South Australia and part of New South Wales. Also found in New Zealand. It also is considered an important weed in the Argentine pampas areas of South America. Appears to be well adapted to Mediterranean regions similar to the California central to southern coasts. Appears to be in grassland or coastal scrub-like communities abroad similar to those currently invaded in California.


Sources of information:

Parsons, W.T. 1973. Noxious Weeds of Victoria. Inkara Press, Melbourne. Pg. 70-73.
Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Reviewed Scientific Publication

Artichoke thistle was presumably introduced to California in the mid-1800s as the cultivated, edible cardoon. Escape from cultivation and subsequent reversion to its 'wild', aggressive biotype probably cntributed to its invasive spread. Escaped cultivation in California in 1860-1864 according to botanical surveys. The most successful invasions are in Contra Costa and Orange counties but also in the rangelands of San Diego, Santa Barabara, and other rangelands on California with coastal influence.


Sources of information:

Thomsen, C.D. , G. Barbe, W. Williams, and M. George. 1986. Escaped artichokes are troublesome pests. California Agriculture March-April 1986 ppg 7-9;
Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;


Question 3.2 Distribution/Peak frequency? D Reviewed Scientific Publication
Describe distribution:

Infestations are heaviest in rangelands south of the San Francisco bay area especially those subject to coastal influence. Populations are especially heavy in Contra Costa and Orange Counties. Seeds germinate with any significant rain in late November and December. Rosettes grow vigorously during the cool winter months and plants will bolt to form flowerheads in the spring. Leaves will dies back in the summer as seeds are maturing and falling out of the flowerhead. Artichoke thistle behaves as a typical winter annual thistle species originating from the Mediterranean region.


Sources of information:

Kelly, M. Cynara cardunculus. In, Invasive Plants of California's Wildlands. Eds., C. Bossard, J. Randall, and M. Hoshovsky. UC Press, Berkeley;


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 Unknown
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: 8
Total unknowns: 1
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 scrubD, < 5%
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 grassland
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 woodland
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

  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest
  • Sonoran Desert