Source: California Invasive Plant Council


URL of this page: http://www.cal-ipc.org/site/paf/315
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Cal-IPC Plant Assessment Form

For use with "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands"
by the California Invasive Plant Council and the Southwest Vegetation Management Association

Table 1. Species and Evaluator Information

Species name
(Latin binomial):
The official Latin binomial name for this species. Specify only one name here. Additional species names may go into the Synonyms field.

Cynara cardunculus

Synonyms:
Additional Latin binomial names for this species. Separate multiple names with a ; character. Please avoid narrative descriptions, and list only the binomial names.
Common names:
Common names for this species. Separate multiple names with a ; character.
artichoke thistle; cardoon; wild artichoke
Evaluation date:
The date(s) when this species PAF was filled out, modified, or reviewed. This is free-form text, so it may include multiple dates or other notes.
08/12/04
Evaluator #1 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 committee members: Carla Bossard, John Randall, Cynthia Roye, Jake Sigg, Peter Warner
Committee review date: 2/11/05
List date:
Re-evaluation date(s):
General comments
on this assessment:
Enter any additional notes about this assessment, such as factors affecting the reliability or completeness of the answers, likely affects of impacts, or research which is not specific to California but is still relevant in the evaluation of this species.

Table 2. Criteria, Section, and Overall Scores

Overall Score

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistribution
AA BAnyHighNo Alert
AC DAnyModerateAlert
BA BA BModerateNo Alert
BA BC DModerateAlert
BC DAnyLimitedNo Alert
CAA BModerateNo Alert
CAC DLimitedNo Alert
CBAModerateNo Alert
CBB DLimitedNo Alert
CCAnyLimitedNo Alert
DAnyAnyNot ListedNo Alert

Moderate

Alert Status

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistributionAlert
AA or BC or DAlert
BA or BC or DAlert

No Alert

Documentation

The total documentation score is the average
of Documentation scores given in Table 2.

Reviewed Scientific Publication4 points
Other Published Material3 points
Observational2 points
Anecdotal1 points
Unknown or No Information0 points

4 out of 5

Score Documentation
1.1 Impact on abiotic ecosystem processes
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).

Select the one letter below that best describes this species’ most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
B. Moderate Reviewed Scientific Publication
Impact
Section 1 Scoring Matrix
Q 1.1Q 1.2Q 1.3Q 1.4Score
AAAnyAnyA
ABA,BAnyA
ABC,D,UAnyB
AC,D,UAnyAnyB
BAAAnyA
BABAA
BAB,CB-D,UB
BAC,D,UAA
BAC,D,UB-D,UB
BBAAA
BC,D,UAAB
BB-DAB-D,UB
BB-DB-D,UAnyB
BD,UC,D,UA-BB
BD,UC,D,UC,D,UC
C-D,UAAAnyA
CBAAnyB
CA,BB-D,UAnyB
CC,D,UAnyAnyC
DA,BBAnyB
DA,BC,D,UAnyC
DCAnyAnyC
DD,UAnyAnyD
UAB,CAnyB
UB,CA,BAnyB
UB,CC,D,UAnyC
UUAnyAnyU


Four-part score
BABD

Total Score
B
1.2 Impact on plant community
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.

Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.

Select the one letter below that best describes this species’ impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
A. Severe Reviewed Scientific Publication
1.3 Impact on higher trophic levels
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species’ net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species’ nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.

Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.

Select the one letter below that best describes this species’ impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
B. Moderate Reviewed Scientific Publication
1.4 Impact on genetic integrity
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.

Select the one letter below that best describes this species’ impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
D. None Reviewed Scientific Publication
2.1 Role of anthropogenic and natural disturbance in establishment
Assess this species’ dependence on disturbance—both human and natural—for establishment in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.

Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.

Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential—this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential—this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential—this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential—this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
B. Moderate Reviewed Scientific Publication
Invasiveness
Section 2 Scoring Matrix
Total pointsScore
17-21A
11-16B
5-10C
0-4D
More than two U’sU


Total Points
12

Total Score
B
2.2 Local rate of spread with no management
Assess this species’ rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.

Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
B. Increases less rapidly Reviewed Scientific Publication
2.3 Recent trend in total area infested within state
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.

Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
C. Stable Reviewed Scientific Publication
2.4 Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
A. High Reviewed Scientific Publication
2.5 Potential for human-caused dispersal
Assess whether this species is currently spread—or has high potential to be spread—by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.

Select the one letter below that best describes human-caused dispersal and spread:
A. High—there are numerous opportunities for dispersal to new areas.
B. Moderate—human dispersal occurs, but not at a high level.
C. Low—human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
B. Moderate Reviewed Scientific Publication
2.6 Potential for natural long-distance dispersal
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species’ fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species’ fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).

Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
C. Rare Reviewed Scientific Publication
2.7 Other regions invaded
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.

Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
C. Already invaded Reviewed Scientific Publication
3.1 Ecological amplitude/Range
(see Worksheet C)
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread—the species invades at least three major types or at least six minor types.
B. Moderate—the species invades two major types or five minor types.
C. Limited—the species invades only one major type and two to four minor types.
D. Narrow—the species invades only one minor type.
U. Unknown.
A. Widespread Reviewed Scientific Publication
Distribution
Section 3 Scoring Matrix
Q 3.1Q 3.2Score
AA, BA
AC,D,UB
BAA
BB,CB
BDC
CA,BB
CC,DC
DAB
DB,CC
DDD
A,BUC
C,DUD
UUU


Total Score
B
3.2 Distribution/Peak frequency
(see Worksheet C)
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
D. Very low Reviewed Scientific Publication

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".
Short citations may be used in this table. List full citations at end of this table.

Section 1: Impact

Reviewed Scientific Publication B Question 1.1 Impact on abiotic ecosystem processes
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).

Select the one letter below that best describes this species’ most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
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.

Reviewed Scientific Publication A Question 1.2 Impact on plant community composition,
structure, and interactions
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.

Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.

Select the one letter below that best describes this species’ impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
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.

Reviewed Scientific Publication B Question 1.3 Impact on higher trophic levels
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species’ net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species’ nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.

Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.

Select the one letter below that best describes this species’ impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
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.

Reviewed Scientific Publication D Question 1.4 Impact on genetic integrity
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.

Select the one letter below that best describes this species’ impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
Identify impacts:
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

Reviewed Scientific Publication B Question 2.1 Role of anthropogenic and natural disturbance
in establishment
Assess this species’ dependence on disturbance—both human and natural—for establishment in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.

Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.

Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential—this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential—this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential—this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential—this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
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;

Reviewed Scientific Publication B Question 2.2 Local rate of spread with no management
Assess this species’ rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.

Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
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.

Reviewed Scientific Publication C Question 2.3 Recent trend in total area infested within state
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.

Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
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;

Reviewed Scientific Publication A Question 2.4 Innate reproductive potential
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
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

Reviewed Scientific Publication B Question 2.5 Potential for human-caused dispersal
Assess whether this species is currently spread—or has high potential to be spread—by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.

Select the one letter below that best describes human-caused dispersal and spread:
A. High—there are numerous opportunities for dispersal to new areas.
B. Moderate—human dispersal occurs, but not at a high level.
C. Low—human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
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;

Reviewed Scientific Publication C Question 2.6 Potential for natural long-distance dispersal
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species’ fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species’ fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).

Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
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;

Reviewed Scientific Publication C Question 2.7 Other regions invaded
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.

Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
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

Reviewed Scientific Publication A Question 3.1 Ecological amplitude/Range
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread—the species invades at least three major types or at least six minor types.
B. Moderate—the species invades two major types or five minor types.
C. Limited—the species invades only one major type and two to four minor types.
D. Narrow—the species invades only one minor type.
U. Unknown.
Describe ecological amplitude, identifying date of source information and approximate date of introduction to the state, if known:
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;

Reviewed Scientific Publication D Question 3.2 Distribution/Peak frequency
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
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, 1 points
Dense infestations produce >1,000 viable seed per square meter Yes, 2 points
Populations of this species produce seeds every year. Yes, 1 points
Seed production sustained over 3 or more months within a population annually Yes, 1 points
Seeds remain viable in soil for three or more years Yes, 2 points
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, 1 points
Total points: 8
Total unknowns: 1
Total score: A
Scoring Criteria for Worksheet A
A. High reproductive potential (6 or more points).
B. Moderate reproductive potential (4-5 points).
C. Low reproductive potential (3 points or less and less than 3 Unknowns).
U. Unknown (3 or fewer points and 3 or more Unknowns).
Note any related traits:
Return to Table 2

Worksheet B - Arizona Ecological Types is not included here


Worksheet C - California Ecological Types
 
(sensu Holland 1986)

Major Ecological Types Minor Ecological Types Code
A means >50% of type occurrences are invaded;
B means >20% to 50%;
C means >5% to 20%;
D means present but ≤5%;
U means unknown (unable to estimate percentage of occurrences invaded)
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, coastal prairieD. < 5%
Meadows, and other Herbvalley and foothill grassland
CommunitiesGreat 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)  
Distribution (highest score)  
Return to Table 2

Addendum J - Jepson Regions Infested
 
Click here for a map of Jepson regions

Infested Jepson Regions:
Check the boxes to indicate the Jepson floristic provinces in which this species is found.














Addendum L - External Links & Resources

Cal-IPC Plant Profile
The Cal-IPC Plant Profile for this species.
http://www.cal-ipc.org/ip/management/plant_profiles/Cynara_cardunculus.php
Calflora Plant Profile:
The Calflora Plant Profile for this species.
http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=2568
CalWeedMapper:
Load CalWeedMapper with this species already selected.
http://calweedmapper.cal-ipc.org/maps/?species=65