Source: California Invasive Plant Council


URL of this page: http://www.cal-ipc.org/site/paf/312
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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.

Crataegus monogyna

Synonyms:
Additional Latin binomial names for this species. Separate multiple names with a ; character. Please avoid narrative descriptions, and list only the binomial names.
Crataegus apiifolia, C. curvisepala, C. dissecta, C. oxyancanthana, C. oxyacantha var. monogyna, C. oxyacantha v. paulii, Mespilus monogyna, Oxyacantha apiifolia, others.
Common names:
Common names for this species. Separate multiple names with a ; character.
English hawthorn; common hawthorn; oneseed hawthorn; May tree; singleseed hawthorn; azzarola; neapolitan medlar; oneseed hawthorn; whitethorn;
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.
7/30/2004
Evaluator #1 Brianna Richardson, Project Manager
California Invasive Plant Council
1442-A Walnut St. #462, Berkeley, CA 94709
510.843.3902
brichardson@cal-ipc.org
List committee members: Peter Warner, Joe DiTomaso, Cynthia Roye, John Randall, Jake Sigg, Alison Stanton
Committee review date: 8/27/2004
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.
Questions 2.2, 2.3, 1.4, and 3.2 need further exploration. A preserve in Willamette Valley, Oregon had to be abandoned because the Crataegus monogyna infestation was so severe it could not be controlled with available resources. This should serve as a warning that this plant has the potential to be a serious invader. (Bossard, CC, JM Randall, MC Hoshovsky. 2000. Invasive Plants of California's Wildlands. UC Press.) This completed PAF was previewed by Jake Sigg, prior to committee review. August, 2004.

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

Limited

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

3.4 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.
D. Negligible 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
DBCC

Total Score
C
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.
B. Moderate 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.
C. Minor 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.
C. Minor / Low 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.
A. Severe 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
15

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
B. Increasing less rapidly Observational
2.4 Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
C. Low Other Published Material
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.
A. High Other Published Material
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.
A. Frequent 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 Other Published Material
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.
B. Moderate Other Published Material
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
C
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 Observational

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 D 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:
Grubb refers to a 1979 study by Key in which soils under C. monogyna were found to have higher amounts of plant-available phosphorous and nitrate than grassland soil. Little importance is placed on the nutrient-enriching properties of C. monogyna in the literature.

Sources of information:
Grubb, P.J., W.G. Lee, J.Kollmann, J.B.Wilson. 1996. Interaction of irradiance and soil nutrient supply on growht of seedlings of ten European tall-shrub speices and Fagus sylvatica. Journal of Ecology V.84: 827-840.

Reviewed Scientific Publication B 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:
C. monogyna has more conspicuous fruit than native C. douglasii suksdorfii, making it more attractive to robins. This may result in C. monogyna having more dispersal success when the two spp are found in the same location. C. suksdorfii is a rare plant. In a NY study, C. monogyna had a cover >25% in patches >100 sqmtr. Can form dense thickets excluding all understory plants. Can replace open grassland habitat with a dense shrub and small tree layer. Can be severe, forming dense stands and eliminating understory layers. May compete directly with the rare C. suksdorfii for dispersal services of birds. May create shrub or tree layer in grasslands.

Sources of information:
Salabanks, R. 1993. Fruiting plant attractiveness to avian seed dispersers: Native v. invasives Crataegus in western Oregon. Madrono V.40 n.2: 108-116. Hunter, J.C., J.A.Mattice. 2002. The spread of woody exotics into the forests of a northeastern landscape, 1938-1990. Journal of th eTorrey Botanical Society 129(3): 220-227. Oregon State University website: www.orst.edu/dept/ldplants/crmo-i.htm. Garry Oak Ecosystems Recovery Team website: www.goert.ca/resources/invspecies.htm. Observational, Peter Warner, John Randall, Jake Sigg, Joe DiTomaso, 2004.

Reviewed Scientific Publication C 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:
Insect pollinated. C. monogyna has more conspicuous fruit than native C. douglasii suksdorfii, making it more attractive to robins. Seeds may be eaten by mammals. Creates dense thickets that can impede movement, and is covered in thorns. May impede the movement of larger mammals. Thorns may interfere with herbivores, or may damage the mouths of herbivores and frugivores. Provides food for birds and small mammals.

Sources of information:
Salabanks, R. 1993. Fruiting plant attractiveness to avian seed dispersers: Native v. invasives Crataegus in western Oregon. Madrono V.40 n.2: 108-116. DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Bass, D.A. 1990. Dispersal of an introduced shrub (Crataegus monogyna) by the brush-tailed possum (Trichosurus vulpecula). Australian Journal of Ecology V.15: 227-229. Weed Info website: www.weedinfo.com.au

Reviewed Scientific Publication C 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:
Readily hybridizes with several other Crataegus spp. including the native North American spp. C. douglasii Lindley. Hybridizes with the rare C. suksdorfii in Oregon. A. Williams is not aware of any native Crataegus in RNP. No information available about possible hybridization occuring in CA. Can hybridize with native (and rare native ssp), but it is unclear if this is happening in the state.

Sources of information:
DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Salabanks, R. 1993. Fruiting plant attractiveness to avian seed dispersers: Native v. invasives Crataegus in western Oregon. Madrono V.40 n.2: 108-116. Andrea Williams, Redwood NP, personal communication 8/3/04 (phone) Observational, Peter Warner, 2004.

Section 2: Invasiveness

Reviewed Scientific Publication A 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:
Australia study: C. monogyna occurred more frequently on roadsides than in farmland, where it was only found where planted as hedge. No disturbance noted in most accounts of establishment.

Sources of information:
Lane, D. 1979. The significance of noxious weeds on roadsides in agricultural areas of Victoria, Australia. Weed Researc. V.19: 151-156. Many reviewed publications refer to invasion sites.

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:
In Australia, the local range of C.monogyna expands at 120m/yr. In NY study, the rate of spread was not great over a ~50 yr. period, and the authors believe it is not likely to increase (in mature, deciduous forests). No information on rate of spread in CA. Different sites experience different rates of spread.

Sources of information:
Salabanks, R. 1993. Fruiting plant attractiveness to avian seed dispersers: Native v. invasives Crataegus in western Oregon. Madrono V.40 n.2: 108-116. Hunter, J.C., J.A.Mattice. 2002. The spread of woody exotics into the forests of a northeastern landscape, 1938-1990. Journal of th eTorrey Botanical Society 129(3): 220-227. Observational, Peter Warner, Jake Sigg, 2004.

Observational B 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:
Increasing slowly throughout the state.

Sources of information:
Observational, Peter Warner, Jake Sigg, 2004.

Other Published Material C 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:
Crown and upper portion of main roots develop suckers if trees are damaged or disturbed. Cannot pollinate itself. Reproductive maturity at 10 yrs old. 2 points.

Sources of information:
DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Observational, Peter Warner, John Randall, Jake Sigg, Joe DiTomaso, 2004.

Other Published Material A 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:
Commonly sold horticulturally. Numerous opportunities for plant to be introduced to new areas.

Sources of information:
www.naturehills.com and numerous other on-line sites.

Reviewed Scientific Publication A 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:
Seeds dispersed primarily by animals, especially birds, possibly mammals. May also disperse with water, soil movement. Seeds are not damaged (and do germinate) after passing through the guts of possums. Seeds readily consumed by birds, sometimes preferentially.

Sources of information:
Salabanks, R. 1993. Fruiting plant attractiveness to avian seed dispersers: Native v. invasives Crataegus in western Oregon. Madrono V.40 n.2: 108-116. DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Bass, D.A. 1990. Dispersal of an introduced shrub (Crataegus monogyna) by the brush-tailed possum (Trichosurus vulpecula). Australian Journal of Ecology V.15: 227-229.

Other Published Material 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:
Invasive in Willamette Valley, OR. Noxious/invasive in Victoria, South, and Western Australia. In British Columbia it's found in wetland and lake margins. Invades similar habitats to the ones it's found in in California. Invades wetlands in BC, isn't noted as doing so in CA, but does prefer more moist grasslands and may exist in wetlands in CA. Conservatively a C, could be a B.

Sources of information:
DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Plants for a Future Database: www.scs.leeds.ac.uk Garry Oak Ecosystems Recovery Team website: www.goert.ca/resources/invspecies.htm.

Section 3: Distribution

Other Published Material B 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:
Riparian areas, woodland, grassland (where moist). Invades 2 major ecological types in CA.

Sources of information:
DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Observational, Peter Warner, Joe DiTomaso, 2004.

Observational 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:
Colonizes forest and woodland understories on the San Francisco peninsula and the norhter SF Bay area (Marin and Sonoma counties). North coast, north coast ranges, SF Bay region, central coast. Arkansas, Illinois, Montana, Oregon, Tennessee, Utah, Washington, Wisconsin, northeastern US. Inhabits less than 5% of any ecotype in CA.

Sources of information:
DiTomaso, J., E. Healy. Weeds of California and Other Western States. unpublised. Observational, Peter Warner, Joe DiTomaso, 2004.

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
Dense infestations produce >1,000 viable seed per square meter No
Populations of this species produce seeds every year. Yes, 1 points
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years Unknown
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 Yes, 1 points
Total points: 2
Total unknowns: 1
Total score: C
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:
Root suckers sprout when tree is damaged or disturbed.
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 scrub
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, coastal prairie
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)D. < 5%
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)  
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/Crataegus_monogyna.php
Calflora Plant Profile:
The Calflora Plant Profile for this species.
http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=8429
CalWeedMapper:
Load CalWeedMapper with this species already selected.
http://calweedmapper.cal-ipc.org/maps/?species=167