Plant Assessment Form

Crataegus monogyna

Synonyms: Crataegus apiifolia, C. curvisepala, C. dissecta, C. oxyancanthana, C. oxyacantha var. monogyna, C. oxyacantha v. paulii, Mespilus monogyna, Oxyacantha apiifolia, others.

Common Names: English hawthorn; common hawthorn; oneseed hawthorn; May tree; singleseed hawthorn; azzarola; neapolitan medlar; oneseed hawthorn; whitethorn;

Evaluated on: 7/30/04

List committee review date: 27/08/2004

Re-evaluation date:

Evaluator(s)

Brianna Richardson, Project Manager
California Invasive Plant Council
1442-A Walnut St. #462, Berkeley, CA 94709
510.843.3902
brichardson@cal-ipc.org

List commitee members

Peter Warner
Joe DiTomaso
Cynthia Roye
John Randall
Jake Sigg
Alison Stanton

General Comments

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? Limited
Alert Status? No Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes D Reviewed Scientific Publication
Impact?
Four-part score DBCC Total Score
C
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels C. Minor Reviewed Scientific Publication
1.4 ?Impact on genetic integrity C. Minor/Low Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Reviewed Scientific Publication
Invasiveness?
Total Points
15 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 B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
C. Low Other Published Material
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal A. Frequent Reviewed Scientific Publication
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Other Published Material
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? D Reviewed Scientific Publication
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.


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Reviewed Scientific Publication
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.


Question 1.3 Impact on higher trophic levels? C Reviewed Scientific Publication
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


Question 1.4 Impact on genetic integrity? C Reviewed Scientific Publication

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
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
B Reviewed Scientific Publication
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.


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


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

Increasing slowly throughout the state.


Sources of information:

Observational, Peter Warner, Jake Sigg, 2004.


Question 2.4 Innate reproductive potential? C Other Published Material
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.


Question 2.5 Potential for human-caused dispersal? A Other Published Material
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.


Question 2.6 Potential for natural long-distance dispersal? A Reviewed Scientific Publication
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.


Question 2.7 Other regions invaded? C Other Published Material
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
Question 3.1 Ecological amplitude/Range? B Other Published Material

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.


Question 3.2 Distribution/Peak frequency? D Observational
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
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
Total points: 2
Total unknowns: 1
Total score: C?

Related traits:

Root suckers sprout when tree is damaged or disturbed.

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 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, Meadows, and other Herb Communitiescoastal prairie
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)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): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada