Plant Assessment Form

Cotoneaster lacteus

Synonyms: Cotoneaster parneyi

Common Names: milkflower cotoneaster; Parney's cotoneaster

Evaluated on: 9/6/04

List committee review date:

Re-evaluation date:


Caroline Christman, Habitat Restoration Intern
National Park Service, Natural Resources Dept., The Presidio
Presidio Natural Resources Field Office, 1539 Pershing Dr.San Francisco, CA 94129
Cynthia L. Roye/Associate State Park Resource Ecologist
California State Parks, Natural Resources Division
P.O. Box 942896Sacramento, CA 94296-0001
(916) 653-9083

List commitee members

Carla Bossard
John Randall
Cynthia Roye
Jake Sigg
Peter Warner2/11/05

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 2 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes D Observational
Four-part score DBBD Total Score
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels B. Moderate Observational
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Other Published Material
Total Points
13 Total Score B
2.2 ?Local rate of spread with no management U. Unknown
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Observational
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal A. Frequent
2.7 ?Other regions invaded U. Unknown
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Observational
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
U. Unknown Reviewed Scientific Publication

Table 3. Documentation

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

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? D Observational
Identify ecosystem processes impacted:

I have not observed any impact on ecosystem processes. I have not observed any impact on ecosystem processes. However, my observations are limited to land managed fairly intensively. Therefore, for example, the fire regime is already drastically altered (there are no fires) and it is difficult to say whether cotoneaster in a different setting would an impact on fire occurrence.
Cotoneaster may influences natural erosion processes, such as reducing erosion in old sand dunes and coastal bluffs, this erosion creates opening in coastal scrub for rare and endangered dune and serpentine annual plants. It is not clear whether the extensive root system of the cotoneaster impeded erosion more than the larger scrub plants such as Lupins chamissonis, Bacharis pilularis, Ceanothus thyrsiflorus, etc.
From the horticultural literature it seems that Cotoneasters do not impact the nutrient and mineral dynamics of the soil, as they are considered a possible candidate for planting in any well-drained soil and not noted to effect plants around them. However, the impact of one or two cotoneasters may be negligible though greater numbers are not.

Sources of information:

C. Christman, Observation,
Sigg, J., 2000. Cotoneaster spp. in Bossard, C., J. Randall, and M. Hochovsky. Invasive Plants of California Wildlands. University of California Press. Berkeley, Ca.
The Sunset Western Garden Book.ed. Brenzel, Kathleen. Sunset Publishing Corporation, Menlo Park, CA. 2001

Question 1.2 Impact on plant community composition,
structure, and interactions?
B Other Published Material
Identify type of impact or alteration:

Cotoneaster can quickly come to dominate a scrub or grassland area on sandy or clay soils, and even on serpentine soils and extirpate native species. In many areas of coastal California the Cotoneaster, at 3m tall, will be the tallest plant and shade out native scrub and grasses, in forested areas Cotoneaster seedlings will compete with seedlings from native trees. The Cotoneaster grows quickly in comparison to native scrubs, has a large root system that can extend beyond the canopy of a smaller Cotoneaster, and produces berries which are very popular with birds which spread the seeds. Additionally, the Cotoneasters are highly adaptable and can grow in moist (near waterways) or dry soils, and even in the thin, rocky soils underlying native grasslands. California's grasslands have been severely reduced by the proliferation of non-native annual grasses and are especially difficult to restore. Cotoneaster are able to grow in grasslands, shade out nativegrasses and create areas with higher organic matter and moisture which favor weedy grasses. Cotoneaster spread very rapidly which intensifies the risk to many of our native ecosystems.

Sources of information:

Sigg 2000.

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

Reduces habitat for burrowing rodents such as voles and shrews, reduces habitat for bird species such as quail that require open grassy areas for seed foraging, reduces space in which raptors can hunt. Reducing habitat for rodents and some birds will in turn reduce food source for raptors, foxes, coyotes and other carnivores. Coastal areas of california are defined by areas of scrub and oak interspered with open areas in which grasses and annual forbs persist, this pattern is constantly changing depending on erosion, rainfall, and natural progression from open sand into scrub and eventually oak woodland. However, Cotoneaster grows and spreads much more quickly than native plants and fills in open areas in scrub and covers grasslands when not rigorously controlled. It's dense roots and branches can effectively close off the area under its canopy making it inhospitable to rodents and difficult for larger birds to penetrate.

Sources of information:

C. Christman, Observation

Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

Not aware of any ability to hybridize with natives, but have found no information on this. Cotoneaster is in the rosaceae family and might be able to hybridize with native rosaceae, though it seems unlikely as there are no native plants in the same genus.

Sources of information:

no information

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

Cotoneaster can invade wildlands without any dramatic anthropogenic or natural disturbance. I have observed Cotoneaster growing in undisturbed scrubland, grassland and forested areas. Because birds eat the berries and drop the seed in scat, disturbance is not necessary for the spread of the seed. Additionally, Cotoneaster are well-adapted to many soil types and can do well in full sun or aprt shade conditions. It is likely that the fragmentation of wildlands has been at least partly responsible for this spread, Cotoneasters are a popular horticultural plant (in part because they attract birds!) and they are often cultivated close to wild areas. It has been noted by Jake Sigg that the oldest Cotoneasters seen in the wild are only 15 to 20 years old and that a change in genotype mighy have allowed Cotoneasters to spread more rapidly in the recent past as they have been cultivated in California since 1854.

Sources of information:

C. Christman, Observation.
Sigg 2000

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


Sources of information:


Question 2.3 Recent trend in total area infested within state? B Other Published Material
Describe trend:

Increasing steadily, unable to quantify Cotoneaster has only recenly been noted as a wildland invader, but so far has spread significantly along the coast, esp. near urban areas where it has been in cultivation for many years. It seems likely that as the population of California grows and housing along the coast becomes denser, the Cotoneaster will be brought into local gardens and will spread from them into wild areas. It does not seem likely to spread inland as it prefers the cooler, moister climate of the coast.

Sources of information:

Sigg 2000

Question 2.4 Innate reproductive potential? B Observational
Describe key reproductive characteristics:

Unsure how quickly it reaches sexual maturity, probably no more than 3 years, a single plant can produce thousands of berries, they fruit every year, the fruit is produced during the fall months and stay on the plant throughout the winter, seedlings can sprout without being eaten, as shown by many seedlings germinating directly beneath the parent plant, unsure how long seeds are viable in the soil, produce seed from self-and cross- pollination, does not spread by rhizomes or root structures, but does resprout like crazy when cut.

Sources of information:

C. Christman, Observation.
Sigg 2000

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

Used in public and private ornamental cultivation. First, I worked in the nursery industry in the past and have sold Cotoneasters (believe me, I have been chastened). Second, there are hundreds of websites advertising many species and varieties of Cotoneaster for sale by mail order or at local nurseries, all over the USA and in many other countries. All of these websites give information on planting and caring for your Cotoneaster.

Sources of information:

C. Christman, Observation
Sigg 2000

Question 2.6 Potential for natural long-distance dispersal? A
Identify dispersal mechanisms:

Birds and other animals eat fruit and move seed over range. Fruit can be moved by flowing water.

Sources of information:

C. Christman, Observation
Invasive Plants of California Wildlands. Sigg, Jake, on www.
Weeds of California and Other Western States. DiTomaso J, Healy E. As yet unpublished

Question 2.7 Other regions invaded? U
Identify other regions:

Noted as invading Australian bushland (different websites say there are 6 or 9 species that have invaded Australia: C. pannosa, C. franchettii, C. lacteus and C. gluacophylla are esp. problematic there, Cotoneaster pannosa and C. franchettii, very similar species, are noted in Hawaii and South Africa.

Sources of information:

Iziko, Museums of Cape Town:
Ecoaction Australia:

Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Observational

Cotoneaster can be found in all coastal ecosystems except foredunes, as I know from observation, and it is found mainly in an area around Los Angeles, an area around the San Francisco Bay, along the central coast near Big Sur, and in far Northern California near the border with Oregon. It was introduced to the state in 1854 for ornamental purposes. I have no information on where else it may be or what percentage of total ecosystem in California it has invaded. I would guess around 5%-10% for riparian woodland, and more like 20% for coastal scrub and prarie, considering how reduced in size and number these ecosystms are. However, I have no information to prove this. Per Worksheet C, invades 5 major types, on enter text here

Sources of information:

C. Christman, Observation
Invasive Plants of California Wildlands. Sigg, Jake, on www.

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


Sources of information:

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Unknown
Dense infestations produce >1,000 viable seed per square meter Unknown
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually Yes
Seeds remain viable in soil for three or more years Unknown
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes No
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 4
Total unknowns: 3
Total score: B?

Related traits:

seeds spread by birds and other animals w, also spread by water movement and human cultivation. It is likely that a single plant can produce several thousand seeds per year, depending on plant size and vigor, but I have seen nothing documenting this. Different Cotoneaster species may hybridize

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
DunescoastalU, Unknown
Scrub and Chaparralcoastal bluff scrubU, Unknown
coastal scrubU, Unknown
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieU, Unknown
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 woodlandU, Unknown
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forestU, Unknown
North Coast coniferous forestD, < 5%
closed cone coniferous forestC, 5% - 20%
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): C
Distribution (highest score): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Southwest