Plant Assessment Form

Poa pratensis

Synonyms: Paneion pratense (L.) Lunell., several subspecies

Common Names: Kentucky bluegrass; smooth meadowgrass

Evaluated on: 3/23/05

List committee review date: 08/07/2005

Re-evaluation date:

Evaluator(s)

Elizabeth Brusati, project manager
California Invasive Plant Council
1442A Walnut St. #462, Berkeley, CA 94709
510-843-3902
edbrusati@cal-ipc.org
Joseph M. DiTomaso
University of California, Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu

List commitee members

Jake Sigg
Peter Warner
Bob Case
John Knapp
Elizabeth Brusati

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes U Reviewed Scientific Publication
Impact?
Four-part score UBCC Total Score
C
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels C. Minor Other Published Material
1.4 ?Impact on genetic integrity C. Minor/Low Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Other Published Material
Invasiveness?
Total Points
11 Total Score B
2.2 ?Local rate of spread with no management C. Stable Other Published Material
2.3 ?Recent trend in total area infested within state C. Stable Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Other Published Material
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Other Published Material
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Other Published Material
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
C. 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? U Reviewed Scientific Publication
Identify ecosystem processes impacted:

unknown


Sources of information:

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

Outcompetes native species. Bluegrass' dense rhizomes allows it to penetrate between native species, reducing species diversity and altering native floristic composition (1).


Sources of information:

1. Sather, N. Element Stewardship Abstract for Poa pratensis, Poa compresa. The Nature Conservancy, Arlington, VA. Available: http://tncweeds.ucdavis.edu


Question 1.3 Impact on higher trophic levels? C Other Published Material
Identify type of impact or alteration:

Considered a good forage in the eastern US, but not in western states because its biomass is reduced in areas of low rainfall (1). In mixed-grass prairies, it is less nutritious than native species and has a shorter season than native grasses (2).


Sources of information:

1. DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.
2. Sather, N. Element Stewardship Abstract for Poa pratensis, Poa compresa. The Nature Conservancy, Arlington, VA. Available: http://tncweeds.ucdavis.edu


Question 1.4 Impact on genetic integrity? C Other Published Material

In Europe, seed production is reported to be primarily apomictic (asexual), but in the U.S., Kentucky bluegrass is known to hybridize with several other Poa species. In California, it hybridizes with Sandberg bluegrass [Poa secunda J. S. Presl], a native species in California, and fowl bluegrass [Poa palustris L.], which is thought to be non-native in California.


Sources of information:

DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.


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

Inhabits many disturbed and undisturbed plant communities in California, especially those with northern exposure or high mountain areas (1). Very common turf species and is often found in disturbed sites. Also invades disturbed and undisturbed areas in Colorado (2).


Sources of information:

DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.
2. Weaver, T., J. Lichthart, and D. Gustafson. 1989? Exotic invasion of timberline vegetation, Northern Rocky Mountains, USA. Gen tech rep INT(270): 208-213.


Question 2.2 Local rate of spread with no management? C Other Published Material
Describe rate of spread:

Does not seem to spread very rapidly locally.


Sources of information:

DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.


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

Already present throughout California, so probably not spreading much.


Sources of information:

DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.


Question 2.4 Innate reproductive potential? B Other Published Material
Describe key reproductive characteristics:

Rhizomatous perennial grass. Well known for its ability to survive and thrive on successive defoliations (like lawnmowers) (1). In Europe, seed production is reported to be primarily asexual, but in the US it hybridizes with other species (2). After four years, production levels off at 4000 panicles/sq.m and 100 seeds per panicle. Despite high seed production, new plants are rarely produced from seed in an established prairie. Seeds can germinate from a depth of 42 in. (1).


Sources of information:

1. Sather, N. Element Stewardship Abstract for Poa pratensis, Poa compresa. The Nature Conservancy, Arlington, VA. Available: http://tncweeds.ucdavis.edu
2. DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.


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

Has escaped cultivation in California and elsewhere. Very common turf and lawn species and has ample opportunities to be moved by humans.


Sources of information:

DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.


Question 2.6 Potential for natural long-distance dispersal? C Other Published Material
Identify dispersal mechanisms:

Rhizomes and seeds can move in water, particularly after flooding event, but most populations are not next to water.


Sources of information:

DiTomaso and Healy. 2006. Weeds of California. UC DANR Publ. #3488.


Question 2.7 Other regions invaded? C Other Published Material
Identify other regions:

Native to Eurasia. Present in all contiguous states (1). Naturalized in Canada from Labrador to the west coast. There is disagreement whether populations in the northern states are actually native (2).


Sources of information:

1. DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States
2. 1. Sather, N. Element Stewardship Abstract for Poa pratensis, Poa compresa. The Nature Conservancy, Arlington, VA. Available: http://tncweeds.ucdavis.edu.


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Other Published Material

Present throughout California to 3500m. Invades roadsides, pastures, rangelands, grassland, riparian areas, shrubland, coniferous forest and associated meadows. Tolerates partial shade or alkaline to saline soil. Grows best in cool, moist places on soils rich in organic matter and with full sun exposure (1).


Sources of information:

DiTomaso, J., and E. Healy, in prep. Weeds of California and Other Western States.


Question 3.2 Distribution/Peak frequency? C Observational
Describe distribution:

Widespread but not frequently encountered. Some botanists believe that populations in undisturbed high mountain meadows of the western states are native.


Sources of information:

DiTomaso, observational.


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
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 No
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 5
Total unknowns: 0
Total score: B?

Related traits:

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal 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 prairieC, 5% - 20%
valley and foothill grasslandD, < 5%
Great Basin grasslandD, < 5%
vernal pool
meadow and seepD, < 5%
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 forestD, < 5%
lower montane coniferous forestC, 5% - 20%
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): A
Distribution (highest score): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • CA Floristic Province
  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest
  • Great Basin Province
  • Modoc Plateau
  • Sierra Nevada East
  • Desert Province
  • Mojave Desert
  • Sonoran Desert