Plant Assessment Form

Oxalis pes-caprae

Common Names: Bermuda buttercup; buttercup oxalis; sour grass

Evaluated on: 5/22/03

List committee review date: 06/06/2003

Re-evaluation date:

Evaluator(s)

Joe DiTomaso
UC Davis
Weed Science Program, Robbins Hall, Univ. California, Davis CA 95616
530-754-8715
DiTomaso@vegmail.ucdavis.edu

List commitee members

Joe DiTomaso
Peter Warner
Alison Stanton
Carla Bossard
Cynthia Roye
Jake Sigg
Doug Johnson
Brianna Richardson

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Other Published Material
Impact?
Four-part score BBCD Total Score
B
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels C. Minor Anecdotal
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Other Published Material
Invasiveness?
Total Points
14 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Other Published Material
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate 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? B Other Published Material
Identify ecosystem processes impacted:

Causes soil enrichment and stabilization of semi-stable areas, altering ecosystem nutrient cycling.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html


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

Outcompetes native vegetation for light and space. Also inhibits germination of ntive species in Australia. Pigs root our plant causing more soil disturbance. Not studied much in US, but expected to do the same. Observational info from A. Pickart indicated similar impacts.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; Sigg, J. 2003. CalEPPC News 11(1):7-8; Observational-DiTomaso, Pickart


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

Expected to have negative impact on wildlife forage because of toxicity. Insoluble oxalate crystals are poisonous to livestock. Not eaten by animals because taste is undesirable.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; Sigg, J. 2003. CalEPPC News 11(1):7-8; Parsons, W.T. and E.G. Cuthbertson. 1992. Noxious Weeds of Australia. Inkata Press, Sydney.


Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

None No report of seed production in North America or Australia.


Sources of information:

Ornduff, R. 1987. Annals of the Missouri Bot. Garden 74:79-84


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

Can establish in dunes without disturbance but readily established with disturbance. Plant is also grown as a garden ornamental and spreads at the urban wildland interface. Movement is only by bulbs.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; Sigg, J. 2003. CalEPPC News 11(1):7-8; Parsons, W.T. and E.G. Cuthbertson. 1992. Noxious Weeds of Australia. Inkata Press, Sydney.


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

Observed and reported to increase exponentially in a stabilized sand dune.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; Sigg, J. 2003. CalEPPC News 11(1):7-8; Observational-Pickart


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

No real data on statewide trend. Not being controlled much so expected that it is increasing. Been in California for some time, exploding locally but probably only increasing slowly statewide.


Sources of information:

Observational-DiTomaso


Question 2.4 Innate reproductive potential? B Reviewed Scientific Publication
Describe key reproductive characteristics:

Reproduces by bulbs. No seed production in North America or Australia. The weight of new bulbs and bulblets in 1 year can be 10x that of the parent bulb and as much as 10,000 lb/acre.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print); Parsons, W.T. and E.G. Cuthbertson. 1992. Noxious Weeds of Australia. Inkata Press, Sydney; Ornduff, R. 1987. Annals of the Missouri Bot. Garden 74:79-84


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

Dispersal of bulblets can occur by garden refuse, soil contamination, and equipment.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html


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

No seed dispersal, bulblets move by dispersal by birds. Short distance dispersal by pigs.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; Observational-DiTomaso


Question 2.7 Other regions invaded? B Reviewed Scientific Publication
Identify other regions:

A wildland and agricultural weed of Australia, India, Iberian peninsula, Italy, Greece, other areas of Europe, and North Africa. Can be found in tropical areas and even semi-arid regions.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html; Parsons, W.T. and E.G. Cuthbertson. 1992. Noxious Weeds of Australia. Inkata Press, Sydney; Peirce, J.R. 1997. Plant Protection Quarterly 12(3):110-119


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

In wildlands, it is found in forested areas, on coastal bluffs and dunes. A significant agricultural problem around the world and frequent urban escape both coastal and inland. Have been introduced in the US since at least 1925.


Sources of information:

Tu, M. 2003. Weed Alert! Oxalis pes-caprae TNC website. Tncweeds.ucdavis.edu/alert/alrtoxal.html


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

Most common in coastal dunes, particularly from Monterey County northward.


Sources of information:

Observational-DiTomaso


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. No
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 No
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere Yes
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
DunescoastalC, 5% - 20%
desert
interior
Scrub and Chaparralcoastal bluff scrubD, < 5%
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 woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forestD, < 5%
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): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Desert Province
  • Mojave Desert
  • Sonoran Desert
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest