Plant Assessment Form

Ludwigia hexapetala

Synonyms: Jussiaea grandiflora (M. Michelli) Greuter & Burdet; Jussiaea repens L var. grandiflora M. Michelli; Jussiaea uruguayensis Camb.; Ludwigia uruguanyensis (Camb.) Hara var. major (Hassler) Munz

Common Names: creeping waterprimrose; Uruguay waterprimrose

Evaluated on: 4/2/04

List committee review date:

Re-evaluation date:


Lily Verdone
Sonoma State University, Marin-Sonoma Mosquito Vector Control District
po boox 751 Monte Rio Ca 95462
cell 707 974 0033 home 707 865 9484

No list committee members listed

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? High
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes A. Severe Reviewed Scientific Publication
Four-part score AABU Total Score
1.2 ?Impact on plant community A. Severe Observational
1.3 ?Impact on higher trophic levels B. Moderate Observational
1.4 ?Impact on genetic integrity U. Unknown Observational
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Total Points
15 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Observational
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)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Observational
2.6 ? Potential for natural long-distance dispersal B. Occasional Observational
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Reviewed Scientific Publication
Total Score C
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? A Reviewed Scientific Publication
Identify ecosystem processes impacted:

Species alters sedimentation and water flow, sequesters nutrients, creates anerobic conditions Species forms large, dense mats of vegetation above and below the water surface. Root and vegetative growth trap sediment, block hydrolic flow and shade soil and water surfaces disturbing natural ecosystem processes

Sources of information:

Ellmore, G.S., 1981. Root dimorphism in Ludwigia peploides (Onagraceae): Structure and gas content of mature roots. American Journal of Botany, 68: 557-568.
Verdone, Lily, 2004. From data collected in the Laguna de Santa Rosa, Sonoma County, Ca. 2003-present.
Westerdahl, H.E. and Getsinger, K.D. (editors), 1988. Aquatic Plant Identification and Herbicide Guide Volume II: Aquatic Plant and Susceptibility to Herbicides. US Army Corps of Engineers Waterways Experiment Station. Technical Report A-88-9.

Question 1.2 Impact on plant community composition,
structure, and interactions?
A Observational
Identify type of impact or alteration:

Species out competes native aquatic and terrestrial vegetation, covers open water and terrestrial zones impacting native fauna, lowering species diversity and creates habitat benifical for disease vectors Once established, the species dominates and out competes native vegeation covering aquatic and transitional zones with a dense canopy above and below the water surface. Dense vegetative growth covers areas of once open water, degrading bird habitat, blocking fish passage and lowering the quality of water. The dnese canopy allows for standing water and moist conditions to persist years round creating ideal condtions for mosquitoes, possible West Nile Virus vectors.

Sources of information:

Main Sonoma Mosquito and Vector Control District, 2004. Observations and collection data from the Laguna de Santa Rosa, Sonoma County, Ca., 2000-present.
Verdone, Lily, 2004. From data collected in the Laguna de Santa Rosa, Sonoma County, Ca. 2003-present.

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

Reduction of open water and riverine habitat for fish, migratory birds and waterfowl Possible reduction in connectivity in fish passages to upstream tributaries (example of Salmon moving up the Russian River Watershed through the Laguna de Santa Rosa) due to plant growth blocking waterways, lowering water quality (sedimentation, anerobic conditions and high nutrient levels). Reduction of open water may reduce nesting, feeding, breeding and resting sites for watrfowl and migratory birds (as seen in the Laguna de Santa Rosa, part of the Pacific Flyway).

Sources of information:

Verdone, Lily, 2004. From data collected in the Laguna de Santa Rosa, Sonoma County, Ca. 2003-present.

Question 1.4 Impact on genetic integrity? U Observational

Unknown, low possibility of hybridization Species was tested for seed viability in Fall 2003, results conclued population of species in the Laguna de Santa Rosa produces sterile seeds

Sources of information:

Verdone, Lily, 2003. Lab experiment: Testing for seed viability using Tetrazolium. Sonoma State University,

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

The species establishes in areas with disturbed hydrology, high nutrient loading and flooding. Spread may be facilitated by nursery cultivation/commercial use and animals. Species favors areas of shallow, stagent, nutrient rich water such as flood control channels, irrigation ditches, holding ponds, ect. Species established in upland areas through flood deposition and is possibly spread by waterfowl. It may be used in bioremediation to remove excess nutrients and herbicides from agriculutral waters and waste water treatment ponds (as in Ludwigia peploides).

Sources of information:

Bayer, D.E. and Rejmankova, E., 1990. Removal of herbicide residua and nitrates from agricultural waters by aqutic plants. WRC Project W-727. Report of Water Resources Center. University of California, Riverside, CA. 32 pp.
DiTomaso, J. M. and Healy, E.A., 2003. Aquatic and Riparian Weeds of the West. University of California Agriculture and Natural Resources. Oakland, CA. pp. 253.
Verdone, Lily, 2004. From data collected in the Laguna de Santa Rosa, Sonoma County, Ca. 2003-present.

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

Rate of spread for species is rapid, in ideal conditions, exponential In the Laguna de Sata Rosa, Sonooma County, Ca. Ludwigia hexapetala coverd approximately 1450 acres in roughly 3 miles of main channel of 100% cover in 2 years.

Sources of information:

Verdone, Lily. 2004. GIS/GPS mapping of the Laguna de Santa Rosa, Sonoma County, Ca. August 2003.

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

Trend of infestation is increasing. Exact rate of spread is unknown, possibly due to lack of information on the species as well as the difficulty to identify the species from others in its genera which are phenotypically plastic. Using Sonoma Coutny as an example, the species has been documented in herbarium specimens and other reliable sources for over 25 years. Only in the last two - five years has the growth been documneted as invasive or weedy. In that time, the species has grown exponentially.

Sources of information:

California Department of Fish and Game, 2003. Invasive Exotic Plant Control on California Department of Fish and Game Lands During 2002. Office of Spill Preventation and response. Administrative Report 03-001.
Vedone, Lily, 2004. Finding from the North Coast Herbarium, Sonoma State University and the Jepson Herbarium, U.C. Berkeley. Agust 2003.

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

Species reproduces vegetatively (roots, rhizomes, plant fragments) and produces only non viable, sterile seeds. Species is polyploid (2n=80), polyploides are characterized as having non viable seeds and vegetative growth. Seeds were tested from the Laguna de Santa Rosa population and found not to be viable. Literature shows Ludwigia peploides to reproduce sucsessfully when 95% of the stem material is removed.

Sources of information:

Rejmankova, E., 1992. Ecolgy of creeping macrophytes with special reference to Ludwigia peploides (H.B.K.) Raven. Aquatic Botany. 43 283-299.
Verdone, Lily, 2003. Lab experiment: Testing for seed viability using Tetrazolium. Sonoma State University,

Question 2.5 Potential for human-caused dispersal? B Observational
Identify dispersal mechanisms:

Commercial use, spread through waterways, possible spread by boat and/or eqipetment Species could have been sold in the past or present as an aquatic nursery plant or used in bioremediation applications to sequester excess nutrients in foul waters. It is know to spread through waterways.

Sources of information:

Verdone, Lily, 2004. From data collected in the Laguna de Santa Rosa, Sonoma County, Ca. 2003-present.

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

Long distance dispersal includes vegetative propagules transported by flowing water and may also include movement by waterfowl. Main dispersal is by moving water. The species has been documented to be consumed and possibly transported by ducks and other waterfowl in the Laguna de Santa Rosa and the Delta regions.

Sources of information:

Verdone, Lily, 2004. Email conversation with Thomas Moore, Bay/Delta Cluster Biologist Natural Resources Conservation Service. May 14, 2003.

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

Lakes, ponds, slow moving streams and marshes throughout California and other Western and Southern States Considered a State noxious weed in Florida, Oregon, Washingtion, North Carolina and Oklahoma.

Sources of information:

Invasive Plants of the Thirteen Southern Sates. Accessed online at:
North Carolina Center for Agriculture Services. Accessed online at:
Washington State Department of Ecology: Water quality home. Accessed online at:

Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Reviewed Scientific Publication

Freshwater aqutic systems (lakes, ponds, reservoirs, rivers, streas, canals), Bog and marsh, riparian and bottomland Species is an aquatic freshwater vascular plant able to persist in dry transitional zones

Sources of information:

Hickman, J.C. (editor)., 1996. The Jepson Manual Higher Plants of California. University of California Press. Berkeley, CA.

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

Percent of distibution is unknown for this species no information

Sources of information:

no information

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 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: 6
Total unknowns: 0
Total score: A?

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, reservoirsU, Unknown
Aquatic Systemsrivers, streams, canalsU, Unknown
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
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plainU, Unknown
Bog and Marshbog and fenU, Unknown
marsh and swampU, Unknown
Riparian and Bottomland habitatriparian forestU, Unknown
riparian woodlandU, Unknown
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
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): -

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest
  • Modoc Plateau