Plant Assessment Form

Myriophyllum aquaticum

Synonyms: Enhydria aquatica, Myriophyllum brasiliense, M. proserpinacoides

Common Names: parrotfeather; Brazilian watermilfoil; parrotfeather watermilfoil; thread-of-life;

Evaluated on: 3/28/05

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 DiTomaso
University of California-Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu

List commitee members

Joe DiTomaso
Alison Stanton
Joanna Clines
Cynthia Roye
Doug Johnson

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 Other Published Material
Impact?
Four-part score AABD Total Score
A
1.2 ?Impact on plant community A. Severe Other Published Material
1.3 ?Impact on higher trophic levels B. Moderate Other Published Material
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Other Published Material
Invasiveness?
Total Points
16 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 Observational
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 B. Occasional Other Published Material
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
C. Limited 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? A Other Published Material
Identify ecosystem processes impacted:

Forms large surface or subsurface mats that impede wateflow.


Sources of information:

DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Large mats displace native aquatic vegetation.


Sources of information:

DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Large floating mats create mosquito habitat and impede recreational activities (1). Can shade out algae that serve as the basis of the aquatic food web (2).


Sources of information:

1. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.
2. Anonymous. 2005. Parrotfeather (Myriophyllum aquaticum (Vell.) Verdc.). Written findings of the Washington State Noxious Weed Control Board. Available: http://www.nwcb.wa.gov/weed_info/written_findings/


Question 1.4 Impact on genetic integrity? D Other Published Material

There are three native species of Myriophyllum in California, but this species does not produce any seed and is extremely unlikely to hybridize with the natives.


Sources of information:

Hickman, J. C. (ed.) 1993. The Jepson Manual, Higher Plants of California. University of California Press. Berkeley, CA
DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Inhabits both areas with natural disturbance, such as river channels, and calmer waters with less disturbance (1). Can survive drawdowns of water in irrigation channels (2). Appears to be adapted to high nutrient environments (2).


Sources of information:

1. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.
2. Anonymous. 2005. Parrotfeather (Myriophyllum aquaticum (Vell.) Verdc.). Written findings of the Washington State Noxious Weed Control Board. Available: http://www.nwcb.wa.gov/weed_info/written_findings/


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

Has been observed to spread very rapidly in most aquatic systems.


Sources of information:

DiTomaso and Anderson, observational.


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

Still spreading.


Sources of information:

DiTomaso, observational.


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

Only populations in native range develop seeds. Creeping rhizomes produce numerous roots at nodes. Stems develop fine adventitious roots at lower nodes and on stem fragments. Male and female flowers develop on separate plants. Cultivated and naturalized plants in California are typically female (1). Rhizomes stored in a refrigerator for one year were able to regenerate (2).


Sources of information:

1. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421
2. Anonymous. 2005. Parrotfeather (Myriophyllum aquaticum (Vell.) Verdc.). Written findings of the Washington State Noxious Weed Control Board. Available: http://www.nwcb.wa.gov/weed_info/written_findings/


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

Escaped from aquaria. Can be spread by dumping of aquarium water or by catching in boat propellers.


Sources of information:

1. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Can cling to the feet and feathers of waterbirds or be carried downstream by waterflow.


Sources of information:

1. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Native to South America. Present along the west coast, in the southeast, and along the Atlantic seaboard (1). Inhabits warm temperate to tropical regions worldwide but is not as widespread as Eurasian watermilfoil (2). Scoring as C because seems to inhabit the same habitats elsewhere as it does in California.


Sources of information:

1. USDA, NRCS. 2005. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
2. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Introduced from South America as a pond ornamental in the late 1800s to early 1900s. Grows best in tropical regions, can survive freezing by becoming dormant. Typically in water to 1.5m deep. Tolerates soft to very hard water and a pH range of 5.5 to 9.0. Does not tolerate brackish water. Requires high light conditions. Occurs in ponds, lakes, rivers, streams, canals, and ditches. Usually lives in still or slow-moving water, but occasionally in faster-moving water of streams and rivers. Occurs in North Coast, Cascade Range foothills, central-western region, and south coast to 500m (1).


Sources of information:

1. DiTomaso, J.M., and E. H. Healy. 2003. Aquatic and Riparian Weeds of the West. University of California, Agriculture and Natural Resources Publication 3421.


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

Mainly in irrigation canals and in some ponds. Not as common as Eurasian watermilfoil


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. 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, reservoirsD, < 5%
Aquatic Systemsrivers, streams, canalsD, < 5%
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 woodland
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): C
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

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