American Eelgrass | Vallisneria americana Michx.

Some American Eelgrass

California Pest Rating for
            Vallisneria americana Michx.: American eelgrass
Hydrocheritales: Hydrocharitaceae
Pest Rating: D | Proposed Seed Rating: N/A


Initiating Event:

Vallisneria americana was observed growing in water district pond in Shasta county in 2007. Vallisneria species have been intercepted by county and at CDFA border stations in 2011, 2016 and 2018. This species is introduced to California. It has been given a temporary rating of Q by CDFA. A pest rating proposal is required to assign a permanent rating.

Synonyms: Vallisneria neotropicalis (ITIS Database)

History & Status:

BackgroundVallisneria americana is a submersed perennial plant that is common in both still and fast flowing waters. It is a popular aquarium plant. It needs 5 cm thick of rich soil, full light and water temperature of 18-20 degrees Celsius for cultivation (Lady Bird Johnson Wildflower Center 2016).

Vallisneria americana grows from underground runners, and forms tall underwater meadows. Its leaves are approximately one-inch wide and several feet long and arise in clusters from the roots. The leaves have rounded tips and raised veins. The upper leaf parts often float on the water surface. This species produces separate male and female flowers. Female flowers are more conspicuous. Mature flowers detach and float on the surface of water. The fruit is a banana-like capsule and contains tiny seeds (University of Florida, 2018).

The native range of Vallisneria americana incudes Asia, Australia, North America, Central America, and South America. It prefers slow moving water and is mainly found in lakes, ponds and streams at least 10 feet deep. Fishes and invertebrates use this species as a refuge. This plant also grows in brackish water and in rivers with various salinity levels (Brand, 2015).

Worldwide Distribution:  Vallisneria americana is widely distributed in eastern North America and is present in Canada, Cuba, Dominican Republic, Guatemala, Haiti, Honduras, Jamaica, Mexico and the United States. (IUCN Red List of Threatened Species).

In the Unites States, Vallisneria americana is present in the eastern states and specimens have been collected from Connecticut, Florida, Illinois, Louisiana, Minnesota, North Carolina, Ohio, Vermont, Virginia and Wisconsin (Wunderlin et-al., 2018) and spreading towards the west coast, being reported in Washington, Arizona, New Mexico, Texas, Nebraska (Lady Bird Johnson Wildflower Center 2016).

Official ControlVallisneria americana has been reported as a harmful organism in Indonesia and Timor-Leste and is under official control (USDA- APHIS- PCIT).

California Distribution: Vallisneria americana has been observed occurring naturally in Shasta county and a voucher specimen has been confirmed by the CDFA Plant Pest Diagnostics Center (Consortium of California Herbaria, 2018).

California InterceptionsVallisneria species have been intercepted few times by CDFA, through border station inspections and through weed and vertebrate surveys (Pest and Damage Report Database, 2018).

The risk Vallisneria americana (American eelgrass) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Vallisneria americana grows in lakes and slow-moving rivers, primarily in neutral to basic waters (IUCN). It grows from stoloniferous clumps submerged under water. In shallow waters, its leaves can float the on surface of the water. It can grow well in wetland gardens and habitats. It is likely to grow in lakes, ponds, reservoirs and rivers in California. (Lady Bird Johnson Wildflower Center 2016) It receives a Medium (2) in this category.

 Evaluate if the pest would have suitable hosts and climate to establish in California.  Score:

Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Vallisneria americana do not require one host but can occur wherever environmental conditions are favorable for its growth and establishment. It receives a Medium (2) in this category.

Evaluate the host range of the pest.

Low (1) has a very limited host range.

Medium (2) has a moderate host range.

High (3) has a wide host range.

3) Pest Dispersal Potential:  Vallisneria americana reproduces through seeds in its natural habitat, but flowering is rare and most reproduction is through vegetative spread via runners in aquariums. These runners root and form a new plant. It is likely to disperse through water and humans. As it is dioecious with male and female flowers on different plants, it is unlikely to produce seed in an introduced population. Therefore, only vegetative reproduction is likely. It receives Low (-1) in this category.

Evaluate the natural and artificial dispersal potential of the pest.

– Low (1) does not have high reproductive or dispersal potential.

Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Vallisneria americana is good source of turtles and other aquatic wild life. It is also good for wetland gardens and habitats. This species is most likely to be introduced through aquarium plants that are discarded. If established, Vallisneria americana could impede water flow in irrigation canals and storage ponds. It could affect drainage of water bodies and can impact their agricultural and recreational use (CABI 2018). Once this species is well established, it can be difficult to remove. Vallisneria americana can serve as a nursery for fishery species. It can also stabilize shorelines and improve water quality by filtering. It receives a Low (1) in this category.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: G

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 1

Low (1) causes 0 or 1 of these impacts.

Medium (2) causes 2 of these impacts.

High (3) causes 3 or more of these impacts.

5) Environmental Impact:  Vallisneria americana is an important food to canvasback ducks. Its dense underwater structures provide a great habitat for fish and invertebrates (New England Wild Flower Society 2011-2018). Vallisneria americana provides both food and refuge for many aquatic species. Like Vallisneria spiralis, this species may form dense beds resulting in displacement of native aquatic plants (MAF Biosecurity New Zealand 2010). Because Vallisneria americana is a common species of submerged aquatic vegetation in low salinity estuarine areas, it seems likely to become established in wetlands in California (Rozas and Minello, 2006). It receives a Medium (2) in this category.

Environmental Impact: A

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Vallisneria americana  (American eelgrass) Low (8)

Add up the total score and include it here.

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Vallisneria americana has been found growing in a settling pond in northern California but has not fully established in the state and receives a Low (-1) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Low (7)


Vallisneria americana has been observed growing in a man-made pond in a very limited area of California. Suitable aquatic habitats exist for this species in parts of CA. However, despite the widespread use of this species as an aquarium plant for over a century and its ability to spread vegetatively in open waters, it has not yet established in California.

Conclusion and Rating Justification:

Vallisneria americana has been only observed in California in 2007 and has not caused any significant impacts to state agriculture and the natural environment. Though it is popular in the aquarium trade, it is not established in CA except for a small area in Shasta county despite its widespread distribution in North America and elsewhere. Therefore, a “D” rating is justified.


Brand, R. 2015. Jungle Val – How to Grow and Take Care for Jungle Vallisneria. Aquarium Tidings. Your source for aquarium information since 2010. Retreived  7/17/2018.

CABI. 2018. Invasive species compendium. Vallisneria spiralis (eel weed). Retrieved    7/23/2018.

CDFA Pest and Damage Report Database. 2018. Vallisneria americana. Plant Health    and Pest Prevention Services. CA Department of Food and Agriculture. Retrieved 07/18/2018.

Center for Aquatic and Invasive Plants. 2018. University of Florida. Institute of Food        and Agricultural Sciences. Retrieved 7/18/2018.

Consortium of California Herbaria. 2018. Data provided by the participants of the CCH.             University of California. Retrieved 7/23/2018.

Integrated Taxonomic Information System (ITIS) on-line database. ITIS Report.    Vallisneria americana Michx. Taxonomic Serial No. 38591. Retrieved 07/23/2018.

IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-1. Retrieved 7/28/2018.

Lady Bird Johnson Wildflower Center. 2016. Inspiring the conservation of native plants.  Vallisneria americana Michx. University of Texas, Austin. Retrieved 7/18/2018.

MAF Biosecurity New Zealand. 2010. Eelgrass: Vallisneria spiralis. Eelgrass:        Vallisneria spiralis. Retrieved 7/24/2018.

New England Wild Flower Society, 2011-2018. Vallisneria americana Michx.  180 Hemenway Road, Framingham, MA 01701. Retrieved 7/24/2018.

Rozas, L. P. and Minello, T.J. 2006.  Nekton use of Vallisneria americana Michx. (wild             celery) beds and adjacent habitats in coastal Louisiana. Estuaries and Coasts      29:297-310. Retrieved 07/23/2018.

USDA Natural Resources Conservation Service. 2018. PLANTS Profile. Vallisneria  americana Michx. USDA NRCS National Plant Data Team. Retrieved 7/24/2018.

USDA Phytosanitary Certificate Issuance & Tracking System (PCIT), Phytosanitary Export Database (PExD). Harmful organism report: Vallisneria americana. Accessed 07/17/2018.

Wunderlin, R. P., Hansen, B.F., Franck, A. R., and Essig, F.B., 2018. Atlas of       Florida Plants [S. M. Landry and K. N. Campbell, USF Water Institute.] Institute for Systematic Botany, University of South Florida, Tampa. Retrieved 07/24/2018.


Raj Randhawa, 1220 ‘N’ Street, Room 221, Sacramento CA 95814, (916) 654-0317,

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6650;


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Pest Rating: D |  Proposed Seed Rating: N/A

Posted by ls