Trapa natans - L.
Water Chestnut
Other Common Names: water chestnut
Taxonomic Status: Accepted
Related ITIS Name(s): Trapa natans L. (TSN 27170)
Unique Identifier: ELEMENT_GLOBAL.2.149241
Element Code: PDTRA01010
Informal Taxonomy: Plants, Vascular - Flowering Plants - Other flowering plants
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Myrtales Trapaceae Trapa
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Trapa natans
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (30Sep2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Delaware (SNA), Massachusetts (SNR), New York (SNA), Pennsylvania (SNA), Vermont (SNA), Virginia (SNA)
Canada Ontario (SNA), Quebec (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

Distribution
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U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States DEexotic, MA, NYexotic, PAexotic, VAexotic, VTexotic
Canada ONexotic, QCexotic

Range Map
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Ecology & Life History Not yet assessed
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Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: Medium
Rounded I-Rank: Medium
I-Rank Reasons Summary: Trapa natans outcompetes native plants, does not seem to need major disturbance to invade, has extremely aggressive reproductive characteristics, and is difficult and costly to control. Its current range is from Vermont to Virginia. It is continuing to expand its range in the Northeast and possibly the Great Lakes, but following an eradication program in the Chesapeake Bay region it is relatively rare in that area.
Subrank I - Ecological Impact: Medium
Subrank II - Current Distribution/Abundance: Low
Subrank III - Trend in Distribution/Abundance: High/Medium
Subrank IV - Management Difficulty: Medium/Low
I-Rank Review Date: 09Dec2003
Evaluator: Tomaino, A.
Native anywhere in the U.S?
Native Range: Europe, Asia, and Africa (Swearingen et al. 2002).

Download "An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for their Impact on Biodiversity". (PDF, 1.03MB)
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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: Established outside cultivation (Kartesz 1999).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: It can occur in any freshwater setting but prefers nutrient-rich lakes and rivers (Swearingen 2002).

Subrank I - Ecological Impact: Medium

1. Impact on Ecosystem Processes and System-wide Parameters:Moderate significance
Comments: Reduces dissolved oxygen; extremely low dissolved oxygen is common in large beds dominated by Trapa natans (Caraco and Cole 2002). Forms dense floating mats, severely limiting light (Swearingen 2002). At high density, 95% of incident sunlight is intercepted by Trapa plants (Juget and Rostan 1973 in Groth et al. 1996).

2. Impact on Ecological Community Structure:Moderate significance
Comments: Replaces the submersed layer of native aquatic macrophytes (Kiviat 1993 in Caraco and Cole 2002).

3. Impact on Ecological Community Composition:High significance
Comments: Out-competes native plants (Ruiz et al. 1999). Over a five-year period, a pond in MA which had originally had a varied aquatic flora, became a virtual monoculture of Trapa (Groth 1996). Negatively impacts fish and waterfowl (Ruiz et al. 1999). Creates poor habitat for sensitive fish and invertebrates due to the low disolved oxygen (Caraco and Cole 2002). Out-competes submersed vetetation that waterfowl prefer, endangering feeding and wintering grounds for many ducks (McSpirit 1997).

4. Impact on Individual Native Plant or Animal Species:Unknown

5. Conservation Significance of the Communities and Native Species Threatened:Moderate significance
Comments: It can grow in any freshwater setting (Swearingen et al 2002). Since it can be spread to new sites easily (McSpirit 1997), and is extremely prolific when at low density (Groth et al. 1996), it seems it may threaten high quality common ecological communities. It does prefer nutrient-rich lakes and rivers (Swearingen et al 2002). Anthropogenically caused eutrophication seems to aid its spread (Ruiz et al. 1999).

Subrank II. Current Distribution and Abundance: Low

6. Current Range Size in Nation:Moderate significance
Comments: East Coast States from Vermont to Virginia (Kartesz 1999).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:Low significance
Comments: Most problematic populations occur in the Connecticut River valley, Lake Champlain region, Hudson River, Potomac River and the upper Delaware River (Swearingen et al. 2002).

8. Proportion of Nation's Biogeographic Units Invaded:Low significance
Comments: Less than 20%, based on Kartesz (1999) and TNC (2001). Trapa natans is found in approximately 9% of the HUC 4-digit level watersheds in the United States, inferred from Kartesz (1999) and USGS (2002).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Low significance
Comments: Invades a tidal freshwater river, slow moving non-tidal rivers, lakes, and ponds (McSpirit 1997; Swearingen et al. 2002, Caraco and Cole 2002).

Subrank III. Trend in Distribution and Abundance: High/Medium

10. Current Trend in Total Range within Nation:Moderate significance
Comments: Continuing to expand its range in northeastern states (McSpirit 1997)' it has recently spread to Long Island (Jordan 2005). Following an eradication program that extended into the 1960's, it has been relatively rare in the Chesapeake Bay region (Ruiz et al. 1999). Trapa has been reported in the Great Lakes Basin (Mills et al. 1993 in Groth 1996). MIght it be spreading in the direction of the Great Lakes region?

11. Proportion of Potential Range Currently Occupied:Medium/Low significance
Comments: It is prohibited from sale in most southern states (Swearingen et al. 2002), suggesting it may be known capable of spreading there. Trapa has been reported in the Great Lakes Basin (Mills et al. 1993 in Groth 1996) indicating that it could possibly spread throughout that region. Roughly 10-90%, based on USDA (1990).

12. Long-distance Dispersal Potential within Nation:Moderate significance
Comments: Thorny nutlets may cling to objects that humans transport (ie. boats, fishing equipment) and also to birds (Swearingen et al. 2002). However, the fruit is large; most fruits fall to the bottom of the water body in which they were produced (Groth et al. 1996).

13. Local Range Expansion or Change in Abundance:High significance
Comments: In Lake Champlain, its total biomass increased tenfold from one year to the next (Bogucki et al. 1980 in Groth 1996). The species is capable of extremely rapid increase and readily recovers from weeding efforts if these are not sustained (Groth et al. 1996).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:High/Moderate significance
Comments: Trapa does not seem able to only establish in areas with "major" disturbance. Trapa is expanding in Lake Champlain (Bogucki et al. 1980 in Groth et al. 1996) which does not seem to qualify as a site with "major" disturbance.

15. Similar Habitats Invaded Elsewhere:Unknown

16. Reproductive Characteristics:High significance
Comments: Reproduces readily by clonal growth and reproduces by seed (Groth et al. 1996). Fragments easily with fragments capable of becoming established elsewhere (Groth et al. 1996). Seeds can remain viable for up to 12 years (Swearingen et al. 2002).

Subrank IV. General Management Difficulty: Medium/Low

17. General Management Difficulty:High/Moderate significance
Comments: Control of Trapa is difficult and costly (Groth et al. 2002). The species is capable of extremely rapid increase and readily recovers from weeding efforts if these are not sustained (Groth 1996). Complete removal of plants prior to July is imperative as plant parts can spread and seeds set occurs in July (Swearingen et al. 2002). Eradication is difficult because seeds may remain viable for 12 years (Swearingen et al. 2002). No biological controls have been approved, manual, mechanical, and chemical techniques are used (Swearingen et al. 2002).

18. Minimum Time Commitment:Medium/Low significance
Comments: Seeds may remain viable for up to 12 years but most will germinate in the first two years (Swearingen et al. 2002). Thus, most efforts would seem to be concentrated in the first few years.

19. Impacts of Management on Native Species:Medium significance/Insignificant
Comments: Manual, mechanical, and chemical techniques are used (Swearingen et al. 2002). Because this species out-competes other plants, and is not good habitat for native animal populations, collateral damage seems like it might not be extensive. No collatoral damage mentioned in references found.

20. Accessibility of Invaded Areas:Insignificant
Comments: Plant is aquatic, so generally publically accessible. Much along major valleys, so road access generally good.
Authors/Contributors
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Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Bickerton, H. 2016. Spread of European Water Chestnut (Trapa natans L.) to the Rideau River in Ottawa. Trail & Landscape 50(3): 124-129.

  • Caraco, N. F. and J. J. Cole. 2002. Contrasting impacts of a native and alien macrophyte on dissolved oxygen in a large river. Ecological Applications 12(5): 1496-1509.

  • Groth, A. T., L. Lovett-Doust, and J. Lovett-Doust. 1996. Population density and module demography in Trapa natans (Trapaceae), an annual, clonal aquatic macrophyte. American Journal of Botany 83(11): 1406-1415.

  • Jordan, M. 2005. Weed spread on Long Island, NY (New York, USA). Posting to TNC Invasive Species Listserve: Digest #142 (October 2005). Online. Available: http://tncweeds.ucdavis.edu/listserv.html (Accessed 2005).

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • McSpirit, K. 1997. Common nuisance aquatic plants in New York State. New York State Department of Environmental Conservation Lake Services, Albany, NY.

  • Ruiz, G. M., P. Fofonoff, A. H. Hines, and E. Grosholz. 1999. Non-indigenous species as stressors in estuarine and marine communities: Assessing invasion impacts and interactions. Limnol. Oceanogr. 44(3, part 2): 950-972.

  • Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

  • The Nature Conservancy. 2001. Map: TNC Ecoregions of the United States. Modification of Bailey Ecoregions. Online . Accessed May 2003.

  • U.S. Geological Survey. 2002. Subregion Hydrologic Unit Boundaries (4-Digit). Version 2.3. January 2002.

  • USDA Agricultural Research Service. 1990. USDA Plants Hardiness Zone Map. Misc. Publ. Number 1475.

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