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Water Chestnut (Trapa natans)

Water Chestnut (Trapa natans), an aquatic plant, belongs to the family Trapaceae. It is not to be confused with another aquatic plant of tather similar name, Chinese water chestnut (Eleocharis dulcis) of the family Cyperaceae, which is a popular ingredient in Southeast Asian and Chinese cooking.

Origins and distribution
The Trapa natans plant is presumably a native of the paleotropical and warm temperate regions of Eurasia. Their natural range of growth includes parts of Southern Europe, Africa and Asia. It has been grown in Europe since the neolithic times and was used commonly as food by the ancient Europeans. An easy-growing plant, it has became naturalised in parts of the USA since it was first introduced into North America around 1874. These plants grow in streams, ponds and shallow water bodies, such as freshwater estuaries, and on exposed mud flats.

Description 
The chestnut is a perennial plant with a crop harvested annually. Its roots are fine, long and many in number. The plant has large leaves that float on water. The leaves are triangular, fan-shaped and have toothed edges. Some leaves are submersed in water and these leaves are feather-like with very fine segments. They remain whirled around a submersed stem. The fruits of Trapa natans are nut-like, one to two in in diameter with four sharp barbed spines. The chestnut plant is propagated mainly through seeds. A single seed can give rise to 10 to 15 plant rosettes. The seeds can stay viable for up to 12 years.

These plants are classified as noxious weeds. A fierce competitor in shallow waters, it propagates itself quickly and forms mats across a wide area of a water. In the process, it kills fish, plants and endangers other forms of aquatic life by sucking out oxygen from the water and limiting the passage of light into water, required for photosynthesis. The nearly impenetrable mats make it difficult for a boater to paddle or drive through, and its thorny seeds cut the feet of people standing in the water. These mats are usually formed along the shoreline.

Usage
Food
The fruits are boiled or roasted. They can also be dried and ground into flour, which is sometimes used as a substitute for arrowroot flour. The fruits are a good source of nutrition with 16% starch and 2% protein. When raw, the fruits are juicy and crisp, when cooked, the flesh softens but it still remains crunchy. Various species of the plant, under the same genus of Trapa, are grown across the world. In China, Japan and Korea, the kernels of Trapa bicornis are eaten boiled or are used in many regional dishes. They are also preserved in honey and sugar. In India and Pakistan, flour is made out of the seeds of Trapa bispinosa, which is known to the people of Kashmir as "singhara nut" .

Medicine
Fruits of the Trapa natans plant are used in making liniments for the cure of elephantiasis, rheumatism, sores and sunburn. It is also said to have cancer-preventing properties.

Variant names
Common name: Chestnut.
Scientific name: Trapa natans.
Chinese name: Ling or ling chio.
Other common names: Jesuit nut, Jesuit's nut, water caltrops, metal caltrops, waternut, bullnut, European water chestnut.



Author
Thulaja Naidu Ratnala 
 


References
Hsuan, K. (1990). The concise flora of Singapore: Gymnosperms and dicotyledons (p. 85). Singapore: Singapore University Press.
(Call no.: RSING 581.95958 KEN)

Vaughan. J. G., & Geissler, C. (1997). The new Oxford book of food plants (p. 36). Oxford: Oxford University Press.
(Call no.: R 641.303 VAU)

Sunset Publishing Corporation & Thomson Corporation Company. (1991, August). They're not bland. Fresh water chestnuts are a taste discovery; recipes. Sunset, 187(2), 96.

Clark, M. (2000, April 19). Food chain. The New York Times, p. 7.

Marinelli, J. (1999, June 22). The new oxford book of food plants; reviews. Whole Earth, p.26.

McKinnon, R. (1997, December 21). Can water chestnuts be grown in Queensland? Sunday Mail, p. 18. 

Reilly, J. (2003, July 6). Have you seen this plant? Invasive, alien water chestnut is clogging local waterways; shore dwellers and experts are mobilizing to beat it back. The Post-Standard, p. 1.

Zentz, R. (2002, September 27). Grow your own chestnuts, then roast them for a treat. The Californian, p. 2.

Down on the do-gooders. (1995, September 9). The Washington Post, p. 15.


Further Readings
Germplasm Resources Information Network. (2003). Taxon: Trapa natans L. Retrieved September 5, 2003, from
www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?36824

Purdue University. (1996). Water chestnut. Retrieved September 5, 2003, from  newcrop.hort.purdue.edu/hort/newcrops/Crops/WaterChestnut.html

University of Florida. (2002). Aquatic, Wetland and invasive plant particulars and photographs, Trapa natans, water chestnut. Retrieved September 5, 2003, from aquat1.ifas.ufl.edu/tranat.html

Wayne's World. (n.d.). A horny bull's head. Retrieved January 31, 2005, from waynesword.palomar.edu/ploct95.htm



The information in this article is valid as at 2003 and correct as far as we can ascertain from our sources. It is not intended to be an exhaustive or complete history of the subject. Please contact the Library for further reading materials on the topic.

Subject
Nature>>Plants
Water chestnuts--Southeast Asia
Science and technology>>Agriculture>>Fruit crops

Librarian Recommendations
>> Chinese Water Chestnut (Eleocharis dulcis)


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