| Water caltrop | |
|---|---|
 | |
| Trapa natans | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Myrtales |
| Family: | Lythraceae |
| Subfamily: | Trapoideae Voigt |
| Genus: | Trapa L. |
| Type species | |
| Trapa natans L. | |
| Species | |
Thewater caltrop is any of three extant species of thegenusTrapa:Trapa natans,Trapa bicornis and the endangeredTrapa rossica. It is also known asbuffalo nut,bat nut,devil pod,ling nut,mustache nut,singhara nut orwater chestnut.[1]
The species are floatingannualaquatic plants, growing in slow-moving freshwater up to 5 metres (16 feet) deep, native to warm temperate parts of Eurasia and Africa. They bear ornately shaped fruits, which in the case ofT. bicornis resemble the head of a bull or thesilhouette of a flyingbat. Each fruit contains a single very large, starchy seed.T. natans andT. bicornis have been cultivated in China and the Indian subcontinent for the edible seeds for at least 3,000 years.
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The water caltrop's submerged stem reaches 3.7 to 4.6 metres (12 to 15 feet) in length, anchored into the mud by very fine roots. It has two types ofleaves: finely divided, feather-like submerged leaves borne along the length of the stem, and undivided floating leaves borne in arosette at the water's surface. The floating leaves have saw-tooth edges and are ovoid or triangular in shape, 2–3 centimetres (3⁄4–1+1⁄4 inches) long, on inflated petioles5–9 cm (2–3+1⁄2 in) long, which provide added buoyancy for the leafy portion.
Four-petalled white flowers form in early summer and areinsect-pollinated.[2] The fruit is a nut with four1 cm (1⁄2 in) barbed spines. Seeds can remain viable up to 12 years, although most germinate within the first two years.
The plant spreads by the rosettes and fruits detaching from the stem and floating to another area on currents or by fruits clinging to objects, and animals.
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Bicornin is anellagitannin found inT. bicornis.[3]
The genus has an extensive fossil record, with numerous, distinctive species. Undisputed fossilized seeds have been found inCenozoic strata starting from theEocene throughoutEurope,China andNorth America (though the genus became extinct in North America prior to thePleistocene).[4] The oldest known fossils attributed to the genus are of leaves fromCretaceousAlaska, referred to the species,T. borealis.[5]
The generic nameTrapa is derived from the Latin word for "thistle",calcitrappa, as also is another common name for the watercaltrop.[citation needed]
The plant's name in Japanese ishishi, a word that is also used to mean "a diamond or lozenge shape, a rhombus". The manufacturing groupMitsubishi takes its name and logo of three lozenges from the water caltrop.[6]
It is calledShringataka inSanskrit,[7] which is shortened toShingara inHindi language. In Eastern India, thesamosa (a fried or bakedpastry) is also called Shingara because its shape resembles that of the Shingara fruit.
Water caltrop has been declared aninvasive species fromVermont toVirginia,[8] and is classified as a noxious weed inFlorida,North Carolina, andWashington.[9] As of 2020, bothT. natans andT. bicornis have been reported growing wild in the waterways of the United States.[10] In 1956T. natans was banned for sale or shipment in the US, subject to a fine and imprisonment.[11] The law was repealed in 2020.[12]
T. natans was introduced to the US state of Massachusetts around 1874 as a planting in the Harvard University Botanic Garden. Staff gardener Louis Guerineau took it upon himself to throw seeds into Fresh Pond and other Cambridge waterways. This came to the attention of Medford-based botanist George E. Davenport, who decided to bring seeds and live plants to his friend Minor Pratt, in Concord. He and Pratt seeded a pond near the Sudbury River, and he suspected Pratt of conducting additional distributions. As early as 1879, concern was voiced by botanistCharles Sprague Sargent, director of Boston'sArnold Arboretum, that this non-native species threatened to become a nuisance, based on dense growths reported in Cambridge. Davenport confessed in 1879:[13]
I have several times had plants ofTrapa natans that were collected in the vicinity of Boston, during the present year, brought to me for identification, and I have entertained no doubt as to the manner of its introduction into waters outside Cambridge Botanic Garden. But that so fine a plant as this, with its handsome leafy rosettes and edible nuts, which would, if common, be as attractive to boys as hickory nuts now are, can ever become a 'nuisance' I can scarcely believe.
Water caltrop is so rare in Germany that it is listed as anendangered species.[14]
Fasciolopsiasis is a disease resulting from infection by thetrematodeFasciolopsis buski, an intestinalfluke of humans, endemic in China, Southeast Asia, and India. The fluke can be transmitted via the surfaces of water plants, generallyT. natans seedpods. During themetacercarial stage in their lifecycle, the larval flukes leave their water snail hosts, and swim away to form cysts on the surfaces of the plants. If infected plants are consumed raw or undercooked, the flukes can infect pigs, humans, and other animals.[15]
The fruits are edible raw or cooked, and the seeds can be eaten as well.[16] It is also eaten on the occasion ofMid-Autumn Festival in theSinosphere.
Investigations of archaeological material from southern Germany indicate that the prehistoric population of that region may have relied significantly upon wild water caltrops to supplement their normal diet and, in times of cultivated cereal crop failure, water caltrops may have been the main dietary component.[17]
Water caltrop has been an important food for worship as prayer offerings since the ChineseZhou dynasty. TheRites of Zhou (second century BC) mentioned that a worshipper "should use a bamboo basket containing dried water caltrops, the seeds ofEuryale ferox andcaltrops" (加籩之實，菱芡栗脯). TheChinese Herbal Medicine Summary (本草備要 published in 1694, written by Wang Ang 汪昂) claims that water caltrop can helpfever and drunkenness.[citation needed]
In India and Pakistan, it is known assinghara orpaniphal (eastern India) and is widely cultivated in freshwater lakes. The fruits are eaten raw or boiled. When the fruit has been dried, it is ground to a flour calledsinghare ka atta, used in many religious rituals, and can be consumed as aphalahar (fruit diet) on theHindu fasting days, thenavratas.[18]
It was possible to buy water caltrops in markets all over Europe until 1880. In northernItaly, the nuts were offered roasted, much as sweet chestnuts (Castanea sativa) are still sold today. In many parts of Europe, water caltrops were known and used for human food until the beginning of the 20th century. Today, however, it is a rare plant in Europe. Several reasons for its near extirpation exist, such as climate fluctuations, changes in the nutrient content of water bodies, and the drainage of many wetlands, ponds, and oxbow lakes.[17]
Generally there is a lot of confusion throughout the world about the vegetable called "water chestnut". The first confusion is between the European Trapa and the Chinese Eleocharis. Then people get lost within each of those genera because common names have never been properly matched to stabilised botanical names.
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