Water caltrop

The water caltrop or water chestnut is a floating annual aquatic plant, growing in slow-moving water up to 5 meters deep, native to warm temperate parts of Eurasia and Africa. It bears ornately shaped fruits, each containing a single very large starchy seed. It has been cultivated in China for at least 3000 years for these seeds, which are boiled and sold as an occasional streetside snack in the south of that country.

(This plant should not be confused with the unrelated Eleocharis dulcis, also called water chestnut, and also an aquatic plant raised for food since ancient times in China. Eleocharis dulcis is a sedge whose round, crisp-fleshed corms are common in Western-style Chinese food.)

The water caltrop's submerged stem reaches 12 to 15 ft (3.6 to 4.5 m) in length, anchored into the mud by very fine roots. It has two types of leaves, finely divided feather-like submerged leaves born along the length of the stem, and undivided floating leaves born in a rosette at the water's surface. The floating leaves have saw-tooth edges and are ovoid or triangular in shape, 2-3 cm long, on inflated petioles 5-9 cm long which provide added buoyancy for the leafy portion. Four-petaled white flowers form in early summer and are insect-pollinated. The fruit is a nut with four 0.5 in (1 cm), barbed spines. Seeds can remain viable for up to 12 years, although most will germinate within the first two years.

The plant spreads by the rosette and fruits detaching from the stem and floating to another area on currents or by fruits clinging to objects, birds and other animals.

It was introduced to North America around 1874, and escaped cultivation in the eastern United States, where it has become an invasive species from Vermont to Virginia.

Fasciolopsiasis can be transmitted by the surface of the plants.

External links

• " Multilingual taxonomic information". University of Melbourne.