Chilim or Water Caltrop

Chilim, or floating water caltrop, or floating water chestnut, or devil's nut (lat. Trápa nátans) — an annual aquatic plant; a species of the genus Trapa of the family Lythraceae (Lythráceae), originating from the southern regions of Eurasia and Africa.

Grows in lakes, backwaters and oxbow lakes of slow-flowing rivers, reaching up to 5 m in length. The plant has a characteristic fruit that externally resembles a bull's head, with a single large starchy seed. For this seed the plant has been cultivated in China for at least three thousand years. The chilim seed is boiled and eaten as a light snack.

Chilim has a wide range, including almost all of Africa, many regions of Asia (Turkey, Georgia, Kazakhstan, China, Vietnam and Japan, India and Pakistan) and Europe (central, eastern and southern parts). Due to commercial harvesting of the fruits, complete disappearance is possible.

It prefers silty bottoms of slow-flowing or standing waters. It often forms dense stands.

The stem of the chilim is underwater, develops in spring from the fruit and reaches the water surface. It is 3.6—5 m long. Roots are greenish, pinnately branched, located on the submerged stem and have the appearance of underwater leaves.

The plant has two types of leaves: the first type — submerged — opposite, linear, located along the stem above the roots, situated in the water column; the second — floating on the surface. Floating leaves are at the end of the stem and form a rosette. Leaf blades are oval or rhombic in shape, leathery, with unevenly toothed margins, 2—3 cm long, and are borne on petioles that become swollen by the time the fruits mature, 5—9 cm long, providing them with additional buoyancy.

Flowers are white, located in the leaf axils, pollinated by insects. Each flower has four sepals, petals and stamens. There is one pistil. In the temperate zone it flowers in May–June.

The fruit is a black-brown nut 2—2.5 cm in diameter, with two to four sharp horns. Fruits ripen in August–September. A seed can remain viable for up to 12 years, although it most often germinates within the first two years. The plant reproduces by fruits that detach from the stem and are dispersed by the current to other locations.

Planting: into a non-freezing pond with a thick layer of fertile substrate – the nuts are simply thrown to the appropriate depth. If the pond has no substrate, the nuts are planted in a container and sunk in that form. In winter nuts can be kept at home in the refrigerator, in a jar with water; in spring they begin to germinate on their own.

Care: An essential condition for successful cultivation is the absence in the pond of at least such large mollusks as ramshorn snails and pond snails, which readily eat the young leaves of the water caltrop.

Propagation: by seeds; fruits acquired in spring are thrown into the water. But it is best to sow in small pots filled with silt and place them at a depth of 10–15 cm – in the zone where the water warms up best.

Source: www.wikipedia.org