The water chestnut (Trapa natans) is sometimes incorrectly referred to as the water chestnut. However, this one - Eleocharis dulcis - is not closely related to the annual water chestnut. Trapa natans belongs to the loosestrife family and is found in the temperate to subtropical regions of Europe, Asia and Africa. The aquatic plant, which used to be common in Germany, is now threatened with extinction in this country and was therefore placed under nature protection as early as 1987.

The water chestnut is a very old aquatic plant species

Table of Contents

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  1. origin and distribution
  2. use
  3. appearance and growth
  4. leaves
  5. flowers and fruits
  6. toxicity
  7. location and soil
  8. Plant water chestnuts correctly
  9. care tips
  10. Cut the water chestnut correctly
  11. multiply water chestnut
  12. divide
  13. diseases and pests
  14. species and varieties

    15. origin and distribution

    The water chestnut (bot. Trapa natans) is an annual floating-leaf plant from the genus of the water chestnut family (bot. Trapaceae). The species was already widespread 65 million years ago, in the Tertiary era of geological history and thus at the same time as the dinosaurs. Today, the water chestnut still thrives in the temperate to subtropical climate zones of Europe, Asia and Africa, but due to intensive agriculture and the dwindling habitats in this country it is rarely found in the wild. Therefore, the species is under strict nature protection and may not be taken from nature. In the trade, however, you can get legal offspring that are ideal for natural planting in garden ponds.

    use

    Only the offspring from Europe are suitable for planting in your home garden pond, since the tropical varieties of the same name do not find suitable habitats here and therefore do not thrive. Therefore, always pay attention to the proof of origin when buying! Most offspring of the water chestnut come from Hungary, southern France and Italy.

    Water chestnuts can be planted individually or in groups, depending on the design you want and the space available. The floating-leaf plant also harmonises very well with other native aquatic plants such as heart-leaved pikeweed (bot. Pontederia cordata, violet flowers), European sea jug (bot. Nymphoides peltata, yellow flowers) and yellow water lily (bot. Nuphar lutea).

    appearance and growth

    Water chestnuts are deciduous, herbaceous aquatic plants that only grow for one summer. Their natural location is in stagnant water, where they are anchored near the shore, mainly in 30 to 60 centimeters of water depth in the muddy ground. The underwater stem, which is between one and three meters long, is rooted in the bottom of the lake, and the leaves, which are up to 20 centimeters in diameter, fan out from June to form a rosette of leaves lying on the water surface.

    leaves

    The submarine petioles of the water chestnut are filled with air and therefore act as floating bodies. They provide the necessary buoyancy that keeps the green leaves on the water surface. The fan-shaped to diamond-shaped floating leaves of the species have a characteristic jagged edge and are arranged in a rosette on the water surface. The leaves turn red in summer and then die off in autumn. Also characteristic are the glands on the undersides of the leaves and on the stems, which probably secrete an acid to protect against hungry aquatic animals.

    flowers and fruits

    The inconspicuous, radially symmetrical flowers of the water chestnut are white and appear between July and August. The nut-like fruits of the plant are formed on the stems. They have a hard, dark brown shell, have pointed spines and are angular. The white core of the water chestnut fruit consists of about 20 percent starch and is edible when cooked. In fact, the nutritious water nut was considered a food in earlier times and still is, especially in Asian countries.

    toxicity

    The white inside of the water chestnut is edible, but it should always be eaten cooked or roasted. Raw fruits are considered poisonous, and parasites that are dangerous to humans like to settle on the surface. Furthermore, the aroma, which is slightly reminiscent of chestnuts, only develops during cooking. The hard shell of the fruit is inedible, but can be easily opened with your fingers or a sharp knife and a little effort.

    location and soil

    Water chestnuts only thrive in standing water that is warm and sunny. The plants are unsuitable for streams and other flowing waters, and it is also better not to plant them in fish ponds. Water and the subsoil should be rich in nutrients and low in lime - the water chestnut has little tolerance for lime. Water chestnuts feel most comfortable when the pond water is slightly acidic. You can achieve this by adding pressed peat soil. You can get these in specialist shops. Only plant the plant in ponds that are between 40 and 60 centimeters deep.

    Plant water chestnuts correctly

    The easiest way to settle the water nuts in your garden pond is to sow them instead of planting them. The seeds - the nuts already described - are available from garden retailers. Simply sink them in the water in autumn, they will root themselves in the pond bottom over the course of the next few months and will sprout in the following June. For an average garden pond, you need about two to three plants, but they should not be transplanted near the pump.

    In the spring, specialist shops sometimes offer water chestnut plants, which you can plant out as follows:

    • Place the plants on the calm water surface.
    • Anchor them to the bottom of the pond with a wire.

    The long stalks together with the roots then develop, so that after a few weeks the plant has grown in the garden pond and can provide itself with nutrients.

    care tips

    Provided that the location requirements of the water chestnut - a sunny place in a standing freshwater pond with a water depth of up to 60 centimeters and a sandy-muddy subsoil - are met, any care measures are not necessary. The plant is hardy down to temperatures of at least minus 22 degrees Celsius.

    Once sown, the annual water chestnut practically multiplies by itself for years. As soon as the rosette of leaves dies off in autumn, the nuts sink to the bottom of the pond and overwinter there. In spring long, thin stalks sprout from them, which grow towards the water surface. From June, the leaves develop from this, which finally lie on the water in a floating rosette.

    Cut the water chestnut correctly

    In order not to contaminate the water, you should cut off the withered leaves in small garden ponds or in the aquarium in autumn. In larger ponds, however, this precautionary measure is not necessary.

    multiply water chestnut

    Targeted propagation of the water chestnut is neither necessary nor possible. The plant multiplies all by itself via the trained fruits, provided that the site conditions meet their requirements. The nut-like drupes, which are basically nothing more than specialized overwintering organs, sink to the bottom of the pond in autumn and then sprout to form new plants the following spring. Since each water chestnut develops several fruits during the season, a dense carpet can form on the garden pond over time. In order for propagation to succeed, you should cultivate the water chestnut as the only aquatic plant, because other species would compete for the nutrients present in the water. However, since water chestnuts have a high nutrient requirement for the development of their fruits, they would not develop any fruits and would simply die if the pond was planted again and the nutrient level dropped as a result.

    In autumn, the nuts can be removed before they sink. Keep them in a container of water until you use them again, replacing them regularly. Never use tap water for this, because water nuts do not tolerate lime. Instead, add acidic, pressed peat soil to collected rainwater or similar. In the spring, the seeds can be germinated in warm water and can then be planted outdoors - but before planting, slowly get them used to the climate change so that they don't die from the planting shock.

    If the pond is already densely populated with water chestnuts, you can easily remove partial plants and transplant them into other ponds.

    divide

    Water chestnuts cannot be divided, since each nut only develops a floating stalk with a rosette of leaves.

    diseases and pests

    Diseases are unknown in water nuts, and the aquatic plant is not attacked by pests either. However, care errors or an unsuitable location are problematic.

    tips

    Water chestnuts can also be cultivated very well in a water basin indoors - for example in the conservatory or in a large aquarium. However, no fish may swim in this container. In addition, you must provide the necessary light irradiation with artificial light (e.g. LED plant lamps).

    species and varieties

    Two varieties of the water chestnut are known. The Trapa natans var. natans, which is also native to us, is legally only available as offspring, you may not take the plants that mainly grow in moory or swampy areas in the wild. The offspring available in this country from Italy, Hungary and southern France usually grow well, but do not always produce fruit.

    The species Trapa natans var. bispinosa from China, also known as Singhara water chestnut or Chinese two-thorn water chestnut, is also available from specialist retailers. The leaves of this variety are olive green and typically have seven reddish to reddish brown colored parallel veins on the leaf blade. The species is not hardy here and must therefore be overwintered in artificial light in the conservatory or in a greenhouse.

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Vegetable garden