Duckweed is probably familiar to every reader, after all, in summer many garden ponds are almost completely covered with tiny aquatic plants. In this article you will find out what advantages duckweed has and when and how you need to curb the stock.

Duckweed brings both advantages and disadvantages to the garden pond

Table of Contents

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  1. the essentials in brief
  2. What is duckweed?
  3. Care and containment in the garden pond
  4. Use of duckweed
  5. frequently asked Questions

    6. the essentials in brief

    • Duckweed is the popular name for duckweed, of which the small duckweed is particularly common on calm waters.
    • Duckweed grows on calm and nutrient-rich waters.
    • They get their popular name because ducks and other waterfowl love to eat them. Just like some fish, e.g. B. carp and rudd.
    • Duckweed cleans heavily polluted water bodies and is sometimes used to feed pigs and chickens.
    • However, the plants also spread very quickly and can upset the ecological balance.

    What is duckweed?

    Of course, the term "duckweed" (some might say duckweed) is not the official plant name. The correct name of the aquatic plant is Lesser Duckweed (Lemna minor) and it belongs to the Araceae family. There are also 14 other duckweed species in Germany. So the plant is only called “duckweed” in the vernacular. It is called that because ducks and other pond dwellers love to eat them.

    features and appearance

    The individual plants are tiny: each little plant consists of one to five small, mostly oval leaves, each with a maximum diameter of eight millimeters. These papers float freely on the water surface thanks to air-filled cavities. The plant root protrudes into the water. It not only serves to absorb minerals and other nutrients, but is also intended to stabilize the leaves.

    The small duckweed reproduces mainly asexually by budding, i. H. a new shoot grows laterally on a mother plant. This can remain connected to the mother plant, but can also separate. In this way, duckweed multiplies rapidly, provided the conditions are right - the more nutrient-rich a pond, the faster it is covered with a green carpet. The duckweed population can double every three days, sometimes the plants succeed even faster.

    Is duckweed blooming?

    In fact, duckweed can flower, but this happens only very rarely - asexual reproduction is simply too successful for that. The very small flowers appear between May and June, they are pollinated by insects such as spiders and water striders, but also by snails and even by water movements. Tiny nutlets then form, which contain one or more seeds. These in turn are spread by movements of the water and by aquatic animals, e.g. B. fish or ducks.

    Habitat, occurrence and distribution

    Duckweed prefers standing water

    Duckweed grows exclusively on stagnant or slow-flowing freshwater bodies of water. The aquatic plant is typically found on ponds and ponds, as well as on streams and in sewage and drainage ditches - the main thing is that the water in them is calm and rich in nutrients. The aquatic plant can even be found in polluted waters or waters polluted with sewage. It can be found in temperate climate zones almost all over the world and has even been introduced to Australia and New Zealand.

    Duckweed in the garden pond - care and containment

    If you want to establish the small duckweed in your pond or aquarium, you don't have to do much: the plant is not particularly demanding and multiplies quickly. In fact, duckweed grows like a weed in almost any condition:

    • light requirement: sunny to half-shady
    • water temperature: 0 to 32 degrees Celsius
    • PH value: 3.2 to 10
    • degree of hardness: 2 to 30

    In fact, when it comes to care, it is more important to note that you have to limit growth from time to time so that the ecological balance in the pond does not tip over. If the duckweed covers the entire surface, other aquatic plants will suffocate or die from a lack of sunlight. After all, with this dense, green carpet, not enough sunlight reaches the pond and the plants growing below the water surface.

    water quality

    Duckweed grows where other plants don't stand a chance

    Due to their water-purifying properties, the small duckweed (and other duckweed) is often planted in water bodies contaminated with sewage or agricultural waters. Here the plants multiply very quickly due to the high nitrogen and phosphorus content and at the same time extract these excess nutrients from the water. This means that duckweed grows where other aquatic plants don't stand a chance.

    Thus, the duckweed has valuable ecological value by cleaning up damaged and overturned water bodies. These can then also be used for other aquatic creatures such as more sensitive aquatic plants, fish, frogs and other amphibians, aquatic snails, etc. Of course, this also works in the garden, for example if the neglected pond is to be freed of algae and made habitable again. Due to their absorbent properties and rapid growth, duckweed displaces unwanted algae growth, which is particularly evident in waters rich in nitrogen and phosphorus.

    wintering

    With regard to the winter, you do not have to pay attention to anything. Duckweed are perennial plants that store starch as a reserve in the fall. They then sink to the bottom of the water and spend the winter months there. As soon as it gets warmer again in spring, the little plants climb up again and spread again.

    containment

    To prevent the pond from becoming overgrown with duckweed, you should install the following measures to curb growth at an early stage:

    • do not fertilize during strong growth
    • make sure that fertilizers from the surrounding beds can also be washed into the garden pond
    • Use fish as natural “enemies” for duckweed
    • Carp (e.g. koi) are particularly suitable
    • however, this only works if the pond is large enough
    • Caution: Fish feed is fertilizer for duckweed!
    • Keep ducks or geese on the water property
    • Of course, this only works if you have the space and leisure for it
    • install a fountain in the middle of the pond
    • this ensures water movement and thus ensures that duckweed spreads less quickly
    • Fishing for duckweed with a net

    Don't try to fish out the duckweed with your bare hands - the weeds will stick to you all over. It's easier with a landing net (like those used for fishing).

    digression

    Duckweed in the aquarium - this is what you can do about it

    Duckweed can also quickly become a problem in the aquarium, which is why the plant is not particularly popular with many aquarium enthusiasts, despite its positive properties. Here, too, you have to curb growth through sparing fertilization (be careful with fish food!) and regular netting.

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    How to use duckweed - pros and cons

    Are you also faced with the question of whether you should settle duckweed in your garden pond or not? The following list of advantages and disadvantages of this aquatic plant may help you in making a decision.

    1st benefit: Improvement of water quality

    Duckweed cleans polluted water and is therefore often used for the ecological cleaning of water bodies polluted by agricultural sewage. This is the case, for example, with bodies of water that are close to fields fertilized with manure. In developing and emerging countries in particular, there are numerous projects in which wastewater is cleaned with duckweed and the clean water thus obtained is finally used to irrigate vegetable fields and the harvested, nutrient-rich duckweed is used to feed chickens, pigs and other farm animals.

    But how does water purification work with duckweed? That's easy to explain: the rapidly multiplying plants remove nitrogen and phosphorus in particular from the nutrient-rich water, but also other organic substances. They also filter out other substances, such as heavy metals, and store them in their biomass. As soon as the duckweed is skimmed off, the polluting substances are finally removed from the water.

    2nd advantage: algae killer

    Duckweed is also considered a good algae killer, since the plant deprives the algae of their livelihood - there are simply not enough nutrients left for algae to spread further. This fact is of particular interest for the biological management of garden ponds and in aquaristics.

    3. Indicator of iron deficiency

    If the duckweed turns yellow, the water lacks iron

    The use of duckweed as an indicator of iron deficiency is also primarily relevant in aquaristics. If the water contains too little iron, the leaves turn yellow very quickly. This color allows you to recognize an iron deficiency in good time, before fish or other aquatic plants suffer from it, and you can quickly take countermeasures.

    4th advantage: Robust and undemanding

    Duckweed is extremely hardy and tolerates both severe frost and heat up to 32 °C. Even water with an acidic pH does not bother the plants at all. For these reasons duckweed grows practically everywhere.

    5th advantage: feed

    Surprisingly, duckweed contains high levels of valuable proteins. In terms of amino acids, the inconspicuous plant can even compete with the much-vaunted soybean. So it's no wonder that duckweed is increasingly used in pig and poultry feed - it's cheap to get and chock-full of valuable nutrients.

    digression

    Duckweed - a food of the future?

    For exactly the same reason, some scientists also see duckweed as the food of the future: it can be produced quickly and sustainably, is readily available and is full of valuable proteins. The well-known food chemist Udo Pollmer thinks this is nonsense, after all, the information on the nutrients refers to the dry matter - and duckweed also absorb plenty of toxic pollutants like a sponge. So keep your hands off!

    1. Disadvantage: Content of pollutants

    And indeed, duckweed absorbs all kinds of toxins from the wastewater: the biomass of the plants often contains substances such as arsenic, cadmium, radium, dioxins, residues of medicines and pesticides, and algal toxins. In addition, the aquatic plant forms oxalic acid, which is actually supposed to protect against predators such as water snails. Oxalic acid is also harmful to humans. Therefore, a use as human food or animal feed should be reconsidered, at least if the duckweed grew on heavily polluted waters.

    2. Disadvantage: Displacement of other aquatic plants

    It is not without reason that many gardeners consider duckweed to be a weed, after all the plants multiply very quickly and are difficult to keep in check. If the growth gets out of hand, the plant changes the ecosystem of the pond: the oxygen content of the water drops, as does the incidence of light - which in turn has negative effects on other aquatic plants and many fish - for example trout. If you don't take countermeasures in time, the pond threatens to silt up.

    frequently asked Questions

    Where does duckweed come from?

    Ducks like to eat duckweed

    The duckweed, colloquially known as "duckweed", is found in standing or calm fresh waters almost all over the world, where they are usually introduced unintentionally - for example by ducks and other waterfowl, which transfer the tiny plants from one pond to the other. In aquaria, too, duckweed tends to get by accident, for example through contamination or through use by pond water. Even those who deliberately plant duckweed will soon experience a surprise: if the conditions are right, the plants multiply rapidly and can double in size within just three days.

    Is duckweed good for the pond?

    This question can only be answered with “partly, partly”. On the one hand, duckweed is a high-quality food source for many pond dwellers (in addition to ducks and geese, fish also like to eat the plants), and duckweed also absorbs pollutants from the water and thereby purifies it. These, in turn, also accumulate in the meat of fish and waterfowl, which in turn can be problematic for humans. In addition, the aquatic plant tends to spread very quickly and drastically - with the result that it crowds out other aquatic plants and thus upsets the ecological balance.

    Can you also buy duckweed?

    Yes, you can buy duckweed, especially in specialist shops specializing in aquaristics and in online shops. In addition to Lemna minor, other related species are also available here.

    Can duckweed also be used as fertilizer?

    Rapid growth of the duckweed indicates that it is a nutrient-rich body of water, from which the plants mainly withdraw phosphate and nitrogen, but also other nutrients. To curb the growth of duckweed, you should skim them off from time to time. Then let them dry a little and use them as valuable green manure on vegetable or ornamental plant beds.

    Can I feed my chickens duckweed?

    In fact, you can feed duckweed (dried or freshly fished) to your chickens - they'll be only too happy to munch on the high-protein aquatic plant. Chicken owners with a pond property may have already had this experience, because the poultry pounces on duckweed, wherever it can reach them. However, make sure not to feed them any duckweed from sewage or overturned water bodies - the pollutant levels here are too high and can harm the animals.

    tips

    Ducks and fish alone cannot keep duckweed growth at bay, the plant simply grows too fast for that. So be sure to net or clean the pond thoroughly in the spring when the plants come back to the surface.

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Vegetable garden