How to remove duckweed from the pond

Duckweed is found in many ponds and seems harmless, but it can sometimes spread rapidly and suppress other aquatic plants. How do you recognize it, why can it sometimes be a problem, how do you keep it under control, and how can you remove excess duckweed? You can read all about it below.

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Duckweed is a collective name for several species of duckweed. They are often recognizable by the small, round, green leaves that float in large numbers on the water's surface. Some of the most common species in ponds are dwarf duckweed ( Lemna minuta ), small duckweed ( Lemna minor ), and hummock duckweed ( Lemna gibba ), but there are other duckweed families as well. They are often difficult to distinguish from one another.

Duckweed grows primarily in stagnant, nutrient-rich waters, such as natural ponds, ditches, and sometimes even rain barrels. As the name suggests, duckweed provides food for ducks. It also provides shelter for tadpoles, toad larvae, and all sorts of other aquatic insects, such as damselflies and dragonflies. The plants are rich in protein, and in some parts of the world, duckweed is even eaten by humans.

In small quantities, duckweed is beneficial. It can limit algae growth because it uses the same nutrients from the water. It also nourishes insects, such as the duckweed moth ( moth ), and provides shelter for animals.

Duckweed becomes a problem when it becomes too much and can spread extremely quickly. Sometimes it can double in size within two to three days. If left unchecked, it can cover the entire water surface. This can happen particularly quickly in a mini-pond .

The biggest problem is that too much duckweed reduces sunlight penetration to aquatic plants, especially if your pond is in the shade . This can cause the underwater plants to die, creating a vicious cycle. The dying plants create more nutrients in the water, which benefits the duckweed. Biodiversity also declines when fewer plant species grow.

Preventing duckweed in the pond is difficult. It often ends up in the pond accidentally, for example, via the roots and leaves of pond plants , or by sticking to the feet of birds .

Complete removal isn't necessary – it's better to manage the duckweed, because a little bit of it actually adds life to a natural pond . Read 3 ways to combat excess duckweed.

To remove duckweed, you can use a scoop net to carefully remove it from the water's surface. Leave it at the pond's edge overnight so any aquatic creatures you accidentally scoop up can crawl back to the water.

Tip! Don't remove duckweed when there are tadpoles in the pond, as they're easy to scoop up. The best times are early spring, before the frogspawn hatches, and again in summer once the young frogs and toads have left the water.

In larger ponds, duckweed can also be reduced by animals that eat it, such as ducks, coots, and moorhens, as well as fish like grass carp and koi. Keep in mind that fish, in particular, consume many other pond inhabitants, such as insects and tadpoles.

Tip! If you want greater biodiversity in your pond, it's better to avoid fish altogether or make part of the pond inaccessible to them.

You can also control duckweed by making conditions less favorable for these small floating plants. Floating plants like duckweed and algae draw nutrients from the water column, meaning that when there's less nutrient-rich water, these plants also thrive. Here's what you can do to reduce the nutrient-rich water:

When building a pond, plant as many bankside plants as possible. These plants absorb nutrients and provide sufficient oxygen in the water if the surface is covered with floating plants.
Provide plenty of native (underwater) plants , such as common hornwort ( Ceratophyllum demersum ), common watermilfoil ( Myriophyllum spicatum ), and pondweed ( Potamogeton ). These compete with duckweed and algae for nutrients.

Tip!

To maintain a healthy balance in your pond, it's important to use only native or non-invasive plants. These plants promote greater biodiversity and also have natural enemies, keeping them in check.

Non-native aquatic plants are notorious invasive species , capable of rapidly displacing our natural habitat. Avoid species like narrow-leaved waterweed ( Elodea nuttallii ), water fan ( Cabomba caroliniana ), marsh pennywort ( Hydrocotyle ranunculoides ), and watercress ( Crassula helmsii ) in your pond. Not sure if your plant is suitable? Check tuinernietin.nl .