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Common Duckweed

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Common duckweed

The vast, green mats that sometimes cover the surface of still water, such as ponds, flooded gravel pits and old canals, are actually Common duckweed. A tiny, single plant, it groups together to form 'lawns'.

Scientific name

Lemna minor

When to see

January to December

Species information

Statistics

Individual plant diameter: 1.5-5mm
Root length: 15mm
Common.

About

A familiar sight of freshwater ponds, flooded gravel pits and old canals, Common duckweed multiples by division and can easily form a vast mat that overtakes the surface of pool if left unchecked. As its name suggests, it does provide food for ducks, but it can also provide shelter for spawning Common Frogs and Common Toads.

How to identify

Each tiny, clover-like 'leaf' of Common duckweed has a single root that hangs in the water and is actually an entire plant - this simple structure is called a 'thallus'. Many of these tiny plants are packed closely together to create the yellow-green 'lawn' often seen on the water's surface.

Distribution

Found throughout the UK, but scarcer in North Scotland.

Did you know?

Common duckweed can be highly invasive in a pond, container or even water butt, covering the surface of the water with ease. It can shade out other plants and use up the nutrients available, making it difficult for other wildlife to thrive. If you have a small pond in your garden that is covered in Common duckweed, try raking it out and removing any dead vegetation which might add to its growth, or you could try using a pump to aerate the pond.