Stop 4: Alien Invasion

From unstoppable plants to aggressive animals-not all wildlife on the canal is welcome.

American Signal Crayfish coming out of water onto grass American Signal Crayfish, copyright GBNNS

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World’s worst weed?

You can see Japanese knotweed in the hedges by the canal. This fast-growing plant is listed as one of the world’s worst weeds. It takes over hedgerows, strangling our native plants. Cutting encourages growth, so it is controlled with chemicals.

Garden pond invaders

Exotic pond plants from other countries grow very quickly, smothering the native plants. We have to ensure they don’t destroy our rare, protected plants.

Unwelcome animals

Non-native animals can also be a problem. North American mink feed on water birds and small mammals. This has led to a decline in water voles in the UK.

Our native white-clawed crayfish is threatened by the aggressive invader, the American signal crayfish. 

Keeping vigil

It is vital for our staff to monitor the canal and its wildlife to ensure that non-native species don’t take hold.


Native birds like the sedge warbler don’t mind which plant they perch on.


The next stop point is on a low level waymark post. Keep your eyes peeled or you’ll miss it.

Last date edited: 17 July 2015