Able to withstand British winters and invade a region very rapidly, this innocent-sounding plant has dominated many waterways in its time. Water fern spreads like a sponge across the water and can double in area within a few days.
This reduces light beneath the surface and shades out other native plants, as well as causing de-oxygenation, leading to the death of fish.
The plant is entirely free-floating and so able to grow in any depths, but the water must be still or slow moving for it to properly thrive.
In pioneering science, a ‘biocontrol' has been developed. This is a tiny insect from the plant's natural range, which actually eats water fern. It is a very effective control and can bring this weed under control within a few weeks. We pay a company to supply the insects for us, as and when we need them.