Press release

Weeding out non-native invasive species in Cambridgeshire

Environment Agency crews have been hard at work along the Ely Ouse and River Cam removing tons of Floating Pennywort.

Pennywort in the river looks like a mat

Pennywort in the river looks like a mat

Maintenance teams are more than half way through a 6-week programme, removing the invasive non-native species (INNS) to try to stop it spreading further.

Using floating weed harvesters and lifters, the Environment Agency teams have removed more than 1000 tonnes of wet cut invasive weed, while another team followed up behind, hand removing and spraying the smaller pieces of weed.

Floating Pennywort is normally found in tropical aquaria and garden ponds. It is, however, being found more and more in rivers across the country. It forms very dense mats of vegetation which can grow rapidly (up to 20 centimetres per day) out from the riverbanks.

These mats have the potential to cause serious problems for fish and anglers by suffocating fish and preventing access to the water. The plant also obstructs movements of animals and boats, restricting navigation and recreational use of watercourses.

Darren Trumper, Environment Agency Operations Delivery Team Leader said:

Floating Pennywort has become a major problem for us all in the River Cam and Ely Ouse.

Some of the Floating Pennywort mats we are removing from the riverbanks along the Ely Ouse are 22 metres long and 10 metres wide, and can be a depth size of about 30 millimetres. In one location the teams removed a mat weighing 1.7 tonnes!

An especially worrying factor in the infestation is the invasion of the River Cam Washes, which is a Site of Special Scientific Interest (SSSI) and crucial to all kinds of wildlife.

The rivers and its tributaries in our area provide the perfect breeding ground for Floating Pennywort which has formed dense mats. These block out oxygen and light in what was very good aquatic habitats for fish, and native plants. It also deprives birds and creatures from feeding from the waters.

Native to North America, Floating Pennywort is a fast growing invasive species of freshwater plant. It is widespread and well established in the south and east of England and appears to be spreading rapidly north and westwards.

As such, this makes it one of many high priority invasive non-native plant species in Great Britain.

To see a film of the Environment Agency’s work to remove weed from our rivers please visit their YouTube channel at:

The Environment Agency is also asking people who are out and about to help to track down these problem plants by using a free App called ‘PlantTracker’.

PlantTracker is available free from the iTunes App Store and Android Market by searching for PlantTracker (one word), or from the website where people can also follow the progress of the project and the reports that are coming in.

Images of Invasive Non-Native Species are available on the GB Non-native Species Secretariat website: and on Flickr at

Published 21 November 2014