This project aims to reduce the amount of this very successful invasive species in the river Colne. After promising progress in 2019, Covid 19 restrictions led to setbacks in 2020. The project is at a crossroads, this article explains why and how it was set up, its very valuable initial progress and how it can get back on track and in control of Floating pennywort again.

What is Floating pennywort and Why the Project to Remove it?
Floating pennywort (Hydrocotyle ranunculoides) probably seemed pretty and innocuous when this central American aquatic plant was used to decorate ornamental aquaria. The problem began for us in the UK when it was introduced into a river in the 1980s. Since then it has become such a successful and aggressive, non-native invasive species(NNIS) that it is strangling our watercourses. Displacing everything in its path, it is fast growing, out competing native plants, obstructing river flow and degrading water quality. Not only does it threaten biodiversity, but also our enjoyment of rivers, by for example making fishing and canoeing impossible. Having escaped into the wild, it has spread far and wide from the South East to the North West of England and Wales. It can grow up to 20cm per day, quickly establishing dense mats of vegetation extending from bank to bank. You can find more detailed information here

An Outline of the Pilot Project
The Lower Colne Catchment Floating Pennywort Project began in 2018, in a collaboration between Groundwork South, who manage the Colne Valley Park and the Environment Agency, who provided pilot funding for the initial three years of the project. Over this period, the pilot project aimed to engage stakeholders across the catchment with the issue, to map the presence of Floating Pennywort catchment wide, to provide an action plan for the control of the species and to undertake control work at the highest priority sites in the catchment.

Project Steering Group
A project steering group was formed in 2018, comprising representatives of the Colne Valley Regional Park(CVRP), the Environment Agency(EA), Colne Valley Fisheries Consultative(CVFC), the Canal & Rivers Trust(CRT) and the London Borough of Hillingdon(LBH); who have helped to guide the focus of the project over the initial three years of delivery.

Annual Invasive Non-Native Species Workshops
Three INNS workshops have been organised through the project and are now being run as an annual event, open to all Colne Catchment Stakeholders. The workshops provide an opportunity for attendees to learn how to identify, monitor and control invasive species and have been attended by over twenty local stakeholders. The event also enables attendees to return site specific information to inform future invasive species control work in the catchment, in addition to promoting their own control efforts throughout the past year.


Annual Floating Pennywort Survey of the Lower Catchment
Over the past three years, ColneCAN stakeholders and local volunteers have been mobilised to conduct an annual Floating Pennywort survey of the lower catchment. This collaborative effort has resulted in over 100 new floating pennywort records being added to the CVFC Invasive Species application each year (add link). This has allowed the project to map the distribution, range and severity of floating pennywort across the lower catchment and to monitor how things change as control work is implemented. If you would like to participate in the 2021 survey of the lower catchment please contact the CVRP at This email address is being protected from spambots. You need JavaScript enabled to view it.

The Lower Colne Floating Pennywort Management Plan
Following the completion of the first Floating Pennywort survey in 2018, the CVRP produced a management plan to provide a long-term strategy for floating pennywort control in the catchment. The document provides a reference point for useful information such as management responsibilities and the results of survey work, in addition to outlining an action plan for the control of the species over the next 25 years. This action plan prioritises sites on an upstream to downstream basis, in order to minimise the risk of control sites being recolonised from populations upstream.

Contractor Control Programme
The CVRP have been working with Land & Water Contractor services to deliver the initial recommendations of the management plan. The control programme begun in 2019 and encompassed the upper 6.5km of the species’ range in the catchment, between Harefield and Denham. In 2019 Land & Water successfully controlled the species by applying herbicide to rafts of floating pennywort within the control area. This resulted in a significant reduction in the severity of the species within the control area. The method was successful as it could be implemented from the start of the growth season, ensuring that the rafts of floating pennywort in the river were not able to mature after establishing.

In 2020 control work was halted before it could begin due to COVID 19 lockdown restrictions. Unfortunately, this meant that Floating Pennywort was able to grow unchecked for a number of months throughout lockdown. By the time permission was granted to resume control work by July, floating pennywort in the control area had matured to an extent that the application of herbicide was ineffective. This resulted in the programme being halted after two months of ineffective control. The remaining project budget will now be used to retarget the species in 2021.

Volunteer Control Programme
In April 2019 a Volunteer Removal Fund was launched, to enable local groups to take action outside the contractor control zone. This £10,000 fund was made available to local land managers, environmental groups, angling clubs and NGOs; should they wish to organise a group of volunteers to clear a particular site. This resulted in numerous workdays being held on the Colne and Frays Rivers, with successful applicants including Denham Island Residents Association, London Wildlife Trust, TCV Uxbridge Green Gym and The Willowbank Association.
Further volunteer days were also facilitated by The Colne Valley Parks Landscape Partnership team and their volunteer river rangers, which really helped improve the projects’ coverage of the catchment.

What does the project aspire to achieve in future?
The project is currently at a crossroads and additional funding is required for it to continue. The CVRP applied to the HS2 Community Environment Fund to give the project a new lease of life for the next three years. The plan was for the CVRP to employ a full-time invasive species officer, increase the control area covered by our contractor, facilitate an increased number of volunteer events across the lower catchment and work increasingly to engage landowners with the issue of invasive species.

Disappointingly we heard in January that this application had been unsuccessful. We have been invited to reapply for funding for 2022, but even in the event of success there will be a delay in the delivery of the project for at least a 1 year period. We will be meeting with contacts at the EA in February to try to set out a route forwards for the project and to identify new income streams.

In the meantime, the remaining project budget will be diverted to tackle a new outbreak of Floating Pennywort that has been reported on the River Bulbourne and Grand Union Canal near Hemel Hempstead. Stay tuned to the ColneCAN website for updates as we make progress.

Design by LTD Design Consultants and build by Garganey Consulting. From an original concept by the Herts and Middlesex Wildlife Trust.