Floating Pennywort (Hydrocotyle ranunculoides) is an aquatic plant from the Americas which has started causing major problems on our inland waterways. There appears to be no native control and until now the Environment Agency has kept navigable water ways open through herbicide spraying and mechanical weeding. Neither solution is suitable for long term control as herbicides on water pose a huge risk to the environment and as such the dosages that can be safely used only slow the spread of the Pennywort, and do not eradicate it. Mechanical weeders break the plant up allowing it to spread the following year. The problem is becoming increasimgly serious as it has now made it’s way into smaller water courses adjoining the main rivers where it is far more difficult to control and, in places such as the New Cut here at Kingfishers Bridge, it has entirely covered the surface.
Over the summer we have had Highland cattle grazing on the river banks and the New Cut bank. There is a very clear grazing line into the Pennywort covering the New Cut, out as far as the cattle will wade. In the past we have raked the vegetation out with a 360 digger and piled it for the Buffalo, who love it slightly wilted, but this is the first true indication that it is truly palatable and chosen over almost every other plant in the grazing area. We have considered fencing the buffalo into the New Cut to see how they graze it but the breeding herd can be temperamental and too dangerous with only a temporary fence between them and the public footpath. However, we now have 3 young steers who are much calmer and we hope to do a grazing trial towards then end of next summer once the new fencing is in place and they’ve had a chance to settle away from the main herd.
We have been discussing the various options with Natural England and the Environment Agency and will raise our observations at the Cam Valley Forum in the hope that we can remove Pennywort from our rivers completely over time.
Reserves Manager at the Kingfishers Bridge wetland creation project in Cambridgeshire.