Hydrocotyle ranunculoides growth dynamics and implications for management

Hydrocotyle ranunculoides continue to cause many problems in UK waterways. The estimated costs of control are about £500,000 per annum. In order to understand how the species responds to the environment we have surveyed one of the oldest infested sites at Pevensey levels in Sussex. The plant has spread across many different sized ditches, with different nutrient levels, resulting in different plant morphologies and growth responses. We carried out this work, partly to enable prediction of biomass in uninfested sites, and partly to contribute to the Euphresco project in collaboration with various Dutch organisations, who share the same problems with various non-native species. Understanding how plants react to their environment when management activities are undertaken is also important for non-native species, and we have monitored the success of various management regimes for the control of H. ranunculoides. This talk will describe the effects of various nutrient regimes on the morphology of the plant and report on the success of various management activities in 2009.