Tiny beetles deployed at Kew Ha-ha to tackle invasive waterway plant
6 August 2026 · By Boroughly editorial — AI-assisted, human-reviewed.
Richmond Council has released a colony of specialist beetles into the Kew Ha-ha — a historic drainage channel running along the edge of Kew Gardens — in an effort to control floating pennywort, an invasive plant that can choke waterways and crowd out native species.
Working with CABI (Commonwealth Agricultural Bureau International) and Royal Mid-Surrey Golf Course, the council released floating pennywort weevils (Listronotus elongatus) last month. The small beetles feed naturally on floating pennywort (Hydrocotyle ranunculoides), gradually reducing its growth without the need for chemical herbicides or pesticides.
The Kew Ha-ha presents a particular challenge for conventional removal: the site is difficult to access by hand, and tidal flows regularly bring fresh plant fragments into the water, meaning manual clearance is a near-endless task.
The project, funded through the council's Climate Change Steering Group, will be monitored over the next year to assess how well the weevil population establishes and whether it survives the winter months. Further releases may follow if needed.
The weevils are not expected to eradicate the plant entirely, but the council says they should meaningfully slow its spread and reduce its impact on the local ecosystem — a relatively low-cost and sustainable long-term approach to a persistent problem. Full details are on the Richmond Council website.