Japanese Knotweed

Japanese knotweed in flower

This highly invasive plant forms dense stands with hollow stems that can reach 3 metres tall. Its leaves are large, green and heart-shaped. Towards the end of August, clusters of cream flowers can be seen. For assistance in identifying this plant, you can download a leaflet from DEFRA (PDF, 4.6 MB).

Japanese knotweed is causing huge problems across the country, displacing native vegetation and causing structural damage to properties. It is against the law to plant, or otherwise cause to grow, Japanese knotweed in the wild. If you allow knotweed to spread from your land into the wild, you are breaking the law.
 
Responsibility for knotweed control lies with the landowner or tenant of the land. Knotweed has to be controlled carefully as even tiny amounts of cut stem, crown or underground stem can re-grow and help spread this weed. Knotweed must not be strimmed, flailed or mown, do not chip knotweed material or add knotweed to compost, as it will cause it to spread. The herbicide glyphosate is an effective way to control knotweed, but if you intend to use a herbicide in or near water, you need to obtain the approval of the Environment Agency first. It is also important to follow manufacturer’s instructions regarding protective clothing and safe herbicide use.
 
Download an advisory leaflet for more information on identifying and controlling knotweed (PDF, 341 KB). For further advice on controlling knotweed, contact the Environment Agency on 03708 506 506 (Mon-Fri, 8am-6pm).
 
Chesham Town Council is working with the Chilterns Conservation Board to map this weed. If you have seen these plants growing in Chesham, please contact Kathryn Graves on policy@chesham.gov.uk.

A large infestation of Japanese knotweed had been growing on Town Council land at The Moor in Waterside. In 2010, the Council initiated a successful three-year control programme with a specialist contractor to wipe out this stand using the technique of glyphosate stem injection. This method was chosen as it has minimal environmental impact for the surrounding land.