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Exmoor Knotweed Control Programme

Knotweed Control Programme

Japanese, Himalayan, lesser and giant knotweed are invasive species which can be seen along hedge banks, roadside verges and many of the watercourses on Exmoor. Posing a real threat to some of the native flora and fauna the dense tall thickets have a major impact on nature conservation, archaeology, access, flood defence and the economic value of the land they contaminate.

Control on Exmoor

The Exmoor Knotweed Control Programme has been running for 16 years and now falls under the ENNIS Project. The overall aim of this programme is to control knotweed species within the National Park and its associated river catchments. The programme works closely with Exmoor's communities to map and record the locations and vigour of knotweed infestations within the National Park. Normally it is the landowners responsibility to control invasive species but our programme is currently able to support landowners by offering to treat the knotweed on their land for free. Currently the most effective method of control is repeated spraying with herbicides over several years, which gradually reduces the vigour of the plant.

knotweed spraying

A qualified contractor is commissioned to carry out a programme of herbicide spraying in early autumn (September to November) when the knotweed plants absorb the greatest amount of herbicide. This is considered the most effective time of year because the herbicide causes the greatest amount of damage to the plant.

In total the programme has recorded over 1200 sites across Exmoor National Park. Thanks to the co-operation of landowners and land managers, many sites have greatly reduced in size and vigour, sprouting single shoots or not showing any above ground growth at all. Continued annual treatment and monitoring is vital to controlling the spread of knotweed because of its rapid growth rate and the fact that its rhizomes (roots) can stay dormant in the ground for approximately nine years.

If you have Japanese knotweed on your land and you would like us to include it in our Exmoor Knotweed Control Programme please do get in touch by email or phone. If you are already part of our knotweed control programme and you would like to give consent for next years treatment please complete our online Knotweed Consent Form.

In addition to using herbicide, we are also trialling the organic method of Rootwave technology which essentially gives the plant an electric shock and boils the cells within the plant. The trial is at an early stage, but results look promising so far. Please visit our Rootwave Trials page to find out more


We need your help!

We are working closely with volunteers and local communities to survey and map invasive species within the National Park which will help guide our work controlling them in the future. Please visit our Get Involved page if you would like to report an invasive species you have seen while exploring the National Park or are interested in volunteering with us.

We can also give advice, so if you have an invasive species on your land that you are looking to control please do not hesitate to get in touch by email or phone.