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Japanese Knotweed

Advice for Planners

There is a legal obligation on developers not to allow the spread of Japanese Knotweed but planners also have a vital role in helping to prevent the spread of the plant by ensuring that developers are made aware of the invasive nature of the plant and their legal obligations to prevent its spread. Planners can ensure that the law is complied with and this can include requiring developers to implement a control programme if it is present on or near the site.

Advice for Planners

To allow a co-ordinated approach to the control of Japanese Knotweed in Devon it would be desirable for Local Planning Authorities to have a specific policy within the Local Plan and the emerging Local Development Framework to ensure developers consider Japanese Knotweed and control it on site. Furthermore, planning conditions can be applied to planning permissions where Japanese Knotweed is found on site.

Development Control Officers should check for the presence of Japanese Knotweed when considering planning applications. If you suspect that Japanese Knotweed is on a development site you should request a survey by an ecological surveyor. If its presence is confirmed then a control programme, suitable for that site, should be drawn up as part of the planning application and this should include the safe disposal of Knotweed material. Planning conditions to ensure that the control programme is carried out should be imposed.

For more information visit:

Planning conditions

If Japanese Knotweed is known to exist on site or on a neighbouring site it is advisable to impose a planning condition to prevent spread of the plant which is an offence under the Wildlife and Countryside Act 1981. Soil can be contaminated with Knotweed rhizome up to 7m from the edge of a colony.

Advice to be given to all applicants within known Knotweed zones:

Japanese Knotweed has been reported on or near this site. It is a highly invasive weed that is capable of structural damage. Disturbance will cause it to spread and its movement is controlled by legislation. Under the Wildlife and Countryside Act 1981 it is illegal to cause it to spread in the wild. You are strongly advised to survey the site for the presence of Japanese Knotweed at an early stage and before any site clearance work and, if found, to formulate plans to control or eradicated it. Please note that Japanese Knotweed can be far more extensive than the visible parts on the surface and that the underground parts of the plants may extend laterally up to 7 meters beyond this. Knotweed in adjoining land may affect the site and should be noted and considered. Detailed advice is given in this Devon Knotweed Web Site

Here is an example of a planning condition which you could impose if Knotweed is confirmed on or adjoining the site:

Before any works are undertaken, the site must be surveyed* for the presence of Japanese Knotweed and a copy of this survey sent to the Local Planning Authority. Please note that Japanese Knotweed can be far more extensive than the visible parts on the surface and that the underground parts of the plant may extend laterally up to 7 metres beyond this. Therefore, this survey must also note any knotweed adjoining the site. If Japanese Knotweed is confirmed, full details of a scheme for its eradication and/or control shall be submitted to and approved by the Local Planning Authority prior to the commencement of work on site, and the approved scheme shall be implemented prior to the commencement of the use of the building(s).

*by an approved environmental consultant

Further Reading:

Child, L.E. and Wade, P.M., The Japanese Knotweed Manual , Packard Publishing Limited, Chichester , 2000, 123 pp, ISBN 1085341-127-2.

Further Sources of Information

For further advice:

Contact the Devon Knotweed Forum on nature@devon.gov.uk

Back to Knotweed Homepage