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Japanese knotweed: What you need to know

Japanese knotweed is an invasive non-native species introduced into the UK in the early 19th Century

Japanese knotweed in flower

Introduction

Japanese knotweed (Fallopia japonica) is native to Japan, Taiwan and northern China, and was introduced to the UK in the early 19th century as an ornamental plant. It is a perennial plant, growing each year from its extensive underground rhizomes, and spreads rapidly both by natural means and as a result of human activity.

Japanese knotweed is spread by fragments of rhizome or stem being transported to new sites. Very small fragments of stem/rhizome can give rise to new plants. The plant forms dense stands, outcompeting our native vegetation and causing nuisance and structural damage.

Responsibilities

The responsibility for controlling Japanese knotweed always lies with the landowner. 

This is the case for all sites including river banks. Natural Resources Wales do not own rivers or river banks (unless they are within our landholdings or on land for which we are responsible eg NRW nature reserves and Welsh Government Woodland Estate).

NRW does carry out treatment of invasive species on our own land and on our flood risk management assets, but we are not responsible for treating invasive species on rivers and banks owned by other parties.

If you are unable to find out who owns the land in question, you can contact the Land Registry via the link below:

https://www.gov.uk/search-property-information-land-registry

Legal position

It is not an offence for a landowner to have Japanese knotweed growing on their land.

There is no legislation which requires landowners to control Japanese knotweed. However, if it can be proven that Japanese knotweed is causing a nuisance, it may be possible to use Community Protection Notices (see below), or to pursue the matter under common law.

It is an offence to deliberately cause the spread of Japanese knotweed.

Wildlife and Countryside Act 1981

Japanese knotweed is listed on Schedule 9 of the Wildlife and Countryside Act 1981 (WCA 1981) and is subject to Section 14 of this Act. It is an offence to plant or cause this species to grow in the wild. This means that deliberate actions which cause the spread of Japanese knotweed, eg strimming or dumping contaminated material, may constitute an offence. Allowing Japanese knotweed to spread naturally into neighbouring land is not an offence.

Japanese knotweed offences under the WCA 1981 are enforced by the police and local authority. Therefore, if you see somebody deliberately causing the spread of Japanese knotweed, you should contact your local police station.

Anti-social Behaviour, Crime and Policing Act 2014

Community Protection Notices can be issued by local councils or the police under the Anti-social Behaviour Crime and Policing Act 2014. These notices can be issued to individuals or organisations to compel them to control invasive species in situations where invasive species are having a detrimental effect on the quality of life of others.

NRW does not issues these notices. Contact your local authority or the police if you require more information. Further guidance can also be found on the Home Office website.

Read more detailed information about the legal position on Japanese knotweed (Cornwall Council website). The information applies to England and Wales.

Treatment and control of Japanese knotweed

Sprayed Japanese knotweed

DO NOT strim or mow Japanese knotweed.

Doing so is likely to significantly increase the risk of spreading the plant and therefore could constitute an offence.

Cutting and digging are NOT effective methods for controlling Japanese knotweed, and take many years to have any effect. Japanese knotweed has an extensive underground rhizome system which can be up to several metres deep, therefore it is extremely difficult to dig up all rhizomes, and it is highly likely that rhizomes will remain in the ground which will give rise to new plants. These options also create controlled waste which must be carefully contained and disposed of in a specific manner.

Therefore, householders and landowners are advised not to cut or dig Japanese knotweed.

Japanese knotweed is best controlled by the application of a suitable herbicide.

Glyphosate-based herbicides are commonly used to treat Japanese knotweed. If glyphosate is applied correctly, at the appropriate time of year, it is possible to eradicate Japanese knotweed (though it can take 2-3 years of repeat treatment).

Professional glyphosate products are required as glyphosate products bought at garden centres etc. have limited effect. Professional herbicide products must only be used by suitably qualified individuals who hold the necessary National Proficiency Test Council certificates of competence. Suitably qualified operators may be found locally or via an industry body.

To achieve control of Japanese knotweed, glyphosate must be applied in late summer/autumn after the plant has flowered. Applying glyphosate earlier in the year may stunt growth, but it will not kill the plant. Large mature stands of Japanese knotweed will need to be treated for two or three years to achieve eradication (ie treat once a year in late summer/autumn).

If you wish to use herbicides in a location that is in water, within a protected site, or near a water abstraction, you will need prior written approval from NRW.

Please read more information on applying for approval to use herbicides.

Advice for Contractors and Developers on disposal of contaminated material

Managing Japanese knotweed on a development site may require burning, burial or disposal of Japanese knotweed-contaminated material. Such activities must be done in strict accordance with the Japanese knotweed Code of Practice to avoid committing an offence. Japanese knotweed (or contaminated material) is a controlled waste, and as such must be disposed of at a suitably licensed or permitted landfill.

See the Japanese knotweed Code of Practice for more information.

Further Information

For further information on the identification, control and disposal of Japanese knotweed, and the regulation of pesticides, see the following links.

UK government advice:

https://www.gov.uk/guidance/prevent-japanese-knotweed-from-spreading

Non-Native Species Secretariat Website:

http://www.nonnativespecies.org/home/index.cfm

Health and Safety Executive website for information on regulation of pesticides:

http://www.hse.gov.uk/pesticides/topics/about-pesticides.htm

Biosecurity:

https://naturalresources.wales/guidance-and-advice/environmental-topics/woodland-management/tree-health-and-biosecurity/biosecurity/?lang=en

http://www.nonnativespecies.org/index.cfm?sectionid=119

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