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Japanese Knotweed

Last Modified May 14, 2019

What is Japanese knotweed?

Japanese knotweed is a non-native invasive species of plant. Since it was introduced into the UK as an ornamental garden plant in the mid-nineteenth century it has spread across the UK, particularly along watercourses, transport routes and infested waste areas.


What does Japanese knotweed look like?









Japanese knotweed is a perennial plant with distinctive branching, hollow, bamboo-like stems, covered in purple speckles, often reaching two to three metres high. The plant flowers late in the season, August to October, with small creamy-white flowers hanging in clusters. The underground rhizomes are thick and woody with a knotty appearance and when broken reveal a bright orange-coloured centre. The rhizome system may extend to, and beyond, a depth of at least 2m and extend 7m laterally from the parent plant.

Identifying Japanese knotweed factsheet (PDF)


In the UK there are two main pieces of legislation that cover Japanese knotweed.  These are:

Wildlife and Countryside Act 1981

Japanese knotweed is listed on Schedule 9, Part II of the Wildlife and Countryside Act 1981 making it an offence Under Section 14 (2) (a) of the Act to “plant or otherwise cause Japanese knotweed to grow in the wild”.  

Environmental Protection Act 1990

Japanese knotweed is classed as ‘controlled waste’ and as such must be disposed of safely at a licensed landfill site according to the Environmental Protection Act (Duty of Care) Regulations 1991. The Environment Agency has produced a code of practice in partnership with DEFRA and Network Rail for the management, destruction and disposal of Japanese knotweed. 

In addition, new legislation has brought in potential new powers to deal with serious instances of Japanese Knotweed:

Anti-social behaviour, Crime and Policing Act 2014

The Anti-social Behaviour, Crime and Policing Act 2014 does not explicitly refer to Japanese knotweed or other, similar invasive non-native plants, as the new anti-social behaviour powers are intended to be flexible.

Community protection notices can be used to require someone to control or prevent the growth of plants like Japanese knotweed which are capable of causing serious problems to communities. The test is that the conduct of an individual or body is having a detrimental effect of a persistent or continuing nature on the quality of life of those in the locality, and that the conduct is unreasonable (includes "a failure to act").

We can investigate complaints about Japanese knotweed and may provide advice and recommendations about its treatment.  If matters are not resolved informally we may issue a Community Protection Notice for invasive non-native species like Japanese knotweed. The notice can require the person responsible for the land in which the knotweed is growing to take steps to rectify the problem.

Environment Agency Knotweed Code of Practice (Version 3, amended in 2013) (PDF)


Managing Japanese knotweed is the responsibility of the landowner. Whilst there is no specific statutory requirement to control or eradicate this invasive plant, nor is it necessary to report its presence (it is not listed in the Weeds Act 1959), but what is important is to take action to control its spread quickly.  The new powers under the Anti-social Behaviour, Crime and Policing Act 2014 can be used against landowners who do not deal with Japanese knotweed growing on their land. In the first instance you should contact the landowners and notify them of the Japanese knotweed. It is the landowner’s responsibility to control Japanese knotweed to ensure that it doesn’t spread, but it is not illegal to have Japanese knotweed growing on your land.

If you have Japanese knotweed on your land it is important to ensure that you are not causing a private nuisance by allowing it to spread to adjoining land. The adjoining land owner could take civil action against you in court if Japanese knotweed is shown to have spread.  In certain cases, you may be subject to a Community Protection Notice.  For advice on civil action, please speak to your local Citizens Advice Bureau. 

If Japanese knotweed is found on council land, we as landowners are responsible for the effective control of the plant. If you have identified Japanese knotweed on what you believe is council land, then please contact customer services on 020 8207 2277 and report the location. Customer services will be able to advise you if it is council owned land and will pass your concerns on to the appropriate department.

Treating Japanese knotweed in your garden

Hand pulling or cutting the plant is a good method of control, but it will take several years for the rhizome to die. Be prepared for a lengthy process. Any material which you have pulled out or cut should be left to dry out before burning on site. If you do carry out any burning of the plant, avoid causing a nuisance to your neighbours and advise your local Environmental Health department that you will be burning Japanese knotweed. However, be sure to obtain a D7 waste exemption permit from the Environment Agency before you burn waste material on site. Do not remove the material from your land. Burning the plant on site will prevent spreading. You can also use chemical herbicides, glyphosate is recommended, but treatment will again be on going and lengthy. Glyphosate is the active ingredient in products such as ‘Roundup biactive’ and ‘Glyphos biactive’. Many formulations of glyphosate are suitable for use in or near water and it possesses low toxicity to animals. The bioactive formulations of glyphosate are generally regarded as the most suitable. During autumn the plant draws food stores from dying leaves and canes down to the rhizome. Therefore herbicide treatment during late summer and autumn is the most effective time.

Key action and advice to residents

  •  Do not put Japanese knotweed in your green waste bin.
  •  Do not take Japanese knotweed to any Household Waste Recycling Centres.
  •  Talk to your neighbours and work together to eradicate Japanese knotweed.
  •  Do not accept topsoil onto your land unless it has been checked for Japanese knotweed rhizomes.
  •  Early treatment of Japanese Knotweed is essential. Don’t delay take action quickly.


If you require any further advice regarding Japanese knotweed then please contact the Environmental Health department on 020 8207 7435 or email environmental.health@hertsmere.gov.uk

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