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Guidance note for owners of land infested with Japanese knotweed
23 February 2015

Obviously the normal rule of 'caveat emptor' (buyer beware) applies in relation to any property transaction and the seller or landlord is not under a duty to disclose any information regarding the physical condition of the property. Standard enquiries go some way to deal with this, but a prudent buyer should make specific enquiries about any presence of Japanese knotweed.

Why does Japanese knotweed present a problem for landowners?

Japanese knotweed is highly invasive and can penetrate concrete, foundations and walls – weakening their structure. It is also very difficult to eradicate, even a very small part of root or stem can re-infest land.

Physical damage to the structure of buildings and the supporting land affects the value, marketability and insurability of the land. To eradicate or remove Japanese knotweed can be expensive (the government estimates the cost to remove all Japanese knotweed from the UK at £2.6 billion) and its presence will deter many potential buyers. There is also the risk of criminal or civil liability for owners and occupiers of land infested with Japanese knotweed.

Offences and liability relating to Japanese knotweed to which landowners should be aware

The EU Parliament and Council Regulation 1143/2014 “on the prevention and management of the introduction and spread of invasive alien species” (EU Invasive Alien Species Regulation 2014) came into force on 1 January 2015. This required member states to eradicate and manage a number of invasive species – including Japanese knotweed. Such management to include preventing introduction and spread, undertaking early eradication and introduce penalties for breach.

There are a number of specific offences whereby a Landowner could be criminally liable, these are summarised below:


    • Planting or causing to grow Japanese knotweed in the wild under the Wildlife and Countryside Act 1981 carries penalties of a fine, imprisonment (up to two years on indictment), or both;

    • Specific offence of deliberately introducing Japanese knotweed into Great Britain under the Habitats Regulations 2010 carries a penalty on indictment or an unlimited fine;

    • Where Japanese knotweed poses a threat to biodiversity, environmental, social or economic interests. A landowner will be required to enter into a Species Control Agreement (SCA) with the authority which obligates the landowner to take measures to control the Japanese knotweed.

      a. If the parties do not reach agreement, the authority can issue a Species Control Order (SCO) which compels the landowner to take action. The authority also has the power to enter the property for surveillance purposes or carry out works;

        b.    Failure to comply with the SCO is a criminal offence which carries a penalty of a fine and/or imprisonment.

  • There are also offences under the Environmental Protection Act 1990 for depositing of, or breaching a duty to take reasonable steps, to ensure the Japanese knotweed is disposed of lawfully without causing harm or pollution;

  • A local authority can also serve a notice on the owner or occupier of land under the Town and Country Planning Act 1990 requiring them to remove or manage Japanese knotweed if it adversely affects the amenity of neighbouring or adjoining land. Failure to comply with such notice results in a fine up to £1000. The authority also has the power to step in and undertake works, recovering their costs from the occupier.

However, despite the above, there is no general duty on an owner or occupier of land to control, remove, eradicate or treat Japanese knotweed. However, omission to take action or measures to control knotweed, or negligence or recklessness, leading to knotweed spreading to the wild is sufficient to establish a liability.

An owner/occupier could also be liable for common law or statutory nuisance if the knotweed spreads to neighbouring land. The owner/occupier would be liable to pay compensation.

Specific guidance for landowners and developers

Landowners: The Property Care Association (PCA), which has members who treat invasive plants, has formed a group which seeks to provide a set of standards for treatment to lessen the risk for homeowners, lenders and insurers. This group has worked with RICS, who have recently published a RICS information paper which is designed to provide information and explanation to RICS members about Knotweed. The PCA have published their own code of practice which can be found via the CML website.

The RICS information paper standardises the methods used to assess risks and quantify any costs associated with the management of knotweed on residential property. In particular, when carrying out a survey or valuation, the report must note the presence of knotweed on the property.

The RICS paper measures risk based on:

  • The presence of Japanese knotweed;

  • Distance from buildings on the property (7 metres is the threshold);

  • Damage already caused by the Knotweed?

Given the potential risk liability for offences outlined above and possibility of regrowth – if intending to carry out remediation work it is advisable to use a contractor accredited with the PCA.

Buyers and Developers: The Environment Agency has published specific guidance for developers (EA: Managing Japanese Knotweed on development sites: the knotweed code of practice (version 3, 2013)). This advises how to:

  • Prevent spread or further contamination of knotweed;

  • Manage knotweed problem, including use of herbicides;

  • Use other methods of control;

  • Treat and dispose of Knotweed;

  • Long-term management of Knotweed on site.

Ultimately there is a risk associated with developing sites with a history of knotweed. There is no standard approach taken by lenders and it should be discussed with any intended lender to find out their specific attitude and requirements.

Relief is available for companies who incur expenditure in removing knotweed from a contaminated site under the Land Remediation Relief Scheme. This extends to contamination by knotweed after the land was acquired by the company claiming such relief – e.g. if the knotweed was introduced by fly-tippers.

Consistent with our policy when giving comment and advice on a non-specific basis, we cannot assume legal responsibility for the accuracy of any particular statement. In the case of specific problems we recommend that professional advice be sought.

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