Japanese knotweed is a fast-growing, resilient plant with an invasive network of roots (rhizomes) that that can damage buildings, concrete, roads, paving, retaining walls and other structures. Its presence on or near a property can significantly reduce its value or even make it unsaleable (sellers are required to disclose the presence of knotweed on their property during the conveyancing process). Many lenders will refuse to lend on properties affected by knotweed or, at the very least, require evidence of a treatment plan to eradicate the plant as a condition of lending.
The plant’s rhizomes can survive extreme temperatures and can extend 7 meters horizontally and 3 meters deep. To eradicate knotweed the roots need to be destroyed and the part of the plant above the surface needs to be controlled repeatedly over a number of years. A glyphosate herbicide is commonly used to kill and control the growth and spread of knotweed. Where the land is to be developed, digging up the rhizomes may be a quicker solution. Japanese knotweed is, however, a controlled waste under the Environmental Protection Act 1990 and its disposal is regulated by law; this requires disposal at a licensed landfill site and a registered waste carrier must be used to remove the plant from the site.
Whilst there is no general duty on a landowner to control, remove or report the presence of Japanese knotweed, a prudent landowner will take prompt action to control and eradicate the spread of the plant so as to prevent his neighbours or the local authority taking action against him.
If Japanese knotweed spreads onto neighbouring land, the neighbouring owner may be able to bring a claim against the landowner on the basis of common law private nuisance and claim compensation for:
- Loss of enjoyment or amenity of his property (which may be the diminution in value of the property);
- The cost eradicating the knotweed; and/or
- An injunction requiring the landowner to take continuing action to control the knotweed.
In Network Rail Infrastructure Ltd v Williams and another  EWCA Civ 1514, the Court of Appeal clarified that:
- Physical damage to land or buildings is not an essential requirement of the neighbour’s cause of action – root contamination on the neighbouring property can be sufficient; and
- Nuisance can be caused by inaction or omission as well as by positive action – a landowner with reasonable or presumed knowledge of the existence of Japanese knotweed on his land, who fails to take reasonable steps to stop it spreading, can be liable to his neighbour.
In Smith v Line (case number C00TR216) 2017, the County Court granted a mandatory injunction requiring the defendant to contract with a specialist contractor to deal with the knotweed on her land. The Court held that the spread of the knotweed onto the claimant’s land was akin to a trespass and unduly interfered with his enjoyment of his property, despite no physical damage to land or buildings.
A person who fails to take reasonable measures to control knotweed that results in the plant spreading to the wild, or being negligent or reckless about that occurring, could be liable for the criminal offence of causing it to grow in the wild under section 14 of the Wildlife and Countryside Act 1981. On conviction a person may be liable to an unlimited fine and/or 2 years imprisonment.
Specific offences also apply for deliberate planting and release of Japanese knotweed into the wild; this includes incorrect handling and transportation of contaminated material and plant cuttings. The person disposing of, and transporting, such waste is under a duty of care to ensure its proper disposal.
Enforcement action by Local Authority
A local authority can serve a notice on an occupier of land requiring it to remedy the condition of land within a specific period where, in the local authority’s opinion, the amenity of an area (or adjoining area) is adversely affected (section 215, Town and Country Planning Act 1990 (TCPA 1990)). The local authority must give a landowner a minimum of 28 days’ notice to remedy the knotweed. If the occupier fails to comply with the notice, the local authority can:
- Prosecute them in the magistrates’ court. On conviction the occupier will be liable for a fine not exceeding level 3 on the standard scale (currently up to £1000); and/or
- Step in to undertake the necessary works and recover its costs from the occupier.
Community protection notice under the Anti-social Behaviour, Crime and Policing Act 2014
Local authorities have the power to serve a community protection notice on an individual or company if it has reasonable grounds to believe that both the conduct (which includes a failure to act) of that individual or company:
- is having a detrimental effect, of a persistent or continuing nature, on the quality of life of those in the locality; and
- is unreasonable.
This power has been used by local authorities to compel landowners to take action to eradicate knotweed on their property. Breach of the community protection notice, without reasonable excuse, is a criminal offence, subject to a fixed penalty notice or prosecution. On summary conviction for breaching a community protection notice, an individual is liable to a fine not exceeding £2,500 and a company is liable to an unlimited fine. The local authority can also step in to remedy the problem. Bristol City Council recently prosecuted a residential property company on behalf of seven neighbouring owners for breach of a community protection order that required the company to remedy the detrimental effect of knotweed growing on its property on its neighbours. The court fined the company £18,000 plus costs and ordered it to remedy the problem within 28 days, including obtaining a plan from a specialist company detailing how the issue should be resolved.
Recent court decisions and the action taken by Bristol City Council underline how important it is for landowners to take steps to identify any Japanese knotweed present on their properties and to implement a proper and responsible land management system to prevent its spread and eradicate growth. When treating Japanese knotweed landowners must make sure they use only approved herbicides and comply with the regulations as to its disposal. The best solution is to appoint a competent contractor who can provide an insurance backed guarantee.