Japanese Knotweed: Legal Consequences

Japanese Knotweed is an invasive plant that grows and spreads rapidly. Excavation or multi-year treatment plans are the only way to get rid of it and even these might not be permanent solutions.

Whilst it is not illegal to have Japanese Knotweed on your land or property, allowing it to spread outside your boundaries or not informing others of its presence may have legal consequences. This article explores, through case law, the responsibilities of those who have Knotweed on their property and other recent legal disputes on the topic.

Nuisance: Diminishing Property Value

Davies v Bridgend County Borough Council [2023]

In this very recent case, the Council’s land had Knotweed growing on it and despite treatment, the roots remained. Mr Davies brought a claim against the Council alleging the value of his property had diminished because of the ‘blight’ that was Knotweed. The Court of Appeal agreed that the presence of Knotweed could amount to a nuisance if it was not ‘trivial’. There was no need to demonstrate a risk of damage to structures on neighbouring land or an increased difficulty in developing the land. The Knotweed was held to be a ‘continuing nuisance’ due to the ongoing encroachment onto Mr Davies’ land. Mr Davies was awarded damages reflecting the diminution in the value of his property.

Liability can accrue by a positive act as well as inaction. If the landowner knows Knotweed exists on their land and fails to use reasonable means to eradicate it, they could be held liable for Nuisance. In the case above, complete excavation would have been more appropriate than just treatment.

Misrepresentation: Declaring Knowledge of Knotweed

Downing v Henderson (2023)

When selling his property, Mr Henderson confirmed that it was not affected by Japanese Knotweed. Mr Downing upon purchasing the property subsequently found the invasive plant in the garden. The Defendant was ordered to pay £32,000 in damages which included the reduction in value and costs of investigating and excavating the weed and costs of £95,000 for his misrepresentation upon sale.

Responsibility for controlling Japanese Knotweed will likely be that of the landowner. Landowners considering selling (or letting) their property should consider conducting a high-level Japanese Knotweed survey, highlighting potential problems, and anticipating any issues which may affect the sale.

Surveyors: Responsibility to Alert the Buyer’s

Ryb v Conways Chartered Surveyors [2019]

The claimant in this case had very poor eyesight and relied heavily on the full building survey he commissioned when purchasing the property. Mr Ryb spent £10,000 removing the Knotweed after its discovery but was awarded a much larger damages sum of £50,000 based on the evidence that arose; Knotweed was present when the survey was conducted at the property, Mr Ryb’s investment in the house had been reduced and the Knotweed interfered with his “ability fully to use and enjoy the land”.

Learning from this case, buyers should carefully scrutinise replies to enquiries and survey reports to check if the existence of Japanese Knotweed has been disclosed. If the property was previously affected, then the reports should include a proper treatment plan and provide an appropriate guarantee which should be assignable to the buyer.

Summary

Several legal disputes have arisen from the presence of Japanese Knotweed. If you are concerned about the effects of Japanese Knotweed on your property…

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