Beware Japanese Knotweed

Tim Smith
Tim Smith

Published: February 22nd, 2023

7 min read

Japanese Knotweed is a non-native plant that can inhabit both urban and rural areas. People do not want this plant on or near to their property. It is a very invasive species that has the ability to spread and can cause damage to the structure of buildings as well as being both difficult and expensive to get rid of.

The Court of Appeal have recently handed down judgment in the case of Davies v Bridgend County Borough Council [2023] EWCA Civ 80 in what will be likely be an important authority relating to the value of such claims.

The Facts

The Claimant in this claim was the owner of a terraced property in Bridgend in South Wales. The property had a garden to the rear which backed on to Council owned land comprising an embankment leading to a cycle path on an old railway line. There was Japanese Knotweed growing along the cycle path at the bottom of the embankment and there was evidence of further Japanese Knotweed growth along the top of the embankment. The Claimant became aware of Japanese Knotweed on his property in 2017. The Defendant Council had started treating the knotweed in 2018 but were found to have been aware of its presence since 2013 and were therefore held to have been in breach of its duty owed in nuisance to the Claimant between the years 2013 to 2018.

The breach was accepted and the issue on appeal was whether or not the Defendant owed a continuing duty to the Claimant in respect of the residual reduction in value to the Claimants property.


At first instance the claim for residual diminution in the value of the Claimant's property was dismissed in accordance with the judgment in Network Rail Infrastructure Ltd v Williams and another [2018] EWCA Civ 1514 on the basis that this was pure economic loss and therefore irrecoverable.

However, the Court of Appeal found the Williams case had been misinterpreted. On the facts of the case the Claimant's land had been diminished in value and his enjoyment of his property had been negatively affected. Consequential losses including the reduction in value to the property were therefore recoverable.

Causation was also in issue. The Defendant argued that the rhizomes causing the Japanese knotweed encroachment on the Claimants property had spread there in 2004 and therefore the Defendant's failure to treat the encroachment between 2013 to 2018 made no difference. This argument was rejected by the Court of Appeal on the basis that the encroachment was ongoing and therefore the Claimants claim for interruption of his legal right to the quiet enjoyment of his property was also ongoing. The actual date of historic encroachment was not a defence to this claim. The nuisance persisted and had been caused by the Defendants breach.


This case serves as a timely reminder to Defendants of the issues they face with regards to Japanese Knotweed and the potential consequences for failure to act. The case clarifies the interpretation of Williams. Defendants may be liable for claims relating to diminution in value where the Claimant's quiet enjoyment of the land has been encroached upon or interfered with. Defendant local authorities need to be aware of the areas of Japanese Knotweed across their boroughs particularly where it is growing adjacent to privately owned residential property. Such areas should be subject to treatment plans. Spraying or injecting the stems with approved herbicide can be an effective treatment and this is usually carried out over a period of at least 3 years.

Tactically Defendants can keep the costs of dealing with claims relating to Japanese Knotweed down by instructing single joint experts were possible. They should also consider the true value of the claim at the outset as it may be the case that the matter can be dealt with on the small claims track which again will serve to reduce the overall costs of dealing with the same. Upon receipt of a letter of claim should it be the case that if the Japanese Knotweed is not already being treated, treatment should be commenced on a without prejudice basis as soon as possible. Should the Claimant deny the Claimant access to their property for the purposes of treatment it can be argued that they failed to mitigate their loss.

For more information contact [Tim Smith](<mailto:<a href=>) or Jade Johnson.

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