16th March 2023

The war on Knotweed: why eradication isn’t always the answer

Samuel Isaac

Trainee Solicitor

Brought over to the UK in the 19th century, Japanese Knotweed was originally intentionally planted primarily as an ornamental garden plant and for erosion control.

Since then, it has caused havoc across the land with landowners believing that discovery of the plant in their garden is akin to a death sentence for their property. However, new guidance suggests that this approach is unhelpful and might only further exacerbate the reactionary response from buyers, banks and the courts.

The significant change comes from the Royal Institute of Chartered Surveyors (RICS) who released new guidance in October that suggests a change in approach towards the management and control of Japanese Knotweed.

Rather than focusing on the complete eradication of the plant, the guidance recognises that eradication is not always a helpful or practical objective and that the focus should instead be on management and control. RICS argues that while physical removal may be necessary in some circumstances, this option should be used sparingly as there are many environmental concerns with complete eradication programmes. Most interestingly, the guidance states that Japanese Knotweed rarely causes structural damage to substantial buildings such as dwellings - contrary to what is often reported in the press.

This should expel a sigh of relief from those landowners who have found the plant on their property and fear having to pay for extensive management plans. However, the recent case of Davies v Bridgend County Borough Council muddies the waters.

The key issue in this case was the interpretation of the 2018 case Williams v National Rail, which had previously been understood to rule that the diminution of value of a property due to Japanese knotweed from a neighbouring property was 'pure economic loss' and therefore not subject to a remedy in tort. However, Birss LJ argued in Davies that this was a misreading of Williams and that the court in that case had actually awarded recoverable damages for the 'residual diminution in value' of the property.

The judgment contended that diminution from knotweed should not be considered pure economic loss because it is a 'natural hazard' that causes physical interference and damage to the claimant's land, thus diminishing the land's value and impeding the claimant's quiet enjoyment and use of it. Therefore, Birss LJ argued, knotweed's presence on a claimant's land, to a non-trivial extent, should be considered damage for the purposes of the tort of nuisance.

Crucially, the court did not consider whether Knotweed is actually damaging to the land, but rather whether it will affect the land's value - be that through actual damage or simply the market's perceived taboo against knotweed. Without a shift in public attitude as suggested by RICS to one that is more realistic and pragmatic and that doesn't fear the plant, claims like those seen in Davies will only become more common, invading our courtrooms like... well... weeds.