Japanese Knotweed and the Emergence of “Proximate Nuisance”: the Far-Reaching Consequences of Having JKW on your Land.

16 Mar 2017

When they sued Network Rail because the long-established infestation of Japanese Knotweed (“JKW”) on the rail embankment had devalued their properties, little did Mr. Williams and Mr. Waistell know that they would be expanding the boundaries of liability for property damage in nuisance.

After a 3-day trial in the County Court in Cardiff, Mr. Recorder Grubb found that the presence of JKW on the Defendant’s property was an actionable nuisance, as it interferes with the quiet enjoyment of land.

The far-reaching consequence of the decision is that the JKW became actionable when it grew within 7m of a built structure on the Claimants’ land, before it had spread onto the neighbouring property. Hence my description of it being a “proximate nuisance”.

The Facts of the Case

The Claimants own neighbouring semi-detached bungalows in Maesteg, South Wales, which adjoin a railway embankment. Unusually, the properties have no back garden and the rear wall of each bungalow abuts an access path belonging to Network Rail. There is JKW growing on the access path and down the embankment.

In 2013 the Claimants each contacted the Defendant’s customer service department to complain that they could not sell their houses because of the JKW.

While the respective JKW experts seemed to agree on very little, they were agreed that the stand of JKW was at least 50 years old, which pre-dated either Claimant owning his property, and that there was no evidence of physical damage to either bungalow.

However, the Claimants’ case was that because of the presence of the JKW in the vicinity of their buildings, a surveyor would classify it as Category IV risk and few, if any, of the mainstream residential lenders would accept the properties as security. As such, there was a limited pool of potential purchasers and a reduction in the market value of the bungalows. Both expert valuers believed that there would be a residual diminution in the value of the properties even after the JKW was treated because of the approach of the lenders.

Network Rail had been aware of JKW in the locality since 2008 as part of its track inspection regime and had been controlling the weeds so far as required to maintain visibility on the line.

The Law

There are a number of important aspects of the decision:-

  1. Following the line of authority in tree roots cases following Delaware Mansion Ltd v Westminster City Council [2001] UKHL 55, the judge held that encroachment by the JKW rhizomes is not actionable unless there is physical damage.

  2. It was accepted that, as JKW is a naturally occurring hazard, the Defendant was under a measured duty of care to do what is reasonable in the circumstances to prevent or minimize the risk to the neighbour’s land (see Leakey v National Trust for Places of Historic Interest or Natural Beauty [1980] QB 485)

  3. The judge held that, by analogy with ‘affront cases’ (for example, Law v Florinplace Ltd [1981] 1 All ER 652), a nuisance could be merely proximate and there was no requirement for an emanation from the Defendant’s land over the Claimants’ land as the basis of liability.

  4. Even though there was no physical damage and no affect on the utility of the land, the judge found that the amenity value of a property is not simply the use and enjoyment of the land, but can include the ability to dispose of it at a proper value. He rejected this as being equivalent to pure economic loss.

Interestingly, the affront cases were not relied on by the Claimants and those cited by the judge concerned applications for interim injunctions to restrain a positive act by the landowner (in Laws this was running a sex shop). The authorities were not final determinations that a proximate nuisance is actionable.


The judge found that Network Rail should have known of the risk the plant posed to the Claimants’ properties, following the publication of materials by RICS and the Property Care Association in 2012.

Even though the Defendant’s primary objective in the management of lineside vegetation is to ensure the safe operation of the rail network, the judge held that it should have done more to eradicate the JKW near the Claimants’ properties after it constructive knowledge.

At trial, the Claimants ‘stepped back’ from their claims for a mandatory injunction to compel Network Rail to treat the pernicious weed, preferring damages in lieu.

Based on the judge’s interpretation of the law, the Claimants were awarded the costs of treatment of the JKW and the residual diminution in value of their bungalows assuming that treatment had taken place.


Irrespective of whether the decision is right, the judgment has serious ramifications for landowners.

Firstly, if they do not take appropriate steps to discharge their measured duty of care and control or eradicate JKW from growing within 7m of their neighbour’s buildings, landowners could be liable in nuisance. Just imagine if each local authority which has JKW growing on amenity space is sued by the local residents…

Secondly, where will the categories of proximate nuisance end? Landowner can do many things on their land which may detract from the value of the neighbouring properties: are they all to be actionable, without more?

For those of you as yet unfamiliar with the plant

JKW (Fallopia japonica) is clump-forming hardy perennial, which produces fast growing stems of up to 2m tall. It spreads by a system of continually growing underground stems called “rhizomes” and is reportedly able to propagate from a small amount of rhizome, even after a significant period of dormancy. It can take a number of years to treat the weed with chemicals.

While it is an offence under s.14(2) of the Wildlife and Countryside Act 1981 to cause JKW to grow in the wild, it is not unlawful to have the plant on your land.

It is possible to eradicate the plant by digging out the rhizomes, but any soil removed must be disposed of at a licensed landfill site, as it is classified as controlled waste under the Environmental Protection act 1990.

As the RICS guidance note, “Japanese Knotweed and residential property” (2012) notes it “…has caused problems in the residential market because of concerns about the damaging effects of this invasive plant. However, these concerns are often based on misunderstanding and overreactions.” The document then lists its common effects on built structures, which include exploiting existing cracks in pipework, growing between paving slabs, undermining garden walls with shallow foundations and pushing over poorly founded sheds and other insubstantial outbuildings.


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