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Japanese Knotweed - Buyers Beware!

Japanese Knotweed (‘JKW’) is a pernicious weed which has made headlines in recent years.  From infesting a 200 hectare site designated for the 2012 London Olympics, to cases in homeowners’ back yards, its growth looks set to continue.

Landowners should give careful consideration to the presence of JKW on their property or neighbouring land. Those who have JKW on their land may incur civil and/or criminal liabilities if JKW is not handled correctly.


What is Japanese knotweed?

JKW is an invasive non-native species.

JKW was introduced to the UK in the early 19th Century as an ornamental plant. However the rapidly growing, bamboo-like plant has now caused wide spread infestation, and is particularly common in Greater London, South Wales and the South West.

Its ability to cause structural damage to buildings is a major concern for any house buyer. JKW can grow a distance of at least 7 metres, with a depth of at least two metres, producing roots which are able to upset foundations, undermine retaining walls and disrupt drainage systems.

Its resistance to cutting led to the government making it an offence to plant or otherwise cause JKW to grow in the wild under the Wildlife and Countryside Act 1981, with those guilty of the offence facing up to two years’ imprisonment and/or a fine. Further to this, the Environmental Protection Act 1990 identifies JKW as a controlled waste, requiring registered waste carriers to dispose of it.

The impact of JKW on properties

Properties which are in close proximity to JKW are less attractive to prospective buyers and are subsequently devalued.

The treatment for JKW is costly and time-consuming, and contaminated soil must be deposited by a specialist in designated landfill sites.

Further to this, the dangers that JKW poses to buildings means owners may find it difficult to get building insurance for their property. Equally, mortgage lenders are less willing to lend where JKW is present, even if the JKW is on another’s land.

The following recent cases show the impact of JKW on landowners.

Williams and Waistell

In 2017, two separate claims were brought in private nuisance against Network Rail in Williams v Network Rail Infrastructure Ltd and Waistell v Network Rail Infrastructure Ltd (collectively ‘Williams and Waistell’).

In Williams and Waistell, the claimants were the adjoining owners of two semi-detached bungalows. The bungalows abutted an access path which led to an embankment, which was owned by Network Rail. The embankment had been infested with JKW for over 50 years, and the JKW had spread along the access path to the claimants’ land.

The claimants argued that the JKW on Network Rail’s land had encroached upon their land, thus causing nuisance. In turn, the claimants sought an injunction requiring Network Rail to eliminate the JKW on their property, and damages, in respect of the diminution in value of their land.

The court held in the absence of any physical damage to their property, that the claimants had failed to make out a claim for encroachment. The fact that there was a risk of damage did not constitute a private nuisance.

However the court found that the claimants were able to show that the presence of the JKW on their properties had unlawfully interfered with their use and enjoyment of their land on the basis that:

  • The presence of JKW led to the diminution of value in their land; and
  • Network Rail had breached its duty of care to the claimants by allowing the nuisance to continue.

The court awarded the claimants damages in respect of a treatment programme with an insurance backed guarantee, and for diminution in value of their property. However injunctive relief was deemed inappropriate on the facts.

Smith v Line

In Adam Smith and Eleanor Smith v Rosemary Line (2018) (‘Smith v Line’), the claimants had purchased their property from the defendant, who retained the adjoining land. In 2003, the claimants found that JKW had encroached onto their land from the defendant’s property. Ten years later the claimants were able to successfully eradicate the JKW from their property. The claimants asked the defendant to remove the JKW which grew in close proximity to their boundary. However the defendant did not take reasonable steps to eradicate it.

The claimants therefore brought a claim in nuisance on the basis that the JKW had encroached their land, and that the presence of JKW interfered with the enjoyment of their land.

It was found that the presence of JKW on the defendant’s land resulted in the value of the claimants’ property being reduced by 10%. However, as in Williams and Waistell, the court held that physical damage could not be established. Rather, it was found that the JKW on the defendant’s land interfered with the amenity of the claimants’ land. The court granted damages and a mandatory injunction requiring the defendant to treat the JKW.


The invasion of JKW shows little sign of retreat.

With this in mind, buyers should take care before proceeding with the purchase of a property which may be invested with JKW.

The need to be diligent when checking for JKW is reflected in the general pre-contract enquiries for all commercial properties, which has been recently updated to include provision for JKW.

This means that when sale enquiries are made into the physical condition of a commercial property, the seller should make reasonable efforts to check for its existence.

Equally, owners should be aware that the presence of JKW on their property can be viewed as a nuisance before it even encroaches onto neighbouring land. It is therefore important that any handling of JKW is carried out early on and done so in accordance with the law.

Please contact a member of the Property Dispute Resolution Team if you require assistance –


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