A Knotty problem

A recent court decision has highlighted the risks to landowners with Japanese Knotweed on their land of allowing it to spread to adjoining land, or even allowing it to grow close to boundaries with adjoining land.

Japanese Knotweed is an invasive non-native species of plant that was introduced into the UK in the 19th century as an ornamental garden plant. It is now a significant problem across the UK. It can cause considerable damage to buildings and infrastructure. The government estimates that the costs of eradicating it across the UK would be £2.6bn.

A recent ruling in the Cardiff County Court in two joined cases involving the owners of two residential properties in South Wales and Network Rail Infrastructure Limited (Network Rail) has highlighted the impact of Japanese Knotweed on property values and the importance for landowners and occupiers of properly managing Japanese Knotweed on their land. The two claimants, Mr Williams and Mr Waistell, owned two adjoining semi-detached bungalows in Maesteg, South Wales, adjacent to an access path owned by Network Rail leading to a railway embankment. A large stand of Japanese Knotweed had been growing on Network Rail's land for at least 50 years.

The claims

Mr Williams and Mr Waistell each sued Network Rail for private nuisance. They claimed that the Japanese Knotweed on Network Rail's land had either encroached on their land or grown within close proximity of their land, in each case resulting in a diminution in the value of their respective properties. They claimed that even if the Japanese Knotweed was treated, the price that they could obtain on the sale of their properties would be diminished, and claimed an injunction requiring Network Rail to treat and eliminate the Japanese Knotweed on its land, and damages for the diminution in the value of their respective properties.

The court's ruling

The court found that, on the evidence, there was no proof of damage to the claimants' properties, so their claims for encroachment failed. However, it found that the presence of the Japanese Knotweed on Network Rail's land amounted to an unlawful interference with their quiet enjoyment or amenity of their property. It ruled that the amenity value of a property can include the ability to dispose of it at a proper value and the evidence was that, even if the Japanese Knotweed was treated, the values of the claimants' properties were below the normal market value.

Once the court had established that the presence of the Japanese Knotweed on Network Rail's land could amount to an unlawful interference with the claimants' quiet enjoyment of their respective properties, it then had to consider: (1) whether Network Rail had knowledge of the nuisance caused by the Japanese Knotweed and (2) whether it had acted reasonably in preventing or minimising the known risk of damage to the claimants' properties.

Network Rail admitted that it had knowledge of the presence of the Japanese Knotweed on its land, but it denied that its knowledge imposed any duty on it to eradicate or otherwise remove the Japanese Knotweed prior to receiving complaints from the claimants in 2013. The court disagreed, on the basis of guidance on managing Japanese Knotweed published by the RICS and the Property Care Association in 2012/2013. Although Network Rail had undertaken some treatment of the Japanese Knotweed between 2013 and 2016 (including spraying it with herbicide), the court found that treatment to have been inadequate.

The claimants initially sought an injunction requiring Network Rail to eradicate the Japanese Knotweed on its land, but they subsequently changed their minds and sought damages to pay for treatment with an insurance-backed guarantee instead, as they were not satisfied that Network Rail would treat the Japanese Knotweed properly. The court therefore awarded Mr Williams £16,420 in damages for the cost of a treatment programme and insurance backed-guarantee, the residual diminution in value of his property after treatment, miscellaneous loss and general damages. It awarded Mr Waistell £14,620 for the cost of a treatment programme and insurance-backed guarantee, the cost of a Japanese Knotweed survey and the residual diminution in value of his property after treatment.

Comment

As a County Court decision, the case is not binding precedent, but there is no reason why it should not be followed in similar cases, as it is based on the principles of private nuisance set out in the leading High Court, Court of Appeal, House of Lords and Supreme Court cases. It may be fact-specific, but it also appears from the court's comments that the claimants would have succeeded in their encroachment claims if the Japanese Knotweed had actually caused physical damage to their properties.

Apart from the obvious risk of a private nuisance claim such as in this case, what are the other considerations for owners and occupiers of land with Japanese Knotweed growing on it?

• As an owner or occupier of land, it is your responsibility to deal with any Japanese Knotweed growing on it.
• Do not allow Japanese Knotweed to spread outside your land - causing it to grow in the wild is an offence under the Wildlife and Countryside Act 1981, carrying maximum penalties of an unlimited fine and two years' imprisonment. Allowing it to spread to an adjoining property may also amount to a statutory nuisance, giving the local authority a power to serve an 'abatement notice' requiring it to be controlled. Breach of an abatement notice is an offence.
• Environmental regulators now have powers to serve 'species control orders' on landowners and occupiers requiring them to control Japanese Knotweed on their land. Breaching a species control order is also an offence.
• When treating Japanese Knotweed, there are a number of regulatory issues to consider - for example, only approved herbicides may be used and there are strict controls on the management of Japanese Knotweed waste. The safest solution is to use a competent contractor who can provide an insurance-backed guarantee.