In the recent years there has been a greater awareness of the threat posed by Japanese Knotweed in the UK.
Japanese Knotweed has been described by The Environment Agency as “indisputably the UK’s most aggressive, destructive and invasive plant” as a result of its very fast growing nature it poses risks to properties within seven metres of the plant. When it comes to the extermination of this invasive plant it requires great determination and time and can be very costly. The presence of Japanese Knotweed on a property can affect both the value when arranging a mortgage and when it comes to selling.
There has been a very important recent case, Williams and another v Network Rail Infrastructure Ltd  EWCA Civ 1514;  PLSCS 120 where it was held that when Japanese Knotweed encroaches on a property owner’s land, the property owner does not have to prove physical damage to the property to bring an actionable claim for private nuisance. It allows a property owner to seek an injunction requiring that neighbour to control Japanese Knotweed on their land on the basis of any anticipatory damage because it affects the amenity value and quiet enjoyment of his or her property. This provides a remedy for those whose property is threatened with the encroachment of Japanese Knotweed from any neighbouring properties and confirms that, even if there is no actual physical damage to the property, the presence of Japanese Knotweed can affect amenity value.
In this case the court awarded the claimants damages for the costs of treating the invasive Japanese Knotweed and for the diminution in the value of the property as a result of the presence of knotweed together with its interference with the quiet enjoyment or amenity value of their properties.
On the purchase of residential properties standard enquiries specifically raise the question about the presence of Japanese Knotweed and it is important that sellers are very careful when replying especially when a seller does not occupy the property or has not occupied the property for a while due to it being let etc and replies such as ‘not so far as the seller is aware’, puts the seller under a risk of being found liable for misrepresentation. Equally it is important for Buyers of a property to be cautious of the presence of Japanese Knotweed and they should raise immediate enquiries with the agents, their surveyors and solicitors to establish the presence of the same.
As a general rule it is important that property owners are aware of the potential liability that they are exposed to by the presence of Japanese Knotweed and upon becoming aware must act immediately in making arrangements for the control and treatment.