Japanese knotweed is a term that troubles homeowners and landowners because it is an invasive plant species that can rapidly get out of control and cause significant damage to buildings and neighbouring land.
Landowners should take care that they do not have Japanese knotweed growing on their property, but more particularly, they do not allow it to spread onto neighbouring land and buildings. Japanese knotweed is not the only invasive species that can cause damage, as various forms of invasive bamboo can also be as problematic.
However, rest assured that specialist firms can provide clearance and treatment plans to remediate the land and stop issues from recurring.
What is Japanese Knotweed, and why is it an issue?
It is an invasive and rapidly spreading plant that can cause extensive damage to buildings or land. It is a problem if it encroaches onto your land because it would have to be disclosed if you were selling your property, and mortgage lenders can be difficult about lending if it is present. In many instances, however, a lender will have no issue with lending it if it can be shown that a management care programme is in place to stop the spread.
How do you identify Japanese knotweed?
Advice should be taken from someone with specialist plant knowledge to identify whether it is knotweed or contained or spreading.
How to make a Japanese knotweed claim
The first thing to do is get specialist advice on whether the plant you are concerned about is actually Japanese knotweed. There are specialist arboricultural firms that can help to identify plant species to give you some clarity about whether it is Japanese knotweed that you have spotted in your garden.
Once you have an expert opinion that it is Japanese knotweed that is growing in your garden, and an expert view that it is not originating in your garden but spreading from elsewhere, then you should in the first instance try and have a conversation with your neighbour to see if they recognise that they have Japanese knotweed on their land, and to enquire if they are willing to pay to take steps to remove the knotweed from their own land and your land. If you are concerned that damage has been caused to your land or property due to the knotweed, you should also ask them if they are prepared to accept responsibility for remedying any damage caused to your land.
Hopefully, you will be able to have a cooperative dialogue with your neighbour in many instances. Once they realise that Japanese knotweed is present, they will be keen to take steps to remove it as soon as possible, not only from your land but also from their own land.
If they are not willing to engage with you or are uncooperative, then it may be necessary to seek specialist property litigation advice as to what you can do next to force the neighbour to deal with the issue. Your solicitor will likely recommend a legal letter before action is sent to your neighbour, relying on legal nuisance as a basis upon which you are entitled to take action against your neighbour.
In the very worst cases, if your neighbour ignores the legal letter before action, it may be necessary to issue Court proceedings against them to force them to take the issue seriously.
Defending Japanese knotweed claims
If you find yourself on the receiving end of a complaint from your neighbour or a 'letter before action' asserting that Japanese knotweed has spread from your land onto neighbouring land, you should, in the first instance, take your own expert advice on whether or not it is Japanese knotweed that is present. Once you have clarity on whether or not it is Japanese knotweed that is growing in your garden, you should also ask the expert to give you advice on whether the origin of the knotweed is from your garden or the garden next door.
Even if you are advised that your garden is the source of the knotweed, there may still be defences if Court proceedings for legal nuisance are issued against you.
What do I have to do if I find Japanese knotweed in my garden?
You are not obliged to control, remove, eradicate or treat knotweed, but a failure to take reasonable measures to control knotweed that results in the plant spreading to the wild or if you are negligent or reckless about that occurring can amount to the offence of causing it to grow in the wild under section 14 of the Wildlife and Countryside Act 1981. Therefore, if you identify knotweed on your land, it would be prudent to take quick action to control its spread.
You are not obliged to report it to the environment agency or to any local authority.
Do I have any legal liability if I find Japanese knotweed on my land?
If you plant Japanese knotweed on your land or allow it to spread onto neighbouring land, the neighbour might be able to take legal proceedings against you based on a private nuisance, claiming compensation for the loss of enjoyment or amenity (which might amount to a decrease in the value of your property) or the costs of removal.
An injunction against reinfestation or action required to control the knotweed are also other remedies that may be available.
The usual principles of nuisance apply in this context. The nuisance has to be substantial or unreasonable and could arise from a single incident or a state of affairs.
One of the leading cases in this area is a 2018 Court of Appeal case between Network Rail and Mr and Mrs Williams.
The claimants were adjoining owners of two semi-detached bungalows in South Wales. Both of their bungalows abutted a railway embankment and access path which was owned by Network Rail. The railway embankment and path had been infested with knotweed for over 50 years and had persistently spread to the bungalows' land. The Court, when making its decision, took into account that:
"The proposition that damage was always an essential requirement of the cause of action was not entirely correct. The concept of damage in this situation was elastic."
Nuisance can be caused by inaction or omission as well as a positive activity. An occupier could be liable for a continuing nuisance created by another person if, with reasonable or presumed knowledge of its existence, they failed to use reasonable means to bring it to an end when they had more than enough time to do so.
An occupier would also be liable if they failed to act with reasonable speed to remove a hazard on their land that they knew about and where it was foreseeable that it would damage their neighbour's land, such as knotweed.
2024 also saw an important case in this area in the Supreme Court. In Davies v. Bridgend, the Supreme Court allowed the local authority to appeal against the Court of Appeal's decision the previous year in a private nuisance case concerning Japanese knotweed that had encroached on adjoining land.
The landowner originally claimed damages based on the decrease in the value of their property caused by the presence of knotweed, which was coming onto their property from the local authority's neighbouring land.
The first Court found that the encroachment had existed when the landowner brought their property, at a time before an actionable case in nuisance arose, and that meant that the neighbour's failure to treat the knotweed had not in fact materially contributed to the diminution in the value of the property. The decrease in value would have occurred in any event, meant there was no causal link between the breach of duty and the diminution in value claimed.
The Court of Appeal found that if the value of the neighbouring property had decreased as a result of an interference with the quiet enjoyment or amenity due to the Japanese knotweed, then damages in nuisance for the decrease in value would be available. However, the Supreme Court overturned this decision.
Should you buy a house with Japanese knotweed?
There is no issue with buying a house where knotweed might be present in the garden, so long as it is being treated under a care plan and carefully monitored. It is no longer to be feared as it once was.
We can help you bring a claim against a neighbouring landowner if you find that Japanese knotweed is spreading from their land onto yours. Alternatively, we have a wealth of experience defending claims if you find yourself in the unfortunate position of a neighbour claiming that Japanese knotweed is spreading from your land onto theirs.
This information is for guidance purposes only and does not constitute legal advice. We recommend you seek legal advice before acting on any information given.
