Luke Foot


DATE PUBLISHED: 30 Aug 2023 LAST UPDATED: 21 Jun 2024

Japanese knotweed – a growing cause for concern?

The discovery of Japanese Knotweed, otherwise known as fallopian japonica, can be a headache for homeowners as it can prove expensive to both remove the plant and repair the damage caused. The invasive plant can not only decrease the value of a property, but may also hinder the owner’s ability to sell, insure and mortgage.

Homeowners only need to carry out a quick search online to discover the Japanese Knotweed hotspots in their local area. This year, statistics suggest that Weymouth, Lyme Regis and Charmouth are Dorset’s hotspots.

Below we explore the impact of a recent Court decision concerning this topic.

Sellers beware

Earlier this year, in the case of Downing v Henderson, the purchaser of a £700,000 house in South West London successfully sued the seller for misrepresentation and failing to disclose that the property had a knotweed infestation.

The case came about after the seller had completed the Property Information Form, a standard form used in the conveyancing process, and answered “No” to the question of whether the property was affected by the plant. However, expert evidence later showed that Japanese Knotweed had previously stood up to 2 metres tall in the garden to the property and had been treated with herbicide in the past. Accordingly, the Court found that the seller would have reasonably known about the Japanese Knotweed and, particularly, at the time it was sold.

The Court ultimately ruled in favour of the purchaser and awarded £32,000 (representing the cost of removing the knotweed and reduction in value of the property) plus £92,000 as to legal costs.

This ruling not only highlights the importance of being entirely transparent during the conveyancing process, but also emphasises the need to deal with Japanese Knotweed both promptly and adequately.

Neighbouring infestation

Another circumstance where a homeowner may need to deal with Japanese Knotweed is when it derives from neighbouring land but has encroached onto their property. In this instance, the cause of action will differ from the above and, instead, could create a case for damages under the tort of nuisance.

A few years prior to Downing, in the case of Network Rail Infrastructure v Williams, it was established that encroachment of Japanese Knotweed can give rise to a nuisance claim despite there being no physical damage caused.  Instead, the very presence of Japanese Knotweed spreading from the neighbouring land was sufficient it itself as it posed a risk of future physical damage to the property. The Court ultimately found that this nuisance caused interference to Mr Williams’ quiet enjoyment of his property and, as a result, he was entitled to damages from his neighbour.

Alternatively, the Court has also found, particularly in Smith v Line, that injunctive relief is available for homeowners whose neighbours have allowed Japanese Knotweed to encroach onto their property.

Public Bodies

Leading on from the above, it is of course not always the case that your neighbour is a private individual, it may well be that the neighbouring land is owed by a public body, such as Network Rail or perhaps the local Council.

In the very recent case of Davies v Bridgend County Borough Council, it was found that the Council’s land had the knotweed infestation and, despite treatment, continued to encroach onto the neighbours’ land. The Court ultimately found that the knotweed was a ‘continuing nuisance’ and awarded Mr Davies damaged that reflected the diminution in the value of his property.

The points to take away

Homeowners should take caution and consider the following:

  • Survey: The potential purchaser of a property should be mindful as to whether their homebuyers survey will also investigate and report on Japanese Knotweed. The purchaser may need to instruct an independent Japanese Knotweed survey if they have any concerns regarding the possible presence of this invasive plant.
  • Insurance: As for the Seller, whilst the existence of Japanese Knotweed on their property may scare off potential purchasers, having an insurance backed treatment plan for the issue should be considered.
  • Mortgage: Pursuant to the terms of the loan, mortgage lenders often require the borrower to disclose the existence of Japanese Knotweed immediately once discovered. Upon being notified, the lender may expect the homeowner to instruct a treatment plan which can prove costly. In other circumstances, the prospective purchaser may face having its mortgage offer denied or withdrawn.

Lastly, a homeowner dealing with a Japanese Knotweed issue should seek immediate legal advice.

How can Ellis Jones help?

If you would like to discuss any issues relating to the above, please contact a member of our Dispute Resolution team on 01202 525333 or by emailing who can advise on the best approach.

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