If you have Japanese knotweed in your garden – or suspect it may be present – you may be wondering whether you have to remove it, whether you need to tell a buyer and whether it could prevent you from selling your home.
The good news is that having Japanese knotweed on your property is not, in itself, illegal. However, what you tell a buyer about it is important. Giving an incorrect or misleading answer could potentially lead to a legal claim long after the sale has completed.
Japanese knotweed is an invasive plant that can grow rapidly and spread through its underground root system, known as rhizomes. It can grow through cracks and gaps in hard surfaces and, in some circumstances, cause damage to structures. It can also affect the value and mortgageability of a property. Importantly, you are not automatically required to remove Japanese knotweed from your own garden.
However, there are legal restrictions around allowing it to spread in the wild and disposing of it. Japanese knotweed and soil containing its roots are also classed as controlled waste, meaning they cannot simply be put in a household or garden waste bin. If the plant is spreading, you could also face action from a local authority. For most property sellers, however, the biggest legal risk comes not from having the plant – but from what you tell the buyer about it.
When selling a residential property, your solicitor will normally ask you to complete a TA6 Property Information Form.
Since 30 March 2026, Law Society Conveyancing Quality Scheme (CQS) firms have been required to use the sixth edition of the TA6 for new residential sales. The latest version is shorter and written in plainer language than the previous edition. The form specifically asks about Japanese knotweed. Questions 8.6 and 8.7 ask whether the property is affected by Japanese knotweed and whether there has been a survey or management plan.
Importantly, the form provides three possible answers where appropriate:
The inclusion of “not known” is helpful because Japanese knotweed can sometimes be difficult to identify, particularly where it is dormant or underground. The Law Society’s guidance generally considers a property to be at risk where Japanese knotweed is growing on the property or within three metres of the boundary.
The key principle is simple:
Answer the questions honestly and based on what you know.
If you genuinely do not know whether Japanese knotweed is present, “not known” may be the appropriate answer. However, you should not use “not known” to avoid disclosing something you are already aware of.
For example, if you know that Japanese knotweed was previously found in the garden and treated, you should disclose this. Simply ticking “not known” because the plant is no longer visible could potentially be misleading.
A particularly important point for sellers is that ticking “no” is not simply saying that you have not personally noticed Japanese knotweed.
It is a positive statement that the property is not affected.
If a buyer relies on that answer when deciding to purchase the property and later discovers that Japanese knotweed was present, they could potentially bring a claim for misrepresentation.
In a 2023 County Court case, a buyer purchased a property in southwest London for £700,000.
The seller had answered “no” to the Japanese knotweed question. After moving in and clearing the garden, the buyer discovered Japanese knotweed behind a bush near the shed. The seller argued that he genuinely believed his answer was correct because the plant had been hidden. However, expert evidence showed that the knotweed had previously grown to around two metres high and had been treated with herbicide while the seller owned the property. The court found that the seller could not genuinely have believed that the property was unaffected.
He was ordered to pay approximately £32,000 in damages, together with the buyer’s legal costs, which could be as much as £95,000. The overall financial consequences were therefore substantial.
The sixth edition of the TA6 makes it clearer that “not known” can be a legitimate answer.
Japanese knotweed can remain dormant underground, and it is not always possible for a homeowner to know whether it is present without specialist investigation. If you genuinely have no knowledge of Japanese knotweed at your property, you should not feel that you have to commission an expensive survey simply to be able to complete the form. However, if you have previously been told about Japanese knotweed, received treatment, had a survey carried out or have other information suggesting it may be present, you should tell your legal advsier.
If you discover Japanese knotweed – or receive new information about it – between completing the TA6 and exchanging contracts, tell your solicitor straight away. They can advise you on what needs to be disclosed to the buyer. It is always better to raise the issue early rather than risk the buyer discovering it later.
Japanese knotweed can create another potential legal issue if it spreads onto neighbouring land.
In Network Rail Infrastructure Ltd v Williams [2018] EWCA Civ 1514, the Court of Appeal confirmed that a neighbour may have a claim where Japanese knotweed roots encroach onto their land, even if there has not yet been physical damage.
However, the Supreme Court’s decision in Davies v Bridgend County Borough Council [2024] UKSC 15 clarified that the timing and cause of the loss are important. In that case, the claimant could not recover for a reduction in value that had already occurred before the council was in breach of its duty. If Japanese knotweed is close to your boundary, it is sensible to deal with the issue rather than assume that there is no potential liability.
There is a common misconception that a property affected by Japanese knotweed cannot be mortgaged. That is no longer the general position.
The previous seven-metre rule has been replaced by a more proportionate approach. The RICS professional standard introduced four management categories, based on the actual risk and impact of the Japanese knotweed rather than simply measuring its distance from a building.
This means that the presence of Japanese knotweed does not automatically make a property unmortgageable. However, individual mortgage lenders may have their own requirements, particularly where the infestation is considered serious or is affecting a building or the use of the garden.
Don’t panic – and don’t try to deal with it yourself with a spade and weedkiller.
Instead:
1. Tell your legal adviser
Be open about what you know, including any previous treatment or surveys.
2. Get specialist advice
Consider arranging a survey from an appropriately qualified specialist, such as a contractor accredited by the Property Care Association or the Invasive Non-Native Specialists Association.
3. Get a management plan if treatment is required
If treatment is recommended, ask for a written management plan and appropriate insurance-backed guarantee.
A transferable guarantee can provide reassurance to both the buyer and their mortgage lender.
4. Keep the paperwork
Keep copies of surveys, treatment records, management plans, guarantees and invoices.
These documents can be valuable when selling the property and help demonstrate that the issue has been identified and properly managed.
If you’re selling a property and are unsure how Japanese knotweed could affect your sale, our property and conveyancing team can advise you on what you need to disclose and help you understand your options.
