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24 May 2024 < Back

Invasive plants: To disclose or knot?

Nic Seal's (founder of Environet) guest blog, Invasive Plants: To Disclose or Knot?, delves into the disclosure obligations regarding invasive weeds in property transactions, particularly focusing on Japanese Knotweed. Nic highlights recent guidance changes and discusses homeowner challenges, legal implications and potential inclusion of other invasives like Bamboo.

There is no clear-cut obligation to disclose the presence of invasive weeds when selling a property, with the notable exception of Japanese Knotweed. But how can homebuyers, sellers and their professional advisers determine if a property is “affected” by Japanese Knotweed? Nic Seal founder of Environet.

New Trading Standards “material information” guidance, published in December 2023 requires estate agents to declare the presence of Knotweed at the earliest opportunity – in other words, on the property particulars. Meanwhile, the updated TA6 form, newly released by the Law Society, contains a revised Knotweed question asking, “Is the property, or an area adjacent to or abutting the boundary, affected by Japanese Knotweed?”.

In this blog I will discuss the impact of these changes, including how a seller is best advised to respond to the TA6 question, the course of action a buyer should then take, and the legal implications where the agent or seller provides false information.

I will also look at the equally problematic invasive Bamboo and consider whether it should be included on the TA6 or under material information guidance in the future.

“Material information” to be disclosed by agents

Over the last few months, estate agents and sellers have been getting to grips with new “material information” requirements which came into force at the end of last year to try and reduce fall throughs. Agents are now required to disclose up front any material information which may affect a buyer’s decision to purchase a property.

Although it’s yet to be tested in court, it’s our interpretation that an agent who is aware of the presence of Knotweed on a property should disclose it on the property particulars, rather than waiting until a buyer is interested. This could make it more difficult to drum up interest in the property. 

Even though agents have long had to disclose Knotweed, it’s far preferable from their point of view to attract a buyer first who is genuinely interested in the property, before explaining its Knotweed history. But under the new requirements, failure to disclose it on sales particulars could amount to a breach under Regulation 6 of the Consumer Protection from Unfair Trading Regulations 2008.

What’s changed on the TA6? 

The revised wording makes it clearer to sellers that they must identify whether there is Japanese Knotweed present not only on their property, but also “adjacent to or abutting” the boundary. The Guidance Notes advise that those who respond “No” must be certain there is no Knotweed present, including rhizome hidden beneath the ground and within three metres of the property. 

It’s difficult for sellers to give a definitive response, since the requirement to know with absolute certainty what’s beneath the ground in your neighbour’s garden (which you may not even have sight of, never mind access to) means it’s virtually impossible to be conclusive. I expect we’ll see even more sellers opt for the “Not known” response, leaving it up to the buyers to undertake their own enquiries. 

The rather ambiguous word “affected” remains. Sellers are caught out all the time by innocently stating “No”, indicating that their property is not affected, without realising that even if Knotweed has been treated or removed by the previous owners, for example, there remains a residual risk and the correct response in such cases would in fact be “Yes”.

In our view, “affected” should include Japanese Knotweed next door, and historical infestations that have been treated or removed, even if there has been no evidence of the plant for several years. This is still not clear enough in the Explanatory Notes. 

How should sellers - and buyers - respond? 

Clearly, if Knotweed is visible or if the seller is aware of its presence, the answer to the Knotweed question is definitively “Yes”.  But that leaves the vast majority who can’t be certain.

For them, the safest response is to tick “Not known” and, for a belt and braces approach, provide accompanying evidence of a professional Knotweed survey with a warranty showing the property to be Knotweed-free to the best of their knowledge.

Where a seller has ticked “Not known”, the onus moves onto the buyer to carry out further investigations. It’s recommended that conveyancers advising buyers in this situation can reduce their risks with a professional Knotweed survey/warranty, or with a Japanese Knotweed indemnity policy before progressing.

If a conveyancer ignores a “Not known” and fails to recommend their client carries out further checks, they themselves could be at risk of a professional negligence claim if Knotweed later emerges.

The RICS Guidance also changed in 2022

In early 2022 Royal Institution of Chartered Surveyors (RICS) published a new Guidance Note for surveyors, following a Parliamentary Inquiry which concluded that the approach to Japanese Knotweed in the UK was ‘overly cautious’. The infamous ‘7 metre rule’ was scrapped, giving surveyors more leeway to use their professional judgement when assessing Knotweed risk. 

In my view, RICS failed to give enough weight to encroachment risk to buyers, since under the new guidance, even if Knotweed is within three metres of the property’s border, which is clearly an encroachment threat, surveyors are only required to flag it in the lowest risk ‘Category D.’

In fact, the presence of Knotweed in an adjacent property is arguably worse than its presence in the subject property since you have no control over rectifying it or forcing the owner to do so. Instead, if the neighbour fails to act, you have no choice but to wait until the moment encroachment occurs before pursuing legal recourse.

On seeing a Category D tick on their survey, homebuyers may be given a false sense of security when in fact the risks are substantial. In my view, Knotweed on an adjacent property should be flagged in ‘Category B’.

It’s certainly possible, likely even, that The Law Society’s revisions to the TA6 wording are a direct response to the ‘dumbing down’ by RICS in 2022, which in my opinion went too far and left homeowners exposed to unnecessary risk. Despite the obvious challenges in doing so, it’s now much clearer to sellers in the actual question wording, rather than just the accompanying guidance, that they must also consider next door. 

Seller ignorance and dishonesty still poses risks to buyers 

The results have just come in from our annual YouGov survey exploring consumer attitudes towards invasive plants. The results show that nearly one in ten sellers would not disclose when selling a property with Knotweed, despite the likelihood of a legal case against them when it’s discovered.

Based on approximately 1 million residential transactions that took place in 2023, with an estimated 5% of properties in the UK affected by Knotweed, as many as 4,500 homebuyers could be duped into buying a property where the plant is present every year.

The survey also showed that despite 77% of people claiming to be aware of Japanese Knotweed, only 12% could correctly identify it from a gallery of six photos of different plants, including bindweed and lilac. Even those who make an honest attempt to check their garden for Knotweed may still unknowingly give a false response.

The legal implications of providing ‘false information’ 

In January 2023, a homebuyer in Raynes Park successfully sued their seller for misrepresentation after he failed to declare that Knotweed was present behind the shed in the garden of the property. The seller had answered ‘No’ to the Knotweed question on the TA6 form and argued that he ‘reasonably believed’ he was telling the truth when he did so.

The judge stated the seller’s case was undermined by his claiming he did not know what was behind the shed, and the fact that there was evidence the Knotweed had been herbicide treated in the past. He was ordered to pay £32,000 damages plus legal costs in the region of £200,000.

In my view, even if no Knotweed is identified, due to the underground rhizome risks, and the fact that for most older properties it will be impossible to know the full history, it’s still safer to answer “Not known” than “No” on the TA6. For agents, to ensure they stay on the right side of material information regulations, Knotweed presence - even historical - should be disclosed at the commencement of property marketing.

Could Bamboo and other invasives be next? 

Bamboo is at least as problematic as Knotweed in terms of the damage it can cause to homes and gardens, and the speed at which it spreads, resulting in a greater propensity for damage compared to Knotweed over a shorter timeframe. Yet, properties with significant Bamboo infestations can be bought and sold with no lending restrictions, and no legal requirement for information to be disclosed by the seller.

There are signs that mortgage lenders are beginning to look more closely at the problem. It’s now becoming more common for Bamboo to be flagged as an issue by a chartered surveyor, which usually prompts a specialist survey and a remediation plan being put in place to satisfy all parties.

A surveying framework and lending restrictions, similar to those applied to Japanese Knotweed, would provide some protection to innocent homebuyers who unwittingly inherit a problem that could subject them to costly removal and repair work - and even a legal claim from a neighbour. I wouldn’t be at all surprised to see this implemented for Bamboo within the next few years and possibly other invasives following thereafter. 

In summary, these combined changes have helped clarify the position on Japanese Knotweed for the benefit of all parties, but time will tell if it results in a reduction in litigation for encroachment, misrepresentation, as well as professional negligence. 

Thank you to Nic Seal of Environet for this in depth and thought provoking blog. 



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