Homebuyers in the UK are being warned that they could unknowingly buy a property affected by Japanese knotweed after it emerged that some sellers are failing in their legal obligation to disclose it.

A YouGov survey of over 2,000 people found that 9% of respondents admit they would say nothing when selling a property with knotweed and quietly attempt to deal with it themselves, despite the likelihood of a legal case against them when it’s discovered.

It is a legal requirement for sellers to respond honestly to the Japanese knotweed question on the TA6 form, which is completed as a standard part of the conveyancing process.

Based on approximately 1 million residential transactions that took place during 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 home, unaware that the invasive plant is present. Once a transaction has completed, they have little choice but to either swallow the cost of removal or treatment themselves or pursue legal action against the seller.

Of those surveyed, 3% stated they have already found themselves in the unfortunate position of discovering Japanese knotweed after they purchased a property.

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 photographs of different plants, including bindweed and lilac.

Buyers and sellers who are unsure whether a plant could be knotweed are advised to check carefully online for pictures showing its appearance at the specific time of year, to account for seasonal changes, or commission a professional survey.

Nic Seal, founder of Environet, which commissioned the poll, said: “Discovering knotweed growing in the garden after you’ve bought a property is a very unpleasant and worrying situation to be in. If it can be proven that the plant was present at the time of sale, there is a very good chance of success in a legal case against the seller.

“Therefore, anyone who answers ‘No’ to the Japanese knotweed question on the TA6 form needs to be 100% certain that the property is not affected, which means no live rhizome under the ground of the property or abutting in the neighbouring land. That’s a difficult undertaking, so the general advice is to respond Not known”