Japanese knotweed is no longer the deal-breaker it once was, with almost a third of Brits prepared to purchase an affected property, albeit at a reduced price.

As awareness grows of the UK’s most invasive plant and the treatments and guarantees available to deal with it, many homebuyers believe it’s a problem that can be solved.

These are the major findings of new YouGov research commissioned by Environet UK.

While half of those aware of the plant would walk away from a property which had Japanese knotweed, this is significantly less than the 78% figure of two years ago, suggesting people are becoming increasingly pragmatic in their approach to the problem. 

Of those who said they would proceed with the purchase at a reduced price, the majority (26%) would expect a discount of between 6% and 10%, while 15% would expect to knock off just between 1% and 5%. A further 15% would seek to reduce the price by more than a quarter. 

Environet reports that a 10% reduction in the purchase price is typical in cases where property has been affected by Japanese knotweed, dropping to around between 2% and 5% if it has been professionally treated.

Japanese knotweed can now be removed at any time of the year, using a digging-out method that sifts the earth to remove all rhizome roots from the infected soil. Once the problem has been tackled in this way or using a longer-term herbicide treatment and an insurance-backed guarantee has been secured, almost all mortgage lenders will lend against the property and sales can proceed unhindered.

Environet MD Nic Seal said: “With an estimated five per cent of all UK properties now affected by Japanese knotweed, either directly or indirectly, it’s encouraging to see homebuyers becoming increasingly rational in their approach. If left untreated, Japanese knotweed can cause considerable damage to a property which is why buyers and lenders are right to insist that there is a professional treatment plan in place before they agree to proceed. 

“Due to the stigma around Japanese knotweed the property value will almost certainly be impacted, but all that’s required is a sensible renegotiation of the price. People are realising it doesn’t have to be a deal-breaker.”

Paul Raine, director of Expert Surveyors Ltd, added: “The key to selling an affected property is a Japanese knotweed management plan from a reputable specialist. Always be honest if the property you’re selling is or has been affected, or it could come back to bite you in the form of litigation from your buyer further down the line.”

Japanese knotweed was first introduced into the UK from Japan in the 1850s as an ornamental plant, but it is now number one on the Environment Agency’s list of the UK’s most invasive plant species. Growing up to three metres high, it spreads rapidly between May and September and can push up through asphalt, cracks in concrete, driveways, cavity walls and drains.

Environet estimates that up to 900,000 UK households are affected, reducing property values by almost £20bn.

4 July 2019