Japanese Knotweed is wiping £21.4billion off the value of property in the UK, new estimates suggest.

More than 1.5 million homes are affected, according to research from invasive plant removal specialist Environet.

And property values are typically reduced by around 5%, equivalent to £13,500 per home.

Knotweed ‘stigma’

Sellers are legally required to declare the presence of Japanese Knotweed, which can deter buyers even after an infestation has been treated.

This ongoing knotweed stigma continues to weigh on saleability and property values, according to Environet.

Separate research conducted by Environet found almost a third – at 32% – of people would not buy a property impacted by Japanese knotweed under any circumstances.

While a similar number would consider it if there was a professional treatment plan in place, and an appropriate discount on the price.

In response, sellers are increasingly moving away from cheaper herbicide treatment, which controls but does not fully remove the plant, opting instead for excavation where the root system is dug out of the ground, Environet says.

A significant proportion of buyers still won’t touch an affected property under any circumstances.”

Emily Grant, Director at Environet, says: “Despite the fact knotweed is now much better understood than it was a few years ago, and many people are now quite pragmatic about it, a significant proportion of buyers still won’t touch an affected property under any circumstances.

“As a result, we’re seeing a clear shift towards permanent removal of knotweed, particularly where a sale is on the horizon and the priority is preserving value and avoiding delays.”

And Andrew McColl, Chairman at the Residential Property Surveyors Association (RPSA), says: “Discovering Japanese Knotweed can have significant financial implications, as removal and management plans are often costly and may require anywhere from five to ten years to fully implement.”

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