Japanese knotweed is continuing to impact the UK housing market in 2026, with new research from Environet estimating that around 7% of homes are affected.
If Japanese knotweed is identified on your property, the study shows it can lead to an average property value reduction of about 5%, raising significant concerns for homeowners preparing to sell or renovate.
With millions of properties potentially impacted and homeowners becoming increasingly cautious, the study reveals how a problem many assume is rare could be closer to home than they think.
Article continues belowThe scale of Japanese knotweed across UK homes
Environet’s research suggests that Japanese knotweed now affects around 1.5 million homes across the UK, equating to roughly 7% of the housing stock.
The plant is particularly common in urban and post-industrial areas, where it has spread over decades, but its impact is not always immediately visible.
For homeowners, this means the risk can extend beyond their own garden, with neighbouring infestations also influencing property surveys and sales.
Property values and buyer behaviour
According to the study, homes affected by Japanese knotweed see an average reduction of around 5% for their house prices, which can amount to significant financial losses depending on the property.
Separate polling conducted with YouGov found that many buyers remain wary, with a substantial proportion unwilling to purchase a property affected by knotweed under any circumstances. This ongoing caution continues to affect demand, often leading to renegotiations or failed sales.
Emily Grant, director at Environet, said: “For most people, their home is their biggest asset, yet over 1.5 million households are seeing their property value undermined by knotweed.”
She added that “a significant proportion of buyers still won’t touch an affected property under any circumstance,” despite improved understanding of the issue in recent years.
Costs, delays and long term management for homeowners
Beyond the immediate hit to property values, Japanese knotweed can lead to long-term costs and delays for homeowners.
Treatment plans often take several years to complete and may be required before a property can be sold or mortgaged.
Andrew McColl, chairman of the Residential Property Surveyors Association, said: “Discovering Japanese knotweed can have significant financial implications, as [Japanese knotweed] removal and management plans are often costly and may require anywhere from five to 10 years to fully implement.”
How should this impact homeowners
For homeowners, the findings reinforce the importance of early identification and professional management.
While knotweed does not necessarily make a property unsellable, failing to address it can reduce value, delay transactions and limit buyer interest.
As a result, more sellers are opting for formal treatment plans and guarantees before listing their homes, particularly in Japanese knotweed hotspot areas where the plant is known to be more prevalent.
