Japanese knotweed continues to affect the UK housing market in 2026, with new research from Environenet estimating that around 7% of homes are affected.
If Known as Japanese knotweed On your property, studies show it can drop the average property value by about 5%, which raises significant concerns for homeowners preparing to sell or renovate.
With millions of properties potentially affected and homeowners becoming increasingly cautious, studies show how many rare problems may be closer to home than they think.
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The prevalence of Japanese knotweed in homes across the UK
of the environment Research suggests that Japanese knotweed now affects around 1.5 million homes across the UK, which is around 7% of the housing stock.
The plant is particularly common in urban and post-industrial areas, where it has spread over decades, but its effects are not always immediately apparent.
For homeowners, this means the risk can extend beyond their own garden, with neighborhood nuisances also influencing property surveys and sales.
Property values and buyer behavior
According to the study, homes affected by Japanese knotweed saw an average reduction of 5%. house pricesWhich can amount to significant financial loss depending on the property.
A separate poll conducted with YouGov It has been found that many buyers are wary, significantly unwilling to purchase property affected by knotweed under any circumstances. This ongoing caution continues to affect demand, often leading to renegotiations or failed sales.
Emily Grant, director of Environet, said: “For most people, their home is their biggest asset, yet more than 1.5 million households are seeing their property value undermined by cancer.”
She added that despite a better understanding of the issue in recent years, “a significant proportion of buyers still won’t touch the affected property under any circumstances.”
Costs, delays and long-term management for landlords
In addition to the immediate impact on property values, Japanese knotweed can lead to long-term costs and delays for homeowners.
Remediation plans often take several years to complete and may be required before the property can be sold or mortgaged.
Andrew McCall, Chairman Residential Property Surveyors Associationsaid: “Discovering Japanese knotweed can have significant financial implications, viz (Japanese knotweed) away And management plans are often expensive and may require five to 10 years to fully implement.”
How should this affect homeowners?
For homeowners, the findings reinforce the importance of early identification and professional management.
While knotweed doesn’t necessarily make a property unsaleable, failure 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, especially Japanese knotweed hotspot areas Where the plant is known to be more prevalent.
