AN ONLINE map shows the severity of Japanese knotweed sightings across the UK.

The heatmap reveals that, in central Reading alone, there have been 67 reported knotweed occurrences within a 4km distance of the town.

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The plant is becoming a highly litigious issue among both homebuyers who unwittingly purchase affected properties and homeowners who are subject to encroachment of the invasive plant from neighbouring properties, according to new research released by YouGov and Environet UK.

In a survey of more than 2,000 British adults, two thirds (66 per cent) of people in the south east who are aware of the plant would sue the seller if knotweed was discovered after they bought a property.

Due to the cost of treatment and the potential negative impact on a property’s value, it’s tempting for sellers to claim ignorance of a Japanese knotweed problem.

But as awareness of Japanese knotweed grows, now standing at 81 per cent in the south east, people are becoming better informed about the laws that govern both the sale of affected properties and those that protect victims of encroachment – and a large proportion are willing to pursue litigation if necessary to recover their losses.

To view the map and check your postcode area, click here.

Nic Seal, Founder and MD of Environet UK said: "Now more than ever it’s vital that sellers are honest and declare that there is, or could be, knotweed growing on their property.

"Awareness among the general public is now so high and there’s such a strong precedent set in the courts that it’s likely they will end up paying the price further down the line if they answer dishonestly or claim not to know of its presence.

"In fact, it’s quite easy for a Japanese knotweed expert to tell how long an infestation has been there and, in encroachment cases, the source of the infestation."

Awareness of the law around encroachment is also high, with 71 per cent of respondents in the south east realising they could be liable for the cost of treatment if Japanese knotweed originating on their property spreads to their neighbour’s land.

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However, only one third (32 per cent) were aware they could also be liable for all legal fees and just 23 per cent knew that they could also be liable for diminution, or fall, in the value of their neighbour’s home.

This can easily run into tens of thousands of pounds – or much more if the knotweed encroaches into multiple properties.

Homeowners can easily face bills of around £30,000 from an encroachment claim, rising to £70,000 or more if the claim succeeds in court. If the knotweed spreads to more than one property then the bill could climb even higher.