Bristol has retained its position as England’s leading Japanese knotweed hotspot, recording more than twice the infestation density of any other area.
Analysis by Environet identified 1,324 incidences across Bristol, equivalent to 32.29 per square mile. Merseyside ranked second at 13.45 per square mile, followed by Greater London at 7.67. Greater Manchester and Lancashire completed the top five, recording 7.49 and 7.00 incidences per square mile respectively.
The rankings draw on more than 100,000 verified sightings from Environet’s Exposed: The Japanese Knotweed Heatmap, including company enquiries, public records and reports submitted by members of the public.
Former docklands and industrial centres feature prominently in the rankings, reflecting the historic movement of contaminated soil through construction and infrastructure projects.
Environet estimates that Japanese knotweed affects 7% of UK homes, equivalent to more than 1.58m properties. Its research suggests an infestation typically reduces a property’s value by approximately 5%, or £13,500.
The invasive plant can also obstruct property transactions, damage buildings and create legal disputes when it spreads across boundaries.
Emily Grant, director at Environet, says: “Japanese knotweed is now firmly established across England, with former industrial and port areas recording by far the highest concentrations.
“While there are significant hotspots in the south such as Bristol and London, the north of England accounts for more than half of the top 20 hotspots by infestation density.”
