Bristol records highest density of Japanese knotweed in England – Environet
The city reported 32.29 incidences per square mile, more than twice the density seen in Merseyside at 13.45.
Bristol remained the Japanese knotweed capital of England in 2026, according to figures from Environet’s Exposed: The Japanese Knotweed Heatmap.
The city reported 32.29 incidences per square mile, more than twice the density seen in Merseyside at 13.45.
Greater London ranked third with 7.67, followed by Greater Manchester and Lancashire.
Knotweed was present in every county, with an average of 1.1 occurrences per square mile in England and 3.9 in Wales, impacting more than 1.58 million homes.
Emily Grant, director at Environet, said: “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.
“My advice to anyone living or buying a home in a Japanese knotweed hotspot is to familiarise yourself with what it looks like and check your garden regularly during the growing season.”
Grant added: “At this time of year, an established knotweed plant can be identified quite easily by its hard bamboo-like canes and distinctive bright green shield-shaped leaves which grow in a zig-zag pattern along the stem.
“The earlier it’s spotted, the easier and cheaper it is to deal with, and with a professional treatment plan in place homeowners have a much better chance of preserving the value of their property.”
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