Japanese knotweed hotspots in Lancashire revealed in map

The latest data from Environet shows how many infestations of the plant have been recorded in the county.

Some areas are known to have more Japanese knotweed than others – let’s take a look.

What is Japanese knotweed and why is it a problem?

Japanese knotweed is an invasive plant that can cause chaos in our homes and gardens.

Environet's latest data shows that 857 infestations were recorded in Preston alone (Image: Environet)

The plant “is a fast-growing and strong clump-forming perennial, with tall, dense annual stems. Stem growth is renewed each year from the stout, deeply-penetrating rhizomes (creeping underground stems).

“Although orginally introduced to Britain as an ornamental garden plant, Japanese knotweed is an invasive non-native species”, explains The Royal Horticultural Society (RHS) website. 

Japanese knotweed hotspots in Lancashire

According to Environet, Japanese knotweed has been found in Lancashire – 3,530 infestations to be exact.

Its latest data shows that 857 of these infestations were recorded in Preston while a further 541 were spotted in Blackburn.

Chorley has 365 infestations while Burnley has 310.

In Accrington, 236 infestations have been recorded.

Preston ranks in 5th place on the national Japanese knotweed hotspots list, after Swansea, Bolton, Bristol and Cardiff.

With a total of 3,530 known infestations across Lancashire, there are 1.1 occurrences of knotweed in every 1km2.

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Nic Seal, founder of Environet, said: “At this time of year knotweed has emerged from the ground and by the end of April or early May it will be growing as much as 10cm per day and covered in bright green heart-shaped leaves.

“The best way to protect your property is to make sure you know what knotweed looks like, so you can act early if it appears in your garden or is threatening to encroach onto your property.

“Yorkshire is home to some significant knotweed hotspots such as Rotherham and Sheffield. Anyone living near or moving to one of these areas should check their garden carefully and enter their postcode into Exposed to find out how many occurrences are nearby and if in doubt, seek expert help.”