WITH the summer growing season well and truly over, an invasive plant specialist has revealed Cheshire Japanese knotweed hotspots for 2024.

Analysis by Environet is based on the latest data from the specialist’s online tracker, which is updated with new verified sightings reported by Environet’s team and members of the public throughout the year.

Now populated with almost 60,000 known infestations of Japanese knotweed, Exposed: The Japanese Knotweed Heatmap has monitored the spread of the plant species across the UK over the last six years, helping homeowners and buyers stay informed about the risk level near their property.

Users can enter their postcode to discover the number of knotweed sightings nearby, with hotspots highlighted in yellow, orange and, in the worst affected locations, red. Tapping into the growing trend for citizen science, people can also add sightings to the heatmap if they suspect a plant may be knotweed, by uploading a photo to be verified by experts.

There are a total of 1,319 verified knotweed sightings in Cheshire, or 0.56 incidences in every 1km². In the national Japanese knotweed hotspots list, Cheshire is the 13th worst affected county in England.

Chester has the fifth highest number of incidences in the county, with 110 encounters with the invasive species recorded. Northwich (116), Widnes (121), and St Helens (242) all have more, with Warrington having the highest number (284).

Over the next few weeks knotweed will start to die back, as temperatures cool and light levels drop, sending the plant into its dormant winter phase. Its green leaves will die and fall from the branches, the stems will turn brown and brittle, and after the first few frosts the plant will have completely died back, leaving only the dead canes remaining. However, the plant will re-emerge next spring, so autumn and winter is the ideal time to excavate it when the garden is not in use.

Tackling knotweed costs the UK economy nearly £250 million a year and homeowners are one of the groups most at risk – not only from potential damage to their property, outbuildings and gardens, which can be costly to repair, but also from legal risks arising from encroachment or when properties are sold. Whilst it isn’t illegal to have knotweed growing on your land, legal disputes can arise when it’s allowed to spread across property boundaries and when sellers fail to declare it to buyers.

Environet estimates that approximately 5 percent of homes are currently affected by Japanese knotweed, either directly or neighbouring an affected property, typically impacting property prices by around 5 percent - or up to 10 percent in severe cases.

Emily Grant, director of Environet, said: “With over 60,000 known infestations of Japanese knotweed on our heatmap, we have a clear picture of its prevalence across the England and Wales. Knotweed is easily identifiable during summer, but it’s a perennial plant so as we head through the autumn and into winter, the above-ground growth dies back and it becomes much harder to spot.

“The best way to protect your property is to be aware of the risks and ensure you can identify knotweed at different times of the year. If you do have knotweed on your property, it’s wise to act immediately to treat or remove it before it has the chance to spread further. With professional assistance knotweed can be dealt with and the value of a property largely restored. If you’re buying or selling a property, consider instructing a Japanese knotweed survey to check for any sign of the plant on the property and its surroundings.”