Specialist Environet UK has used data from its interactive online tracker to pinpoint the most prominent locations where Japanese knotweed will grow.
And while Wigan itself isn’t considered a hotspot, it’s surrounded by places that are – with Bolton being the worst-hit place both in Greater Manchester and nationally with 684 infested within a 4km radius.
St. Helens ranked third in the national rankings, reporting 441 infestations.
The knotweed hibernates in winter, but begins to grow in March or April, with red or purple spear-like shoots emerging from the ground that quickly develop into lush green shrubs with pink-speckled stems and bamboo-like canes.
With nearly 55,500 known occurrences of Britain’s most invasive plant, Exposed is the most comprehensive online record of knotweed infestations, charting the plant’s spread across the country.
Users can enter their zip code to know the number of nearby sightings, with hotspots highlighted in yellow, orange, and worst-case red.
The map allows homeowners to understand the risk knotweed poses to their home or one they are considering buying.
For homeowners, the plant can pose serious problems if left unchecked, with the potential to grow through cracks in concrete, paved driveways, paths, drains, and cavity walls. The roots can grow up to 3 m deep and spread horizontally up to 7 m.
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While serious property damage is rare, thanks to a regulation mandating that knotweed must be treated when a property is sold to a buyer using a mortgage or when it encroaches across a garden boundary, it often interferes with the use of the garden and causes litigation between neighbors and can affect the value of a property by around five percent.
Homeowners and buyers unsure if a property is infested with knotweed can now enlist the help of a specially trained trio of sniffer dogs, Mick, Mack and Buddy, who will search a property for the unique scent of the plant’s rhizome, even where they are slumbering underground or have been deliberately hidden.
Knotweed currently affects about five percent of homes directly or indirectly, according to Environet research, but sales can proceed as long as a professional treatment plan with an insurance-backed guarantee is in place to the satisfaction of mortgage lenders.
Nic Seal, Founder and CEO of Environet said: “Japanese knotweed tends to strike fear in the hearts of homeowners, but as long as they are aware of its presence and take steps to remove it before it does serious damage or themselves spreads out neighbor’s property, no need to panic.
“By publishing Greater Manchester 2022 hotspots, we hope to raise awareness and encourage people in the area to watch for signs of knotweed early in the growing season so they can act quickly if needed.
“Anyone who lives near or is moving to one of these hotspots would be wise to carefully survey their yard, enter their zip code into Exposed to find out how many known occurrences are nearby, and when in doubt seek expert help within claim.”