Whitehall, a neighborhood in Darwen, Lancashire, has emerged as the area with the highest number of Japanese knotweed infestations in the UK, according to recent data. The invasive plant, known for its rapid growth and destructive underground root system, can severely damage gardens, devalue properties, and complicate property sales. In the BB3 2 postcode alone, which falls within Blackburn with Darwen, 92 cases of knotweed were recorded. The borough itself has been identified as the most affected, with 2,135 infestations reported, averaging 40 per square mile.
One homeowner, Nathan Hannaway, 33, is currently involved in a civil dispute after discovering a significant knotweed infestation in the garden of his £430,000 home, purchased in August of the previous year. Hannaway claims the infestation was not disclosed by the seller on the TA6 Property Information Form, a document designed to provide buyers with crucial information about a property. The Law Society advises sellers to be truthful on this form, warning that inaccuracies can lead to compensation claims.
Hannaway was quoted £15,000 for the removal of the plant, a cost that has significantly impacted his renovation budget and plans for the garden. He described the excavation as revealing an unbelievable amount of the invasive species. His neighbor, Brian Hartley, 84, noted that knotweed has appeared in his own garden over the 30 years he has lived there, emphasizing its tendency to spread rapidly if not managed.
Wider Impact and Management Efforts
Beyond residential gardens, areas like Blackburn Old Cemetery are also struggling with knotweed infestations. Fresh clumps have been cordoned off to prevent lawnmowers from spreading the plant's fragments. Maurice Ffelan, a member of the Friends of Blackburn Old Cemetery, described the plant as difficult to eradicate, noting its potential to grow up to 10 feet tall and spread significantly in a single season.
Volunteers in the area are reportedly using glyphosate weedkiller injected into the plant's stems in an attempt to kill the extensive underground root system. However, Ffelan cautioned that mowing can inadvertently spread the plant, leading to new outbreaks the following year.
Data from Environet, an invasive plant specialist, which compiles over 100,000 verified sightings, indicates that many of the UK's knotweed hotspots have histories linked to heavy industry, mining, railways, and soil movement. The plant was sometimes deliberately planted to stabilize riverbanks and railway embankments.
Emily Grant, Operations Director at Environet, highlighted that Japanese knotweed "does not respect boundaries" and can lead to legal action if it encroaches onto neighboring properties. She stressed that the stigma associated with the plant can cause substantial financial damage and that ignoring the problem is not advisable. Propertymark, a professional body for estate agents, considers knotweed to be material information that must be disclosed during property transactions, as it can lead to reduced prices, transaction delays, and collapsed sales.