Britain's three-mile knotweed jungle along River Roding could leave riverside homes unsellable

A three-mile-long invasion of Japanese knotweed along the River Roding in east London is feared to be the largest in Britain, with residents warned the infestation could render nearby homes unsellable. The knotweed intertwines with native reeds along both riverbanks, overtaking scrubland and creating what conservationists describe as dead space along a tidal stretch that supports wildlife and carbon-absorbing vegetation.

River guardians and volunteers say the knotweed has spread the full length of the river’s easterly reach, with newbuild estates located just yards from the water. Paul Powlesland, river guardian at the River Roding Trust, said the species has been spreading for years and is now “taking over an entire bank,” leaving acres that should be reed beds and other plants dominated by knotweed. He warned that if the plant advances further, remediation could cost millions of pounds and potentially make nearby flats unmortgageable.

The knotweed spreads via underground rhizomes, a characteristic that makes it exceptionally difficult to eradicate. Rhizomes can form a crown at the plant’s center and extend up to seven metres, allowing the weed to push through tiny cracks, walls and even concrete. Experts say the threat is widespread: the plant can affect close to a million homes across the United Kingdom and can cost homeowners thousands in damages and removal costs. Removal remains challenging because it is only effectively killed within a short spraying window—between flowering and the first frost.

Volunteer groups working to contain the River Roding infestation face time pressure. Phil Sturgeon of Protect Earth, the charity aiding the river, said they are racing against the weather and the season, noting that spraying with glyphosate is controversial but currently the only method that works for killing the root system. He added that the operation has a limited window and that they have only a couple of weeks left before frost ends the spraying period. The effort is undertaken amid broader concerns about the climate crisis and the role of local action in preserving ecosystems and infrastructure.

Environmental and property impacts extend beyond aesthetics. The river edge is lined with tidal reed beds that absorb carbon, naturally filter sewage, and provide habitat for birds and insects. When knotweed dominates, those ecological functions are displaced. Emily Grant, director of operations at Environet, said the affected area would cost hundreds of thousands of pounds to clear if addressed professionally, and in private properties, owners could pursue remedies or even claims when a landowner fails to act. Grant emphasized that the rhizome system can be carried along watercourses, spreading the problem downstream and cross-border, which complicates containment efforts.

Local residents reported they were unaware of the knotweed’s growth until recently. Asif Noaman, a nearby postman, said many neighbors had no idea a problem existed and that awareness among the roughly 400 residents on the estate was essential to prevent further spread. Javed Iqbal, a resident, spoke of his concern for his family and the community, acknowledging the threat while questioning how a plant could have such a broad impact.

Transport and infrastructure interests are not untouched by the infestation. Parts of the land along the river are owned by Transport for London and Network Rail, and the encroachment has prompted concerns about potential damage to railway lines and other critical assets. TfL stated it is aware that some land by the River Roding has been affected and that measures are underway to treat and control knotweed. Network Rail indicated it was willing to investigate specific locations if concerns are identified. Inquiries to DEFRA and the Environment Agency regarding the knotweed situation were pending at the time of reporting.

The case highlights the economic and ecological stakes of invasive species on urban waterways. Knotweed, long recognized by the Environment Agency as one of the UK’s most aggressive and destructive invasive plants, continues to challenge conservation groups, municipalities, and homeowners alike. Without coordinated government plans to map and contain outbreaks, experts warn that costs could escalate as patches multiply and spread along further reaches of river systems. Analysts say early, comprehensive intervention—paired with ongoing maintenance—offers the best chance to mitigate long-term damage to both properties and ecosystems.

As authorities and agencies weigh their next steps, residents on the River Roding face an uncertain horizon. The knotweed’s advance underscores the need for timely action, sustained funding for eradication efforts, and clearer guidance for communities living beside vulnerable waterways.