Britain's largest knotweed jungle grows along the River Roding, threatening riverside homes

A three-mile stretch of the River Roding in east London is emerging as Britain’s largest knotweed infestation, a developing crisis that advocates say could leave riverside homes unsellable if not controlled. The invasive plant has spread along both banks, intertwining with native reeds and choking scrubland as it advances toward newbuild estates that sit just yards from the water. Volunteers and local custodians of the river say the problem has been building for years and now demands urgent attention.

The knotweed has overtaken acres of riverbank habitat on the east London stretch, with local volunteers from Protect Earth and the River Roding Trust reporting that the infestation runs the length of the three-mile tidal section. River guardian Paul Powlesland described the spread as a relentless progression that has already displaced reed beds, nettles and other plants: "There are acres that should be full of reed beds, rich nettle and plants but the only thing alive is knotweed." He warned that if the plant continues to advance, remediation could cost millions and push flats closer to the water into an unsellable category.

Knotweed spreads via underground rhizomes that can form a crown extending up to seven metres. The plant can grow through tiny cracks, walls and even concrete, and experts say it threatens nearly a million homes across the UK. Environment Agency officers have described Japanese knotweed as indisputably the UK's most aggressive, destructive and invasive plant. Removing it is notoriously difficult: the most effective approach relies on a narrow spraying window—the period after flowering and before the first frost—when herbicides can reach rhizomes rather than just the aboveground stems.

Those working to treat the River Roding site say they are racing against time. Phil Sturgeon, a volunteer with Protect Earth, said the crew sprays during dry spells and notes that the window is closing: "We’re spraying it with glyphosate, which is controversial but it’s the only thing that works. In September, the saps and sugars go down into the roots and when we spray them the glyphosate hops on and goes down into the rhizomes. This then kills the whole plant rather than just the stem, but it has to happen two or three weeks before frost." He estimated the entire affected area would cost hundreds of thousands of pounds to clear.

The river’s edge is framed by tidal reeds, which capture carbon and filter sewage, while also supporting birds and insects. The encroachment of knotweed creates what Powlesland calls "dead space" along the river and raises concerns about broader ecological damage. He noted that knotweed can ride on tidal currents, breaking off and spreading to new locations, compromising the biodiversity of the corridor and threatening nearby infrastructure.

Local residents, many of whom were unaware of the scale of the invasion, described how the issue has not been on their radar. Asif Noaman, a local postman, said he talks to residents daily and has found that about 400 people on the estate know little about the knotweed. "There are around 400 people that live on this estate and they need to be made aware of this, it’s absolutely terrifying," he said. Javed Iqbal, a resident who moved to the area for its riverside appeal, expressed frustration at the situation: "We love the river, my twin girls play around here. It’s ridiculous, we can’t afford to move anywhere else. But I don’t see how a plant could do that."

Experts warn that the knotweed’s impact goes beyond aesthetics. Emily Grant, director of operations at Environet, said the river edge provides a fertile ground for knotweed to spread, and that treating miles of infestation would require substantial investment. "If treated professionally, the damage would cost hundreds of thousands of pounds. The reality is a lot of areas are already too far gone. It would take a huge investment to bring it back around. If it does start encroaching onto private property then those property owners would be able to write to the land owner and if they failed to do anything they could bring a claim against them," she said. Grant added that the plant’s rhizomes can be carried along watercourses, meaning the problem can migrate from one breach to another and threaten broader ecological balance, making the knotweed a significant environmental concern.

A Transport for London spokesperson said the agency is aware that some land by the River Roding has been affected and that measures are already being taken to treat and control the knotweed. Network Rail indicated it was not currently aware of specific issues but said it would investigate if a location or concern is identified and encouraged anyone with information to come forward. The Daily Mail has sought comment from DEFRA and the Environment Agency.

The case highlights a broader tension at the intersection of climate, ecology and infrastructure. Knotweed’s aggressive spread undermines riverbank habitats that sequester carbon and provide ecological services, and its potential to compromise rail and road corridors raises questions about resilience in flood-prone, urbanized river systems. Advocates urge a coordinated government response—mapping the extent of infestations, funding containment, and enforcing remediation strategies—to prevent further spread and protect both ecosystems and property values.

The knotweed issue on the River Roding sits at the intersection of urban development, environmental management and climate-driven pressures on local ecosystems. While the plant’s precise origins along the river remain unclear, experts note that knotweed was introduced to the UK in the 19th century as an ornamental species and has since become a persistent threat to biodiversity and property across the country. In many cases, the costs of containment and restoration can run into hundreds of thousands of pounds, reflecting not only the scale of the problem but the long-term investment needed to prevent recurrence as climate patterns shift and urban ecosystems evolve.