Japanese knotweed against house front landscape Japanese knotweed against house front landscape

Warm, wet winter triggers “unprecedented” demand for Japanese knotweed management

Warm and wet conditions throughout winter and spring is leading to unprecedented demand for invasive plant management, a plant expert has warned.

The speed of spring growth of Japanese knotweed is creating additional summer challenges for property developers as the spread of this and other invasive plant species threatens building projects, landscaping and properties. 

Andrew Ford, director of invasive weed specialists Inspectas Land Remediation, said: “The presence and damaging effects of Japanese knotweed is well-known and documented, but what we have seen this year more than any other, is how the early emergence of its growth in the spring is impacting projects in the summer.

“The speed of the spread is quite staggering but when you consider that Japanese knotweed originated in a hostile, volcanic landscape and can regrow from a root fragment that’s no bigger than a fingernail, it’s easy to see why, with the right conditions, it is flourishing in 2024 and becoming even harder to get rid of.

“Because Japanese Knotweed is already a significant problem for property developers and land-owners, we are urging fast action if an infestation is suspected because the wet spring conditions have been perfect for rapid growth and damaging spread.” 

Listed by the World Conservation Union as “one of the world’s most invasive species”, Japanese knotweed was introduced into Great Britain in 1825 and today costs UK developers and homeowners millions of pounds per year to manage and eradicate as its aggressive root systems and speed of growth takes its toll on concrete, brick work, tarmac and the value of property prices.

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Traditional means of controlling Japanese Knotweed using Glyphosate herbicide – a process administered by local authorities and specialists across the country – can be a good starting point. However, according to Andrew, the problem runs far deeper.

“Japanese knotweed has above-ground and below-ground propagules that can extend as deep as 2-3m making it even harder to control with chemicals. Using too much chemical, or applying chemical at the incorrect time of the year can seriously thwart any realistic possibility of bringing the plant under control,” Andrew continued. “Disturbing the soil around the Japanese knotweed should also be avoided because this can lead to new growth and expansion into areas previously not affected.”

He added: “The best solution is to arrange a survey with a specialist for fast identification and a plan of action – whether complete eradication through excavation or administering just enough herbicide to put the plant into dormancy.

“Spring and summer are always busy times for any land remediation project but following this year’s exceptionally wet winter and perfect spring growing conditions, we are experiencing unprecedented demand for identification and management of this resilient and aggressive plant that has the potential to wreak havoc on landscapes, infrastructure and ecosystems.”

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