A thermoelectric device which zaps plant roots is promising gardeners a new solution to tackling invasive Japanese knotweed without resorting to damaging weedkillers.
The RootWave machine, created by a British start-up, promises to effectively boil the roots of the invasive weed, with an electric tool that delivers 5kv of power directly to the plant.
It has already been trialled by Transport for London, English Heritage and the Arsenal football club, among others.
It will now be offered for homeowners by the Japanese Knotweed Agency, which promises the treatment can be more effective in tackling the problem than chemicals, with the majority under control in the first visit.
A 5-10 year treatment plan will cost around £3,000 and include the operatives and machinery.
Japanese knotweed is one of the most stubborn invasive species in the UK and affects around 1.5m properties. The weed can smother native species, as well as causing damage to buildings, walls and drainage systems.
Homeowners must declare its presence before selling their property, and could face prosecution if they allow it to spread unchecked. It is classified as controlled waste and can only be disposed of at licensed landfill sites.
“Japanese knotweed is exceptionally difficult to kill because it roots so deeply and so extensively,” said Guy Barter, the chief horticulturist at the Royal Horticultural Society.
Thermoelectric treatment provides a potential chemical-free alternative to the use of weedkillers such as glyphosate, amid concern over their impact on the environment.
Green groups say the use of glyphosate can harm biodiversity, especially if the spray hits surrounding insects or plants.
A study last year from researchers at the University of Konstanz in Germany suggested that its widespread use could damage wild bee colonies.
The UK will review the use of glyphosate in 2025, but dozens of councils and organisations have already banned its use on their own land. The RHS is among gardening outlets to have removed the weedkiller from sale.
TfL, which has purchased two Rootwave machines, has found them to be “highly effective”, allowing them to replace the work of 12 with just three employees, according to Craig Ward, a project manager of TfL.
But Mr Barter said that while the theory of thermoelectric treatment is sound, its efficacy remains unproven.
If it lives up to its promises, it would be “a very useful advance in avoiding the use of herbicides,” he said.
“It would be wonderful if it was a silver bullet, but I’ve yet to see any evidence,” he said.
Mr Barter said gardeners should be advised against treating Japanese knotweed themselves with herbicides. “Applying herbicides can beat it down but then the wretched thing, up it comes again two years later,” he said.
Alan Hoey, the managing director of the Japanese Knotweed Agency, said the company had already received enquiries from many homeowners and schools since it launched the service in December.
“Anything that reduces the amount of chemicals used in the UK is a step in the right direction,” he said.
There have been other attempts to tackle the problem without resorting to chemicals. The organisers of the 2012 Olympic Games spent some £70m on a four-year effort to tackle an extensive invasion discovered at the site in east London.
Alongside the use of more traditional weedkillers, developers also dug an extensive trench at the site, where they buried much of the Japanese knotweed.
