Japanese Knotweed

Posted 1 week ago

Japanese Knotweed… The scourge of construction & railway workers

Listed by the World Conservation Union as the world's most invasive species, it is the scourge of railway workers, construction engineers and householders alike. Japanese Knotweed is a tenacious foreign invader native to Asia that companies such as ourselves commonly encounter whilst out on site. What's more, it's something that our ecology surveyors are regularly asked to investigate and report upon.

Japanese Knotweed arrived in Europe in the 1820s as a decorative plant, with gardeners attracted to it for its similarity to bamboo. It can reach 3 metres in height, and its roots can spread to more than 6 metres underground.

The ability to thrive in all types of soil plus a complex and destructive root system make it a particular threat to buildings and infrastructure. It costs the UK government millions of pounds every year to manage and eradicate and can even prohibit people from selling their homes.

Plans for the eradication of Japanese Knotweed range from mass extermination (currently considered too expensive an option at just over £1.5 billion) to the introduction of a knotweed controlling louse. It remains a massive problem in the UK but earlier this autumn a brand new code of practice was released with guidelines for managing Japanese Knotweed.


The problem of Japanese Knotweed

Japanese Knotweed's invasive nature and resilience to hostile environments means that it can, and does, cause extensive damage to properties, road verges, rail infrastructure and flood defences with a powerful root system capable of forcing its way through brick and concrete.

The successful eradication of knotweed is challenging, time-consuming and, as mentioned, costly. It can cause significant problems for people trying to sell their homes as lenders have been known to refuse a mortgage on an affected property or even properties in a neighbourhood where knotweed is present. The cost to homeowners in terms of falling value and treatment of knotweed is currently estimated at £166 million per year.

The new document was developed by the Invasive Non-native Specialists Association (INNSA) to replace the now defunct Environment Agency publication Managing Japanese Knotweed on Development Sites.

Since its launch at the end of September 2017, Code of Practice - Managing Japanese Knotweed has become the most downloaded document on the Environment Agency’s website.

Chairman for INNSA, James Sherwood-Rogers, said: “Expected to be a go-to document for all developers, planners and contractors who may encounter Japanese knotweed in the course of their work, the new Code of Practice will provide a clear understanding of what is required and recommended when managing infested land in an appropriate way.”


Knot in North Wales

The destructive nature of Japanese Knotweed coupled with the lure of lucrative financial gain has led to the establishment of many specialist companies dedicated to the eradication of the weed. In North Wales, a former call-centre worker set up in business after being moved by the plight of an elderly householder.

Iestyn Jones of Dolgellau, said: “When I was working for Natural Resources Wales, I took a call from an elderly lady who was very distressed by her Japanese Knotweed.

“As she had no internet access, I did some research for her but a Google search returned no results for any professional removal firms in North Wales."

In 2013, Iestyn visited the Royal Welsh Show and made contact with an organisation that delivered courses in pesticide applications. He was awarded a specific Japanese Knotweed qualification and has since launched his own business in North Wales.

Utilising the latest technology, Iestyn's company, Japanese Knotweed Removal Wales (JKRW), has recently formed a partnership with a licensed drone operator to survey infestations. Clear, up to the minute data obtained from the drone footage is already proving to be more effective than a reliance on Google maps alone.

He said: “I am confident that we can show clients a 50% reduction in knotweed each year, leading to eventual eradication."

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