Struggling to deal with Japanese Knotweed in YOUR garden? Scientists test 8 methods to control weeds
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It has been growing unchecked all over Britain since it was introduced nearly 200 years ago.
But scientists reveal it may be possible to rule Japanese Knotweed after testing the most effective ways to manage the rogue plant.
In the assessment of eight different methods, experts found that glyphosate-based herbicides were the cheapest, most durable, and most effective at tackling the alien species.
On the other hand, using cover crops to starve the weeds was the worst method tested, with the highest cost and the most damaging impact on the environment.
These findings come at a time when there are more than 50,000 known Japanese knotweed pests across the UK, dominating gardens, railway lines and vacant lots.
Invasive Japanese Knotweed (pictured) is a known killer of other plant species in the UK
Japanese Knotweed is a known killer of other plants, releasing chemicals that choke their growth and prevent sunlight from reaching them.
The weeds can grow to a soil depth of nearly 40 inches and live up to 20 years, according to pest controllers Japanese Knotweed Ltd.
To spot it, gardeners should look for its recognizable zigzag stem structure and white flowers that bloom in summer.
On its website, Japanese Knotweed Ltd said: ‘When Japanese Knotweed is allowed to spread or disturb, it can grow under sidewalks and buildings and cause structural damage where it finds a weakness in the structure.”
As part of the latest research, numerous herbicides were used to spray plants or surrounding soil, including brands such as Glyfos ProActive, Depitox and Picloram.
Each of the eight methods took a different stance on the use of these herbicides or geomembranes, alternating use in different seasons of the year.
Scientists also changed the amounts of herbicides each with, for example, glyphosate varying between 37 lbs and 47 lbs (16.9 and 21.62 kg) per hectare.
Among other things physical techniques also complemented some approaches, including manually removing knotweed and digging and twisting each underground stem (rhizome).
Glyphosate herbicides are the cheapest and most effective at controlling weeds (file image)
In general, the most effective methods saw glyphosate sterilization applied only in the fall or both summer and fall.
Not only was this considered the most cost-effective, but it also took much less time than other methods.
It also had the least adverse environmental impact with its low concentration of 37 lbs (16.9 kg) and 40 lbs (18.43 kg) per ha.
Geomembranes are said to be the most damaging due to numerous factors, including the plastic required to manufacture them.
Researcher Sophie Hocking, from the University of Swansea, wrote in The conversation: ‘We found geomembrane cladding the most damaging. This was due to the production of the plastics needed to manufacture the geomembranes, as well as the preparation of the soil needed to install them.
‘And we also found that digging as part of a knotweed management program was also less sustainable due to the CO2 emissions caused by the use of machines.
There are over 50,000 known Japanese Knotweed pests across the UK and the plant is notorious for its ability to spread and cause damage to building structures
“In light of the current climate crisis, minimizing greenhouse gas emissions is vital. As we aim to be carbon neutral in the UK by 2050, we need to think carefully about the sustainability of the approaches we use to manage Japanese Knotweed and other problematic invasive plants.”
Controlling Japanese Knotweed has now become a legal requirement in the UK and management costs are estimated to be £165 million a year, according to a Study from 2010.
Despite its presence here, the plant can also survive in extreme environments – be it on the side of volcanoes or in freezing temperatures.
Japanese Knotweed Ltd added: ‘Knotweed can resurface and regrow on its own at any time, but especially if the contaminated soil is disturbed.
“In developing a site affected by Japanese Knotweed and due diligence and monitoring of Japanese Knotweed has not been performed, the developers risk legal action for professional negligence.
“Ignoring knotweed can lead to regrowth during or after construction, appearing through hard and soft landscape areas and even in the fabric of buildings themselves.”
Top tips for protecting your property
Like it or not, knotweed can endanger any property across the country. Check the map to see if you live in an area at risk for the invasive plant.
Simply enter your zip code to check for the number of verified infections within a 4 km radius. The worst affected locations are marked in red, orange and so on.