The spread of a rapidly-growing plant in a Lancashire village could increase the risk of flooding and cause damage to historic buildings, councillors have warned.
Japanese knotweed has taken root in various parts of Croston - including alongside the retaining walls of the River Yarrow, which burst its banks just over three years ago.
A meeting of Chorley Council’s liaison committee heard that if the rapacious plant weakened the river’s retaining walls, it would make the Boxing Day floods of 2015 “look like a tea party”.
“We owe to it our residents to do something and we should take a lead on it,” Cllr Alan Whittaker told a meeting of Chorley Council’s liaison committee.
He was speaking after Croston Parish Council presented a detailed plan which it had drawn up to tackle the problem.
The strategy involves recruiting volunteers, first to map the areas where knotweed can be found and then to treat it - but that process requires specialist training.
Chemical injections directly into the stem of the plant are thought to be the most effective way to kill it, although that can still take up to four years. However, the cutting or digging up of knotweed can increase its spread by distributing parts of the plant which can grow elsewhere.
Croston parish councillor Peter Fenemore appealed for help from the overarching councils at borough and county level to assist in clearing it from public areas in the village. He added that co-operation from landowners would also be required.
“There is real potential for damaging the infrastructure,” Cllr Fenemore said.
“Knotweed cannot grow through modern concrete, but it can penetrate tarmac and masonry. The foundations of many buildings in Croston are stones stuck together with clay - and knotweed is present quite close to them.”
One councillor also said that local authority staff needed better training to be able to identify the plant.
“It took me three months to get an area of growth acknowledged as being knotweed,” Astley parish councillor, Laura Lennox, told the meeting. “In the end, I told them that if it was found not to be knotweed, I’d eat it.”
Chorley Council’s deputy chief executive, Chris Sinnott, pledged to contact other borough councils to discuss the possibility of developing a strategy to weed out the plant across Central Lancashire.
WHAT IS JAPANESE KNOTWEED?
Japanese knotweed is a perennial plant whose roots penetrate deeply into the ground. It has heart or shovel-shaped leaves, crimson pink buds in spring and a creamy white flower in late summer - but it can easily be confused with other plants.
The weed can grow up to seven feet tall during the summer and dies back in winter. However, it is notoriously difficult to remove and spreads easily, which is why it is classed as controlled waste and has to be disposed off at licensed landfill sites - never in green waste or general household rubbish.
Chemical controls can kill the plant and there are companies which specialise in knotweed removal.
Cutting or strimming should be avoided, because the smallest fragments of the plant can take root elsewhere, worsening the problem. Whilst it is not illegal to have knotweed in your own garden, householders have a responsibility to control it so that it does not have a "detrimental impact" on a wider area.
Anybody selling their home has to declare to a purchaser whether Japanese knotweed is present.
Source: Royal Horticultural Society