Japanese knotweed explosion threatens more property sales

The invasive plant is rife in Britain and spreading quickly to new locations, writes Rachel Mortimer

Homeowners have been warned of a “worrying” increase in Japanese knotweed cases after reports of the invasive plant jumped by almost a third.

There are more than 29,000 cases of the fast-spreading weed confirmed in Britain, a rise of 28pc over the past five years, according to research by Horticulture Magazine.

The plant has “spread like wildfire” and put tens of thousands of homeowners at risk of costly property damage and difficulty selling. Many banks have been reluctant to offer mortgages on homes where Japanese knotweed is present or nearby, rendering the property unsellable in some cases.

In some counties reports of the plant, which is notoriously difficult to kill, have increased by more than 70pc. In South Yorkshire, Hampshire and West Sussex confirmed cases are now 77pc, 73pc and 72pc higher than five years ago, according to Horticulture.

There are thought to be a further 19,700 unconfirmed cases of Japanese knotweed in Britain and experts have warned that thousands more cases are likely to have gone unreported.

Thomas O’Rourke of Horticulture Magazine said: “There has been a worrying increase in confirmed knotweed cases, despite the pandemic having affected data recording at many environmental organisations. The impact on homeowners can be devastating – as well as damage to property, cases can lead to costly civil dispute claims and difficulties when selling your property.” Mortgage lenders usually require a professional treatment plan and insurance-backed guarantee for afflicted properties, Mr O’Rourke added. The presence of Japanese knotweed close to a property can wipe significant sums from its value and can even cause sales to fall through. When purchasing a property buyers are advised to instruct a surveyor to look for evidence of the plant on the premises. But even this can fail. When one landlord bought a £58,000 Victorian terraced house in Aberdare, south Wales, last year he ensured that a surveyor visited the property before completion. He was told there was no Japanese knotweed on the premises and he proceeded to complete

Homeowners can spend thousands solving Japanese knotweed issues

the purchase. However, when a lettings agent visited the house soon afterwards he spotted the feared plant in the garden immediately.

“He spotted it poking up through our decking and we discovered the neighbouring garden was infested,” the landlord said. “When we bought the property one of the options was to do it up and sell it on, but that won’t be possible now. I expect the weed has knocked around 20pc off its value.”

He has now begun a treatment plan that will cost him £3,000 and take five years to eradicate the plant completely. The plan has a 10-year guarantee, but because of the presence of the plant in the neighbouring garden he will not be able to refinance the house. He is now pursuing the surveyor, who he believes is liable for the costs.

Japanese knotweed is often found close to railways because of its historic and widespread use to support tracks and embankments. It is expected to have grown rapidly this year and will “come back even stronger” after a frosty April delayed the growth of other plants.

There have been recent instances of property owners winning substantial payouts from Network Rail and local councils in knotweed disputes. Gary and Sharon McDonald, landlords of The Tame Valley pub in Dukinfield, Greater Manchester, were awarded £8,000 by Tameside Council because of the weed growing from a nearby cemetery on to both their private garden and the pub beer garden.

Earlier this year four homeowners in south Wales won tens of thousands of pounds in a claim in connection with Japanese knotweed which had been growing on their properties for almost a decade. The residents, who live on the same road in Ammanford, Carmarthenshire, settled for a combined £42,500 in damages from Network Rail, which maintains Britain’s railways.

Nic Seal of knotweed specialists Environet said the plant was “without doubt Britain’s most destructive and invasive plant”.

“It’s not illegal to have knotweed growing on your land, but it is illegal to allow it to spread to an adjacent property, which could land you on the wrong side of a legal claim,” he said.

Last year Environet began training sniffer dogs to find knotweed. The dogs can cover a garden in minutes and will “freeze” if they find the plant. The company is so confident of the dogs’ accuracy that they offer a five- year guarantee if knotweed is not detected on a property.

The Royal Institution of Chartered Surveyors recently claimed Japanese knotweed was no longer a “death sentence” for property sales. It said the plant had been demonised by “myths and misconceptions”. But this stance has yet to be adopted by lenders, to which the weed remains a huge red flag.

Mick is one of the sniffer dogs specially trained to detect Japanese knotweed. He can search a garden in minutes

Confirmed cases of the problem plant have soared in some areas