Map reveals Japanese knotweed hotspots in UK as invasive plant wrecks thousands of homes – is your town on the list?
Tackling knotweed costs the UK economy nearly £250million a year
THE worst areas in the UK for Japanese Knotweed have been revealed with more than 50,000 infestations across England and Wales.
On average there is one occurrence of the invasive plant in every 3km².
South Wales is one of the worst affected regions, with four locations on the national hotspots list – and nearby Bristol has the highest number of sightings of any location in England.
Swansea tops the list with 1,350 infestations while Bristol is not too far behind with 1,121.
Bolton, Greater Manchester, is in third place with 1,010 infestations.
The invasive plant specialist has drawn up a map to see which are the worst affected areas.
Japanese Knotweed usually emerges in March or April and grows rapidly to reach a maximum height of just more than 8ft by mid-summer.
It can be identified by its hard, bamboo-like canes and distinctive shield-shaped bright green leaves which grow in a zigzag pattern along the stem.
Mature plants flower in August, becoming covered in clusters of delicate tasselled creamy-white flowers.
Knotweed does not produce viable seeds as all the plants in the UK are female, so it is usually spread accidentally through the movement of soil or gardening waste, or via rivers and streams when pieces of rhizome break off and take hold in new locations.
Tackling knotweed costs the UK economy nearly £250million a year and homeowners are one of the groups most at risk – not only from potential damage to their property, outbuildings and gardens, which can be costly to repair, but also from legal risks arising from encroachment or when properties are sold.
Whilst it isn’t illegal to have knotweed growing on your land, if it is allowed to cross a boundary into an adjacent property, legal disputes can arise between neighbours.
Similarly, when properties are sold, sellers are asked a direct question about whether knotweed is present, even if hidden beneath the ground or within 3 metres of the boundary, and those who fail to declare it can be sued by their buyer for misrepresentation.
Environet estimates that approximately 5 per cent of homes across the UK are currently affected by Japanese Knotweed, either directly or neighbouring an affected property, typically impacting property prices by around 5 per cent – or up to 10 per cent in severe cases.
Emily Grant, Director of Environet, said: “Vigilance is the best way to protect your property from the risks posed by Japanese knotweed.
“Make sure you know what knotweed looks like and how it differs from other common garden weeds like ivy and bindweed, so you can keep an eye out for it in your garden and neighbourhood.
“Knotweed is easily identifiable during summer, but as we head through the autumn and into winter, the above-ground growth dies back and it becomes much harder to spot.
“It’s also easier to conceal, so anyone viewing a property to buy should be extra careful.
“There are lots of horror stories out there but the with professional help, knotweed can be successfully treated and a property’s value can be largely restored.”
It comes as the Wildlife and Countryside Link (WCL), which represents 83 nature organisations, warned that recent flooding and warming temperatures have increased the risk of problem species already in the UK growing and spreading.
This includes Japanese Knotweed, which can cause structural damage, Giant Hogweed, with sap that can cause burns to skin, and Himalayan Balsam, which out-competes native species and increases flood risks.
The WCL said the volatile conditions have also increased the risk of new species establishing themselves in the UK, like the Red Imported Fire Ant, Chinese Mitten Crab and Chinese Mystery Snail, which are making their way across Europe.
Richard Benwell, WCL chief executive, said: “Invasive species are already one of the biggest threats to the UK environment, from smothering waterways to outcompeting native species.
“They also cause billions of pounds in damage a year to homes and businesses, and even pose risks to human health.
HOW TO SPOT JAPANESE KNOTWEED
HOW to spot Japanese Knotweed and what to do if you find it.
GARDENING expert, Kendal Platt, who runs Adventures with Flowers, said: “Japanese knotweed shoots look similar to bamboo shoots growing 2-3metres tall.
They are hollow and coloured red in the Spring and turn green in the summer.
Their leaves which appear in Spring are shield or heart-shaped with a pointed tip and grow at staggered intervals along the length of the shoots.
They can grow up to 20cm long and die back in winter leaving just the brown dead looking canes above ground.
The flowers appear in late summer as bunches of creamy white flowers growing in amongst the leaves.
It spreads through its rhizomes (underground root system) which are dark brown on the outside and orange on the inside.
They can burrow up to 3 metres under ground causing damage to buildings and break easily, so can be hard to remove completely.
If you find it in your garden it’s important to call in a specialist Japanese Knotweed removal company.
They use a glyphosate based herbicide which when injected into the plant at the right time of year can kill it.
It may take a few years of repeated application to eradicate the plant completely from your property which is why many removal companies recommend a glyphosate treatment programme over a number of years.
“Investment in a fully-funded inspectorate and a strong invasive species strategy could make a contribution to halting nature’s decline and creating a more resilient economy.”
Dr Rob Collins, director of Policy and Science at The Rivers Trust, said the weather conditions over winter have left its local trusts “struggling to keep a wave of invasive species at bay” as wet weather scuppers their efforts.
“The Government must properly support local conservation groups nationwide who are working tirelessly to stop our waterways being smothered by nature invaders,” he said.
The coalition is calling for the annual invasive species biosecurity budget to triple to £3million with a further £3million to fund a permanent dedicated invasive species Inspectorate.
Responding to WCL’s recommendations, a Defra spokesperson said: “Invasive species threaten our native biodiversity and cost the economy billions every year, which is why we support the Invasive Species Inspectorate in carrying out their role to protect the nation’s biosecurity.
“Through our Invasive Non-Native Species Strategy, we remain committed to going even further to detect, protect and eradicate the threats they pose, while increasing co-ordination and co-operation with the public, land managers and businesses to deliver this.”
