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Japanese knotweed map of Britain shows London at epicentre of outbreak

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The Japanese knotweed map of Britain: Scourge of invading plant blighting UK is revealed in heatmap showing areas worst hit by infestations

  • Online heatmap, created by Environet, pinpoints thousands of infestation of the invasive Japanese knotweed 
  • Hotspots are marked from yellow through to red depending of the severity of the pesky plant's infestation
  • Epicentres have been located across outer London, Merseyside, Lancashire and Bristol through the heatmap

By Faith Ridler For Mailonline

Published: 11:43 EST, 18 February 2019 | Updated: 13:15 EST, 18 February 2019

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Areas blighted by pesky Japanese knotweed have been revealed by a new interactive heatmap of infestations across the UK.

The online map, created by Environet, pinpoints thousands of infestations of the notoriously invasive weed up and down the country.

The plant has a vigorous growth, advancing up to four inches a day in the summer, and its roots or rhizomes spread far underground causing structural damage to buildings.

If the plant is found growing within 23 feet of a property, mortgage applications can be refused unless there is a plan in place to eradicate it.

The online map, created by Environet , pinpoints thousands of infestations of the notoriously invasive weed up and down the country (Pictured, reports of the plant in outer London)

The plant has a vigorous growth, advancing up to four inches a day in the summer, and its roots or rhizomes spread far underground causing structural damage to buildings (Pictured, growth in south Wales)
The plant has a vigorous growth, advancing up to four inches a day in the summer, and its roots or rhizomes spread far underground causing structural damage to buildings (Pictured, growth in south Wales)

The plant has a vigorous growth, advancing up to four inches a day in the summer, and its roots or rhizomes spread far underground causing structural damage to buildings (Pictured, growth in south Wales)

Even if the seller carries out the expensive work, the stigma associated with the plant means property values can decrease by up to 10 per cent.

But those looking to buy a house can now check whether an area is blighted by the weed on the Exposed: The Japanese knotweed Heatmap website.

It allows people to search by postcode to discover the number of reported sightings nearby or note any new sightings.

Knotweed hotspots are marked from yellow through to red depending of the severity of the infestation. 

Epicentres have been located in outer London, Merseyside, Lancashire and Bristol. A belt between Newport and Swansea, and another between Nottingham and Sheffield, are also home to high volumes of the weed.

Japanese Knotweed is prevalent around Fort William and Ventnor on the Isle of Wright.

Epicentres have been located in outer London, Merseyside, Lancashire and Bristol. A belt between Newport and Swansea, and another between Nottingham and Sheffield, are also home to high volumes of the weed
Epicentres have been located in outer London, Merseyside, Lancashire and Bristol. A belt between Newport and Swansea, and another between Nottingham and Sheffield, are also home to high volumes of the weed

Epicentres have been located in outer London, Merseyside, Lancashire and Bristol. A belt between Newport and Swansea, and another between Nottingham and Sheffield, are also home to high volumes of the weed

Knotweed hotspots are marked from yellow through to red depending of the severity of the infestation (Pictured, infestations in Nottingham and Derby)
Knotweed hotspots are marked from yellow through to red depending of the severity of the infestation (Pictured, infestations in Nottingham and Derby)

Knotweed hotspots are marked from yellow through to red depending of the severity of the infestation (Pictured, infestations in Nottingham and Derby)

And in Cardiff, there are 414 occurrences within a 2.5 square mile area of the city centre.

The tool was created by Nic Seal of Environet UK, who said: 'This heatmap will enable us to build a nationwide picture of the Japanese knotweed problem and give the general public the information they need to assess the risk locally, particularly when buying a property.

'It will also be a useful tool for homeowners who want to be aware of infestations near their property which could spread, putting their home at risk.

'The site is already well populated, but this is an ongoing project. The more people who report sightings, the more effective it will become.'

People can search by postcode to discover the number of reported sightings nearby or note any new sightings (Pictured, sightings in Bristol)
People can search by postcode to discover the number of reported sightings nearby or note any new sightings (Pictured, sightings in Bristol)

People can search by postcode to discover the number of reported sightings nearby or note any new sightings (Pictured, sightings in Bristol)

The Victorians introduced Japanese knotweed as an ornamental plant but it now grows rampantly along railways, waterways and in parks and gardens (pictured: Sightings in the Isle of Wight)
The Victorians introduced Japanese knotweed as an ornamental plant but it now grows rampantly along railways, waterways and in parks and gardens (pictured: Sightings in the Isle of Wight)

The Victorians introduced Japanese knotweed as an ornamental plant but it now grows rampantly along railways, waterways and in parks and gardens (pictured: Sightings in the Isle of Wight)

The Victorians introduced Japanese knotweed as an ornamental plant but it now grows rampantly along railways, waterways and in parks and gardens.

The Environment Agency brands it as 'indisputably the UK's most aggressive, destructive and invasive plant'.

It can be spotted by red or purple asparagus-like shoots that appear from the ground and grow rapidly, forming hard canes from April or May.

As the canes grow, heart-shaped leaves gradually unfurl and turn green. It blooms in late summer, when it becomes covered in tiny creamy-white flowers.

During the late autumn, the leaves fall and the canes turn brown and die, although they remain standing.

WHAT IS JAPANESE KNOTWEED?

Japanese Knotweed is a species of plant that has bamboo-like stems and small white flowers.

Native to Japan, the plant is considered an invasive species. 

The plant, scientific name Fallopia japonica, was brought to Britain by the Victorians as an ornamental garden plant and to line railway tracks to stabilise the soil.

It has no natural enemies in the UK, whereas in Asia it is controlled by fungus and insects.

In the US it is scheduled as an invasive weed in 12 states, and can be found in a further 29.

It is incredibly durable and fast-growing, and can seriously damage buildings and construction sites if left unchecked.

The notorious plant strangles other plants and can kill entire gardens. 

Capable of growing eight inches in one day it deprives other plants of their key nutrients and water. 

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