AREAS blighted by Japanese knotweed are being mapped by a new interactive map to provides a heatmap of infestations across the UK.

The online map lists the thousands of infestations of the notorious invasive weed that plagues gardens and land up and down the country.

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

In the UK it is believed if the plant which can be three foot tall is found growing within 23 feet of a property it poses a risk so mortgages are often refused unless there is a plan in place to eradicate it.

But even if the seller carries out the expensive work, the stigma associated with the plant means that property values can be a tenth less, even after action is taken to control it.

Now home buyers can 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 to report any new sightings. Knotweed hotspots are marked from yellow through to red depending of the severity of infestation.

Japanese Knotweed can be found in Cumbria.

Stephen Trotter, chief executive of Cumbria Wildlife Trust, said: "Japanese knotweed is one of the world's most troublesome and invasive plants. Outside of its native range, it can cause real problems because it has no natural enemies to keep it in check. In some parts of the UK it can grow rapidly into dense thickets which smother and shade out other plants and species – affecting local wildlife and its conservation. That's why Cumbria Wildlife Trust supports the control and removal of Japanese knotweed.

"While we normally recommend gardeners to go chemical-free in the interests of wild flowers and bees, if you have a Japanese knotweed problem there are few options but to follow the official guidelines which recommend using 'glyphosate' to carefully target and kill the plant."