Hotspots for knotweed – it’s closer than you think

ANEW survey has identified those parts of the Westcountry at greatest risk from one of the most invasive and damaging plants on the planet.

Japanese knotweed was first imported into the UK in the 1840s at Kew Gardens, as an attractive addition to British gardens.

But it can grow up to three metres tall, delve into the cracks in masonry, concrete, driveways, patios, paths and drains – and even get into cavity walls, effectively invading a house.

It can also entirely take over a garden, growing at a staggering rate of up to 10cm per day. And Japanese knotweed can stay dormant underground for 20 years – meaning home owners might not even be aware of it, until it springs into life.

When it first grows, it looks like a red asparagus-like shoot coming out of the ground. It grows into green shrubs with a heart-shaped leaf, and pink-flecked stems.

Once it takes hold, it can be incredibly tough to get rid of.

Environet, a company which helps keep track of infestations, has pinned down the hot-spots of Japanese knotweed across Devon and Cornwall.

With up to 42 outbreaks per 4km radius in parts of Devon and Cornwall, local people are being warned to keep an eye out in areas which are prone to outbreaks.

In Cornwall, the hotspots are: Helford: 42 infestations per 4km radius; Bodmin Moor: 39; Camborne: 38; St Blazey: 34; and Redruth: 23. In Devon, Plymouth tops the list with 25 outbreaks per 4km radius, followed by Axminster: 23; Ilfracombe: 18; Okehampton: 15; and Torquay: 15.

If your home or garden becomes infested with the plant, it is an offence to not report or control the outbreak. The offences range from fines up to jail sentences.

Trained experts can be needed to manage the plant and get rid of it, as it can be daunting for the average homeowner to tackle, given its survivability and persistence.

Dogs can be trained to sniff out the dormant plant, based on a distinctive smell which it gives off through the ground.

Environet suggests reporting sightings and outbreaks wherever they crop up to help stop the plant getting out of control. It puts all reports on to its heat map, which shows which areas are most prone.

Emily Grant, Environet’s regional director for Devon and Cornwall, said: “Knowledge is power when it comes to Japanese knotweed and this heat map is invaluable to homeowners and buyers who want to assess the risk in their local area.

“With the stamp duty holiday extended and lockdown restrictions beginning to ease, the property market is busier than ever – but failing to carry out the appropriate checks for knotweed can turn out to be an expensive mistake.

“Despite its fearsome reputation, with professional help, the plant can be dealt with and the value of a property largely restored.”