The Watford area has been named as the biggest hotspot for Japanese knotweed in Hertfordshire.

As the UK’s most invasive plant enters its spring growth phase, Japanese knotweed expert Environet has revealed the latest hotspots using data from its interactive online tracker heatmap.

The data for 2021 shows there are as many as 61 Japanese knotweed infestations within a 4km radius of Watford, which is more than any other Hertfordshire town.

Following its winter hibernation, knotweed begins to grow in March or April, depending on the local ground temperature, reaching up to three metres in height by mid-summer.

Homeowners spending more time in their gardens this spring may notice purple or red asparagus-like shoots now emerging from the ground and quickly growing into lush green shrubs with heart or shovel-shaped leaves and pink-flecked stems.

Pushing up through cracks in concrete, driveways, patios, paths, drains and even the cavity walls of our homes, Japanese knotweed can reduce a property’s value by 10 per cent and make it difficult to sell.

Environet’s online tracker informs homeowners and potential homebuyers of the local presence of knotweed and the potential risk to their property.

Watford Observer:

Mat Day, Environet's regional director for Hertfordshire, said: "Knowledge is power when it comes to Japanese knotweed and this heatmap 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. I’d urge anyone buying or selling a property, or homeowners wishing to preserve the value of their home, to be vigilant for signs of spring growth and check Exposed to see whether they live in a high-risk area."

According to Environet, the Government estimates it would cost £1.5 billion to clear the UK of knotweed, which first came onto our shores in the 1840s.

Approximately £166m is spent each year on treating the plant in the UK.

The public can help in the fight against knotweed by reporting suspicious plants and attaching a photo to be verified by experts.