Southampton has been named the top Hampshire hotspot for Japanese knotweed.

The city recorded the highest number of verified sightings in the county, according to data from Environet's online tracker, Exposed: The Japanese Knotweed Heatmap.

The interactive map, now showing nearly 60,000 infestations across the UK, allows users to check the number of sightings in their area and report any suspected knotweed.

Hampshire has a total of 588 verified sightings, or 0.16 incidences per 1km², making it the 23rd worst affected county in England.

The invasive plant, which poses a risk to property and gardens, is expected to enter its dormant winter phase in the coming weeks as temperatures drop.

During this period, its green leaves will fall, stems will become brittle, and the plant will die back, leaving only the dead canes. However, it will re-emerge in spring, making autumn and winter the ideal time to excavate it.

Emily Grant, director of Environet, said, “With over 60,000 known infestations of Japanese knotweed on our heatmap, we have a clear picture of its prevalence across the England and Wales.

"The best way to protect your property is to be aware of the risks and ensure you can identify knotweed at different times of the year. If you do have knotweed on your property, it’s wise to act immediately to treat or remove it before it has the chance to spread further."

The presence of Japanese knotweed can significantly impact property prices, typically by around 5 per cent, or up to 10 per cent in severe cases.

It also poses legal risks if allowed to spread across property boundaries or if not declared to buyers when properties are sold.

Tackling the plant costs the UK economy nearly £250 million a year.

Environet estimates that about 5 per cent of homes are currently affected by Japanese knotweed, either directly or by neighbouring an affected property.

The heatmap has been monitoring the spread of the invasive plant across the UK for the past six years, helping both homeowners and prospective buyers stay informed about the risk level near their property or one they wish to purchase.