Do you live in a Japanese knotweed hotspot? New heatmap reveals the UK areas most impacted by this invasive plant

The spread of Japanese knotweed across the UK is always an ongoing concern for homeowners but a new resource could help ease concerns.

This invasive plant, notorious for damaging homes and property values, now has its own interactive tracking tool: the Exposed™ Japanese Knotweed Heatmap. Launched by Environet, the heatmap helps homeowners, buyers and property professionals identify Japanese knotweed hotspots.

Here’s everything you need to know about how the map works, where knotweed is most common and why it’s crucial to be informed.

How does the Japanese knotweed heatmap work?

The Exposed™ Heatmap is an interactive online tool that tracks sightings of Japanese knotweed across the UK.

Built using data from over 57,000 verified infestations, with new reports added daily, the map shows hotspots using a traffic-light colour system. Areas with the highest concentrations of knotweed are marked in red, moderate areas in orange, and low-risk zones in yellow.

If you're concerned about having to kill Japanese knotweed, homeowners and prospective buyers can search the map by entering their postcode to see if their property is in a high-risk area.

Sightings can also be reported by the public, making it a collaborative tool for tackling knotweed’s spread. These reports are said to be verified to ensure accuracy, keeping the heatmap current and reliable.

Where are the worst and least affected areas?

The data reveals that no corner of the UK is entirely safe from Japanese knotweed, but certain regions are more heavily impacted than others.

Worst-affected areas:

• Cardiff leads the UK with 6.74 incidences of knotweed per km², making it the top hotspot.
• Swansea and Bridgend follow, with 3.58 and 2.9 incidences per km², respectively.
• In England, Bristol tops the list with 5.18 incidences per km², followed by Merseyside and Greater London.

Least-affected areas:

• While knotweed is present in every 10 km² across the UK, rural areas and smaller counties tend to see fewer incidences.
• Regions such as the East of England and parts of Scotland in particular have reported fewer occurrences of Knotweed infestations.
• However, even low-risk zones are not immune, as the plant’s underground rhizome system can spread rapidly.

Why is it important to know where Japanese knotweed is common?

Understanding where knotweed is most prevalent is essential for protecting your home and investment.

Emily Grant, Director of Environet and expert in knotweed management, explains: "Knotweed is a highly invasive plant, and its underground rhizome system means it can spread quickly, even to areas previously unaffected. Staying informed about its presence nearby is essential to protecting your home and investment."

With knotweed present in every 10 km² across the UK, it’s important to remember that no area is entirely immune. Grant adds: "Being aware of the risks through tools like the heatmap ensures you can act quickly if knotweed appears. Early action can prevent it from spreading and causing significant damage to property values."

For homeowners in less-affected areas, using the heatmap and monitoring for potential sightings can provide added security. Proactively checking for knotweed ensures you stay ahead of any potential issues, safeguarding your property from this invasive threat.

What to do if you're in a high-risk area?

If you’re in a high-risk area or suspect knotweed on your property you shouldn't panic but you should immediately take these steps:

• Get a survey: Arrange a professional Japanese knotweed survey, especially if you’re selling or buying a home.
• Report sightings: Help improve the heatmap by reporting knotweed infestations online. Upload photos for verification to ensure the map remains accurate.
• Take action quickly: Knotweed won’t go away on its own. Seek professional help to treat or remove the Japanese knotweed and prevent it from spreading further.

With costs for Japanese knotweed removal running into thousands for professional excavation, keeping on top of the latest sightings could save you money in the long run.