BODMIN and Liskeard have been named Cornwall’s worst hotspots for Japanese knotweed, with new figures revealing the invasive plant continues to pose a threat to homes and property across the county.

Data released by invasive plant specialist Environet shows both towns have 69 verified sightings of Japanese knotweed, placing them joint top of Cornwall's hotspot rankings for 2026.

Penzance follows with 57 sightings, ahead of Truro (50), Helston and Launceston (42 each), Falmouth (38), Redruth (34), Camborne (32) and St Austell (31).

Overall, there have been 1,259 verified sightings of the invasive plant across Cornwall – the equivalent of almost one incident for every square mile.

Japanese knotweed is one of the UK's most troublesome invasive species. If left untreated, its extensive underground root system can spread beneath neighbouring land, damage buildings and hard surfaces, delay house sales and even lead to legal disputes between property owners.

Cornwall’s 2026 Japanese knotweed hotspots revealed
Cornwall’s 2026 Japanese knotweed hotspots revealed (Environet)

Environet says research carried out with Censuswide this year suggests around seven per cent of UK homes are affected by knotweed, with impacted properties typically losing around five per cent of their value – an average of £13,500.

The rankings are based on verified public sightings, enquiries received by Environet and reports submitted through its online Japanese Knotweed Heatmap.

Emily Grant, director of Environet, urged homeowners to stay vigilant. She said: “Japanese knotweed is now firmly established right across the country, which means homeowners everywhere should know what to look for. The earlier it’s spotted, the easier and cheaper it is to deal with.”

During the summer months, the plant can be identified by its tall bamboo-like stems, bright green shield-shaped leaves arranged in a zig-zag pattern and, later in the season, clusters of creamy-white flowers.

Anyone who believes they have Japanese knotweed on or near their property is being encouraged to seek professional advice before it has the chance to spread further.