As the Japanese knotweed growing season gains momentum, invasive plant specialist Environet has released the latest hotspot map for Gloucestershire in 2025. According to updated data, there have been 628 confirmed sightings of this invasive species across the county.
Environet’s Japanese Knotweed Heatmap now contains over 100,000 verified records of the UK’s most troublesome invasive plant and is continuously updated with new confirmed sightings. This makes it the most comprehensive online resource for tracking Japanese knotweed nationwide.
Residents can enter their postcode on the heatmap to see how many sightings have been reported nearby. Hotspots are color-coded in yellow, orange, or red to indicate increasing severity, helping homeowners and prospective buyers assess the risk posed to their properties.
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The public can also help by reporting new knotweed findings through the ‘Add Sighting’ feature, which requires attaching a photograph for expert verification.
The top 10 knotweed hotspots in Gloucestershire and South Gloucestershire for 2025 include several locations where the plant is especially prevalent (Gloucestershire areas in bold).
Japanese knotweed was first introduced to the UK during the Victorian era through plant specimens sent to Kew Gardens. Initially celebrated by gardeners unaware of its invasive potential, it has since spread widely, now appearing in an average of 1.1 locations per square mile across England.
In early spring, knotweed begins to sprout quickly, developing into dense shrubs with distinctive pink-speckled stems, heart-shaped leaves, and bamboo-like canes. Its underground root system can extend up to three metres deep and seven metres horizontally, easily penetrating cracks in concrete, tarmac, drains, and cavity walls.
Although severe structural damage is rare, mortgage lenders require that knotweed issues be resolved before a property is sold. This often causes disputes between neighbours and can reduce property values by approximately 5%. A 2023 DEFRA study estimated the annual cost of managing knotweed in the UK at nearly £250 million.
Emily Grant, Director of Environet, stated, “Mapping verified sightings helps raise awareness about local risk levels and promotes early detection and treatment. Early action is crucial to prevent knotweed from becoming firmly established and causing damage.”
“At this time of year, the plant is in full growth and easy to identify by its bright green, heart-shaped leaves arranged in a zigzag pattern along the stems. Mature plants flower around August, producing clusters of tiny white blooms.”
“If you believe you have found Japanese knotweed near your property, you can email a photo to [email protected] for a free identification. If confirmed, a survey will assess the infestation and recommend treatment options such as excavation, herbicide application, or a combination of methods.”
“Public involvement is vital in controlling knotweed. By reporting sightings promptly, homeowners contribute significantly to managing this invasive plant and protecting property values.”