Overview
- Environet’s live tracker, Exposed: The Japanese Knotweed Heatmap, published in July 2026, maps verified sightings and public reports and has been used by local outlets to publish town and county hotspot counts.
- Environet’s research with Censuswide estimates roughly 7% of UK homes are affected — about 1.58 million properties — with an average property value loss of around 5% or £13,500 per home.
- The heatmap shows clusters in former industrial and port areas with large local counts, for example Merseyside (3,393 incidents), Bristol among the worst hit, Birmingham (320), Ipswich (133) and Salisbury (88).
- Biology makes control hard: knotweed in the UK rarely seeds, its rhizomes can spread up to seven metres and tiny fragments can regrow; Environet offers free photo ID by email and professional surveys when presence is confirmed.
- The map aggregates Environet enquiries, public ‘Add Sighting’ submissions and datasets from bodies such as the National Trust and Natural England, so apparent rises in sightings may reflect added sources and could drive higher demand for surveys and treatment services.