Haywards Heath and East Grinstead among top hotspots for Japanese knotweed in Sussex

Data from Environet shows the knotweed hotspots for 2026, based on verified sightings from its live online tracker, Exposed: The Japanese Knotweed Heatmap. Visit www.environetuk.com/exposed-japanese-knotweed-heat-map.

Environet specialises in the removal of Japanese knotweed, bamboo and other invasive plants, and the company works with house builders, developers, councils and homeowners.

Environet director Emily Grant said: “At this time of year, an established knotweed plant can be identified quite easily by its hard bamboo-like canes and distinctive bright green shield-shaped leaves which grow in a zig-zag pattern along the stem. The earlier it’s spotted, the easier and cheaper it is to deal with.”

The company said there are 938 verified sightings of knotweed across both East and West Sussex, which is equivalent to 0.63 incidents every square mile. Environet said the plant, if left unmanaged, can damage buildings, hinder property sales and lead to legal disputes if it spreads across property boundaries.

Research conducted by Environet in partnership with Censuswide in 2026 showed that seven per cent of UK homes – more than 1.58 million properties – are affected by it. The company said property values are commonly reduced by about five per cent.

According to Environet, these are Sussex’s top ten Japanese knotweed hotspots, showing rank, location and verified sightings: =1. Hove, East Sussex, 43 =1. Hastings, East Sussex, 43 =3. Brighton, East Sussex, 38 =3. Haywards Heath, West Sussex 5. St Leonard’s on Sea, East Sussex, 36 6. Horsham, West Sussex, 34 7. Crowborough, East Sussex, 31 8. Bexhill-on-Sea, East Sussex, 26 9. East Grinstead, West Sussex, 23 10. Eastbourne, East Sussex, 21

A spokesperson said: “The rankings are based on invasive plant specialist Environet’s own enquiries, public sources and verified sightings submitted by members of the public using the map’s ‘Add Sighting’ feature. Homeowners and homebuyers can enter their postcode to discover the number of known sightings within a five-mile radius, with hotspots highlighted in yellow, orange, or in the worst cases, red.”

The signs of Japanese knotweed are: upright canes that can reach two to three metres high; dense clusters of stems that emerge from a central crown in the ground; large green shield-shaped leaves with a pointed tip that grow alternately up the stem; cone-shaped tassels of small white flowers, which emerge on the upper canopy by late summer.

Knotweed was Introduced to Britain as a garden plant in the Victorian era. Environet said it has spread across the UK through the movement of contaminated soil, waterways and more than 150 years of industrial activity, construction and infrastructure works. It does not reproduce by seed in the UK but its root system can extend up to seven metres laterally beneath the ground and even small fragments can regenerate into new plants.

Visit www.environetuk.com.