Invasive Species (Japanese Knotweed, Giant Hogweed)

Invasive non-native species on construction sites include Japanese Knotweed, Giant Hogweed, and Himalayan Balsam.
Japanese Knotweed grows through concrete and tarmac and reduces property values; its spread is a legal offence.
Giant Hogweed sap causes severe phototoxic burns when skin is exposed to sunlight after contact.
It is an offence under the Wildlife and Countryside Act 1981 to cause these species to spread in the wild.
Japanese Knotweed-contaminated soil is classified as controlled waste requiring specialist disposal.
Construction activities including earthworks, soil movement, and vegetation clearance can spread invasive species.
Even small fragments of Japanese Knotweed rhizome in moved soil can establish new plants at the destination.
Giant Hogweed can grow to 5 metres tall and is typically found along riverbanks and disturbed ground.
Site-specific invasive species management plans must be prepared before any earthworks in infested areas.
The Environmental Protection Act 1990 classifies Japanese Knotweed soil as controlled waste for disposal purposes.

Legal offence	Causing Japanese Knotweed or Giant Hogweed to spread is a criminal offence with unlimited fines.
Burns from Hogweed	Giant Hogweed sap causes severe third-degree phototoxic burns, blistering, and permanent scarring on exposed skin.
Waste classification	Knotweed-contaminated soil is controlled waste. Incorrect disposal leads to prosecution and site contamination elsewhere.

Do

Don't

Survey the site for invasive species before starting any earthworks or clearance.
Prepare a site-specific invasive species management plan for infested areas.
Wear full skin cover including gloves and face shield when near Giant Hogweed.
Treat Japanese Knotweed with herbicide under a specialist management plan before excavation.
Dispose of Knotweed-contaminated soil at a licensed facility with a waste transfer note.
Mark the extent of invasive species infestations on the site plan clearly.
Brief all operatives on identifying Knotweed, Giant Hogweed, and Himalayan Balsam.
Clean plant and equipment before moving from infested to clean areas of the site.
Seek medical advice immediately if Giant Hogweed sap contacts skin.
Record all invasive species management actions for the project environmental file.

DON'T move soil containing Japanese Knotweed without a management plan in place.
DON'T touch Giant Hogweed with bare skin; its sap causes severe chemical burns.
DON'T strim or mow Giant Hogweed as this sprays sap over a wide area.
DON'T dispose of Knotweed-contaminated soil in general fill or at unlicensed sites.
DON'T move plant or vehicles from infested areas without cleaning them first.
DON'T ignore small Knotweed plants; even tiny fragments regenerate rapidly.
DON'T cut down Giant Hogweed without full protective clothing and face protection.
DON'T expose skin to sunlight after any contact with Giant Hogweed sap.
DON'T assume invasive species are only a summer problem; Knotweed rhizomes survive winter.
DON'T compost or burn Japanese Knotweed waste on site; it requires licensed disposal.

See also: Protected Species Awareness | Site Clearance and Vegetation Removal

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