A weed that can grow up to 12ft (four metres) tall and causes skin damage to humans is being stamped out in part of West Sussex.
Horsham District Council is working with landowners to eradicate giant hogweed from the area.
Public health chief Nigel Haverson said the plant was harmful and invasive.
He said the sap, which contains a chemical that can cause painful, long-term skin damage, could be released by brushing a stem or leaf stalk.
Mr Haverson said the council already controlled the weed on its own land, and was working with landowners in a bid to stop the spread.
Under the Wildlife and Countryside Act 1981, it is an offence to plant giant hogweed or to cause it to grow, he added.