The alert is being sounded over Giant Hogweed - dubbed Britain’s most dangerous weed.
National trade body Property Care Association says the plant has injured a number of children as well as adults across the UK.
The warning follows a call for action last month from residents near Horsham after Giant Hogweed - which can grow to a height of five metres - was spotted growing in a number of places in the district.
Now the Property Care Association is urging vigilance.
Dr Peter Fitzsimons, technical manager of the association’s invasive weed control group, said: “Giant Hogweed’s sap is extremely toxic to the skin in sunlight, making it a danger to public health.
“Youngsters are more likely to come into contact with the plant during the summertime and the mix of warm weather and rain has provided good conditions for the weed to take hold this year.
“Giant Hogweed is also spreading across a wider area, meaning that people are more likely to encounter it.
“If anyone comes into contact with any part of the plant, followed by exposure to sunlight, they can sustain severe blistering to the skin and discomfort, and this reaction can recur for many years.”
Giant Hogweed can produce up to 30,000 to 50,000 seeds, which can survive in the soil for a number of years.
Dr Fitzsimons added: “The general public, as well as local authorities, statutory agencies and landowners on whose property people can come into contact with the plant, should be aware of the risks and Giant Hogweed needs to be controlled and managed professionally.”
West Sussex County Council uses specialist treatment methods for harmful weeds, such as Giant Hogweed and Japanese Knotweed.
A spokesman said: “If residents notice any of these weeds on the highway, they are urged to please report this directly to us online via https://www.westsussex.gov.uk/roads-and-travel/make-an-enquiry-or-report-a-problem-with-a-road-or-pavement/make-an-enquiry-about-a-road-or-pavement/ so we have all the details needed to investigate.”
The Property Care Association has produced a guidance note on managing Giant Hogweed. See http://www.property-care.org/wp-content/uploads/2014/12/Guidance-Note-Giant-Hogweed.pdf.