The Glastry Clay Pits on the Ards Peninsula, the Belfast Waterworks and the Balloo Nature Reserve in Bangor have all suffered invasions by non-native aquatic plants.

Warning gardeners to beware of the danger of planting invasive plants in their ponds, Northern Ireland Environment Agency (NIEA) last night identified a series of plants that can quickly choke other plants through their excessive growth and also spread to other areas.

John Early of Northern Ireland Environment Agency Biodiversity Unit (NIEA) said: “Many invasive aquatic plants spread easily by fragments.

“This means that just one fragment escaping from a pond or fish tank could lead to a whole river or lake becoming infested.”

Invasive aquatic plants include the curly waterweed, parrot's feather, floating pennywort, Nuttall’s pondweed, New Zealand pigmyweed, water fern and the fringed waterlily

The NIEA’s advice is to properly compost unwanted aquatic plants away from waterways.