Floating pennywort is a highly invasive plant which grows up to 20cm per day.
Its dominating presence can smother habitats, block water flow, crowd out native plants and take oxygen from fish and insects. It also causes major problems for boaters and other craft users, with its long, fleshy stems tangling in propellers and oars.
Like Japanese knotweed, floating pennywort also has the ability to grow from minuscule fragments, making its removal incredibly difficult and expensive.