Floating pennywort has escaped from garden ponds and can spread at a rate of 20cm per day.

Originating in America, floating pennywort has been used as an ornamental pond plant since the 1990s. However, it has now spread to other areas where it can grow rapidly to the detriment of native species. In summer, it can double in size in less than a week.

Floating pennywort is listed under Schedule 9 to the Wildlife and Countryside Act 1981 with respect to England, Wales and Scotland. As such, it is an offence to plant or otherwise cause this species to grow in the wild.

Floating pennywort can be either free-floating or rooted, and forms dense mats of vegetation growing horizontally, and can be found above or below the water surface. Single leaves rise up out of the water on a fleshy, pale green stalk attached to the horizontal stem, with a pink tinged stalk.

The bright green leaves are kidney shaped and bluntly toothed, normally wider than they are tall, and are around 7cm in diameter.

As an aquatic plant, it is found in any still or slow-moving water in lakes, ponds, streams, ditches and canals. It prefers areas of full sun. It is found all year round, though during the colder winter months will reduce in size and retreat to shallow waters/banks.

Floating pennywort grows rapidly and forms dense mats of vegetation outcompete other aquatic plants, preventing light from reaching below the surface. It can deplete water of oxygen, and cause nutrient overload when it dies back.

It impacts navigation and recreational use of watercourses, as well as disrupting local habitats and impacting the native species that live there.