Most Unwanted: Floating pennywort
Hydrocotyle ranunculoides
Habitat: Freshwater
Threat: Clogs waterways and negatively impacts on native species and ecosystems
Status: Established
What is it?
Floating pennywort resembles a very large, robust version of the native Irish marsh pennywort (Hydrocotyle vulgaris L.). It is a creeping, stoloniferous, perennial aquatic plant, with floating or emergent leaves. The leaves have long stalks and roundish leaf-blades about 2 – 6cm across. Flowers are pale-coloured, tiny, and are followed by small, round, dry fruits.
Habitat
Freshwater aquatic systems
Impact
Blocks water bodies and may lead to an increased risk of flooding.
Deoxygenating the water killing fish and other fauna.
Outcompete native plant species.
Where is it from
Native to North America but now known in Central and South America. The species has colonised Southern Europe as well as The Netherlands. The species was brought to Britain in the 1980’s and has been reported at 35 sites in southern England and south Wales.
Where is it now
In Ireland, Floating Pennywort was initially recorded from a clay pit on the Ards Peninsula in Co. Down, in 2002, and it is now known from a mill weir on the Six Mile Water, at Dunadry, in Co. Antrim
How did it get here
Trade of garden pond plants.
How can it spread in Ireland
Trade of garden pond plants and dispersal by natural means such as water flow dow stream and flood events. The species has also been sold incorrectly labelled as the native non invasive Marsh Pennywort.
Additional reading
Habitas Invasive Alien Species in Northern Ireland
Download the Floating Pennywort Management Plan
