Floating pennywort

Hydrocotyle ranunculoides


Photo credit: ©Trevor Renals
Hydrocotyle ranunculoides
  • Freshwater aquatic systems

Widely Spread Species:
  • Under Article 19 of Invasive Alien Species Regulation (1143/2014) Floating pennywort has been identified as a Widely Spread Species in Northern Ireland and as such, management measures have been put in place to minimise its impacts.

Similar Species:
  • Marsh pennywort. Hydrocotyle vulgaris L: Grows on damp ground in bogs and fens. Always rooted in the ground, never free-floating. Floating pennywort has a larger with stalk attached between lobes of kidney shaped leaf.

  • 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 arising from nodes on its stem which also produce a profusion of fine roots. The nodes occur at 20-60mm intervals along the horizontal stem which is fleshy. Shiny, kidney-shaped leaves with crinkled edge, frequently broader than long.
  • The waxy leaves have long fleshy stalks and roundish leaf-blades about 2 – 6cm across. Flowers are pale-coloured, tiny, and are followed by small, round, dry fruits.
  • Flowers are rare, but if present, they appear between July and August. It can grow up to 20cm a day. It varies little throughout the year, although in the winter it is most likely to be found at the water’s edge.
  • Download N.I.E.A ID guide

Origin and Distribution:
  • 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.

  • Blocks water bodies and may lead to an increased risk of flooding.
  • Deoxygenates the water killing fish and other fauna. Outcompetes native plant species.

How did it get here?
  • Trade of garden pond plants.

Where is it found in Ireland or Northern Ireland?
  • It is found in Ireland and Northern Ireland.
  • More information can be seen at NBDC and NBN Atlas NI.

You can help by reporting any sightings:

Static Distribution Map as of December 2019 - Courtesy of CEDaR

Further Resources:
Prevent Spread:
  • Promote native species and biodiversity - use alternative, native plants
  • Know what you are buying/growing and source native Irish seed and plants
  • Do not swap plants and cuttings
  • Clean plants before adding to ponds (dispose of water away from water courses)
  • Follow control advice and watch out for hitchhikers - inspect new imported purchases for invasive pest and pathogens
  • Clean equipment before moving between waterbodies
  • Never collect plants from the wild
  • Safe disposal of plant material and growing media  
  • Report all sightings. 

  • Download the posters and promote in your area.

Current Legislative Position (Listed on 03 August 2016)
  • This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Non Native Invasive Species Team in the Northern Ireland Environment Agency on 028 9056 9558.

Species Related Files:

Invasive Species Ireland

Invasive Species Ireland