Floating pennywort

Hydrocotyle ranunculoides

Overview

Habitat: Freshwater aquatic systems

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.

 

Description: 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. Can grow up to 20cm a day. Varies little throughout the year, although in the winter it is most likely to be found at the water’s edge.

 

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.

 

Impacts: 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? 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

 

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  
 

BE PLANT WISE!!

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Invasive Species Ireland

Invasive Species Ireland