Fringed water lily

Limnanthemum peltatum, N. nymphaeoides, N. peltata

Overview

Photo credit: ©Craig Mabbett
Common name:
  • Fringed water lily

Also known as:
  • Floating heart, fringed water lily, yellow floatingheart, Entire marshwort
  • Synonyms: Limnanthemum peltatum, N. nymphaeoides

Description;
  • N. peltata is an aquatic, bottom-rooted perennial with long branched stolons extending up to one metre or more that lie just beneath the waters surface. The node on the stolons typically produces a plant and many thread-like roots. Leaves are heart-like to almost circular in shape and are 3-10 cm long on long stalks that arise from creeping underwater rhizomes. The leaves are frequently purplish underneath, with slightly wavy, shallowly scalloped margins. The flowers are bright yellow, 5-petalled and 3-4 cm in diameter. The flowers are held above the water surface on long stalks, with one to several flowers per stalk. The flower edges are distinctively fringed giving the common name of Fringed waterlily. The fruit is a capsule up to 2.5cm long containing numerous seeds. The seeds are flat, oval and about 3.5mm long with hairy edges (GISD, 2009).

Origin and worldwide distribution:
  • N. peltata is native to Eurasia and the Mediterranean. It has been introduced to Ireland, Denmark, Sweden, Switzerland, North America and New Zealand.

Impacts:
  • N. peltata is a very aggressive plant that is capable of rapid growth and spread which can displace native species, reduce biodiversity, limit recreation, diminish aesthetic value, and decrease water quality and flow. Presently, it is locally established in lakes and ponds in Ireland where it thrives in shallow (<1.5m deep) and nutrient rich water bodies. Impacts include (Department of Conservation and Recreation, 2004):
    • Dense floating mats of N. peltata can form on the water’s surface, restricting light to the complete exclusion of other native plants
    • Decreasing the air exchange between the water’s surface and the atmosphere
    • Thick floating mats have prevented fishing, boating, swimming and other activities in a ponds and lakes
    • The loss of recreational and aesthetic value can cause a decline in surrounding lake property value
    • Algae, a major component of the base of the food chain, can be shaded out by dense mats of N. peltata. The resulting decline in algae can disrupt the entire food web in a lake
    • N. peltata may form dense single species stands that often do not provide ideal habitat or food for native wildlife and may limit access to the water for some species. These native wildlife populations may be forced to relocate or perish, ultimately resulting in a loss of biodiversity and a disruption in the balance of the ecosystem
    • Sediment levels increase with increasing N. peltata abundance
  • N. peltata is known to colonise slow moving rivers, lakes, reservoirs, ponds and swamps 0.5 to 4 metres deep. It can also grow on damp mud. Available habitat is widespread in Ireland. Its range will be extended by natural and anthropogenic means which results in an island wide distribution potential.
  • Predictions based on our current knowledge of the habitats most susceptible to invasion will allow us to identify priority areas for control and prevention. Proximity to known populations of N. peltata should be used to prioritise local preventative measures but on a national scale, remote and isolated populations are likely to occur at geographically distant sites due to the vectors and pathways associated with this species.

How did it get here?
  • It was imported as an ornamental pond plant. It can be spread through the horticulture trade, and recreational and industrial boats, as well as through animals, water currents and human clothing and equipment.

Is it found in Ireland or Northern Ireland?
  • There are several sites in Ireland and Northern Ireland. 
  • More information can be found at NBDC and NBN Atlas NI.

Methods for prevention
  • Report all sightings to CEDaR.
  • Know what you grow.
  • Plant native species.
  • Don't swap cuttings or plants with others if you don't know what it is.
Invasive Species Ireland

Invasive Species Ireland