What is it?
Water primrose, Ludwigia grandiflora, is an attractive but highly invasive plant that grows in or alongside ponds, lakes and wetlands. Grows from fragments. Native to South America but is causing serious economic and environmental problems in France and England. It has recently recorded in a small number of artificial garden ponds in Co Kerry but has not yet been recorded in the wild.
How do you identify it?
- Long red stems that grow horizontally on water or mud; the stems will also emerge to 1 m above the water surface. Stems can grow to 5 m in length.
- Most plants have alternate dark green leaves of two types: emerged long and slender (willow like) and floating oval forms.
- Large yellow flowers, each with 5 petals.
Why are we concerned?
In suitable waters this plant grows very rapidly and establishes large, dense (often impenetrable) surface and sub-surface vegetation carpets. These can block watercourses and interfere with boating, cruising, angling, irrigation, drainage and other water uses. Dense stands will deplete dissolved oxygen from the water, resulting in fish kills, compete with native species for space and resources, and reduce biodiversity.
How do we stop the spread of this species?
Do not purchase from garden centres or accept cuttings.
If you see this invasive plant in a garden centre or in a garden pond, report the sighting immediately to the emergency response number 1890 347424.
Distribution of water primrose in Ireland
Data from Biodiversity Maps held by the National Biodiversity Data Centre www.biodiversityireland.ie 2011