Stop The Spread

Ponds can be a great addition to any garden and create a wonderful feature to be enjoyed all year round. However, if they aren’t cared for properly some common pond plants can take over your ponds. They can also become established in the wild and cause severe damage to the environment. The Be Plant Wise campaign is designed to educate retailers and customers about the problems caused by invasive aquatic plants, and to encourage customers to seek advice on the most suitable plants for their pond and to promote better pond management.

  • Be Plant Wise by not moving pond plants around. Even tiny plant fragments can lead to problems, so be careful when maintaining your pond and disposing of waste water.
  • Any waste water should be emptied away from streams, rivers, ponds, lakes and loughs, or drains that flow into them. Even disposing of waste pond water over the garden fence could mean that fragments of invasive plant end up in the drainage system and ultimately in the rivers and streams. Also make sure to clean all equipment after use and to follow the same guidelines for disposal of cleaning water as for waste water.

If retailers and customers choose plants that are better suited to their garden pond and take care to dispose of all aquatic plants responsibly it will help us prevent the spread of invasive aquatic plants.

Why is the issue important?

Whether you are interested in the environment or not, the problems caused by invasive  species affect us all. For a start, they cost us billions of pounds/euro – for example it has been estimated that they may cost as much as £2 billion every single year in Britain alone while estimates for Europe as a whole suggest invasive species cost at least €12 billion per annum.

But invasive species are not only an economic problem, they are also a well known threat to our environment. From challenging the survival of our rarest species to damaging some of our most sensitive ecosystems, the biodiversity impacts of invasive  species are severe and growing. Their impact is now so significant that they are considered to be one of the greatest threats to biodiversity worldwide.

It’s not just our wildlife that suffers, invasive  species can also have an impact on the way we live. For example, if invasive aquatic plants become established in the wild they can clog our waterways, exacerbate flooding, disrupt the navigation of boats, interfere with recreational activities (such as fishing), and remove oxygen from the water, which can harm fish.

It’s also important to remember that the effect of an invasive  species is not a one off event. Once a species has been introduced the persist and escalate as the species spreads further. If we don’t act, the problem of invasive  species will continue to escalate at an ever increasing rate, causing us to feel more of the impacts and incur more cost every year.

Find out more

You can watch the EcoEye feature on invasive species on the Inland Fisheries Ireland website. This feature highlights some of the issues which can be avoided by being Plant Wise:

A selection of aquatic plant species which can cause problems in the wild include:


  • Curly waterweed – Lagarosiphon major: has caused major problems in Lough Corrib, Galway as well as at a dam in Dundrum, Co.Down.
  • Nuttall’s pondweed – Elodea nuttallii: has caused problems in Lough Erne – especially in 2010.
  • New Zealand Pigmyweed – Crassula helmsii: also known as Australian stonecrop it grows in 3 forms – submerged, semi-emergent and emergent. It has caused problems in Lady Dixon Park and Glastry clay pits.
  • Brazilian waterweed – Egeria densa: risk assessments have shown this is one to watch – known to be on sale.
  • Canadian Pondweed – Elodea canadensis: a widespread long established species which has been present since the mid 19th century. It has mainly settled down in most parts of Ireland but was documented as being highly invasive in the first 50 years following its initial introduction. It is still however known to cause problems in still flowing nutrient rich waterbodies such as disused sections of the Ulster canal.


  • Parrot’s feather – Myriophyllum aquaticum: has been known to cause problems in ponds. As of yet no known problematic ‘wild’ sites have been identified in Ireland or Northern Ireland but several sites in GB have experienced problems. Was eradicated from a high risk pond next to Portmore lough.
  • Water primrose – Ludwigia peploides and Ludwigia glandiflora: known to be on sale. A slightly warmer climate could benefit these species’. It was recorded recently in ponds in County Kerry. It is not known to occur in the wild in NI. Experience in France and Southern England has shown its potential to be highly invasive.
  • Water hyacinth – Eichornia crassipes: known to be on sale. A slightly warmer climate would benefit this species. It cannot survive overwinter outdoors in our current climate but it could potentially cause short term problems over the warmer summer months. Not known to occur in the wild. It has caused significant problems in Spain and Portugal.
  • New Zealand Pigmyweed – Crassula helmsii: comes in 3 forms – submerged, semi-emergent and emergent. Has caused problems in Lady Dixon Park and Glastry clay pits and Castlegregory, County Wexford.


  • Floating pennywort – Hydrocotyle ranunculoides: first recorded in NI in 2002. Known to occur at 6 sites of which 3 have been eradicated and 2 have control programmes ongoing. It has caused significant problems at Glastry clay pits and a mill race at Dunadry (now eradicated). It was also released into the River Lagan in Oct 2010.
  • Fringed waterlily – Nymphoides peltata: known to cause problems at the Belfast Waterworks upper pond and a number of other sites in Ireland.
  • Water fern – Azolla filiculoides: known to cause problems at Clea lakes near Killyleagh. It particularly likes still flowing stagnant water.


  • American skunk cabbage – Lysichiton americanus: known from a few sites where it can form extensive monocultures around the edges of lakes where it can extend its growth into adjacent wet wooded areas.

More information on six of these species is provided on the ‘Know what you grow‘ page.

Invasive Species Northern Ireland

Invasive Species Northern Ireland