Defra and the Scottish government are calling on Britain's gardeners to help stop the spread of invasive aquatic plants that damage the natural environment and cost the economy millions. 

The 'Be Plant Wise' campaign highlights five of the worst offending plants wreaking havoc on wildlife and waterways.

Gardeners often unwittingly exacerbate the problem by disposing of unwanted pond plants without composting them properly, throwing out pond water or fish tank water incorrectly, or accidentally introducing species to the wild. A whole river can be strangled just from one fragment of plant.

Fast-growing, floating pennywort, New Zealand pigmyweed, water-primrose, parrot's feather and water fern - all of which are commonly found  in garden ponds - are some of those named as posing significant problems in the wild, with the potential to cost the nation millions of pounds if they continue to expand at their current rate. Many of these plants grow to such an extent that they form dense mats which can look like dry land and so pose an additional danger of drowning to people and livestock.

Natural Environment Minister Huw Irranca-Davies launched the new public campaign with the support of gardener, Charlie Dimmock, from the banks of the River Wandle, in London, which is choked with floating pennywort.  

Irranca-Davies said: 'From the River Severn to the smallest stream, our waterways are being invaded. We all know about grey squirrels and Japanese knotweed but how many people know that invasive aquatic plants can out-compete native species, choke waterways, harm native wildlife, disrupt the navigation of boats, interfere with recreational activities, such as fishing and boating, and exacerbate flooding?'

'Gardeners can do their bit to help stop the spread by knowing what they grow in their ponds and disposing of unwanted plants with the utmost care. I'm really pleased that many retailers are already taking steps to ensure people know what they're buying and advising customers on how to dispose of plants properly. This is vital to halt the spread and prevent our waterways from getting overrun.'

The problem is already affecting many major landmarks, including the New Forest in Hampshire, the River Soar in the East Midlands, Richmond Park in London, Roadford Lake in Devon, and Horsepond in Corfe Castle, Dorset.

The sheer scale of the problem threatening Britain's waterways, wildlife, leisure activities, farming and tourism can be seen in France where water-primrose is known to be present at over 500 sites and is the most recent invasive plant to reach Britain's shores.  In France control costs run into several million euros a year.

Charlie Dimmock, championing the campaign for gardeners said: 'Ponds and rivers give us a bounty of amazing wildlife, but sometimes the balance can be upset, harming our natural biodiversity. Pond-lovers, like me, must all play our part in making sure invasive aquatic plants don't cause serious damage to our beautiful waterways. By being plant wise in our gardens we can help protect natural habitats in the wild and ensure all ponds and rivers thrive.'

Visit  www.direct.gov.uk/beplantwise  to find out more about the campaign and learn how to spot and manage invasive aquatic plants.