Water primrose Ludwigia grandiflora is an ornamental perennial plant native to South and Central America, associated with wetlands and marginal zones of watercourses, ditches, ponds and lakes. The plant has been introduced into the UK through the ornamental aquatic plant trade.

It primarily spreads by vegetative fragments and forms dense carpets of growth that exclude native biodiversity, increases flood risk and siltation and degrades amenity. A coordinated GB eradication programme commenced in 2009. In 2010, the GB Non-Native Species Secretariat Programme Board issued a risk assessment that identified a high risk of establishment and spread across the whole UK. This was largely based on the impact it was already having elsewhere in Western Europe, particularly France (right). For this reason, water primrose became the target of the first Invasive Species Action Plan, which described procedures for its eradication in GB and tasked the coordination of that role to the Environment Agency. Due to concern over potential escapement and spread of this species, prior to 2014, the sale of water primrose had been discouraged by a voluntary code of practice. To prevent any further introductions, in April 2014 water primrose was banned from sale in England and Wales.

Water primrose is predominantly found in Southern England, but has been found as far north as Scarborough (below). To date, all sites north of the Severn valley are believed eradicated. Water primrose has the potential to invade a variety of habitats, particularly ponds, lakes, wetlands, ditches and other watercourses. The current stage of invasion suggests that it is mostly confined to primary and secondary sites of introduction. With respect to flowing water courses, only one river location and three ditch sites have so far been invaded. One of those ditches at West Bay, Dorset, has proved to be one of the most intractable sites to date; having been mechanically excavated once and sprayed 22 times over a nine-year period without yet eradicating the infestation.

Fortunately, it hasn't been detected in Shropshire, but we depend on people to let us, CEH or the Environment Agency know if it is spotted here. Please report any sightings of the plant to alertnonnative@ceh.ac.uk

If you have the plant on your land, don’t let it spread. Contact the Environment Agency for
advice on how to remove it 03708 506 506.