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(Ludwigia grandiflora, Ludwigia peploides and Ludwigia uruguayensis)
Banned From Sale after April 2014. A non-native invasive plant.
Originally introduced as an ornamental and water garden plant. The water primrose bears bright yellow flowers but can cause havoc if released in the wild. It is difficult to distinguish between the non-native species of Ludwigia and they are often incorrectly labelled so it may be necessary to seek expert advice.
What's the problem?
Water primrose can have a devastating effect on native habitats. Its rampant growth out-competes native species and can clog waterways, with its dense vegetation contributing to flooding. It spreads primarily by stem fragments but also by seeds which means it can spread quickly and it can make eradication difficult. It has been particularly problematic in parts of Europe; in the UK it is on a Rapid Response list, meaning that any known sites, of which there have been a handful, are targeted for immediate eradication.
Rapid Risk Assessment
***** Critical Risk
Plantlife campaigned long and hard to have this species banned from sale. As of April 2014 it will be in England and Wales. This species is also listed on Schedule 9 of the Wildlife and Countryside Act in England and Wales therefore, it is also an offence to plant or otherwise cause to grow these species in the wild.
Removing water primroses
Regular cutting (at least every 6-9 weeks during the growing season - cut more frequently if necessary) will help to weaken the plant. In your garden pond you can thin using a rake. Cut material must be removed from the water as soon as possible and all fragments need to be removed to prevent regrowth (or spread downstream if you are clearing an area of river). Careful pulling out of stems by hand will help eradicate small colonies and after cutting.