Yellow-flowered aquatic plant common in French gardens is illegal to plant
Once established, it spreads rapidly in water systems, with even small fragments capable of forming new plants
Ludwigia grandiflora can reach up to 4 metres in length
Maria Papworth/Shutterstock.
Homeowners in France may unknowingly have this aquatic flower in garden ponds without realising it is strictly regulated in France under environmental law.
The species, known as Ludwigia grandiflora, is listed as an invasive alien species under both French and EU regulations. Despite this status though, the flower can still be seen in several parts of France, particularly in the west and south.
The plant, originally from South America, was introduced to Europe in the 19th century as an ornamental aquatic plant. It quickly became popular due to its bright yellow flowers and floating stems, with people purchasing them for their ponds, before it began escaping cultivation and spreading in the wild.
Once established in natural environments, it grows particularly well in still or slow-flowing water, allowing it to spread through connected rivers and wetlands.
However, it can then form thick floating mats across the surface of the water, blocking light and reducing oxygen levels in the water.
This can affect native aquatic plants, disrupt fish and amphibian habitats, and gradually alter wetland ecosystems. It can also slow water flow and lead to the build-up of sediment, making rivers, canals and drainage systems more difficult to manage.
The plant, once established, is difficult to control. Even very small fragments can break off and grow into new plants.
What the law says in France
Based on the ministerial order of February 14, 2018, it is prohibited to possess, sell, transport, cultivate, or intentionally introduce certain listed invasive plants.
Penalties can reach up to €150,000 and three years’ imprisonment in the most serious cases, particularly where species are intentionally introduced or allowed to spread into the natural environment.
What to do if you have one in your garden pond
Gardeners are advised not to keep or plant Ludwigia grandiflora, even in contained ponds, as fragments can still escape and spread into the environment.
If you find one in your garden pond, it is advised not to try to remove it yourself without guidance and report it to your local authorities.
