Floating water plantain (Luronium natans) can be found in two different forms. In shallow water, it develops with floating oval leaves, in deep water it has submerged rosettes of narrow leaves. The flowers usually occur singly, on long stems from the leaf joints, and are white with yellow spots at the base of the petals.
Floating water-plantain seems to flourish best where the water is open, and where there is some disturbance. It does not seem to be able to tolerate competition from other aquatic vegetation, and populations fluctuate considerably in size as a result of dredging operations, or when the water levels drop to expose the bottom. In spite of the fact that over half of the recent (post-1980) records for this species have been from canals, plant populations seem to be more stable at natural sites than artificial ones, such as canals and similar habitats.
This species is found scattered across western Britain, with records in Wales, the West Midlands and northern England. It has also been introduced to some ditches in the Norfolk Broads and a few places in Scotland. The plant is endemic to Europe. Floating water-plantain seems to have spread eastwards from its 'home' territory of mid and North Wales, in particular Snowdonia, as a result of the building of the canal systems in the 19th century. Many of the plant's recent records have been from canals.
The floating water-plantain is listed under Annexes II and IV of the Habitats Directive and Appendix I of the Bern Convention, Schedule 4 of the Conservation (Natural Habitats, etc.) Regulations 1994, Schedule 8 of the Wildlife and Countryside Act, 1981 and is classified as Least Concern (LC) on the IUCN Red List (1).
The threat to this plant comes mainly from the opening up of the canals to leisure craft, which stirs up the mud and ooze increasing the turbidity of the water. In rivers, its preferred habitat has been reduced greatly by straightening of channels, dredging and pollution.
Floating water-plantain is listed in the UK Biodiversity Action Plan (UK BAP), and is included in English Nature's Species Recovery Programme. There are a number of organisations involved in protecting the future of this plant, including the Countryside Council for Wales, and British Waterways who are the lead partner. Amongst the measures proposed are the provision of 'sanctuary' areas of the canal, protected by piling, where the water-plantain can grow without excessive disturbance and where the turbid water stirred up by boat traffic will not cause harm. It has also been proposed that where canal restoration might involve damage to the plant populations, reserves should be created for the water-plantain so that it can be re-introduced following completion of the engineering work.
The UK Biodiversity Action Plan for this species is available at UK BAP.
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