A stoloniferous perennial of mesotrophic or oligotrophic lakes, pools and slow-flowing rivers, and abandoned or little-used canals. In deep water it persists as rosettes of submerged leaves, sometimes with cleistogamous flowers, but it produces floating leaves and flowers freely in shallower water or on exposed mud. 0-450 m (Bugeilyn, Monts.).
In Britain, L. natans has been lost from many of its lowland sites because of eutrophication. However, some populations, particularly of the submerged form, have been overlooked until recently in both Britain and Ireland; it may still be under-recorded.
Suboceanic Temperate element.
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Light (Ellenberg): 8
Moisture (Ellenberg): 11
Reaction (Ellenberg): 5
Nitrogen (Ellenberg): 3
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.3
July Mean Temperature (Celsius): 14.7
Annual Precipitation (mm): 1229
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 91
Count of 10km squares in Ireland: 3
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.24
External Species Accounts
Scarce Atlas Account
Luronium natans (L.) Raf.
WCA Schedule 8 species
L. natans is an aquatic plant which is currently found in two main habitats. Its most important natural habitat is in slightly acidic and oligotrophic lakes, where it grows in water up to 2 metres deep, with species such as Callitriche hamulata, Isoetes lacustris, Littorella uniflora and Lobelia dortmanna, or on bare mud exposed by falling water levels. It is also found in canals, where it grows in circumneutral or slightly basic, mesotrophic water, often with Elodea nuttallii, Lemna minor, Sparganium emersum and a range of Potamogeton species. In canals it apparently relies for its survival on periodic disturbance, which can be provided by light boat traffic in navigable waters or by periodic dredging or the control of marginal vegetation elsewhere. L. natans is also found in a slow-flowing, mesotrophic stretch of the Afon Teifi, and it was recorded in the past from a variety of other natural habitats, including streams, ditches, lowland lakes and pools. It is established as an introduction in the Norfolk Broads (Driscoll 1985) and also recorded as an alien in Scotland.
L. natans is a stoloniferous perennial. In fast-flowing water or deep water, or in sites which are shaded or turbid, it can persist as rosettes of submerged leaves. In shallow water or on wet mud it produces floating or terrestrial leaves and flowers and fruits freely. Reproduction is both vegetative and by seed. Populations in lakes appear to be largest when water levels are low and much mud is exposed, and in canals they are often greatest after major disturbance.
The populations in oligotrophic, upland lakes appear to be stable. During the nineteenth century the species spread into the canal system and these new sites more than offset losses of lowland, mesotrophic sites caused by eutrophication and habitat destruction. Since 1970 populations in canals have declined because of the increase in recreational boat traffic.
L. natans is endemic to Europe. It is a predominantly western European species, but extends eastwards to Yugoslavia, Bulgaria and Poland. It is rare and decreasing over much of its European range.
L. natans has recently received special protection under Appendix I of the Bern Convention and Annexes II and IV of the European Community Habitats & Species Directive. For a recent review of the ecology and conservation of this species in Britain, on which much of the above account is based, see Willby & Eaton (1993).
C. D. Preston
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols. .
1999. Biology, genetic variation and conservation of Luronium natans (L.) Raf. in Britain and Ireland. Watsonia. 22:301-315. .
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols. .
1997. Aquatic plants in Britain and Ireland. .
1994. Scarce plants in Britain.