A diminutive rhizomatous perennial growing on firm estuarine mud by tidal rivers, and in tidal pans in brackish grazing marshes. It occurs close to the upper limit of tidal influence, avoiding strongly saline areas. It reproduces vegetatively by turions, and by seed, but flowering and fruiting is very poor in many localities. Lowland.
Colonies of E. parvula have been lost due to dredging and the cessation of grazing, which allows the development of taller vegetation. It is easily overlooked, and its discovery in E. Ross in 1999 suggests that it may be found in other northern sites.
European Temperate element; also in E. Asia and N. America.
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Light (Ellenberg): 6
Moisture (Ellenberg): 9
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 5
Salt Tolerance (Ellenberg): 3
January Mean Temperature (Celsius): 4.6
July Mean Temperature (Celsius): 15.3
Annual Precipitation (mm): 1130
Height (cm): 8
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 15
Count of 10km squares in Ireland: 5
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0
Plantatt Conservation Status
RDB Species Accounts
Eleocharis parvula (Roemer & Schultes) Link ex Bluff, Nees & Shauer (Cyperaceae)
Dwarf spike-rush, Sbigfrwynen Morafon
Status in Britain: VULNERABLE.
Status in Europe: Not threatened.
E. parvula is a diminutive perennial restricted to estuaries and brackish grazing-marshes in large tidal rivers in southern and western Britain. There it typically forms discrete, yet often dense, patches in tidal pans and along creek margins on firm bare muddy substrates which are subject to tidal inundation. In virtually all its British localities, it grows close to the upper limits of tidal influence, avoiding the strongly saline conditions associated with many saltmarshes (Byfield 1992). This is reflected in its associates which include Bolboschoenus maritimus, Juncus foliosus, Limosella australis, Ranunculus sceleratus and Veronica anagallis-aquatica, though it apparently never occurs with halophytes such as Aster tripolium, Limonium vulgare and Salicornia species. However, more often than not, E. parvula occurs in mono-dominant stands, without other associates.
In Britain, E. parvula has two centres of distribution: along the coast of southern England from Hampshire to Devon, and along the western coastline of North Wales. In the former area the plant is very rare, occurring in colonies of very limited extent at three localities in Hampshire and Devon. The Welsh colonies, in Caernarvonshire and Merioneth, are generally much more extensive and thriving.
The comparative health of the Welsh populations must in part be due to current habitat management. Because of its very small size, the plant is typically reliant on grazing by sheep or cattle reducing competition from coarser plant species. The Welsh colonies survive in extensive grazing marshes, where traditional grazing is still practised. The effect of grazing animals is also important as the principal mechanism by which the plant spreads: poaching breaks up the mats of E. parvula, which float and are redistributed at high tide when the pans are flooded. In addition, the plants produce small whitish 'bulbils' which presumably act as perennating organs, and are spread by tides and on the feet of grazing livestock. It is not known how important sexual reproduction is to overall recruitment, but certainly in many localities the plant flowers and fruits very poorly. Flowering, when it occurs, is between late August and early October.
The principal threat to the survival of E. parvula comes from a cessation of grazing which results in a rapid succession to brackish swamps dominated by Bolboschoenus maritimus, Phragmites australis or Scirpus lacustris ssp. tabernaemontani from which E. parvula is quickly lost. In addition, river 'engineering' activities such as dredging and dyking have resulted in the loss of certain British colonies. It is, however, an inconspicuous plant which usually grows in an uninviting habitat, and may thus have escaped detection at other sites.
In Europe the plant is generally local, occurring from Fennoscandia southwards to Portugal, former Jugoslavia and south-east Russia (Walters 1980). It has been recorded from several stations in Ireland, but its current status there is uncertain. It is extinct in Germany and Switzerland. Elsewhere it occurs in North and possibly South Africa, central and eastern Asia, India and Java, and North and South America.
A. J. Byfield
Atlas text references
1988. The Irish Red Data Book. 1. Vascular Plants.
2000. Eleocharis parvula discovered in Scotland. Watsonia. 23:341-342.
1995. The conservation of scarce and declining plant species in lowland Wales: population genetics, demographic ecology and recommendations for future conservation in 32 species of lowland grassland and related habitats. (Science Report No. 110).
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1999. British Red Data Books. 1. Vascular plants, edn 3.