Mertensia maritima (Oysterplant)
A perennial herb, usually found on gravelly beaches and shingle but sometimes on sand. It can also colonise earth and rocks tipped at the coast (Randall, 1988). Seeds can survive prolonged immersion in sea water, and dispersion in sea currents enables colonisation of new, but sometimes transient, sites. Lowland.
The distribution of M. maritima has varied markedly since 1800. In Britain expansion in the far north has been balanced by contraction in the south. In Ireland it declined during the last century, but is now increasing. Losses result from storms, recreational pressures, shingle removal and grazing.
European Boreo-arctic Montane element; a coastal species also found in E. Asia and N. America.
Light (Ellenberg): 8
Moisture (Ellenberg): 5
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 7
Salt Tolerance (Ellenberg): 3
January Mean Temperature (Celsius): 3.8
July Mean Temperature (Celsius): 13.4
Annual Precipitation (mm): 1083
Count of 10km squares in Great Britain: 222
Count of 10km squares in Ireland: 29
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.53
Scarce Atlas Account
Mertensia maritima (L.) Gray
This plant grows on exposed beaches where it occurs among shingle or on shingle mixed with sand. More rarely it grows on pure sand, but such colonies are usually short-lived. It occurs around the zone reached by the highest storm tides, and it probably benefits from periodic deposition of decaying seaweed. Frequently it occurs near the mouths of streams, and in very exposed situations it often grows where there is some shelter from rocks to protect it from the full force of the waves. There are usually no associated plants, but occasionally it occurs with strandline species such as Atriplex spp., Galium aparine, Honkenya peploides, Rumex crispus and Tripleurospermum maritimum.
M. maritima is a perennial species with a large taproot. The above-ground parts die back to ground level each winter. It is usually self-pollinated and the seeds are transported by wind and sea. Immersion in seawater does not affect seed germination and seeds have been known to travel at least 450 km. They also seem to be able to remain dormant in situ for several years. Some sand or organic matter is probably necessary for germination. Within individual colonies, numbers fluctuate as a result of erosion or accretion due to storms.
The map shows many old records and the plant is often stated to be declining. However it is a mobile plant which moves from site to site at the whim of storms. At some sites its occurrence for over 200 years is well documented, but at others there is good evidence that it occurred only as a casual for a few years. Within its main range there is no evidence to suggest that there has been an overall decrease, but at the southern edge of its range there is clear evidence of retreat. This is probably due to disturbance from human recreation and shingle removal. The largest and most important populations are in Orkney.
This is a boreal species which occurs around the north Atlantic, Pacific and the Arctic coast of America. On the east coast of Asia subsp. maritima is replaced by subsp. asiatica Takeda. In Europe its main stronghold is in Norway and Iceland, but it extends south to Ireland, Britain and, formerly, Denmark. Elsewhere its southern limit is approximately Maine (USA), Queen Charlotte Islands (Canada) and Riu Kiu Islands (Japan), but as in Europe the records peter into uncertainty. Its southern limit more or less corresponds with the mean January isotherm of 4.5 °C and the mean July isotherm of 19 °C (Scott 1963).
N. F. Stewart
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.
Atlas text references
The Irish Red Data Book. 1. Vascular Plants,
, Dublin, (1988)
Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols,
, Königstein, (1986)
Scarce plants in Britain,
, Peterborough, (1994)
Southward recolonisation by Mertensia maritima (L.) Gray on the coast of north-eastern Scotland,
, Watsonia, Volume 22, p.424-426, (1999)