An annual to short-lived perennial herb, growing on the margins of pools, lakes, rivers and ditches, in clay-pits and wet hollows in marshy fields. Its sites are usually waterlogged in winter, but it occasionally occurs on dry ground. It can tolerate mildly saline conditions. Lowland.
R. maritimus has been lost from some sites in Britain due to drainage, the loss of ponds and the regulation of water levels. However, there are many more records now than in the 1962 Atlas, and the species spreads readily to new sites; its overall distribution is stable. Increasing eutrophication in Ireland has favoured an expansion there.
Circumpolar Temperate element.
Height (cm): 40
Perennation - primary
Perennation - secondary
Life Form - primary
Life Form - secondary
Comment on Life Form
Clonality - primary
Count of 10km squares in Great Britain: 398
Count of 10km squares in Ireland: 17
Count of 10km squares in the Channel Isles: 3
Atlas Change Index: 0.42
Scarce Atlas Account
Rumex maritimus L.
Status: not scarce
Like its relatives R. palustris, Persicaria laxiflora and P. minor, this species is part of the distinctive vegetation that develops on wet nutrient-rich mud as the water-level in ditches, pools and reservoirs falls through the summer. Other typical associates include Bidens spp. and Chenopodium spp. R. maritimus prefers wet, well-illuminated sites that are often calcareous and rich in both nitrogen and phosphorus. Despite the scientific name, R. maritimus is not confined to the coastal zone, though it is tolerant of mildly saline conditions. Although most common on silt and wet gravel in the flood plains of major rivers, suitable situations occur also on old peat cuttings or in wet hollows within grassland. Its chief requirement is for sites with a strongly varying water level where water lies through winter and late into the spring, creating conditions that are inimical for both exacting aquatic and terrestrial species. Such conditions occur on the shores of Breckland meres, for example. R. maritimus is a rare casual on spent ballast and other dry open habitats. Its native distribution is strictly lowland.
R. maritimus is an annual, producing ample seed, and is a pioneer species that is able to colonise new habitats efficiently. Plants can sometimes overwinter and flower again in their second year. In Europe it is an indicator of warm areas, needing a long summer and autumn that evaporates pools and allows seed to mature.
R. maritimus has declined sharply in Britain in the last 150 years, due to the elimination of farm ponds and surplus ditches, the drainage of wet grassland and the increased regulation of water levels (Mountford & Sheail 1989). However, its late flowering and fruiting, together with its use of transient habitats, may lead to it having been overlooked in some areas recently. For example, it is certainly more widespread than was thought in the Cambridgeshire Fenland. It may be encouraged by a more laissez faire attitude to water management and the continued use of ponds by stock and waterfowl.
R. maritimus is somewhat continental in its distribution, being found throughout most of Europe but absent toward the Arctic and the Mediterranean, and rare on the Atlantic seaboard (Jalas & Suominen 1979). It occurs through temperate Asia as far as northern India, China and Japan. In the Americas, it is represented by subsp. fueginus which is found from Quebec and Alaska to Tierra del Fuego, but is mainly montane in the tropics.
J. O. Mountford
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
1988. The Irish Red Data Book. 1. Vascular Plants.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1979)
1981. Docks and knotweeds of the British Isles. Botanical Society of the British Isles Handbook no. 3.
1994. Scarce plants in Britain.