A dwarf procumbent and creeping shrub, typically found on basic ledges and rock crevices on mountains, but also occurring in upland calcareous grassland, on coastal shell-sand in N. Scotland, and limestone pavement in Ireland. From sea level in W. Sutherland and the Burren (Co. Clare) to 1035 m on Ben Avon (Banffs.).
The distribution of this species appears to be stable overall, but populations in the Lake District are now very small. It is better recorded than in the 1962 Atlas.
Circumpolar Arctic-montane element, but absent from eastern N. America.
Light (Ellenberg): 8
Moisture (Ellenberg): 4
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 2
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 2.1
July Mean Temperature (Celsius): 12.4
Annual Precipitation (mm): 1734
Height (cm): 10
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 99
Count of 10km squares in Ireland: 25
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.35
Scarce Atlas Account
Dryas octopetala L.
Dryas octopetala normally grows on basic rocks, usually where the soil is not too deep and drainage is very good. Sites tend to be relatively exposed. Commonly associated plants include Carex flacca and Saxifraga oppositifolia. In north-west Scotland it grows at unusually high densities, the densest sites being found at sea level on wind-blown shell sand where it forms a thick sward. At Invernaver it is a component of a Juniperus communis heath and is found growing amongst Betula pubescens woodland at Loch Cill Chriosd and at Loch Urigill. D. octopetala is found from sea level in the extreme north west of Scotland, as at Durness, to about 1035 metres on Ben Avon.
D. octopetala is a perennial plant flowering in June and July. Pollination is by insects. The seeds are wind dispersed and germinate best on eroded or bare sites. Few new sites have been recorded, indicating that seedling establishment does not occur readily although the plant is widely acknowledged as a colonising species. The plant is creeping in nature and can easily reproduce vegetatively.
The range of this species does not appear to be expanding or contracting significantly, though a number of potential pressures can be identified. One of the major threats to some sites is erosion caused by the large numbers of walkers or grazing stock. In many eases the biggest threat appears to be overgrazing by rabbits which are prolific at several sites.
D. octopetala sense lato is a circumpolar arctic-alpine species. In Europe it is found in montane communities as far south as central Italy.
The characteristic leaves of D. octopetala are found in glacial and late glacial deposits in sites south of its current range in Britain, and elsewhere in north-west Europe (Godwin 1975). For a more detailed account of its present-day ecology, see Elkington (1971). As this plant does not seem to grow on wind-blown shell sand elsewhere in Europe, Scottish populations are internationally significant.
Atlas text references
1988. The Irish Red Data Book. 1. Vascular Plants.
1971. Biological Flora of the British Isles. No. 124. Dryas octopetala L. Journal of Ecology. 59:887-905.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1994. Scarce plants in Britain.