A perennial herb found on mountain rock ledges and grassy slopes on Dalradian limestone and schists, and on base-rich sandstone sea-cliffs and calcareous sand dunes. The larger populations occur at coastal sites in Sutherland. From sea level at Bettyhill (W. Sutherland) to 760 m on Ben Vrackie (E. Perth).
Apart from losses in the 19th century, the distribution of this species appears to be stable, although some sites may be suffering from over-grazing and others from scrub encroachment.
European Boreal-montane element, but absent from the Boreal zonobiome. In mainland Europe O. halleri is strictly montane.
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Light (Ellenberg): 9
Moisture (Ellenberg): 3
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 2
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 2.5
July Mean Temperature (Celsius): 12.9
Annual Precipitation (mm): 1141
Height (cm): 13
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 16
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.16
RDB Species Accounts
Oxytropis halleri Bunge ex Koch (Fabaceae)
Purple oxytropis, Ogsatropas Corcarach
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened. Endemic.
Most populations of O. halleri occur close to sea level on the north and east coasts of Scotland. There it grows on dry cliffs formed from basic Old Red Sandstones and conglomerates, and on calcareous sand-dunes. Associated species on cliff ledges include Geranium sanguineum, Helianthemum nummularium, Sedum rosea and Thymus polytrichus, whilst on cliff-tops it grows in short turf with Carex flacca, Lotus corniculatus, Plantago coronopus, P. maritima and occasionally Scilla verna. On dunes, associates include Anthyllis vulneraria, Astragalus danicus, Galium verum, Koeleria macrantha, Linum catharticum, Lotus corniculatus, Thalictrum minus and, in a few places, Primula scotica. Inland, O. halleri grows on Dalradian limestones and schists at altitudes of 600-760 metres, often in rich swards with such choice species as Astragalus alpinus, Botrychium lunaria, Cerastium alpinum, Draba incana, Persicaria vivipara, Saxifraga oppositifolia and Silene acaulis. Whilst most sites are rather basic, some are not. For instance, it grows on an acidic dyke on Ben Chonzie, and some of its coastal bank habitats are not obviously basic.
This perennial herb flowers between May and July, in montane sites often a month later than on the coast. Small plants frequently occur in the vicinity of larger ones, so reproduction from seed can be inferred. Flowering is inhibited by grazing. Plants in heavily grazed swards can be diminutive, and quite different in appearance from the luxuriant profusely-flowering clumps seen on inaccessible cliffs.
O. halleri was first reported in Britain by Lightfoot in 1777 (as A. uralensis) growing on Carboniferous limestone cliffs near North Queensferry, Fife and on Ben Sgulaird, Argyll. The former site was destroyed by the building of the railway cutting to the Forth Bridge, but the plant is still on Ben Sgulaird. It has a relict distribution in Britain, and is now confined to the north coast of Sutherland, the east coast of Ross-shire, a single site on the Mull of Galloway and three mountains in Perthshire and Argyll. There are eighteen extant localities, some of which support more than one population. Populations vary in size from a few plants at most east coast sites to some large colonies of many thousands extending along hundreds of metres of cliff on the north Sutherland coast. In the absence of detailed long-term monitoring, population trends cannot be discerned. There may be other as yet undiscovered colonies, particularly along the more remote stretches of the north Scottish coast.
On coastal cliff ledges O. halleri is generally protected by its inaccessibility. Elsewhere, encroachment by gorse and scrub and, conversely, the use of fire to control scrub, may both present a threat. One site is in danger of being overshadowed by a commercial forestry plantation. Dune and cliff-top habitats are susceptible to overgrazing by rabbits and domestic livestock. At one locality, the supplementary feeding of livestock has led to excessive nutrient enrichment near a colony of O. halleri, which is now threatened by the vigorous overgrowth of rank grass. In montane habitats grazing could be restricting its distribution.
Elsewhere in Europe O. halleri is strictly montane, being found in the mountains of central Europe, including the Pyrenees, Alps, and Carpathians. There is one known locality in eastern Albania.