A perennial, bulbiliferous and stoloniferous herb of basic rocks. S. rivularis grows on ledges or under overhangs, in damp, steep, N.- to E.-facing gullies, or more rarely in bryophyte-rich flushes on exposed scree. From 795 m in the Lairig Ghru (Easterness) to 1200 m on Ben Nevis (Westerness).
The distribution of S. rivularis has been stable since the 1962 Atlas, though a few old records have been confirmed relatively recently.
Circumpolar Arctic-montane element; absent from mountains of C. Europe.
Count of 10km squares in Great Britain: 21
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.19
RDB Species Accounts
Saxifraga rivularis L. (Saxifragaceae)
Highland saxifrage, Clach-bhriseach t-Slèibhe
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened.
In Scotland, S. rivularis is a plant of areas of late snow-lie and springs that are derived from meltwater. Thus, its occurrence is limited to approximately twenty areas where significant snow patches persist into the summer months. It descends to about 820 metres on Beinn Dearg and ascends to its highest altitude of 1,200 metres on Ben Nevis. All sites have a northerly, north-easterly or easterly aspect and occur on steep, rocky slopes, gullies and crags, though some flush sites are locally much less steep. The plant usually occurs in a matrix of mosses, organic material and sand or gravel in a regularly irrigated or permanently wet skeletal soil, over block scree, on ledges or crevices of crags or in bryophyte flushes. The most constant associates are mosses such as Hygrohypnum ochraceum, Philonotis fontana, Pohlia ludwigii, and P. wahlenbergii var. glacialis, but frequent vascular plant associates include Cerastium arcticum, C. cerastoides, Chrysosplenium oppositifolium, Cochlearia officinalis, Epilobium anagallidifolium, Saxifraga stellaris and Stellaria uliginosa. On a few sites where the substrate is more base-rich, it is associated with Saxifraga cernua, S. cespitosa and S. nivalis.
S. rivularis is a small, stoloniferous perennial forming rather fragile, loose tufts. Bulbils are developed in the axils of the basal leaves during summer and autumn and these germinate before the flowering season, giving rise to slender runners from which develop new plants. The flowering period is dependent on the amount of accumulated snow and the pattern of snow melt; in the same season it is possible to find seed-heads in some populations in July and find flowers in other populations at the end of August. In a poor summer; some populations may not set seed. Most populations consist of a relatively small number of mature plants, many of which produce flowers in a normal year, and a larger number of juveniles, often in a dense tuft, developed from the previous year’s bulbils.
Most populations are in the central Highlands, from Glen Coe in the west to Lochnagar in the east but there are isolated sites from Ben Lawers in the south to the Torridon Mountains and Beinn Dearg in the north. Estimating population size presents considerable problems because of the large numbers of juveniles, but the largest populations in Glen Coe and the Cairngorms exceed 1,000 plants. More isolated populations are usually much smaller, often fewer than 50 plants. Population size varies to an extent because of the inherent instability of many of the sites, but observations of the more accessible populations suggests that they are constant in occurrence though the numbers of plants may fluctuate. Most of the populations are on SSSIs or NNRs and so are safeguarded to some degree, and many sites are either remote or difficult of access which provides further protection. A recent survey of several sites revealed some damage from grazing and trampling by sheep and deer. At least two sites are threatened by erosion caused by increased recreational activity, at least partly owing to the provision of easier access for skiers.
S. rivularis is a widespread species in the arctic extending southwards to Iceland and southern Norway in Europe, to Kamchatka in Asia and in North America to Montana, Newfoundland and southern Greenland. Outlying stations are in California, Colorado and in the Scottish Highlands (Webb & Gornall 1989).
G. P. Rothero
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
1998. Conservation genetics of an arctic species, Saxifraga rivularis L., in Britain. Botanical Journal of the Linnean Society. 128:1-14.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1999)
1989. Saxifrages of Europe.
1999. British Red Data Books. 1. Vascular plants, edn 3.