A small rhizomatous perennial of mountain tops, usually occurring in exposed situations on or near the summit ridge. Habitats include bare stony ground, Racomitrium heath, bouldery crests of solifluction terraces, and sometimes hollows between rocks. The relative importance of sexual and vegetative reproduction in British populations is uncertain. 700-870 m (Seana Bhraigh, E. Ross).
This species was discovered in 1950 in W. Ross, and subsequently at two additional sites in the same vice-county. Its populations fluctuate in size, but appear to be stable in the longer term.
European Arctic-montane element; rare in the Arctic zonobiome and absent from mountains of C. Europe.
Light (Ellenberg): 9
Moisture (Ellenberg): 4
Reaction (Ellenberg): 4
Nitrogen (Ellenberg): 1
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 0.9
July Mean Temperature (Celsius): 10.9
Annual Precipitation (mm): 1982
Count of 10km squares in Great Britain: 3
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
RDB Species Accounts
Artemisia norvegica Fries (Asteraceae)
Norwegian mugwort, Gròban Lochlannach
Status in Britain: VULNERABLE.
Status in Europe: Vulnerable.
This species is one of the most recent additions to the British flora, having remained undetected on a few remote Scottish mountains until 1950. Exclusively a plant of mountain tops, at 700-870 metres, it occurs on or near summit ridges, usually in exposed situations and subject to a severe climate. Habitats include moist sandy or gritty debris in bared areas of sparse vegetation, closed but stony Racomitrium lanuginosum-heath, amongst boulders on flat summit plateaux, the more sheltered hollows between blocks, and exposed bouldery crests of small solifluction terracettes on shallow slopes just below the summit ridge. Associated species include Alchemilla alpina, Carex bigelowii, Deschampsia flexuosa, Festuca ovina, Juncus trifidus, Minuartia sedoides, Salix herbacea, and Racomitrium lanuginosum, and where soils are base-enriched, such species as Antennaria dioica, Gnaphalium supinum and Thymus polytrichus.
A. norvegica is a rhizomatous perennial. Flowering is usually between July and September, the timing and degree of flowering likely to depend on climatic conditions. The numbers of flowers on each stem varies, but at one site where counts have been made, more than half bore two flower heads, and most of the remainder were single. In some years, very few flowers occur, a possible reason being prolonged dry spells in the plant's early growing season. Little appears to be known about its reproductive biology and the relative importance of vegetative and sexual reproduction. It has, however, been suggested that conditions are unsuitable for seed production in normal seasons (Raven & Walters 1956).
It is known from only three mountains in West Ross, each supporting at least several hundred plants. The largest site holds many thousands of plants, while population counts at other sites have ranged between 150 and 'hundreds' of individuals. Some populations are restricted in extent, covering only a few square metres, but the largest comprises colonies scattered over about nine hectares of a summit ridge. Counts of individual plants within a colony have provided some evidence that populations fluctuate in size, presumably in response to climatic or biotic factors. It has been suggested that at one site an apparent population decline could be because of the removal of sheep, which has led to reduced disturbance and the extent of bared ground receptive to dispersed seed. In general, however, populations appear to be reasonably stable.
Two of its sites are safeguarded within SSSIs, one of which is also an NNR. Their relative remoteness affords further protection, and no special conservation measures seem to be required. Botanical collecting is not a significant threat, nor is the plant likely to be of interest to the horticultural trade.
Elsewhere it occurs only in Norway and the northern Ural mountains, and thus has one of the most disjunct and restricted distributions of any of our native plants. The Scottish taxon has been regarded as an endemic var. scotica Hultén (Hultén 1954) on the basis of its different leaf shape, fewer capitula and dwarf growth form. More recent chemical and morphological evidence (Øvstedal & Mjaavatten 1992) indicate some real, albeit small, differences between plants from Scotland and south and south-central Norway, but whether this warrants varietal status is debatable.
M. J. Wigginton
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.