Saxifraga stellaris L., Starry Saxifrage

Account Summary

Growth form and preferred habitats

This typical arctic-alpine, perennial occurs, sometimes in considerable quantity, ie in patches of a 100 or more loose, leafy rosettes bearing leafless flowering stems 4-20 cm tall, in suitably wet, acidic, open sites beside streams, or in flushes where water constantly seeps through the soil, gravel, or across ± bare rock, including occasionally on shady, near vertical, rock faces where there is some seepage of water. Leaves are a fresh green, crisp and slightly fleshy, but not leathery, spathulate, tapering to the base but without a distinct petiole. The star-like flowers are borne in a 12- or more-flowered lax panicle, sepals reflexed and petals white, 4-5 mm, each bearing two yellow spots near the base, anthers coral-pink or vermillion-red, visited mainly by flies (Clapham et al. 1987; Sell & Murrell 2014).

Webb & Gornall (1989) regard S. stellaris as, "somewhat calcifuge", a definition that does not fit it very accurately in the Fermanagh area, since here the acidic preference is absolutely obvious. The previously mentioned authors qualify their verdict however (p. 58), suggesting that the species absence from limestone may be due more to lack of surface water than to chemical factors. It definitely appears that the species requires not just wet conditions for growth and survival, but also the movement of water, be it merely a steady seepage through soil or across rock surfaces, which are often in these circumstances covered with a cushion or carpet of bryophytes. The other major species requirement is for a fairly open habitat, where there is very little or no vascular plant competition, and thus where seedlings and diminutive plantlets can develop and establish. As it grows beside or in flowing water, it inevitably can be carried far downstream from its main site.

Fermanagh occurrence

In Fermanagh, this rather variable species is very rare and is only found along the N scarp of Cuilcagh and near the summit ridge (Cuilcagh Gap), spread across just three tetrads. It can appear as small more or less isolated tufts of a few rosettes, perhaps linked at some stage in their development by stoloniferous stems or, as already mentioned, occasionally it may form larger, crowded patches.

Irish occurrence

Starry Saxifrage is a very scarce and local plant elsewhere in NI, being completely confined to the Sperrins in Cos Tyrone and Londonderry (H36, H40) and the Mourne Mountains in Co Down (H38), where some of the stations have not been seen since 1970 (New Atlas). There is a similar, moderate-altitude mountain distribution around all the major ranges in the RoI, but again it has not been seen in recent years at some of its older stations. S. stellaris is most frequent in Cos Kerry, W Galway, Wicklow and W Donegal (H1, H2, H16, H20 & H35). A gemmiferous variant is found in Connemara, being described as 'frequent' by the Gleninagh River at around 240 m, which flows from the Twelve Pins (or Bens) into the N end of Lough Inagh, Co Galway. It has leafy buds formed in the place of flowers. They are not released from the parent plant, but flop down onto the ground near it, and may root. "Similar plants have been reported from Co Kerry, Northumberland and Scotland, but there are no vouchers and no precise documentation." (Webb & Gornall 1989).

British occurrence

The British headquarters of S. stellaris is very definitely situated in the Scottish mountains, including the border Southern Uplands, but it is also well represented in Cumbria, the N Pennines and in N Wales. It shows little loss, if any, in Britain during the last 60 years (Preston et al. 2002).

European and world occurrence

In Europe, S. stellaris shows a typical arctic-alpine distribution in all the mountains ranges of Europe. S. stellaris subsp. stellaris is absent from the high Arctic, but is found in Iceland and Lapland, and is common in the mountains of Norway, W Sweden and B & I. A form recognised as subsp. alpigena Tem is widespread throughout the Alps and is frequent in the Pyrenees, Romanian Carpathians and the mountains of Bulgaria. It is more local in the mountains of Spain, Portugal, Corsica, Auvergne and the Cévennes, N Apennines and Yugoslavia. The species reaches its southern limit in the Sierra Nevada of Spain and in N Greece. Beyond Europe the range of subsp. stellaris is restricted to S Greenland and a few stations in Labrador and Baffin Island, making it one of the amphi-atlantic plants (Hultén & Fries 1986, Map 1016; Webb & Gornall 1989).

Threats

None.

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