An annual of open situations, predominately in artificial habitats but also in gravelly and sandy places. 0-425 m (Grinton, N.W. Yorks.).
This small overwintering annual is found mainly in very open situations in artificial habitats, including the bases of walls, between paving slabs, on sandy and gravelly paths, forestry tracks and cinders in railway sidings. More natural habitats include gravelly and sandy places on heaths and commons. Generally lowland, but reaching 375 m at Esgair Fraith (Cards.).
Subsp. erecta is found in similar habitats to subsp. apetala, including walls and pavements, paths and tracks, forestry rides, railways sidings, and, exceptionally, saltmarsh turf (Halliday, 1997). 0?425 m (Grinton, N.W. Yorks.).
An annual of maritime rock crevices, cliff-tops, stabilised shingle, dune-slacks and disturbed areas in upper saltmarsh on sandy substrates; also on walls and tracks, in pavements and on sandy roadsides near the sea. A form of it, described as var. alpina, has been recorded at 1210 m on Ben Nevis (Westerness), though the identity of such plants requires confirmation.
This cushion-forming, perennial herb usually occurs in open, unstable habitats with little vascular plant cover, generally growing on soft calcareous schist. It is found in both dry and damp conditions, often growing through a bryophyte mat on a rock face or on gravelly ground. Its wetter sites are subject to periodic flushing. Between 840 m on Meall nan Tarmachan and 1190 m on Ben Lawers (both Mid Perth).
S. nodosa is a plant of damp habitats, principally in mires and springs irrigated with base-rich water, but also in open, calcareous, sandy habitats, especially dunes and dune-slacks and sometimes in drier calcareous grassland. Generally lowland, but reaching 850 m on Glas Moel (Angus).
Natural habitats of this mat-forming perennial include rocks, cliffs and river-banks, but it also grows in a wide variety of artificial, disturbed and fertile habitats, including spoil heaps, mining waste, paths, roadside verges and urban pavements. It is a common weed of horticulture, especially in lawns, and is a particular nuisance in pots. The plant is tolerant of a wide range of soils and can stand heavy trampling. 0-1150 m (E. Scottish Highlands).
A tufted, perennial herb which usually grows on base-rich, well-drained soils. It is a poor competitor, occurring on steep ground, in areas of late snow-lie and areas of severe wind-scour which provide the open conditions it requires. Generally between 700 and 900 m, but reaching 1190 m on Ben Lawers (Mid Perth), and descending to 460 m on the Old Man of Storr, Skye (N. Ebudes).
A perennial, mat-forming herb usually of dry, open, sandy or gravelly places. Habitats include heaths, dry pastures, banks and rocks, grassy slopes near the sea, and especially trackways through heaths and moors. It also occurs on basaltic gravel terraces on the Trotternish Mountains (Skye), accompanying Koenigia islandica. 0-700 m (Mt Brandon, S. Kerry), and reportedly to 835 m on Ben Lawers (Mid Perth).