A procumbent perennial herb found as a well-naturalised garden escape on walls, buildings and stony banks, often in damp, shaded sites. Lowland.
This low-growing perennial calcicole is found in open mountain grassland and on N.-facing Carboniferous limestone cliffs in the Ben Bulben range in Co. Sligo, at altitudes of 400-600 m.
An annual or biennial herb which usually grows in sparsely vegetated, well-drained sites associated with Carboniferous limestone, including peaty depressions on flat slabs, peat in cracks and hollows in limestone pavement, and in open, bryophyte-rich tufaceous flushes. Its seed appears to have considerable longevity. Found only at moderate altitudes between 295 m at Selside and 410 m at Dawson Close (both Mid-W. Yorks.).
This annual, biennial or perennial herb grows on base-rich substrates over limestone, serpentine and other basic rocks, occurring on rocky knolls, screes, river gravels, fell-field, and occasionally on exposed summit ridges. From c. 15 m on Unst (Shetland) to 650 m on Beinn Sgulaird (Main Argyll).
A winter- or rarely summer-annual of dry, usually shallow, neutral to basic soils. It is found in a wide range of open habitats, including rock outcrops, cliffs, screes, walls, spoil heaps from mines and in quarries, railway ballast, waysides and arable field margins. Generally lowland, but reaching at least 610 m at Melmerby Fell (Cumberland).
H. peploides is a succulent perennial herb with creeping stolons that make it well adapted to growing in mobile substrates. It often occurs in abundance on shingle beaches and on shifting sand in foreshore communities. It is one of the pioneer colonists of open foredunes with plants such as Elytrigia juncea. Lowland.
This annual grows on light soils in dry places. Its natural habitat is dry, rocky, calcareous grassland on chalk and limestone. However, it is more frequent in artificial habitats such as abandoned arable fields, quarries, old walls, trackways, railway banks and sidings. Mainly lowland, but reaching 400 m at Langcliffe in the Craven Pennines (Mid-W. Yorks.).
This tufted, calcifugous perennial herb grows in thin humus in dry narrow cracks in slabs of siliceous rocks of Old Red Sandstone age. 510-610 m in the Caha Mountains (S. Kerry and W. Cork).
This cushion-forming montane perennial herb is always associated with strongly base-rich rocks, including limestone and soft calcareous schists. The vegetation is usually open, as the ground on which it usually grows is both easily eroded and subjected to frost-heave. It reaches an altitude of 1180 m on Ben Lawers (Mid Perth), and formerly descended to 120 m on Unst (Shetland).
A loosely tufted but slender perennial herb that has only ever been known in Britain from Widdybank Fell, where it grows in open, gravelly flushes and eroding margins of sikes on metamorphic sugar limestone. The plant is not a strong competitor and is mainly associated with hummock-forming mosses and species such as Carex capillaris, Juncus triglumis, Minuartia verna and Primula farinosa. Upland, from 490 to 510 m on Widdybank Fell (Co. Durham).