Flora of Northern Ireland

Limestone outcrops and limestone pavement

The only limestones that are of any botanical significance in Northern Ireland are Cretaceous Chalk and Carboniferous limestone. They are important for plant ecology, in that they are base-rich rocks and support the growth of acid-hating or lime-loving plants called calcicoles.

Cretaceous Chalk

Chalk above Garron HeadChalk lies below the basalt in Cos Londonderry and Antrim. This forms sea cliffs at some sites such as White Rocks near Portrush in Co Antrim and is exposed in cliffs further inland, or in ravines, at many other sites. The effect on the flora is relatively slight because the total area exposed is small. Also, the basalt, directly above the chalk, is locally capable of supporting all the calcicolous species that chalk can support. Calcicolous species associated with the chalk and basalt include:

Bee orchid (Ophrys apifera) and pyramidal orchid (Anacamptis pyramidalis) are often found in old chalk quarries.

Carboniferous limestone

Limestone pavement at GortmaconnelExtensive outcrops of Carboniferous limestone occur in the south west of the Province in parts of Cos Tyrone, Fermanagh, and Armagh.

Locally there are poorly developed limestone pavements e.g. around Gortmaconnell Rock in Co Fermanagh which tend to develop a hazel scrub or woodland, although this may be removed by grazing. Juniper (Juniperus communis) is plentiful on these outcrops.

The best sites in the Fermanagh limestone area include Knockmore Hill (Dryas octopetala is here), the Carrick Lough area, and the Lough Navar Forest area. Lough Navar Forest has outcrops of lime-rich sandstone which support several interesting species including Asplenium marinum. The limestone lies below the sandstone and forms a majestic escarpment to the south of Lower Lough Erne, known as the Cliffs of Magho (but Robert Lloyd Praeger refers to them as the cliffs of Poulaphuca in his Botanist in Ireland of 1934).

Some plants associated with the Carboniferous limestone and also the lime-rich sandstones of Lough Navar Forest: