The Oak Fern has been found in very few localities around Northern Ireland. In the 1830s it was reported from Knocklayd near Ballycastle, Co. Antrim, but has not been seen there since. For a number of years one plant was known to grow on the Garron Plateau beside the Pollan Burn, but it is feared that recent flooding of the stream may have obliterated it there. There is a recent report of this fern on the rock outcrops near Lough Naroon.
Within the British Isles the stronghold of the plant is in Scotland where it is very abundant, for example, in the ground flora of the native Caledonian pine forests such as the famous Black Wood of Rannoch. The occurrences in north-eastern Ireland have sometimes been attributed to wind-blown spores ariving from south-western Scottish populations, but this is entirely conjectural. Although so rare in the wild in Northern Ireland, it will flourish and spread easily within gardens if introduced into cultivation here.
All names: Gymnocarpium dryopteris (L.) Newman; Thelypteris dryopteris (L.) Slosson; Polypodium dryopteris L.; Dryopteris dryopteris (L.) Christ; Phegopteris dryopteris (L.) Fee