We can never know for sure whether the Druids of the British Isles and Ireland practiced their religion in oak-groves like their continental cousins, but it seems likely. We know that the insular Celts worshipped in groves, or ‘nematon’, and the evidence from Ireland in particular makes it likely that these were oaks. Ireland was covered with oak trees, whose presence still echoes down the centuries in place names such as Derry, Derrylanan, Derrybawn (whiteoak), Derrykeighan and, of course, Londonderry, once Derry Calgagh, the oakwood of a fierce warrior of that name.
Many early Christian churches were situated in oak-groves, probably because they were once pagan places of worship. Kildare, where St. Brigid founded her abbey, derives from ‘Cill-dara’, the Church of the Oak. Legend says she loved and blessed a great oak and held it so sacred that no-one dare harm a leaf of it. Under its shade she built her cell (This ties in neatly with pre-Christian tradition, as the pagan goddess Brigid was daughter to the Sun-God Dagda to whom the oak was sacred).
St. Columcille, also known as Columba, whom many believe to have been a Druid before he embraced the new faith, likewise founded churches in an oak-grove at Derry (Doire), the monastery at Durrow (Dairmag, ‘the Plain of the Oaks’) and a monastery at Kells where he lived under an oak tree. According to the Irish ‘Life of St. Columcille’ a man took some of the bark of his tree to tan his shoes and contracted leprosy as a consequence.
When he was founding the church at Derry, St. Columcille burned down the town and the king’s fort in order to eradicate the works or worldly men and sanctify the site for his church. But the fire blazed out of control and he had to pronounce an invocation to save the grove of trees. He loved these trees so much that he built his oratory facing north-south instead of by the usual Christian orientation of east-west so none would be disturbed. He ordered his successors not to touch any tree that might fall, but to let it lie for nine days (the sacred Celtic number) before cutting it up and distributing the wood among the poor. When later in life he lived at the abbey he founded on the Isle of Iona in Scotland, he declared that although he feared death and hell, the sound of an axe in Derry frightened him more.
Early literature gives more evidence of the importance of the oak to pagan Celts. A great oak was one of the five sacred trees brought to Ireland by the strange being called Trefuilngid Tre-ochair who appeared suddenly at Tara on the day Christ was crucified; an emissary from the otherworld, he bore a branch on which were acorns, apples, nuts and berries which he shook onto the ground. These wondrous fruits were planted into five different parts of Ireland, and from them grew five great trees that oversaw each province until they were blown down by the disapproving winds of the Church in the 7th century. Among these was the great Oak of Mugna which stood in southern Kildare. This ‘bile’ or sacred tree was celebrated in the Edinburgh Dinnsenchas as:
Mughna’s oak-tree without blemish
Whereon were mast and fruit,
Its top was as broad precisely
As the great plain without… 3
It was said to bear nine hundred bushels of acorns 3 times a year and red apples besides, making its Otherworldly origins clear. The moment the last acorn fell, the first blossom of the year appeared, reminding us of the perpetual cycle of death and rebirth.
There were also some places that show traces of pre-Christian groves, however faint. We hear of an oak-grove near Loch Siant in the Isle of Skye that was once held so sacred that no person would dare cut the smallest twig from the trees. Also in Scotland is the sacred oak on the island in Lock Maree. The local story goes that it was once ‘Eilean-a-Mhor-Righ’ (the island of the Great King) who was in fact a pagan god. And in England, the remains of ancient oaks were discovered near the Romano-British temple at Lydney, dedicated to the god Nodons.