Rare fern rediscovered in iconic Cwm Idwal – more than 150 years after last sighting
By Community Correspondent
The Botanical Society of Britain and Ireland (BSBI)1 is thrilled to announce the rediscovery of Holly Fern (Polystichum lonchitis)2 in Cwm Idwal, a glacial cirque in the mountains of Eryri (Snowdonia).
The fern was found by naturalist, author and mountain leader Jim Langley, more than 150 years after it was last seen in the area.
Holly Fern is a rare, slow-growing evergreen species native to Britain and Ireland. It thrives in cool, base-rich, rocky uplands – typically at cliff bases, on ledges, or in limestone grikes – and is long-lived but a poor competitor.
It gets its common name from the edges of its fronds, which have sharply toothed margins and a glossy, evergreen surface that resembles holly leaves.
While still more frequent in parts of the Scottish Highlands and European Alps, the fern has become increasingly rare in Wales and England.
The plant found in Cwm Idwal is a young Holly Fern, raising the tantalising possibility that the species is recolonising the site via spores from other populations within Eryri National Park – or that undetected individuals may have persisted quietly in hidden corners of the cwm.
Its disappearance from Cwm Idwal is believed to be a consequence of Pteridomania or "fern fever", a Victorian craze that saw enthusiasts zealously collecting rare ferns which led to the depletion of several species in the wild. Cwm Idwal, now part of Eryri National Park, was no exception.
“This is a remarkable rediscovery,” said Alastair Hotchkiss, BSBI’s Wales Officer. “The cliffs around Cwm Idwal are seriously challenging terrain for botanists to explore, but the fact that this species remained undetected for over a century and a half is a powerful reminder of how much we still have to learn about our upland flora – and how much we still have to protect.”
Cwm Idwal is celebrated for its rare arctic-alpine plants and spectacular geology.
Its high elevation, north-facing aspect and glacially sculpted terrain have made it a haven for botanical rarities such as Snowdon Lily, Tufted Saxifrage and Moss Campion. It is also home to the endemic Snowdonia hawkweed (Hieracium snowdoniense).
The rediscovery was made by Jim Langley, a BSBI member and an International Mountain Leader and conservationist who runs the educational consultancy Nature’s Work. Jim is co-author of The Alps – A Natural Companion, which combines guided walks with detailed notes on alpine geology, flora and ecology.
Jim said “I have great interest in the arctic-alpine communities of Eryri and have been visiting these sites for many years. On this particular day I was leading a group to a well known and studied site when a small, unusual fern caught my eye low down to the ground. We keyed it out in the field as I had two field botanists on my course and there was a buzz of excitement in the air.”
The rediscovery of Holly Fern not only revives a part of Cwm Idwal’s botanical heritage but also highlights the value of skilled naturalists, and mountaineers with an eye for botany.
Alastair said “It’s encouraging to see that, despite historic losses and modern pressures, some populations of these charismatic ferns are hanging on. We now have an opportunity to monitor this plant to ensure it’s not lost again.”
To see more about the work of BSBI click here www.bsbi.org
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