Joint meeting of the MNA and Liverpool Botanical Society

A cwm, or corrie in Scotland, marks the source of a glacier which has scoured a deep, crater-like hollow in the flanks of a mountain massif. Cwm Idwal is a classic example and has long been popular with geologists, naturalists and climbers. The concept of an Ice Age was first introduced in to this country in the 1840s by Louis Agassiz, a Swiss naturalist. Charles Darwin made several visits and his notes reveal how the evidence was overlooked, scientists just concentrating on the rocks, fossils and structures such as folds and faults rather than the landscape. As in Snowdon’s Clogwyn Du’r Arddu the backwall of Cwm Idwal shows a clear example of a downfold or syncline, best seen in winter when a light fall of snow picks out the ledges.

Although the early morning weather had not been promising it brightened up considerably as we approached Llyn Ogwen via Nant Ffrancon. Only a short distance into the walk we encountered Grey Wagtails by the cascading, boulder-strewn Afon Idwal and our first clumps of Parsley and Hard Fern which became prolific at higher elevations. The wetter terrain away from the path attracted attention with its nodding heads of Common Cotton-grass, a fine display of Bog Asphodel, a thin scattering of Heath Spotted Orchid and small cluster of Round-leaved Sundew amongst Spagnum Moss. The path’s edges had a familiar leaf but larger than usual – this belonged to Marsh Violet. One was actually in flower and duly photographed. The reddish, leafless stems and pale lilac flowers of Water Lobelia were common in the shallow margins of Llyn Idwal, their rosettes of leaves being submerged. On the other side of the path a drystone retaining wall produced a much admired rock garden with so many species packed into such a small area – notably Alpine, Fir, Staghorn and Lesser varieties of Clubmoss, the yellowish-green Lemon-scented Fern with it’s backward-projecting pinnules.

During our lunch break attention was drawn to a Great Crested Grebe diving in the lake, the distinctive calls of Common Sandpipers and a Heron on the far side where later we saw its food source, namely great shoals of minnows, and frogs. While House Martins from the Ogwen centre skimmed the surface three Choughs flew towards Bethesda. A single Small Heath fluttered by in the swirling wind.

As the path steepened we added Milkwort, Wild Thyme and, along the rocky rivulets descending from Idwal Slabs, numerous butterworts with a good haul of insects. The huge boulders in the scree at the foot of Twil Du (Devil’s Kitchen) provided a microcosm of what could be found higher up on the less accessible rock faces and ledges. Mossy Saxifrage was abundant with a little Starry Saxifrage and just one specimen of Alpine or Snowy Saxifrage. The rough surfaces also yielded Mountain Sorrel, Slender St. John’s Wort, Welsh Goldenrod and Roseroot while in the deep shade were Wood Sorrel and Oak Fern. More energetic members scrambled up to the Kitchen where blotches of yellow resolved to be Welsh Poppy and the distinctive, aptly named Globeflower. A Raven’s deep croaks added to the location with its dark, dripping rock faces, as did the screaming calls of a Peregrine and the surprisingly loud song of a Wren, echoing within the Kitchen.

Back down by Llyn Idwal but on its Northern shore an almost hands and knees job to study some aquatics revealed Shoreweed with its very long stamens and Alwort, so concentrated as to form a kind of sward. Further along the shingle beach were several good specimens of the normally submerged Quillwort. Meanwhile the Afon Ogwen by the visitors centre had its inevitable Dipper while the deciduous and coniferous trees had come up with Spotted Flycatcher, Goldcrest, Siskin and Willow Warbler.

David Bryant

Cwm Idwal	Bog Asphodel	Bog Asphodel	Marsh Violet	Water Lobelia	Quillwort

Pictures at Cwm Idwal taken by Maria Knowles