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Trees and plants at Cwm Mynach

Roughly three quarters of Cwm Mynach is wooded with the remaining quarter supporting a range of open ground and aquatic habitats which contribute significantly to the site’s diversity and landscape. To the northern, western and eastern margins of the site, woodland gives way to scrub, heathland, rocky outcrops and bog, while at the site’s heart lies the six-hectare lake Llyn Cwm Mynach and its various inflows and outflows, bordered in places by molinia (grassland) bog which supports bog myrtle and bog asphodel.

Cwm Mynach is peppered with small pockets of ancient semi-natural woodland (ASNW), and oak stand tall against the hills, though the majority of the site was re-planted with conifer in the 1950s and 60s. However, the oaks that remain support a myriad of other species, including ferns, mosses, lichens and liverworts that grow on the bark and create a hanging forest of vegetation. Many of these species are uncommon and the lichen community suggests that the ancient woodland here is an Atlantic oakwood habitat of high quality. A survey in 2009 recorded a total of 82 lichen in the east of Cwm Mynach, with notable remnant populations of upland oakwood mosses, lichens and liverworts.

Moss covers large areas of the woodland floor (Photo: Mark Zytynski/WTML)

 Ash is usually found where the soils are damper or milder. Hazel, rowan, holly and birch are also common, while willow and occasionally alder are found on wet ground.

The conifer species include sitka and Norway spruce and Western hemlock, with some Japanese larch and lodgepole pine. These are being gradually being removed until we have restored the site to predominantly broadleaf woodland.

It rains up to 200 days each year, and this wet environment provides the ideal habitat for rare lichen such as Parmeliella orrescens. The almost constant rainfall means Cwm Mynach is a ‘Celtic rainforest’ – a globally rare habitat. This makes it a hugely important site for plants which thrive in moist conditions.

The six-hectare lake Llyn Cwm Mynach (Photo: Mark Zytynski/WTML)

Throughout spring you’ll find pockets of bluebell glorying in the trees’ dappled shade, with dog’s mercury and the delicate white wood sorrel nodding in the warm spring breeze. These give strong clues to the site’s age as they usually only occur in ancient woods or along old hedgerows. Primrose, violet and celandine relish the cool, wetter soil and can be found alongside stream edges.

Take a stroll around the llyn during summer and you’ll find white and yellow water lilies sitting on the surface of the lake, and floating club-rush and Merlin’s grass peeking through the water as it laps the shore.

Heather and bilberry march across the moorland, a sweeping carpet of rich blues and purples, while bogs and mires are home to plants such as sedges and a tiny upland orchid called lesser twayblade.