The plants growing on the Carneddau need to be extremely hardy to withstand the snow, frosts, and gales they will encounter during the year and those found by sheltered streams in the valleys are very different from those clinging to crevices on windswept rocks. Sheep graze the mountains and impact the composition of the sward, nibbling out the most succulent young growth. Where the sheep are fenced out globe flowers, wood avens, angelica, red campion and roseroot can be found at lower elevations, along with ash, alder, hawthorn, holly and rowan. Higher up on scree there are Welsh poppies and in damp crevices under rocks the rare Wilson's filmy fern. Boggy areas support cotton grass, marsh orchid, sundew and bog asphodel. The better-drained rocky slopes have bilberry, ling, bell heather and cross-leaved heath and the summit ridge has prostrate dwarf willows, sedges, mosses and lichens.