Backstone Bank and Baal Hill Woods one side valley, there is a small population of small-leaved lime, "Tilia cordata", which occurs here close to its northern limit and at an unusually high altitude. On base-rich soils, the woodland typically consists of ash, "Fraxinus excelsior", and wych elm, "Ulmus glabra", over an understorey of hazel, "Corylus avellana", and bird cherry, "Prunus padus", and a rich ground flora that includes lady-fern, "Athyrium filix-femina", male fern, "Dryopteris filix-mas", and hard shield-fern, "Polystichum aculeatum". On more acid soils, sessile oak, "Quercus petraea", and birch, "Betula sp.", are dominant. The under-storey, of hazel, holly, "Ilex aquifolium", rowan, "Sorbus aucuparia", and hawthorn,
Sorbus alnifolia Sorbus alnifolia Sorbus alnifolia (syn. "Aria alnifolia"), also called alder-leafed whitebeam, Korean whitebeam, or Korean mountain ash, , is a species of whitebeam native to eastern Asia in eastern and northern China, Taiwan, Korea and Japan. "Sorbus alnifolia" is a medium-sized deciduous tree growing to 10–20 m tall with a trunk up to 30 cm diameter and grey bark; the crown is columnar or conic in young trees, becoming rounded with age, with branches angled upwards, and slender shoots. The leaves are green above, and thinly hairy with white hairs beneath, 5–10 cm long and 3–6 cm broad, simple, usually