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 × hybrida midrib as separate leaflets. All three polyploid species are apomictic species which breed true without pollination. "Sorbus" × "hybrida" is grown as an ornamental tree in northern Europe, and is locally naturalised in the British Isles. The cultivar 'Gibbsii' has gained the Royal Horticultural Society's Award of Garden Merit. Sorbus × hybrida Sorbus "×" hybrida, the oakleaf mountain ash, Swedish service-tree or Finnish whitebeam, is a hybrid species of whitebeam native to Scandinavia in Norway, eastern Sweden, and southwestern Finland, and locally in the Baltic States in Latvia. It is a medium-sized deciduous tree growing to 10–15 m tall with