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 not closely related to the true ash trees which belong to the genus "Fraxinus", although the leaves are superficially similar. As treated in its broad sense, the genus is divided into two main and three or four small subgenera (with more recent generic assignments in parentheses): "Sorbus" species are used as food plants by the larvae of some moth species—see list of Lepidoptera that feed on "Sorbus". "Sorbus domestica" is used to flavour some apple wines, see "Apfelwein. "Sorbus" species are cultivated as ornamental trees for parks and gardens, and have given rise to several cultivars. The following, of mixed