This type of woodland is associated with areas that are flooded or waterlogged in winter but which dry out in summer. It occurs on periodically-flooded alluvial sites that are well above the limits of regular inundation, and on drumlins and other sites with heavy, poorly-drained clay soils that are subject to waterlogging.
Woodland is dominated by Pedunculate Oak (Quercus robur) and/or Ash (Fraxinus excelsior); other common components include Hazel (Corylus avellana), Hawthorn (Crataegus monogyna), Holly (Ilex aquifolium) and willows (Salix spp.). Alder (Alnus glutinosa) can be locally abundant. The ground flora typically comprises Meadowsweet (Filipendula ulmaria), Primrose (Primula vulgaris), Enchanter’s-nightshade (Circaea lutetiana), Ivy (Hedera helix), Bramble (Rubus fruticosus agg.), Remote Sedge (Carex remota), Golden-saxifrage (Chrysosplenium oppositifolium) and Ramsons (Allium ursinum). When flooding subsides in alluvial sites, exposed channels and depressions may remain wet or waterlogged. Alder (Alnus glutinosa) is often prominent in these situations.