This broad category includes woodlands of permanently waterlogged sites that are dominated by willows (Salix spp.), Alder (Alnus glutinosa) or Ash (Fraxinus excelsior), or by various combinations of some or all of these trees. It includes woodlands of lakeshores, stagnant waters and fens, known as carr, in addition to woodlands of spring-fed or flushed sites. Carr is dominated by Rusty Willow (Salix cinerea ssp. oleifolia) and Alder (Alnus glutinosa). The field layer comprises Creeping Bent (Agrostis stolonifera), Meadowsweet (Filipendula ulmaria), Common Marsh-bedstraw (Galium palustre), Purpleloosestrife (Lythrum salicaria) and Skullcap (Scutellaria galericulata). Mosses such as Climacium dendroides, Calliergon cordifolium and Homalia trichomanoides are characteristic.
Carr occurs on organic soils and fen peats that are subject to seasonal flooding but remain waterlogged even when flood waters recede.
Woodlands of flushed or spring-fed sites are typically dominated by Alder (Alnus glutinosa) or Ash (Fraxinus excelsior) and the ground flora is often ‘grassy’ in appearance with abundant Remote Sedge (Carex remota) and Creeping Bent (Agrostis stolonifera). Other common components of the field layer include Bramble (Rubus fruticosus agg.), Creeping Buttercup (Ranunculus repens), Meadowsweet (Filipendula ulmaria), Common Marsh-bedstraw (Galium palustre), Yellow Pimpernel (Lysimachia nemorum) and Lady-fern (Athyrium filix-femina). This type of woodland occurs on mineral soils or fen peats, and may occasionally be associated with river banks or lakeshores. Note that riparian woodland - WN5 is treated as a separate category.
Also included in this category are woodlands of calcareous spring-fed hollows that are characterised by a mixture of trees including willows (Salix spp.), Alder (Alnus glutinosa), Ash (Fraxinus excelsior) and Downy Birch (Betula pubescens). Greater Tussock-sedge (Carex paniculata) dominates the field layer and tussocks may support species of drier land. Common Reed (Phragmites australis) may be abundant in open wet areas. The ground surface is often treacherous and water-filled hollows and channels typically support aquatic plants.