This category includes wet woodlands of river margins (gallery woodland) and low islands that are subject to frequent flooding, or where water levels fluctuate as a result of tidal movement (in the lower reaches of rivers). Riparian woodland is dominated by stands of willows that may include native (Salix cinerea, S. purpurea, S. triandra) and nonnative (Salix fragilis, S. alba, S. viminalis) species. Alder (Alnus glutinosa) is occasional. The field layer is characterised by broadleaved herbs such as Nettle (Urtica dioica), Creeping Buttercup (Ranunculus repens), Wood Dock (Rumex sanguineus), Meadowsweet (Filipendula ulmaria), Wild Angelica (Angelica sylvestris), Hemlock Water-dropwort (Oenanthe crocata) and Hedge Bindweed (Calystegia sepium). Stands of Reed Canary-grass (Phalaris arundinacea) are common. Indian Balsam (Impatiens glandulifera), an introduced species, is locally abundant. These woodlands often reveal an accumulation of river borne debris, including dead vegetation and plastic, when water levels are low. A fine coating of grey mud on vegetation and tree bases that are regularly submerged and emersed is also characteristic. Willows were widely coppiced and used for basket-making in the past.