British NVC community W5

[1] The habitat is typically a seasonally flooded landscape in which trees can only become established if they are tolerant of waterlogging (mainly only alder and willow) and have a dry foothold, such as a clump of greater tussock sedge.

Around the margins of a lake, grey willow typically forms a distinct band over the deeper water, with increasing amounts of alder beyond that.

These include fibrous tussock-sedge, elongated sedge, cowbane, crested buckler-fern, milk parsley and marsh fern.

Many examples of ancient or semi-natural W5 woodland are now protected as nature reserves or sites of special scientific interest, including those at Wicken Fen, Sweat Mere and Rhos Goch.

[1][2] There is no direct equivalent to W5 in the European EUNIS habitats system, but it is encompassed within the F9.2 willow carr and fen scrub[6] and the G1.52 alder swamp woods on acid peat.

[1] In 1938 Roy Clapham described the hydrosere around Sweat Mere in Shropshire,[2] which includes what is possibly the first example of an ancient woodland alder carr to be recorded.