Reedbeds are wetlands dominated by stands of the common reed Phragmites australis, wherein the water table is at or above ground level for most of the year. They tend to incorporate areas of open water and ditches, and small areas of wet grassland and carr woodland may be associated with them.

The majority are freshwater, but reedbeds are also found in brackish and tidal waters. Common reed is an active coloniser of wet ground or open water and reedbeds form a transition stage in the eventual succession to woodland. In tidal areas or sites which are subject to regular freshwater flooding, a reedbed may persist in a relatively stable state unless there is heavy siltation. Elsewhere, the accumulation of dead vegetation and litter will result in the gradual drying of the bed, allowing invasion of carr, scrub or woodland species.

Reedbed is a rare habitat in Essex, generally occurring as small fragments and largely concentrated in coastal areas or other areas of wetland. The 1993 RSPB Reedbed Inventory suggests there are around 134 ha in Essex, although this is thought to be an underestimate. Using 1993 Inventory data and reedbed definitions, Essex holds approximately 2.75 % of the resource in England (2% in Great Britain). The 2006 survey indicates there are currently 26 significant sites identified in Essex, covering 121ha (EECOS 2006).

A number of bird species in Essex are either wholly or partly dependent on reedbeds. Bearded Tit, Cetti’s Warbler and Marsh Harriers are all Red Data book species breeding in Essex reedbeds. The Bittern is also a Red Data book species which last bred in the county in 1944 and could be expected to breed once again in Essex given a suitable quality and extent of habitat.

Of the five Red Data Book invertebrates that are closely associated with reedbeds nationally, one, the Flame Wainscot Senta flammea, occurs in Essex. Other notable or very local invertebrates associated with Phragmites that occur in Essex are Obscure Wainscot Mythimna obsoleta, Twin-spot Wainscot Archanara geminipunctata, Reed Dagger Simyra albovenosa, Cosmopterix liengiella and Schoenobius gigantella (all Lepidoptera) and Plateumaris braccata (Coleoptera). Also Clubiona juvensis and Hypomma fulvum (Arachnids) and Passaloecus clypealis (Hymenoptera).