Ouse Washes IPA

Location: The IPA spans the Cambridgeshire/Norfolk border, between Earith and Downham Market.

Grid Reference: TL 496 891

Ouse Washes IPA has been recognised as one of 165 Important Plant Areas in the UK.

The key features of this IPA are:

  • The species richness of vascular plants in surface standing waters
  • The species richness of stoneworts in surface standing waters
  • The Ouse Washes is a very large, 17th Century flood control structure designed to contain flood waters coming down the Great Ouse River.

    The washlands (grazing pasture that floods in the winter) are very extensive and are divided into hundreds of fields by a complex ditch system fed from the main river. However, part of the system is fed with waters derived from clean groundwater sources in the adjacent fen landscape.

    Ditches and pools, both here and on the Washes, support a rich stonewort flora dependant on high water quality. It is this flora, including species such as tassel and great tassel stoneworts, for which the IPA is recognised. The site is one of the country’s few remaining areas of extensive washland habitat. It is of particular note for the large area of unimproved neutral grassland communities which it holds, and for the richness of the aquatic flora within the associated watercourse.

    The grassland communities of the area are characterised by such grasses as reed and floating sweet-grass, reed canary-grass, marsh foxtail together with a variety of sedges and rushes. Typical herbs include amphibious bistort, water-pepper and tubular water-dropwort.

    More than 40% of the UK's aquatic plant species (over 260) are found here including mousetail, flowering rush, whorled water milfoil, marsh woundwort, fringed water-lily, greater water-parsnip and the four species of duckweeds.

    The limnological interest of the Ouse Washes is further diversified by the Old Bedford River and River Delph, both good examples of base-rich, sluggish, lowland rivers. The flora includes the fan-leaved water-crow foot, yellow water-lily, arrowhead, long-stalked pondweed, perfoliate pondweed, and river water-dropwort.