Blysmus compressus

There’s only one site left in Oxfordshire where this small grass-like plant can be found.


Flat-sedge is a rhizomatous perennial that can grow up to 45cm tall. It is distinguished from other sedges by its pale-brown terminal inflorescence which is compact and flattened, with spikelets arranged in opposite rows. The stems are smooth and rounded and the leaves, 6-20cm long, are flat and grass-like.


Flat-sedge grows in open areas of damp sedge-rich grasslands, fens, marshes, calcareous flushes, and along margins of streams and ponds. It can also grow in brackish areas near saltmarshes and in dune slacks. This species tends to favour transitional habitats and areas where low-intensity grazing occurs.

Life Cycle

Flat-sedge flowers in early summer and the fruiting heads can be seen until September.

Distribution and threats

In Britain, Flat-sedge is widespread but localised. It is most abundant in the North and West of England and very rare in southern England, with only a few remaining populations along the River Thames and Kennet.

Flat-sedge has declined throughout its range due a variety of threats such as drainage, loss of unimproved damp grasslands, eutrophication, and loss of grazing. Flat-sedge relies on the right level of disturbance in order to keep its habitats open but not overly grazed or trampled. Due to this decline, Flat-sedge is now listed as Vulnerable in the Red data book for Great Britain and Vulnerable on the Red list for England. It was also added as a UK Biodiversity Action Plan species in 2007 and is listed as a rare plant in Oxfordshire.