information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Purple laver (Porphyra umbilicalis)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.



A small red alga (up to 20 cm across) with an irregularly shaped, broad frond that is membranous but tough. The plant attaches to rock via a minute discoid hold-fast, is greenish when young becoming purplish-red and has a polythene-like texture.

Recorded distribution in Britain and Ireland

Abundant on rocky shores throughout Britain and Ireland.

Global distribution



Purple laver is highly adaptable to conditions on different parts of the rocky shore and able to withstand prolonged periods of exposure to the air as well as tolerating a greater degree of wave action than most other red algae. It occurs singly or in dense colonies throughout the intertidal but most frequently at upper levels.

Depth range


Identifying features

  • A small red seaweed, up to 20 cm across
  • Tough irregularly shaped broad frond.
  • Small disc-like holdfast.
  • Greenish when young becoming purplish-red.
  • Has a polythene-like texture

Additional information

Also known as sloke, the plant is boiled and eaten as a jelly in South Wales. Used to make laver bread a famous dish in south Wales and reportedly eaten cold with vinegar in Cornwall.

Listed by

- none -

Further information sources

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  1. Connor, D.W., Brazier, D.P., Hill, T.O., & Northen, K.O., 1997b. Marine biotope classification for Britain and Ireland. Vol. 1. Littoral biotopes. Joint Nature Conservation Committee, Peterborough, JNCC Report no. 229, Version 97.06., Joint Nature Conservation Committee, Peterborough, JNCC Report No. 230, Version 97.06.

  2. Dickinson, C.I., 1963. British seaweeds. London & Frome: Butler & Tanner Ltd.

  3. Hardy, F.G. & Guiry, M.D., 2003. A check-list and atlas of the seaweeds of Britain and Ireland. London: British Phycological Society

  4. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  5. Hiscock, S., 1986b. A field key to the British Red Seaweeds. Taunton: Field Studies Council. [Occasional Publication No.13]

  6. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  7. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

  8. National Biodiversity Network (NBN) Atlas website. Available from:  Accessed 01 April 2017

  9. Norton, T.A. (ed.), 1985. Provisional Atlas of the Marine Algae of Britain and Ireland. Huntingdon: Biological Records Centre, Institute of Terrestrial Ecology.

  10. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin.


This review can be cited as:

Pizzolla, P.F 2008. Porphyra umbilicalis Purple laver. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-09-2018]. Available from:

Last Updated: 29/05/2008