Sea lettuce (Ulva lactuca)

NBN Interactive22-05-2008

Map accurate at time of writing. Visit NBN or OBIS to view current distribution

Researched byPaolo Pizzolla Refereed byAdmin
AuthorityLinnaeus, 1753
Other common names- Synonyms-



A small green alga (up to 30 cm across) with a broad, crumpled frond that is tough, translucent and membranous. It is attached to rock via a small hold-fast .

Recorded distribution in Britain and Ireland

An ubiquitous plant found on all but the most exposed rocky shores, but is probably under-recorded in Ireland.

Global distribution



The sea lettuce is found at all levels of the intertidal, although in more northerly latitudes and in brackish habitats it is found in the shallow sublittoral. In very sheltered conditions, plants that have become detached from the substrate can continue to grow, forming extensive floating communities. The plant tolerates brackish conditions and can be found on suitable substrata in estuaries.

Depth range


Identifying features

  • Up to 30 cm across.
  • Frond broad and crumpled, that is tough, translucent and membranous.
  • Disc like holdfast.
  • Green to dark green in colour.

Additional information

Ulva is sometimes eaten as "green laver", but it is considered inferior to purple laver.

Listed by

- none -

Further information sources

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

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

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

  4. Howson, C.M. & Picton, B.E. (ed.), 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.]

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

  6. NBN (National Biodiversity Network), 2002. National Biodiversity Network gateway., 2008-10-31

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

  8. 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. Ulva lactuca Sea lettuce. 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. Available from:

Last Updated: 22/05/2008