Biodiversity & Conservation

Oarweed - Laminaria digitata

Laminaria digitata

Image Keith Hiscock - Laminaria digitata at low tide. Image width ca 2 m in foreground.
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Distribution map

Laminaria digitata recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Laminaria digitata is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Ochrophyta Brown and yellow-green seaweeds
Class Phaeophyceae
Authority (Hudson) J.V. Lamouroux
Recent synonyms Laminaria cucullata f. longipes, Laminaria cucullata f. apoda.
Map icon Recorded Distribution in Britain and Ireland Most coasts of Britain and Ireland, including Rockall. Scarce along east coast of England, particularly between Ouse and Thames estuaries, due to turbidity and lack of hard substrata. (Information continued in additional information).
Habitat information icon Habitat information Found attached to bedrock or other suitable hard substrata in the lower intertidal and sublittoral fringe, down to a maximum depth of 20 m in clear waters. Laminaria digitata flourishes in moderately exposed areas or at sites with strong water currents. In exposed locations with strong wave action the species may extend upwards into the lower eulittoral. Occurs in rockpools up to mid-tide level and higher on wave-exposed coasts.
Text page icon Description A large conspicuous kelp growing up to 2 m in length commonly found at low water during spring tides on rocky shores. The frond is broad and digitate, glossy and dark brown in colour and lacks a midrib. The stipe is oval in cross section, smooth and flexible and is usually free of epiphytes, although old stipes which have become slightly roughened may support a few epiphytes, notably Palmaria palmata. The kelp is attached by freely branched haptera, which spread out to form a shallow dome-shaped holdfast. Laminaria digitata may be confused with young Laminaria hyperborea plants. However, the stipe of Laminaria hyperborea is circular in cross section, is stiff and snaps easily when bent (although you won't see that in younger plants).
Identifying features
  • Frond is broad, leathery and digitate.
  • Lacks a midrib.
  • Stipe is flexible and smooth, oval in cross section and free of epiphytes except maybe Palmaria palmata in older kelps.
  • Holdfast of freely branched haptera which spread out to form a shallow dome.
  • May be confused with young Laminaria hyperborea plants. However, the stipe of Laminaria hyperborea is circular in cross section and stiff.
Additional information icon Additional information Common names in England also include Tangle, Red ware and Sea girdle. In Ireland common names include Leath and Learach. The length of the frond varies with season, age of plant and location, reaching over 1 m in suitable conditions. The number of frond digits vary with amount of exposure. In shelter these are few and short, but with increasing exposure, they are more numerous (up to 10 or 12) and extend almost to the base of the frond. Reported to store sodium glutamate and thus tasty when dried.

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This review can be cited as follows:

Jacqueline Hill 2008. Laminaria digitata. Oarweed. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 09/02/2010]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=3613>