kelp a name applied both to certain large brown seaweeds and to the ash (a source of iodine and potash) obtained by burning them. The industries devoted to producing the ash were important in the 19th century, but then declined as cheaper sources for the two end products were discovered.
The species sometimes called ‘edible kelp’ is Alaria esculenta, whose long fronds (up to 3.5 m/12') are found on cold and rocky N. Atlantic shores around the low-tide mark. Midribs have been eaten like celery or chopped into salads in N. America; and various cooked kelp dishes have been recorded from such places as Greenland, Iceland, the Faeroes, and Orkney.
