On the shores of Britain, Ireland, Brittany and Norway several seaweeds have been eaten for centuries. Picking them is simple, but you need to know three things: which species are edible, who owns the shore, and how much iodine you are eating.
Species worth knowing
| Species | Where it grows | How it is eaten |
|---|---|---|
| Dulse (Palmaria palmata) | Red fronds on rocks and kelp stalks, lower shore | Dried as a snack, in soups |
| Sea lettuce (Ulva) | Thin green sheets in pools and on rocks | Raw after washing, in salads |
| Sugar kelp (Saccharina latissima) | Long, wavy fronds at the very bottom of the shore | In stocks, like kombu |
| Oarweed (Laminaria digitata) | Broad, split fronds at the lowest water | In stocks, very little at a time |
| Carrageen (Irish moss, Chondrus crispus) | Low, branched tufts, lower shore | To thicken desserts and soups |
| Laver (Porphyra) | Thin, slippery films on rocks, often mid shore | Long cooked (Welsh laverbread) or dried |
On Atlantic shores you will also find sea spaghetti (Himanthalia elongata) and wakame (Undaria pinnatifida), a non-native species that is spreading. Avoid seaweeds of the genus Desmarestia: some species contain sulphuric acid and can upset the gut. Only pick what you can identify for certain.
Iodine: the key warning
Brown seaweeds, kelps above all, store a great deal of iodine. The European Food Safety Authority (EFSA) has set the tolerable upper intake of iodine for adults at 600 µg a day. A small piece of dried kelp can exceed that. Too much iodine disturbs the thyroid, and the symptoms resemble deficiency.
- Treat kelp as a seasoning for stock, not as a vegetable.
- Boiling and pouring off the water reduces the iodine in the seaweed itself, but it goes into the stock.
- Pregnant women, people with thyroid conditions and small children should take particular care and ask a doctor.
- Red and green seaweeds (dulse, sea lettuce, laver) usually have less iodine than kelp, but still more than land vegetables.
Clean water
Seaweeds do not filter water the way shellfish do, but they absorb metals and pollutants from it. Do not pick near harbours, sewage outfalls, the mouths of rivers from towns, or after heavy rain. Sea lettuce grows thickly where water is over-enriched, so plenty of it is no sign of clean water. Leave seaweed washed up on the beach alone, because it may already be rotting.
Are you allowed to pick?
The rules depend on the country and on who owns the shore. Commercial picking needs permission or a licence almost everywhere. Picking for your own use is usually tolerated, but not everywhere.
- United Kingdom. The Crown Estate owns a large part of the foreshore, and other owners the rest. Small amounts for your own use are usually tolerated. Reserves may ban it, as at Seaford Head in Sussex, and on SSSIs and in marine zones you should check the rules.
- Ireland. The foreshore is in principle owned by the State. Commercial harvesting needs a licence, and in some places local harvesters hold traditional rights. Take only a little for your own use.
- France. In Brittany professional seaweed harvesting is regulated and needs a licence. Local rules apply to amateurs; check with the prefecture or on pecheapied-responsable.fr.
- Denmark. Wadden Sea National Park asks you to pick only where access is allowed, and only what fits in a net bag.
How to pick so it grows back
- Cut with scissors or a knife; never pull. Leave the holdfast and the lower part of the frond, and the seaweed will regrow.
- Take a little from many plants rather than cutting one clump to nothing.
- Pick live, attached seaweed, not seaweed from the beach.
- Do not pick more than you will eat or dry within a few days.
- Kelps grow at the lowest water, so watch the tide. The tides for beginners guide explains how.
Starting without risk
To begin, choose two species that are hard to confuse: dulse and sea lettuce. Dulse has dark red, flat, forked fronds and often grows on kelp stalks. Sea lettuce is bright green sheets as thin as cling film. Bring a field guide or photos and compare on the spot. If in doubt, leave it in the sea. A few handfuls are enough for several meals, because seaweed loses most of its weight when dried.
At home
Rinse seaweed in cold water to remove sand and small animals. Dry it somewhere airy or in a dehydrator at a low temperature. Keep dried seaweed in an airtight jar. Eat fresh seaweed within a day or two.
Sources
- Edible seaweed, Wikipedia
- Iodine in biology (upper intake levels), Wikipedia
- Sussex Wildlife Trust, Seaford Head
- Nationalpark Vadehavet, Sankning i Vadehavet
- Pêche à pied responsable (ARS Bretagne), bans
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