Read the shore before you pick

Britain's rocky shores are generous, but they are also busy places where tide, weather, wildlife and water quality all shape what is safe to take. The best foragers spend their first few visits simply looking: learning how far the tide falls, which rocks stay wet, and what grows where. Go on a falling tide, check a local tide table before you leave, and give yourself at least an hour and a half before the sea turns. Wear boots with real grip, take gloves, a cotton bag or basket, and scissors or a sharp knife. Tell someone where you are heading, and never work a swell-battered shore alone.

Take only what you can eat within a few days, cut cleanly rather than tugging, and never strip a rock bare. A shore that is picked lightly recovers quickly; one that is stripped looks bare for a season.

Common edible seaweeds worth learning first

Start with a handful of easily recognised species and learn them properly, in more than one season, before anything reaches your plate.

• Laver (the nori family) — thin, dark purple-red sheets growing on rocks and on larger weeds. It turns olive-green when cooked and is the classic Welsh breakfast, minced with oats and fried.
• Sea lettuce — bright green, translucent and ruffled, at its best in late spring and early summer. Toss it raw into salads or drop it into soups at the last moment.
• Dulse — reddish-brown, leathery, hand-shaped fronds on the lower shore. Wonderful dried and eaten like crisps, or fried briefly until it crisps.
• Pepper dulse — small, crumpled and intensely savoury, with a flavour somewhere near truffle. A few fronds lift a plate of eggs or pasta.
• Sugar kelp and oarweed — the long brown stipes of the lower shore. Slice and blanch them for pickles, or simmer for stock. Cut the stipe above the holdfast so the plant regrows.
• Carrageen — small, tough and purple when growing, blanching pale when dried. It sets puddings and jellies beautifully.

Skip anything soft, smelly or detached and drifting, and never eat seaweed you cannot identify with complete confidence.

Coastal plants that reward a gentle hand

Salt-tolerant plants are often at their sweetest in early summer. Marsh samphire grows on estuary mudflats and salt marsh; snip the tender tops from June to August and steam them with butter. Sea beet, with its glossy, dark green leaves, is common on shingle and sea walls and cooks like spinach. Sea purslane forms grey-green mats on salt marsh, its mealy leaves a fine addition to fish dishes. Rock samphire clings to cliffs and shingle with a powerful aniseed and kerosene flavour — use it sparingly, and take a leaf or two from several plants rather than stripping one.

Leave roots in the ground, take no more than a third of any clump, and step carefully around nesting birds and fragile shingle vegetation.

Rules, permissions and protected places

Hand-gathering for personal use is generally accepted on most foreshore in the UK, but much of that foreshore is privately owned or held by the Crown, and anything commercial needs permission. Rules tighten considerably inside protected sites.

• Check whether you are in a Site of Special Scientific Interest, Marine Conservation Zone, National Nature Reserve or a wildlife trust reserve — many prohibit or restrict picking altogether.
• In Scotland, hand-gathering seaweed for personal use is broadly fine, but mechanical or commercial harvesting requires a licence from the marine regulator.
• Some local bye-laws limit the cutting of larger kelps, and digging up plants is almost always prohibited.
• Rare coastal plants are legally protected. If you are unsure what you have found, photograph it and leave it growing.

If in doubt, ask the landowner or the local harbour office before you fill a bag.

Avoiding polluted water and hidden hazards

Seaweed concentrates whatever is in the water around it, so location matters more than technique. Avoid harbour walls, marina mouths, sewage outfalls, pipes and stream mouths, industrial estuaries, and anywhere with a history of mining. After heavy rain, stay away for at least forty-eight hours, when storm overflows and agricultural runoff are at their worst. Check published water quality information for your stretch of coast, and if the sea is discoloured or a bloom is present, leave it alone.

Brown seaweeds can accumulate iodine and arsenic, so treat them as a garnish and a seasoning rather than a daily staple — especially if you have a thyroid condition. On the rocks themselves, watch for slick weed, barnacle cuts, loose boulders and crumbling cliffs, and keep an eye on the sea behind you.

From shore to kitchen

Rinse your harvest in clean seawater, then in fresh water, and use it within two or three days, wrapped in a damp cloth in the fridge. For longer storage, dry seaweed in a low oven or a warm, airy room until crisp, then keep it in jars, or blanch and freeze it in portions. Laver, oats and a little bacon fat make a proper Welsh breakfast; kelp gives depth to broths; dulse fried for a minute is one of the finest things a British shore offers. Gather small, gather often, and leave the shore richer than you found it.