There is a moment at every island market when the ferry horn sounds and half the stallholders glance at the clock. The van has to be loaded, the return trip takes the best part of a day, and whatever is still on the table when the whistle goes will be eaten at home. That one detail explains why island markets feel different from the ones on the mainland. The season arrives all at once, and it leaves the same way. Knowing what to look for, and when, gets you better food with far less guesswork.

Island produce keeps its own calendar

Wind, salt spray, thin soils and small fields change what can be grown and how it tastes. A grower with half an acre and no cold store has no choice but to pick at ripeness and sell within days, which is exactly why a market carrot can taste so much sweeter than a supermarket one. It also means supply is short. The first courgettes may last an hour. The last of the samphire may be gone before ten.

Ask questions while you can. On an island market stall, the person weighing your beans is usually the person who sowed them, and they will happily tell you which variety is worth buying and how to cook it.

Spring: the hungry gap and the first green things

March to May is the leanest stretch, when last year's stores are running out and this year's crops are barely out of the ground. The stalls look modest and the good stuff goes fast, but the quality of what is there is often outstanding. Frost makes brassicas sweeter, and early greens have a tenderness you cannot buy later in the year.

Look for:

• Purple sprouting broccoli, spring greens, kale and the last of the leeks
• Forced rhubarb, pale and sharp, grown under a bucket or an old pot
• New potatoes, asparagus and salad leaves as the soil warms
• Wild garlic, nettles, sea beet and, later, the first samphire
• Eggs, which pick up as the days lengthen, and sometimes spring lamb
• Seedlings and plug plants raised in local polytunnels

On plants, buy from growers who raise them outdoors rather than in heated glass. A sturdy little plant that has already met a sea breeze will do better in your garden than a soft, leggy one.

Summer: buy early, buy less, eat it the same day

From June the tables fill up and the market becomes a proper event, with queues at the fish stall by half past eight. This is the season for courgettes picked small, tomatoes that smell of the vine, broad beans, peas, bunched herbs, and soft fruit that was in the field at dawn. Gooseberries, currants, strawberries and raspberries all bruise easily, so bring a cool bag and a shallow box rather than stuffing a punnet into a rucksack.

Go in the first hour for choice and the last twenty minutes for conversation. Courgettes and beans are at their best when they are young and firm; if you want them for soup or chutney, ask whether there are larger ones going spare, which stallholders are usually glad to part with. Fish depends on the weather rather than the calendar, so if the boats have not been out, take the advice of the person behind the counter and buy something else.

Autumn: the real harvest

September and October are when island markets earn their reputation. Squash, pumpkins, maincrop potatoes, onions, garlic plaits, apples, pears, damsons, blackberries, chard, cavolo nero and the first proper leeks all turn up together, along with honey, chutneys, cheese and game. Buying in quantity makes sense now, because this is the food that will carry you through to spring.

Choose squash that feels heavy for its size with a firm, dry stalk. Onions and garlic should have papery skins and no soft spots. Apples keep best in a cool, dark, slightly damp place, laid out so they are not touching, and checked every week or so for the one that has gone over.

Making a glut last

Roast tomatoes with garlic and oil, then freeze them in portions for winter pasta. Dry bunched herbs somewhere airy and out of direct sun. Freeze soft fruit on a tray first so the berries stay separate, then bag them. Chutney is the answer to a bowl of green tomatoes, and it will improve for weeks in the jar. If you are preserving anything for storage, follow a tested recipe rather than improvising, and if you have any health concerns about home preserving or unpasteurised produce, take advice from a qualified professional.

Winter: roots, brassicas and shellfish

By December the market thins out, and some islands drop to a fortnightly rhythm or move under cover. What is left is honest winter food: parsnips, swede, celeriac, carrots, sprouts, red and January king cabbage, stored potatoes and squash. Look for shellfish, smoked fish, cheese, eggs and jars, and expect forced rhubarb to reappear before the weather has improved at all.

Ask what was frozen in autumn. A bag of last summer's berries or peas, frozen properly on the day they were picked, will beat anything flown in. Winter is also when you learn which stallholders are still turning up in a force seven, and those are the ones worth buying from all year.

Market etiquette, island edition

Most of the unwritten rules are the same everywhere, but a few matter more when everyone knows each other.

• Take cash, including small notes. Signal is patchy and card machines sometimes fail.
• Bring your own bags, plus a box for eggs and anything fragile.
• Do not rummage. Ask for what you want and let the stallholder choose it.
• Ask "what is good this week?" instead of "is this fresh?" You will get a better answer and a better bag.
• Queue in the order you arrived and let the person buying one loaf go ahead of you.
• Shop early for choice, late for value. Do not haggle over a bunch of herbs.
• If you are visiting, ask whether the stall packs for the ferry. Most will.

A practical last word

Turn up early, take cash, and learn three names. Then cook with what you find rather than hunting for a recipe first. A bag of September damsons, a February celeriac and a punnet of June strawberries each ask for something simple: a crumble, a soup, a bowl with cream. The market will tell you what the island is doing that week if you let it, and the season you shop in will show up on the plate.

Photo: Maria Orlova / Pexels