Britain's riverbanks and water meadows are among the most generous foraging grounds in the country. Damp soil, regular flooding and dappled light produce a larder that shifts week by week from March through to October — wild garlic in the shade, water mint by the shallows, elderflowers frothing over the hedge, then blackberries and hazelnuts as the light fades. But the same water that makes these places lush can also carry pollution, and the same damp ground that grows sweet wild garlic can grow something that will put you in hospital. One rule sits above all the others: never eat anything unless you are certain of its identity.

Six Plants Worth Learning First

Build confidence slowly, with a handful of species you can recognise in your sleep. These six are common, distinctive and genuinely useful.

• Wild garlic (ramsons) — broad, soft, pointed leaves carpeting damp woodland beside streams from March to May. Crush a leaf: it should smell powerfully of garlic. If it doesn't, walk away.
• Watercress — peppery, crisp, growing in clean flowing chalk streams. Raw watercress can carry liver fluke, so cook it thoroughly unless you know the water's history in detail.
• Sorrel — sheep's sorrel with its arrow-shaped leaves in short meadow grass, and larger common sorrel on the bank. Both taste sharply of lemon. Lovely in salads, soups and with fish.
• Nettle — the top four leaves of young plants in April and May, before flowering. Gloves on, then blanch or cook. A free spinach that tastes far better than it sounds.
• Elderflower — flat, creamy, frothy heads in June along hedgerows and river paths. Cordial, fritters, or dried for winter teas. Pick heads that smell sweet, not musty.
• Meadowsweet — frothy cream flower clusters and a deep almond scent, often on damp meadow edges. Excellent in cordials and teas.

The Lookalikes That Demand Respect

Two plant families cause most of the trouble. The first is the carrot family, the umbellifers, whose flat heads of white flowers all look reassuringly similar — and one of which, hemlock water dropwort, is among the most poisonous plants in Britain. It favours exactly the wet ditches, stream edges and marshy ground you are walking through, and its roots are the deadliest part. Hemlock and fool's parsley grow in similar places. The second is the group that mimics wild garlic: young lords-and-ladies leaves, lily of the valley and autumn crocus can all appear in the same woodland. Every one of them lacks that unmistakable garlic smell when crushed. Scent, not sight, is your test.

Reading the Water: Where Not to Pick

Pollution in British rivers is real, and plants take it up. Avoid gathering anything from:

• Below sewage outfalls or storm overflow points, especially for a week or two after heavy rain, when untreated water may have discharged.
• Stretches with blue-green algal blooms, which look like green paint or pea soup on the surface and can be toxic.
• Water downstream of livestock fields, where slurry and parasite-rich run-off enter the river.
• Ground near busy roads, old industrial sites, tanneries or former lead and tin mining areas, where heavy metals linger in the soil.
• Popular dog-walking stretches at ankle height, and anywhere the water itself looks or smells wrong.

If you wouldn't swim in it, don't eat from its banks.

The Countryside Code on the Bank

Respect, protect, enjoy — the three words behind the Countryside Code apply neatly to foraging. Picking leaves, flowers, fruit and fungi for your own use is generally acceptable, but uprooting any wild plant without the landowner's permission is an offence under the Wildlife and Countryside Act 1981, and commercial picking needs explicit permission. On nature reserves, Sites of Special Scientific Interest and land managed by conservation bodies, ask first or simply don't. Keep to paths and public rights of way, use gates properly, close them behind you, and take everything you brought home with you. Remember that riverbanks are fragile: trampled margins erode, and they are also the home of water voles, kingfisher nest burrows and nesting moorhens.

Habits That Keep You Safe

Carry a good field guide and check plants across several seasons so you know them at every stage. Pick one species at a time and keep bags separate. Take only what you will genuinely use, and never strip a patch — leave plenty for wildlife and for next year. Wash everything thoroughly and cook anything from questionable ground. Tell someone where you are going, watch river levels and tides, and wear footwear with real grip; wet clay banks and muddy towpaths catch out experienced walkers every year. Above all, if there is any doubt in your mind at all, leave it growing. There is always another day, another walk, and another plant you will know for certain.