The late-summer hedgerow

There's a particular week in late August when the brambles along a country lane stop being a wall of thorns and dusty leaves and start being a larder. The first berries ripen on the sunny side of the hedge, small and sharp, and then the whole tangle seems to catch up at once. In the south-west you might be picking from mid-August; in the north and in Scotland it can be September before the crop is worth carrying a tub for, and a mild autumn can push good fruit into early October.

Blackberrying is the gentlest introduction to foraging there is. No knife work, no obscure fungi, no risk of a fatal mistake. But it does reward a bit of care, because the same hedge that gives you a crumble also borders roads, spray zones and places where the fruit is best left alone.

Identifying a true blackberry

Our common brambles are a muddle of closely related species, all lumped together as blackberries, and all edible. The fruit gives itself away when you pick it: it comes away easily and leaves the white core behind on the plant, so the berry is hollow. That hollow centre is the single best check. If the core comes away with the fruit, you've picked a dewberry, which is still edible but usually duller in flavour.

Before you pick a berry, glance at the whole plant. Bramble leaves are usually in threes or fives with toothed edges, and the canes are arched and prickly. Things worth leaving well alone:

• Shiny, single black berries sitting one at a time in the leaf joints of a plant with dull green leaves and purple bell-shaped flowers. That's deadly nightshade, and it is genuinely dangerous.
• Black or dark blue berries held in flat-topped clusters on ivy. Ivy berries are poisonous to us and don't ripen until late winter anyway.
• Sloes look similar at a distance, but they're single, round, dusty blue and cling tightly to a woody stem with no hollow centre.

And be strict with yourself about ripeness. A blackberry that is still red or purple-red is hard, mouth-puckering and will leave you with a sore stomach. It will be properly black in a week. Come back.

Pick above dog height

The classic rule of hedgerow foraging is simple: nothing below dog height. In practice that means picking above roughly waist-to-knee height, around 70 centimetres or so, which is about as high as a cocked leg, a fox or a badger will reach. The fruit up there is cleaner, less gritty and less likely to have been rained on by something larger than weather.

That said, the highest, sun-ripened berries are often the best, so it pays to be comfortable. A few practical bits:

• Wear long sleeves, sturdy trousers and boots. Brambles will find bare skin and nettles are usually hiding underneath.
• Carry a walking stick to lift and part canes rather than pushing your face into the hedge.
• Check yourself for ticks afterwards, especially on forearms, waistbands and behind the knees. Countryside ticks are worth being respectful of.
• Watch for wasps, which are slow and grumpy in September and often deep in the same bush.

Steer clear of roads and spray zones

Hedgerows are filters. Whatever is thrown up by traffic or sprayed on the verge ends up in the fruit, and no amount of washing takes it all out. A few places to walk on by:

• Busy, fast roads. Leave hedges within about 50 metres of a heavy, fast-moving road. Exhaust particulates, tyre and brake dust and lead from older fuel all settle on the leaves and fruit.
• Sprayed verges. If the base of the hedge has a brown, dead strip of vegetation along it, that's a strong hint of herbicide use by a council, highways team or farmer. There's usually another hedge nearby that hasn't been treated.
• Railway embankments. These are sprayed, and walking them is both illegal and lethal. Never.
• Private land. In England and Wales the law generally allows you to pick wild fruit and foliage for personal use, but not to dig up plants, and not where local byelaws or site rules forbid it. Fruit on private land belongs to the landowner, so ask first, and keep off protected sites. In Scotland, access rights cover picking wild fruit for your own consumption, with the usual responsibilities attached.

Forage kindly: leave plenty behind

A hedge is not a shop. Blackberries feed blackbirds, thrushes, fieldfares, redwings, wood mice, dormice, foxes and badgers through the autumn, and the high canes you can't reach are exactly the ones that carry the birds through a hard January. Take a third of what's on a good bush, at the very most, and leave the rest.

Move on rather than strip a single patch. Don't drag canes down or snap them off, don't trample the base of the hedge, and don't pick a bush clean and then come back the next day to finish it. Treated that way, a good lane will feed you every year for decades.

Getting your haul home

Use a shallow tub or a wide basket rather than a bag, so the berries don't crush into juice on the way home. Back in the kitchen, tip them out and sort: discard anything mouldy, anything still red, and any berry with a small clean hole, which usually means a fruit fly larva. Many foragers soak berries in cold water with a good pinch of salt for 20 minutes, which persuades anything living to leave, then rinse and drain well. Cooked in a crumble or jam, you'd never notice anyway.

Eat a few raw, straight off the bush, warm from the sun. That's half the point. The rest freeze beautifully spread out on a tray first, then bagged, and will carry you through to February in pies, cordials, vinegar and gin. Take your time, pick high, pick clean, and leave the hedge richer than you found it.