Why sweet chestnuts are worth the effort

Sweet chestnut (Castanea sativa) is one of autumn's finest wild harvests. Likely brought here by the Romans and long coppiced for timber and nuts, it gives a starchy, sweet crop that works beautifully in soups, stuffings, purées and flour. But it arrives wrapped in a spiny husk and has a dangerous lookalike growing nearby. A little care is all that separates a lovely afternoon from a nasty stomach ache.

Telling sweet chestnuts from conkers

Horse chestnut — the conker — is not edible. Its saponins cause cramping, vomiting and diarrhoea, and the two trees are often planted within a few metres of one another. Learn the differences before you pick.

• Leaves: sweet chestnut leaves are long, lance-shaped and simple, glossy green with sharply serrated edges and deep parallel veins. Horse chestnut leaves are palmate — five to seven leaflets spreading like a hand.
• Husks: sweet chestnut husks are covered in masses of fine, needle-sharp spines, like a sea urchin, and usually split to release two or three nuts. Conker husks have fewer, stubbier, bumpy spines and usually hold one large glossy nut.
• Nuts: sweet chestnuts have one flat side and one curved, tapering to a small tuft at the top with a pale triangular scar at the base. Conkers are round, smooth, glossy mahogany with a large round pale scar.

When, where and how to gather

Sweet chestnuts fall from late September through October, usually after the first gales. The trees like free-draining, acidic ground — sandy heaths, gravelly woodland edges, old coppiced woods — and crop best in the south and east. Always have the landowner's permission, and never strip a tree bare: deer, squirrels, jays and mice depend on the crop.

Wear gloves and tread on the husks to split them, or pull them apart carefully. Take only nuts that have fallen free, never ones still clinging to the tree, as they aren't ripe. Carry them in a basket or cloth bag, since plastic makes them sweat and mould. At home, tip them into a bowl of water: any that float are hollowed by weevil grubs or dried out, so discard them, along with any showing a neat round hole.

Preparing and cooking your haul

Raw sweet chestnuts are unpleasant and hard to digest, and they can carry mould. Always cook them.

Score each nut with a shallow cross or single slit through the shell on the flat side, using a small sharp knife. This stops them exploding and lets the steam escape.

• Boiling: 20–25 minutes in salted water, until a knife slips in easily. Peel while hot, when the inner skin comes away readily.
• Roasting: 200°C (180°C fan, gas 6) for 25–30 minutes, cut side up, until the skins curl back. Salt at the end.
• Grilling: under a hot grill or in a dry pan, turning often, until the shells split.

You need to remove both the outer shell and the bitter brown pellicle inside. If the inner skin clings, a few minutes back in the oven loosens it. Underdone chestnuts are chalky; overcooked ones turn to mush.

Three simple ways to use them

• Chestnut soup: soften an onion and a stick of celery in butter, add 400g peeled chestnuts, 750ml stock and a bay leaf. Simmer for 20 minutes, blend, then finish with cream and grated nutmeg.
• Chestnut stuffing: crumble peeled chestnuts with fresh breadcrumbs, fried onion, sage, thyme, a beaten egg and a splash of stock. Bake at 190°C for 30 minutes — excellent with goose, game or a nut roast.
• Sweet purée: simmer peeled chestnuts in milk with a vanilla pod until soft, then blend and sweeten to taste. Serve with cream, or fold through whipped cream for a simple dessert.

Dried slowly in a low oven and ground, chestnuts make a sweet flour that thickens sauces and lends richness to cakes.

Storing your chestnuts

Fresh chestnuts are perishable. Keep them in the fridge in a paper bag for up to a fortnight, or boil, peel and freeze them in portions for up to a year. Dried whole, they keep for months in an airtight jar.

The flowers are a fine late-summer bee plant and young leaves make a mild tea, but the nuts are the real prize. Gather thoughtfully, leave plenty behind, and enjoy one of the most rewarding harvests the British autumn offers.