Crab apples are the quiet backbone of the British hedgerow. Come late September, the field edges and country lanes start to bow under small, hard, fiercely sour apples that nobody would dream of eating raw but which make one of the finest jellies in the British larder. They are the wild ancestor of the orchard apple, packed with pectin, and their sharpness cuts through the sugar beautifully. If you have never made jelly before, this is the one to start with.

What to Look For in the Hedge

Crab apples are small — usually between two and four centimetres across — roundish, and often a little lopsided. They ripen from green through yellow to a flushed red, sometimes with a mottled speckling. Cut one open and you will find a proper apple core with pips, and a calyx or "eye" at the base where the flower once sat. That core is the giveaway, and the taste test is decisive: one bite will make your mouth pucker tight.

Do not confuse them with sloes, which are blue-black with a grey bloom and grow on thorny blackthorn bushes, or with rosehips, which are elongated and orange-red. If in doubt, pick one, cut it, and look for the pips.

Pick from hedges away from busy roads where exhaust and spray settle on the fruit, and always ask permission before foraging on private land. Take a few from each bush rather than stripping one bare — the birds and small mammals rely on them through the winter, and a good rule is to leave two-thirds behind.

Picking and Preparing Your Fruit

Choose a dry day and pick fruit that is firm and unblemished. Windfalls are perfectly usable, though you should discard anything brown or rotten. A few maggot holes are nothing to worry about — cut those sections away.

• Rinse the apples and remove stalks and blossom ends.
• There is no need to peel or core them; the pips, skin and core all carry pectin, which is precisely what you want.
• Chop roughly into halves or quarters — nothing fussy.
• Weigh the prepared fruit, then add roughly 1.2 litres of water for every kilogram of apples.

The Slow Simmer and the Overnight Strain

Tip the fruit and water into a large, heavy-based pan and bring it gently to a simmer. Cook uncovered for around forty-five to sixty minutes, until the fruit has completely collapsed into a soft, pale pulp. Mash it occasionally with a potato masher to help it along.

Now comes the patient part. Scald a jelly bag or a large square of muslin, suspend it over a deep bowl, and ladle the pulp in. Leave it to drip overnight — eight to twelve hours — and do not squeeze the bag. Squeezing forces cloudy particles through and gives you a hazy jelly. If you cannot bear to waste the last of it, squeeze that portion into a separate jug and use it for a second, cloudier batch or for everyday cooking. A kilogram of fruit should yield roughly 700–800 ml of clear juice.

Boiling to a Set

Measure your juice and weigh out 450g of granulated sugar for every 500ml of juice. Warm the sugar in a low oven while you bring the juice to the boil in a wide, heavy pan. Add the warm sugar off the heat and stir steadily until every grain has dissolved — if any crystals remain, they will crystallise the whole batch later.

Once dissolved, bring it back to a rolling boil and stop stirring. Boil hard for ten to twenty minutes. You are looking for a set at 104–105°C on a jam thermometer, but the wrinkle test is more reliable: drop a teaspoon of jelly onto a chilled saucer, let it cool for a minute, and push it with your finger. If it wrinkles and holds, it is ready. If it slides about, boil for another three minutes and test again.

Skim off the foam with a slotted spoon as it rises. A small knob of butter stirred in at the end helps disperse the last of the scum.

Potting, Sealing and Storing

Sterilise your jars by washing them in hot soapy water and drying them in an oven at 140°C for fifteen minutes, or by running them through a hot dishwasher cycle. Pot the jelly while both jars and jelly are hot, filling right to the brim to minimise the air gap.

• Wipe the rims clean with a damp cloth.
• Seal immediately with new, clean lids.
• Label with the date once cool — it keeps for twelve months in a cool, dark cupboard.
• Refrigerate once opened and use within a few weeks.

One kilogram of crab apples will give you four to five jars, which is a handsome return on half an hour of hedgerow wandering.

Variations and Ways to Use It

Plain crab apple jelly is superb, but the base takes flavour beautifully. Tuck a sprig of rosemary, a split vanilla pod, a few cloves, a star anise or a dried chilli into the pan during the initial simmer and strain it out with the fruit. A handful of rosehips or sloes added alongside the apples deepens the colour and the flavour.

Serve it with roast pork, lamb or game, stir a spoonful into gravies and casseroles, or set it on a cheeseboard next to a sharp Cheddar. On hot buttered toast it is very hard to beat — and it is a quiet reminder that the best of British food is often growing free along the lane.