Why Walnuts Grow Where You Least Expect Them

Walk through almost any sizeable town in Britain and you are rarely more than a few streets from a walnut. Common walnut (Juglans regia) was planted in enormous numbers by Victorian and Edwardian gardeners, who liked its handsome grey bark, its aromatic shade and the promise of a free harvest. When those big houses were broken up, the trees stayed. Many now lean over park railings, stand in churchyards, line the backs of allotment sites, or fruit quietly in a corner of a municipal recreation ground where nobody ever looks up.

That is good news for the forager. Walnuts are generous trees, dropping their crop over a fortnight or so, and most of it goes unpicked. A single mature tree can give you more nuts than you know what to do with — and, if you time it right, a free supply that keeps into the following spring.

Identifying a Walnut Before It Fruits

Walnuts are easy to recognise once you know what you are looking at.

• Leaves: long, pinnate and made up of five to nine oval leaflets, with the largest at the tip. Crush one and you get a clean, spicy, almost citrus-and-varnish smell that lingers on your fingers.
• Bark: smooth and silvery-grey on young trees, breaking into pale, diamond-patterned ridges with age.
• Leaf scars: the giveaway. Snap off a leaf in autumn and the scar left on the twig looks uncannily like a small monkey's face.
• Husks: from late summer you will spot round green fruits, hanging singly or in pairs, with a faint seam down the side.

Black walnut (Juglans nigra) also turns up occasionally in parks and arboretums. Its nuts are smaller, its husks do not split so neatly and the shells are famously stubborn, but the flavour is superb and the smell of the crushed leaves is sharper and more resinous.

Timing the Harvest

Do not pick walnuts from the tree. An unripe walnut is a disappointment: the kernel is watery, the husk refuses to part company with the shell, and it will simply shrivel in storage. Wait for the husks to split and the nuts to fall. In southern Britain that usually means late September into October; further north, add a fortnight.

The moment a nut hits the ground, the race begins. Grey squirrels, jays and crows are working the same tree, so visit every day or two during the fall. Pick nuts up promptly, before they sit wet on grass and begin to blacken.

Take gloves — walnut husks stain hands a rich, stubborn brown and can irritate sensitive skin. A bucket or canvas bag is ideal. As you gather, discard anything with a small hole in the husk (the walnut husk fly has been there first) and any nut that feels unusually light. Once husked, a quick test in a bowl of water helps: sound nuts sink, hollow or grub-damaged ones float.

Husking, Drying and Storing

If the husks have split, they should peel away easily with a knife or your fingers; if they cling, leave the nuts in a cool airy place for a few days and try again. Rinse off the worst of the sticky residue and spread the nuts out in a single layer — a slatted tray, an old cooling rack or a cardboard box in a dry shed or airing cupboard all work well. Avoid direct heat, radiators and ovens: too much warmth turns the oils rancid before you have even cracked a shell.

Leave them to dry and cure for three to four weeks, turning them every few days. Properly dried nuts feel light and dry in the hand, the shell is hard and the kernel rattles faintly when shaken. Store them in their shells in a cloth bag or open basket in a cool, dry, dark place, and they will keep for six months or more. Shelled kernels are far shorter-lived: keep them in an airtight jar in the fridge for up to three months, or freeze them.

If any nut is mouldy, black inside, or smells musty, throw it out. Walnuts can carry moulds that are best not eaten.

Green Walnuts and Walnut Leaves

Long before the nuts ripen, in late June, there is another harvest. Green walnuts — picked while the shell inside is still soft enough that a knife passes cleanly through — are the base of nocino, the dark Italian liqueur. Quarter about twenty of them, steep them in a litre of vodka or neutral spirit with sugar, a strip of lemon peel and a few cloves, then leave for six weeks before straining. It drinks best after a year in the bottle, so label it and be patient.

Walnut leaves have their own uses. Dried in a warm, shaded place and crumbled into a jar, they make a pleasant, slightly bitter tea — a spoonful per mug, steeped for five minutes. A handful of fresh leaves laid in the bottom of a jar of pickles is a traditional trick for keeping them crisp.

Walnut Sap, and Foraging Politely

Walnut sap runs in late winter, on the same freeze-and-thaw rhythm as birch. It is sweet, watery and pleasantly nutty, and it boils down into an excellent syrup, though it takes a great deal of sap to make a little. Only tap a healthy tree with a trunk at least 25cm across, drill no more than one hole, and plug it afterwards. In practice, most foragers are better off enjoying walnut leaves, green walnuts and the autumn nut crop.

Etiquette matters here. In a public park you are picking from someone's land, and fallen nuts technically belong to the landowner, so ask the parks department or the estate office first — permission is almost always given for a modest personal harvest. Take a share, leave plenty for the squirrels and for next year's seedlings, never break branches, and never gather on a commercial scale. Do that, and the walnut trees in your local park will keep feeding you for decades.