The walnut tree is a large, long-lived tree known for its aromatic leaves and nutritious nuts. Also called the English, Persian or common walnut, it has been cultivated across Europe for centuries for food, oil and valuable timber.
In autumn, the smooth green husks begin to soften and split, revealing the familiar hard, ridged walnut shell inside. Both ripe walnuts and carefully harvested immature green walnuts can be used in the kitchen.
Green walnuts: June to early July
Ripe walnuts: September to November
Parks, gardens, orchards, old farmsteads, roadsides, hedgerows and woodland edges
Usually 15–25 metres, occasionally up to 30 metres or more
Ripe kernels and immature green fruits collected before the shell hardens
The common walnut is native to parts of south-eastern Europe and Asia but has been planted far beyond its original range. It prefers sunny, sheltered places with deep, fertile and well-drained soil.
Walnut trees are frequently found near old houses, farms, gardens and orchards. Birds and squirrels may also spread the nuts, allowing trees to appear along hedgerows, riverbanks and woodland edges.
The walnut is a broad-crowned deciduous tree with thick, spreading branches. Mature trees often develop an impressive rounded canopy.
The bark is smooth and greyish when young. As the tree ages, it becomes paler and develops deep vertical ridges and fissures.
The leaves are large and pinnate, meaning that several leaflets grow along one central stalk. Each leaf usually carries five to nine oval leaflets, with the terminal leaflet noticeably larger than the others. The leaf edges are mostly smooth rather than sharply toothed.
When gently rubbed, the leaves have a strong, distinctive aromatic smell.
Walnut trees produce separate male and female flowers on the same tree. The male flowers hang in long, green catkins, while the much smaller female flowers appear near the tips of young shoots.
The developing fruit is round or slightly oval and enclosed in a smooth, fleshy green husk. As it ripens, the husk softens, darkens and begins to split away from the hard shell.
Inside the shell is the familiar wrinkled walnut kernel, divided into two main halves.
Black walnut has similar pinnate leaves and green-husked fruits. Its leaves usually have more leaflets, often with finely toothed edges. The fruit is round, with a thick husk and an exceptionally hard, deeply ridged shell.
Black walnut kernels are edible, but the species should still be identified separately because preparation and flavour differ from common walnut.
Butternut produces more elongated, oval fruits rather than the rounder fruits of common walnut. Its leaves and young shoots are often noticeably hairy, and the shell has pronounced lengthwise ridges.
The nuts are edible, but butternut is uncommon in much of Europe and is more often encountered as a planted tree.
From a distance, an unripe horse chestnut fruit may be mistaken for a green walnut. Horse chestnut fruits usually have a leathery capsule with short spines, while walnut husks are smooth.
Horse chestnut also has large, hand-shaped leaves rather than pinnate walnut leaves. Its shiny brown conkers are not edible and must never be confused with walnuts.
Always identify the complete tree—including its leaves, bark and fruit—rather than relying on a fallen nut alone.
The ripe kernel is the main edible part of the walnut. It can be eaten fresh from the shell or dried for storage.
Walnuts can be used in:
Breads, cakes and biscuits
Granola, porridge and breakfast dishes
Salads and roasted vegetables
Pesto and savoury sauces
Stuffings and nut roasts
Walnut butter
Chutneys and preserves
Desserts and confectionery
Cold-pressed walnut oil
Fresh walnuts have a mild, creamy flavour. After drying, their flavour becomes richer and more concentrated.
Immature green walnuts can be harvested before the inner shell hardens. At this stage, a skewer should pass through the entire fruit. They are traditionally used for pickled walnuts, preserves and walnut liqueurs such as nocino.
Walnut oil has a delicate flavour and is particularly suitable for dressings, dips and finishing dishes. Because it oxidises relatively quickly, it should be stored in a cool, dark place and used while fresh.
Walnuts are tree nuts and can cause severe allergic reactions, including anaphylaxis. Anyone with a known or suspected tree-nut allergy must avoid them.
Eat only fresh, healthy nuts. Discard walnuts that are mouldy, rancid, unusually bitter, shrivelled or heavily damaged by insects.
Green walnut husks release a dark juice that stains skin and clothing and may irritate sensitive skin. Wear gloves when processing them.
Do not use leaves, bark or mature husks as ordinary food ingredients. Traditional preparations made from these parts are more concentrated and are not equivalent to eating the ripe kernel.
Whole walnuts can be a choking risk for young children. Never eat an unidentified “walnut-like” fruit without checking the leaves, husk, shell and tree.
Harvest only where collecting is permitted and obtain the landowner’s permission where required.
Choose healthy trees growing away from busy roads, contaminated ground and recently sprayed areas. Gather a modest quantity and leave plenty for wildlife.
Collect freshly fallen walnuts once the green husks begin to split naturally. Do not shake trees forcefully, break branches or damage young growth.
Wear gloves when removing the staining husks. Discard damaged or mouldy nuts, then dry the remaining walnuts in a well-ventilated place before storage.
Harvest immature green walnuts sparingly because every young fruit collected removes a mature nut from the autumn crop.
Walnut trees have been valued for food, household materials and craftsmanship for many centuries.
Traditionally, walnuts were used for:
Leaves and green husks were included in traditional herbal practices, but these preparations should be regarded as historical use rather than instructions for self-treatment. They contain different and more concentrated compounds than the edible kernel.
Walnut kernels contain mainly unsaturated fats and are particularly notable for alpha-linolenic acid, a plant-based omega-3 fatty acid.
They also provide protein, dietary fibre and minerals including magnesium, copper and manganese. Other naturally occurring constituents include polyphenols, ellagitannins, phytosterols and vitamin E compounds.
The precise composition varies according to cultivar, climate, ripeness, storage and processing. Because their oils oxidise relatively easily, shelled walnuts should be kept cool and stored in an airtight container.
Walnut leaves and green husks contain tannins, phenolic compounds and naphthoquinones, including juglone. These contribute to their bitter taste and strong staining properties.
The presence of omega-3 fatty acids, polyphenols or other compounds does not by itself demonstrate that walnuts can prevent or treat disease.
A hard, ridged shell protects the rich, oily kernel.
Walnuts have been cultivated for food, oil and timber for centuries.
Green fruits and mature nuts have different traditional uses.
The husks provide dye and the wood is valued by craftspeople.
Learn how to recognise and explore wild plants, fruits and trees safely.
The botanical name Juglans is traditionally linked to the Latin expression Jovis glans, meaning “Jupiter’s nut”. The walnut was therefore associated with Jupiter, the most powerful of the Roman gods.
A walnut’s wrinkled kernel is often compared to the shape of a human brain, but this resemblance is simply a natural feature of the folded seed.
Walnut husks can stain fingers dark brown for several days. Before synthetic dyes became widely available, this strong natural pigment made the husks useful for colouring textiles, wood and other materials.
