one of the finest nuts of temperate regions. There are a dozen species of walnut tree with edible nuts, in a family which also includes the pecan and other trees which bear hickory nuts. The most important species is the Persian walnut, Juglans regia; sometimes called ‘English walnut’ in the USA. This large and beautiful tree is found wild over a broad area from SE Europe through temperate Asia, most of the way to China.
The fruit is a green drupe, with flesh surrounding a hard-shelled stone or nut. Inside the nut is the edible kernel.
When the fruit is very young and green, the fleshy outside part can be eaten. (At this time the shell is undeveloped, so the entire fruit is edible, although sour in taste.) But as the fruit ripens the fleshy part becomes thin and leathery.
The shell consists of halves separated by a papery membrane, the division marked by a clear seam around the outside edge. This membrane is bitter and has to be removed when the nut is opened. The half-kernels within are convoluted like brains, and their shape has fascinated artists from early times. Indeed, the name for walnut in Afghanistan, charmarghz, means ‘four brains’.
Wild walnuts have been gathered and eaten since prehistoric times. The practice of pressing oil from them is also of great antiquity, as is the use of walnut juice as a dark brown dye. The earliest mention of walnut cultivation comes from ancient Greece. The wild native varieties there bore small and dry nuts, which were not used for oil. But when a superior cultivated variety was imported from Persia, this yielded oil as well as being better to eat. The Greeks called it karyon basilikon or persikon (royal or Persian walnut).
The Romans were prepared to pay a high price for good walnuts. There was a tradition of throwing walnuts at weddings; and couples must have wished that something lighter could have been chosen as a symbol of fertility. The Latin name for the walnut, which has become its botanical one, juglans, means ‘Jupiter's acorn’. (Acorns were a traditional Roman food of longer standing.)
In Europe the walnut has been of particular importance in France. In so far as the French have an equivalent to the term ‘nut’, it is noix, but that word usually indicates the walnut. The walnut was not taken from France to Britain, where climatic conditions make its cultivation difficult, until the 15th century. Its English name may be derived from the old term ‘welsh’, meaning ‘foreign’ or ‘from Gaul’. Recipes for pickling walnuts, green and black, abound in English cookery books of the 17th and 18th centuries, so it must have been grown extensively despite the difficulties.
The Persian walnut had reached China before ad 400. Cultivation became important in Sichuan province, and varieties with extremely thin shells (‘papershells’) were bred.
Early settlers in New England took the walnut to America. Although several good native species were already there, the Persian nut achieved and retains dominance. At present the largest producer is the USA, especially California, where cultivation is concentrated in an area east of San Francisco. Other large producers are Turkey, China, Russia, Greece, Italy, and France.
France, where walnut cultivation takes place mainly in the south-west, is the country where most attention is paid to named varieties. Corne and Marbot, and the group known collectively as Grenobles, are prominent. Noix noisette is a small variety, no bigger than a hazelnut. Noix Cerneau rouge has a red kernel skin. Noix Coque tendre is outstandingly thin shelled.
The walnut-growing areas of Italy are concentrated round Naples, Salerno, and Sorrento. The soft-shelled variety Sorrento is dominant.
Walnuts may be picked at various stages of development, depending on how they are to be used. In large plantations the fruits are usually shaken off the tree by a large and violent device attached to a tractor.
Green walnuts are, as already mentioned, edible whole, but are extremely sour. They are made into pickles, ketchups, marmalade, and jam. There are both European and Asian preparations of these kinds.
Half-ripe walnuts, in which the nut is sufficiently developed to be extracted from the now inedible outside, are preserved in syrup in the Middle East: delicious.
Ripe walnuts are available in the shell, but most are shelled, producing either half-kernels or broken pieces (cheaper, but just as good for cooking). Walnuts in the shell, which are usually bleached to improve their appearance, can be stored for several months.
Ripe walnuts are mostly eaten as dessert nuts or used in cakes, desserts, and confectionery of all kinds, from ice cream to baklava. But they also have many uses in savoury dishes: French walnut soup, and walnut sauces with horseradish or with garlic and oil; Italian dressings for pasta (walnuts are often added to the pine nuts in pesto, and there are other, similar preparations); and E. European and Middle Eastern meat dishes, such as the Persian fesenjan, a rich stew of duck, chicken, game, or lamb with walnuts and pomegranate juice.
Walnut oil is a traditional salad and cooking oil of France, Switzerland, and N. Italy. It is less used than formerly because it has become very expensive. Ripe nuts, of varieties selected for their oiliness, are stored for two or three months before pressing, during which time their milky juice turns to a light, clean oil with a marked and characteristic flavour. Some think walnut oil the supreme salad oil, others dislike it. It does not keep well.
Alan Davidson was a distinguished author and publisher, and one of the world's best-known writers on fish and fish cookery. In 1975 he retired early from the diplomatic service—after serving in, among other places, Washington, Egypt, Tunisia, and Laos, where he was British Ambassador—to pursue a fruitful second career as a food historian and food writer extraordinaire. Among his popular books are Seafood of South-East Asia, North Atlantic Seafood, and Mediterranean Seafood. In 2003, shortly before his death, he was awarded the Erasmus Prize for his contribution to European culture.
