The English walnut is cultivated commercially in North, Central, and South America, Europe, and Asia. China is the leading producer of walnuts. Other important walnut-growing countries are the USA, Iran, Turkey, India, France, and Romania (Prasad, 2003).
The English walnut needs a long, warm growing season, although too much sun can be damaging. Winter chilling is essential — the English walnut needs 700—1500 hours of winter chilling — and cold acclimation needs to be slow. Preferred soils are deep, well-drained alluvial soils with a pH of 6.0—7.5. Walnut trees like space, and should be planted 6—16 m apart (Lyle, 2006).
Walnuts are cultivated extensively for their high-quality nuts, both eaten fresh and pressed into oil. They are also acknowledged for their various health benefits. The wood is of very high quality, and is used to make furniture and gunstocks. The walnut shells are reduced to flour, and have various applications — for example, as fillers in synthetic resin adhesives, in plastics and industrial tiles, and as insecticide diluents. The outer husk, when crushed, yields an oil that is used in the manufacture of soaps, paints, varnishes, alkyd resins, and styrenated oils (Lyle, 2006; Prasad, 2003).
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