Common Walnut, sometimes unhelpfully called English Walnut, is a tree of unsurpassed grace and utility; its epithet means 'of Kings'. Its hardwood is among the most attractive and valuable of any tree, and its edible nuts are an important global commodity. Considered an archaeophyte in Britain and Ireland, introduced to Britain by the Romans.
Its native range traces the ancient Silk Road linking eastern Asia with the Mediterranean, from India to Turkey. At its heart are the extensive walnut-dominated natural forests growing in the foothills of mountains in Central Asia, especially Kyrgyzstan.
Monoecious. Pioneer, fast-growing. Wind-pollinated. Seeds distributed by birds and mammals. Hybridises with other walnut species, including Common Walnut (Hybrid Walnut p. xxx).
Large (35m), often leaning, boldly and sparsely branched, broad-crowned. Bark grey and smooth when young, darkening and ridging with age, sometimes basally burred. Twigs mostly downy, with heart-shaped leaf scars resembling a face and brown chambered pith. Foliage smells strongly of juglone. Leaves pinnate compound, 20-30cm, with 5-9 (usually seven) smooth-margined leaflets, always with a terminal one. Fruit a glabrous ovoid drupe (4-6cm) staining hands black. Black Walnut differs: notched leaf scars, 10-13 leaflets.
A germinating walnut quickly grows a deep taproot, so direct sowing is best, as nursery trees lose it. Plant in deep, fertile, well-drained, sheltered, well-lit sites, avoiding frost hollows. For timber, use non-shading nurse species (ideally nitrogen-fixers like Italian Alder) and prune only in July to limit bleeding. For nuts, choose a grafted cultivar such as 'Broadview', 'Fernette', 'Fernor' or 'Lara'.
Seeds often distributed and consumed by corvids. Like some other walnuts, has an allelopathic impact on neighbouring plants.
Walnut blight causes black spots on leaves, holes and blotches on fruit, and sometimes shoot dieback. Walnut anthracnose affects nut orchards. Thousand cankers disease (p. xxx) is a future threat.
Exquisite hardwood, with pale sapwood and dark chocolate-brown heartwood often swirled with orange and black for striking figure, used in cabinet-making, furniture and veneers (for prestige cars), and the best choice for gunstocks. The edible nuts are a valued crop, and even the shells are used in polishing and cleaning products.
