Persian walnut

Appearance

''Juglans regia'' is a large, deciduous tree attaining heights of 25–35 m, and a trunk up to 2 m diameter, commonly with a short trunk and broad crown, though taller and narrower in dense forest competition. It is a light-demanding species, requiring full sun to grow well.

The bark is smooth, olive-brown when young and silvery-grey on older branches, and features scattered broad fissures with a rougher texture. Like all walnuts, the pith of the twigs contains air spaces; this chambered pith is brownish in color. The leaves are alternately arranged, 25–40 cm long, odd-pinnate with 5–9 leaflets, paired alternately with one terminal leaflet. The largest leaflets are the three at the apex, 10–18 cm long and 6–8 cm broad; the basal pair of leaflets are much smaller, 5–8 cm long, with the margins of the leaflets entire. The male flowers are in drooping catkins 5–10 cm long, and the female flowers are terminal, in clusters of two to five, ripening in the autumn into a fruit with a green, semifleshy husk and a brown, corrugated nut. The whole fruit, including the husk, falls in autumn; the seed is large, with a relatively thin shell, and edible, with a rich flavor.

Habitat

''J. regia'' is native to the mountain ranges of Central Asia, extending from Xinjiang province of western China, parts of Kazakhstan, Uzbekistan and southern Kirghizia and from lower ranges of mountains in Nepal, Bhutan, Tibet, northern India and Pakistan, through Afghanistan, Turkmenistan and Iran to portions of Azerbaijan, Armenia, Georgia and eastern Turkey. In these countries, there is a great genetic variability, in particular ancestral forms with lateral fruiting. During its migration to western Europe, the common walnut lost this character by natural selection on account of competition with other vigorous forest species, such as oaks. They became large trees with terminal fruiting. A small remnant population of these ''J. regia'' trees have survived the last glacial period in Southern Europe, but the bulk of the wild germplasm found in the Balkan peninsula and much of Turkey was most likely introduced from eastern Turkey by commerce and settlement several thousand years ago.

Uses

Walnut heartwood is a heavy, hard, open-grained hardwood. Freshly cut live wood may be Dijon-mustard color, darkening to brown over a few days. The dried lumber is a rich chocolate-brown to black, with cream to tan sapwood, and may feature unusual figures, such as "curly", "bee's wing", "bird's eye", and "rat tail", among others. It is prized by fine woodworkers for its durability, luster and chatoyance, and is used for high-end flooring, guitars, furniture, veneers, knobs and handles as well as Gunstocks.

Methyl palmitate, which has been extracted from green husks of ''J. regia'' has insecticidal properties: at a concentration of 10 mg/ml, it killed 98% of ''Tetranychus cinnabarinus'' in one study.

Cultural

In Skopelos, a Greek island in the Aegean Sea, local legend suggests whoever plants a walnut tree will die as soon as the tree can "see" the sea. This has not been proven as fact; however, it might take some time to find a local arborist willing to take on the job of planting a walnut tree. Most planting is done by field rats . In Flanders, a folk saying states: "By the time the tree is big, the planter surely will be dead." . This saying refers to the relatively slow growth rate of the tree.

In rural villages of the Rađevian region of western Serbia, the head of household would crack a walnut on Christmas morning. If the walnut was sound, it was thought that the coming year would be prosperous. If the walnut was shriveled, the head of household would avert the bad omen by running three times around his house, at the same time shouting what could be paraphrased as "Do not listen, God, to Jack, who is full of cack."