Juglans regia

Juglans regia (the Common walnut, Persian walnut, or English walnut), is the original walnut tree of the Old World. It is native in a region stretching from the Balkans eastward to the Himalayas and southwest China. The largest forests are in Kyrgyzstan, where trees occur in extensive, nearly pure walnut forests at 1,000–2,000 m altitude (Hemery 1998)—notably at Arslanbob in Jalal-Abad Province.

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, with scattered broad fissures with a rougher texture. Like all walnuts, the pith of the twigs contains air spaces, the chambered pith brownish in colour. The leaves are alternately arranged, 25-40 cm long, odd-pinnate with 5–9 leaflets, paired alternately with one terminal leaflet. The largest leaflets the three at the apex, 10–18 cm long and 6–8 cm broad; the basal pair of leaflets much smaller, 5–8 cm long, the margins of the leaflets entire. The male flowers are in drooping catkins 5–10 cm long, the female flowers terminal, in clusters of two to five, ripening in the autumn into a fruit with a green, semi-fleshy 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 flavour.

Additional recommended knowledge

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Essential Laboratory Skills Guide

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Cultivation and uses

The walnut was introduced into western and northern Europe very early, by Roman times or earlier, and to the Americas by the 17th century. Important nut-growing regions include France, Serbia, Greece, Bulgaria, and Romania in Europe, China in Asia, California in North America, and Chile in South America. It is cultivated extensively for its high-quality nuts, eaten both fresh and pressed for their richly flavoured oil; numerous cultivars have been selected for larger and thin-shelled nuts.

The wood is also of very high quality, and is used to make furniture and rifle stocks.

Nutritional value

100 g shelled walnuts provide:

• 15.2 g protein
• 65.2 g fat:
  • 6.1 g saturated fat
  • 8.9 g monounsaturated fat
  • 47.2 g polyunsaturated fat
• 13.7 g carbohydrates, including 6.7 g dietary fiber
• 0.34 mg Thiamin
• 0.54 mg Vitamin B₆
• 98 µg Folate
• 3.4 mg Manganese
• 1.6 mg Copper
• 158 mg Magnesium
• 346 mg Phosphorus
• 3.1 mg Zinc

Etymology and other names

The scientific name Juglans is from Latin jovis glans, "Jupiter's nut", and regia, "royal". Its common name, Persian walnut, indicates its origins in Persia in southwest Asia; 'walnut' derives from the Germanic wal- for "foreign", recognising that it is not a nut native to northern Europe.

Other names include Walnut (which does not distinguish the tree from other species of Juglans), Common Walnut and English Walnut, the latter name possibly because English sailors were prominent in Juglans regia nut distribution at one time.[1] In the Chinese and Korean languages, the edible, cultivated walnut is called 胡桃 (hú táo in Mandarin or 호두 hodu in Korean), which means literally "Hu peach," suggesting that the ancient Chinese associated the introduction of the tree into East Asia with the Hu barbarians of the regions north and northwest of China.

Folklore

In Skopelos, a Greek island in the Aegean Sea, local legend suggests that 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 (subfamily Murinae).

References

• Flora of China: Juglans regia
• Flora Europaea: Juglans regia
• Flora of Pakistan: Juglans regia
• Hemery, G. E. (1998). Walnut seed-collecting expedition to Kyrgyzstan in Central Asia. Quarterly Journal of Forestry 92 (2): 153-157.