Wikipedia

Juglans regia

Juglans regia, the common walnut[1] or Persian walnut[2] amongst other regional names, is a species of walnut. It is native to Eurasia in at least southwest and central Asia and southeast Europe, but its exact natural area is obscure due to its long history of cultivation.

Juglans regia
Mature walnut tree
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Juglandaceae
Genus: Juglans
Section: Juglans sect. Juglans
Species:
J. regia
Binomial name
Juglans regia
Distribution map
Synonyms[citation needed]

J. duclouxiana Dode
J. fallax Dode
J. kamaonica (C. de Candolle) Dode
J. orientis Dode
J. regia subsp. fallax (Dode) Popov
J. regia subsp. kamaonica (C. de Candolle) Mansf.
J. regia subsp. turcomanica Popov
J. regia var. orientis (Dode) Kitam.
J. regia var. sinensis C. de Candolle
J. sinensis (C. de Candolle) Dode

The species has numerous cultivars which produce the edible walnut consumed around the world and produced predominately in China. It is widely cultivated across temperate regions throughout the world including those of Eurasia, Australia, and the Americas.

Description

edit

Juglans regia is a large deciduous tree, attaining heights of 10–25 metres (35–80 feet), and a trunk up to 2 m (6+1⁄2 ft) in diameter, commonly with a short trunk and broad crown.[3][4] The tallest accurately measured specimen is in Lagodekhi Protected Areas in Georgia, 29 m (95 ft) tall, and the stoutest, 9 m (30 ft) girth (2.87 m (9 ft 5 in) diameter);[5] heights of 34 m in the wild in Kyrgyzstan,[6] and 32 m in cultivation in Britain[7] have been reported, but not verified.

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 creamy-white at first, becoming brown in older twigs. The leaves are alternately arranged, 20–45 cm (8–17+1⁄2 in) long, odd-pinnate with (3–)5–9 (most often 7) leaflets, arranged in opposite pairs with one terminal leaflet. The largest leaflets are the three at the apex, 10–20 cm (4–8 in) long and 6–10 cm (2+1⁄2–4 in) broad; the basal pair of leaflets are much smaller, 5–8 cm (2–3 in) long. The margins of the leaflets are entire, but with toothed margins on seedlings, and in the cultivar 'Laciniata'. The leaves open fairly late in the spring (typically mid May in Britain), and are red-brown at first, becoming their mature dark yellow-toned green by mid June. The male flowers are in drooping catkins 5–10 cm (2–4 in) long, and the female flowers are 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 with the husk breaking open; the seed is a large and edible nut with a rich flavour; the shell is thick in wild populations, while most cultivated plants have been selected for a thin shell.[3][4]

  •  
    Seedling; note the serrated leaf margins
  •  
    Young tree
  •  
    Mature tree
  •  
    Bark
  •  
    Buds
  •  
    The new leaves in spring have a distinctive red-brown colour at first
  •  
    Male flower
  •  
    Female flower
  •  
    Fertilized flowers
  •  
    Foliage
  •  
    Fruit
  •  
    Seed
  •  
    Habit (autumn)
  •  
    In winter, France
  •  
    Old tree

Distribution and habitat

edit
 
A walnut tree claimed to be the oldest walnut tree in the world, near Khotan, Xinjiang, China, in 2011
 
In August, Czech Republic

Original habitat

edit

One of the centres of origin and diversity of J. regia is Iran,[8][9] and another further northeast in Central Asia.[2] In Central Asia, genetic diversity is very patchy, with the highest diversity found around Sariosiyo in Uzbekistan,[2] and conspicuously lower in the famous Arslanbob forests[2] (these now thought to be of cultivated origin).[10] Another native glacial refugium population with high genetic diversity is found on the southern fringes of the Alps in northeast Italy.[11] However, as with other old and widespread cultivated plants, it is not easy to reconstruct the original distribution and determine the borders of the past natural ranges. There are many reports concerning the earliest fossil pollen and nuts of J. regia, and the conclusions that various authors draw are somewhat contradictory. Taken together these finds suggest that J. regia possibly survived the last glaciations in several refugia, as the compilation of the data shows most likely southern Europe, the Near East, China, and the Himalaya.[10]

The largest forests are in Kyrgyzstan, where trees occur in extensive forests at 1,000–2,000 metres (3,300–6,600 ft) altitude,[6] notably at Arslanbob in Jalal-Abad Province.[12]

Global introduction

edit

In the fourth century BC, Alexander the Great introduced this "Persian nut" (Theophrastus' καρυα ή Περσική)[13] in Macedonian, Ancient Greek ancestral forms with lateral fruiting from Iran and Central Asia. They hybridized with terminal-bearing forms to give lateral-bearing trees with larger fruit.[clarification needed] These lateral-bearers were spread in southern Europe and northern Africa by Romans. Recent prospections in walnut populations of the Mediterranean Basin allowed to select interesting trees of this type. In the Middle Ages, the lateral-bearing character was introduced again in southern Turkey by merchants travelling along the Silk Road. J. regia germplasm in China is thought to have been introduced from Central Asia about 2,000 years ago, and in some areas has become naturalised. Cultivated J. regia was introduced into western and northern Europe very early, probably in Roman times,[3] and to the Americas in the 17th century, by European colonists. Important nut-growing regions include California in the United States; France, Serbia, Greece, Bulgaria, Romania and Hungary in Europe; China in Asia; Baja California and Coahuila in Mexico; and Chile in Latin America. Lately, cultivation has spread to other regions, such as New Zealand and the southeast of Australia.[14] It is cultivated extensively from 30° to 50° of latitude in the Northern Hemisphere and from 30° to 40° in the Southern Hemisphere. Its high-quality fruits are eaten both fresh or pressed for their richly flavoured oil; numerous cultivars have been selected for larger nuts with thinner shells.[15]

Genetic diversity

edit

J. regia is highly diverse genetically, and has been extensively cultivated for possibly as long as 2,000 years in parts of west Asia and southern Europe.[2][11]

Its closest relative is Juglans sigillata from western China and the far northeast of India;[16] it differs chiefly in leaves with 9–11 leaflets, and nuts with a much thicker, harder shell.[17]

Ecology

edit

It tends to grow taller and narrower in dense forest competition. It is a light-demanding species, requiring full sun to grow well.[4]

Juglans regia is infested by Rhagoletis juglandis, commonly known as the walnut husk fly, which lays its eggs in the husks of walnut fruit.[18]

Other plants often will not grow under walnut trees because the fallen leaves and husks contain juglone, a chemical which acts as a natural herbicide. Horses that eat walnut leaves may develop laminitis, a hoof ailment.[citation needed]

Cultivation

edit
Walnut production (shelled) – 2022
Country (millions of tonnes)
  China 1.40
  United States 0.68
  Iran 0.36
  Turkey 0.34
  Mexico 0.18
World 3.87
Source: FAOSTAT of the United Nations[19]

Walnut trees grow best in rich, deep soil with full sun and long summers, such as the California central valley. Juglans hindsii and J. hindsii × J. regia are often used as grafting stock for J. regia.[20] Mature trees may reach 15 m (50 ft) in height and width, and live more than 200 years, developing massive trunks more than 2.4 m (8 ft) thick.

  •  
    FLORY 34 Series Nut Sweeper during harvest in Glenn County, California
  •  
    FLORY 8770 Harvester during walnut harvest in Glenn County

Cultivars

edit
Further information: Walnut § Cultivars

Walnut cultivars include:

  • Purpurea
  • Broadview
  • Cascade
  • Allegheny
  • Bedco 1
  • Coble #2
  • Hansen
  • Kaiser
  • KY Giant
  • Lake
  • McKinster
  • Somers
  • Utah Giant
  • Colby
  • Greenhaven
  • Reda
  • Shiawassee
  • Perry
  • S-1
  • Looking Glass
  • China-B
  • Champion
  • Northern Prize
  • Placentia
  • Zijing

Pests

edit

Particular cultivars of J. regia may be more infested by R. juglandis than others because of varying walnut husk softness or thickness. 'Eureka', 'Klondike', 'Payne', 'Franquette' and 'Ehrhardt' cultivars are among the most susceptible to infestation.[21]

Production

edit

In 2022, world production of shelled walnuts was 3.9 million tonnes, led by China with 36% of the total harvested, with the United States, Iran, and Turkey as secondary producers (table).

Toxicity

edit

Allergy

edit

Walnuts and other tree nuts are food allergen sources having potential to cause life-threatening, IgE-mediated allergic reactions in some individuals.[22][23]

Uses

edit
Unroasted walnuts
Nutritional value per 100 g (3.5 oz)
Energy654 kcal (2,740 kJ)
13.7 g
Sugars2.6
Dietary fibre6.7 g
65.2 g
Saturated6.1 g
Monounsaturated8.9 g
Polyunsaturated47.2 g
9.1 g
38.1 g
15.2 g
Vitamins and minerals
VitaminsQuantity
%DV†
Thiamine (B1)
28%
0.34 mg
Riboflavin (B2)
12%
0.15 mg
Niacin (B3)
7%
1.13 mg
Pantothenic acid (B5)
11%
0.57 mg
Vitamin B6
32%
0.54 mg
Folate (B9)
25%
98 μg
Choline
7%
39.2 mg
Vitamin C
1%
1 mg
Vitamin E
5%
0.7 mg
Vitamin K
2%
2.7 μg
MineralsQuantity
%DV†
Calcium
8%
98 mg
Copper
178%
1.6 mg
Iron
16%
2.9 mg
Magnesium
38%
158 mg
Manganese
148%
3.4 mg
Phosphorus
28%
346 mg
Potassium
15%
441 mg
Selenium
9%
4.9 μg
Sodium
0%
2 mg
Zinc
28%
3.1 mg
Other constituentsQuantity
Water4.1 g
Link to USDA Database entry
†Percentages estimated using US recommendations for adults,[24] except for potassium, which is estimated based on expert recommendation from the National Academies.[25]

Nutrition

edit

Walnut kernels are 4% water, 65% fat, 15% protein, and 14% carbohydrates. In a reference amount of 100 g (3.5 oz) providing 654 calories, the kernels supply several micronutrients in rich amounts (20% or more of the Daily Value, DV), including the dietary minerals manganese, phosphorus, magnesium, zinc, and copper, among others; B vitamins B6, thiamine, and folate; and dietary fibre.

The fatty acid composition includes 6% saturated fats, 10% monounsaturated fats, and 49% polyunsaturated fats (USDA source).

Dyes

edit

As with all species of walnut, the green outer husk of the fruit is rich in a yellow-brown to dark brown dye; harvesting the nuts often leaves the fingers strongly stained brown, and an extract from the husks can be used for dyeing cloth. The dye has notable antibacterial properties.[26]

Wood

edit

Walnut heartwood is a heavy, hard, open-grained hardwood. Freshly cut live wood may be Dijon-mustard colour, 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, lustre and chatoyance, and is used for high-end flooring, guitars, furniture, veneers, knobs and handles as well as gunstocks.[27]

In culture

edit

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.[28] Most planting is done by field rats (subfamily Murinae). In Flanders, a folk saying states: "By the time the tree is big, the planter surely will be dead." (Dutch: Boompje groot, plantertje dood). These sayings refer to the relatively slow growth rate and late fruiting of the tree.[29]

Benevento in southern Italy is the home of an ancient tradition of stregoneria. The witches of Benevento were reputed to come from all over Italy to gather for the Witches' Sabbath under the sacred walnut tree of Benevento. In 1526, Judge Paolo Grillandi wrote of witches in Benevento who worship a goddess at the site of an old walnut tree.[30] This legend inspired many cultural works, including the 1812 ballet Il Noce di Benevento (the walnut tree of Benevento) by Salvatore Viganò and Franz Xaver Süssmayr, a theme from which was adapted into a violin piece called Le Streghe by Niccolò Paganini.[31] The Beneventan liqueur Strega depicts on its label the famous walnut tree with the witches dancing under it.[32]

Common names

edit
See also: Walnut
 
Illustration from Köhler's Medizinal Pflanzen

The Latin name for the walnut was nux Gallica, "Gallic nut";[33] the Gaulish region of Galatia in Anatolia lies in highlands at the western end of the tree's presumed natural distribution.

Although often called simply "walnut",[4] this does not distinguish the tree from other species of Juglans. Internationally, it is most often called "common walnut"[1][2][6] or "Persian walnut";[11][2][34][35][36] other names include "Madeira walnut",[37] and "English walnut" mainly in North America,[38] possibly because English sailors were prominent in Juglans regia nut distribution at one time.[39] Alan Mitchell comments "The Americans call it 'English Walnut', which is plainly an error by the early settlers when finding the Black Walnut and Butternut growing in their woods, and 'Persian Walnut', which is correct",[7] and Walter Fox Allen stated in his 1912 treatise What You Need to Know About Planting, Cultivating and Harvesting this Most Delicious of Nuts:[40] "In America, it has commonly been known as English walnut to distinguish it from our native species", and occasionally elsewhere.[36][41] The name "Carpathian walnut" refers to a cultivar group of selected cold-tolerant strains with high quality nuts, rather than the species as a whole.[15]

In the Chinese language, the edible, cultivated walnut is called 胡桃 (hú táo in modern standard Chinese), which means literally "Hu peach", suggesting the ancient Chinese associated the introduction of the tree into East Asia with the Hu barbarians of the regions north and northwest of China.[citation needed] In Mexico, it is called nogal de Castilla,[42] suggesting the Mexicans associated the introduction of the tree into Mexico with Spaniards from Castile (as opposed to the black walnuts native to North America).[citation needed]

The Old English term wealhhnutu is a late book-name (Old English Vocabularies, Wright & Wulker), so the remark that the Anglo-Saxons inherited the walnut tree from the Romans does not follow from this name. Old English: walhhnutu is wealh (foreign) + hnutu (nut). Etymologically it "meant the nut of the Roman lands (Gaul and Italy) as distinguished from the native hazel" according to the Oxford English Dictionary.[citation needed]

See also

edit

References

edit
  1. ^ a b c Rivers, M.C., Allen, D.J. (2017). "Juglans regia". The IUCN Red List of Threatened Species. 2017: T63495A61526700. doi:10.2305/IUCN.UK.2017-3.RLTS.T63495A61526700.en.
  2. ^ a b c d e f g Gaisberger H, Legay S, Andre C, et al. (23 June 2020). "Diversity Under Threat: Connecting Genetic Diversity and Threat Mapping to Set Conservation Priorities for Juglans regia L. Populations in Central Asia". Frontiers in Ecology and Evolution. 8. doi:10.3389/fevo.2020.00171. hdl:20.500.11850/425973. ISSN 2296-701X.
  3. ^ a b c Mitchell AF (1974). A Field Guide to the Trees of Britain and Northern Europe. London: Collins. p. 195. ISBN 0-00-212035-6.
  4. ^ a b c d Rushforth K (1999). Trees of Britain and Europe. London: Trafalgar Square Publishing. p. 755. ISBN 0-00-220013-9.
  5. ^ "The thickest, tallest, and oldest Persian Walnuts (Juglans regia)". Monumental Trees. Retrieved 7 November 2024.
  6. ^ a b c Hemery GE (1998). "Walnut (Juglans regia) seed-collecting expedition to Kyrgyzstan in Central Asia". Quarterly Journal of Forestry. 92 (2): 153–157.
  7. ^ a b Mitchell AF (1996). Alan Mitchell's Trees of Britain. HarperCollins. pp. 246–249. ISBN 0-00-219972-6.
  8. ^ "Juglans regia L. | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 18 March 2024.
  9. ^ ResearchGate (November 2014). "Nutritive Value of Persian Walnut (Juglans regia L.) Orchards". ResearchGate.
  10. ^ a b Beer R, Kaiser F, Schmidt K, et al. (1 March 2008). "Vegetation history of the walnut forests in Kyrgyzstan (Central Asia): natural or anthropogenic origin?". Quaternary Science Reviews. 27 (5): 621–632. Bibcode:2008QSRv...27..621B. doi:10.1016/j.quascirev.2007.11.012. ISSN 0277-3791.
  11. ^ a b c Vischi M, Chiabà C, Raranciuc S, et al. (16 March 2017). "Genetic Diversity of Walnut (Juglans regia L.) in the Eastern Italian Alps". Forests. 8 (3): 81. doi:10.3390/f8030081. hdl:11390/1103388. ISSN 1999-4907.
  12. ^ Soni M (27 November 2019). "The world's largest walnut harvest". BBC Home. Retrieved 7 November 2024.
  13. ^ Theophrastus, Enquiry into Plants III.6.2, III.14.4
  14. ^ "FAO corporate document repository: Walnut".
  15. ^ a b Huxley A (1992). Dictionary of Gardening (Royal Horticultural Society, UK). London; New York: Macmillan Press; Stockton Press. ISBN 1-56159-001-0.
  16. ^ Aradhya MK, Potter D, Simon CJ (31 December 2006). "7. Cladistic Biogeography of Juglans ( Juglandaceae) Based on Chloroplast DNA Intergenic Spacer Sequences". Darwin's Harvest (PDF). Columbia University Press. pp. 143–170. doi:10.7312/motl13316-008. ISBN 978-0-231-16891-5.
  17. ^ Grimshaw J, Bayton R (2009). New Trees. Richmond, Surrey: Royal Botanic Gardens Kew. pp. 413–414. ISBN 978-1-84246-173-0. OCLC 428774409.
  18. ^ Boyce, A.M. (December 1929). "The Walnut Husk Fly (Rhagoletis juglandis Cresson)". Journal of Economic Entomology. 22 (6): 861–866. doi:10.1093/jee/22.6.861.
  19. ^ "Production of shelled walnuts in 2022, Crops/Regions/World list/Production Quantity/Year (from pick lists)". UN Food and Agriculture Organization, Corporate Statistical Database (FAOSTAT). 2024. Retrieved 7 November 2024.
  20. ^ "Walnuts in California". Fruit and Nut Research and Information Center, University of California at Davis. 2021. Archived from the original on 17 November 2020. Retrieved 23 January 2021.
  21. ^ Boyce, A.M. (December 1929). "The Walnut Husk Fly (Rhagoletis juglandis Cresson)". Journal of Economic Entomology. 22: 861–866.
  22. ^ "Allergy information for walnut (Juglans regia)". Manchester Academic Health Science Centre, University of Manchester. 18 October 2006. Retrieved 22 January 2021.
  23. ^ Teuber SS, Jarvis KC, Dandekar AM, et al. (1999). "Identification and cloning of a complementary DNA encoding a vicilin-like proprotein, Jug r 2, from English walnut kernel (Juglans regia), a major food allergen". Journal of Allergy and Clinical Immunology. 104 (6): 1311–1320. doi:10.1016/S0091-6749(99)70029-1. PMID 10589017.
  24. ^ United States Food and Drug Administration (2024). "Daily Value on the Nutrition and Supplement Facts Labels". FDA. Archived from the original on 27 March 2024. Retrieved 28 March 2024.
  25. ^ National Academies of Sciences, Engineering, and Medicine, Health and Medicine Division, Food and Nutrition Board, et al. (2019). Oria M, Harrison M, Stallings VA (eds.). Dietary Reference Intakes for Sodium and Potassium. The National Academies Collection: Reports funded by National Institutes of Health. Washington, DC: National Academies Press (US). ISBN 978-0-309-48834-1. PMID 30844154. Archived from the original on 9 May 2024. Retrieved 21 June 2024.
  26. ^ Mirjalili M, Karimi L (2013). "Extraction and Characterization of Natural Dye from Green Walnut Shells and Its Use in Dyeing Polyamide: Focus on Antibacterial Properties". Journal of Chemistry. 2013 (1). Wiley. doi:10.1155/2013/375352. ISSN 2090-9063.
  27. ^ "Harvesting Walnut".
  28. ^ "Skopelos is not for tourists, it is for lovers – Epifanios Skiathitis writes about his island". Travel.gr. 8 September 2021. Retrieved 4 August 2023.
  29. ^ "Column stadsboswachter Maurice: Plantertje groot, boompje dood". Natuurmonumenten (in Dutch). 30 January 2020. Retrieved 4 August 2023.
  30. ^ Grimassi, Raven. Encyclopedia of Wicca & Witchcraft. Llewellyn Worldwide (2000). p. 454.
  31. ^ Gooley D (2005). ""La Commedia del Violino": Paganini's Comic Strains". The Musical Quarterly. 88 (3): 370–427. doi:10.1093/musqtl/gdi012. ISSN 0027-4631. JSTOR 4123230. Retrieved 4 August 2023.
  32. ^ "Liquore Strega". Strega Alberti Benevento SpA. Retrieved 4 August 2023.
  33. ^ "Walnut". Online Etymology Dictionary. 2021.
  34. ^ "Persian walnut (Juglans regia)". iNaturalist. 28 September 2021. Retrieved 7 November 2024.
  35. ^ L.C. van Zyl (2009). "Grafting of Walnut (Juglans regia L.) with Hot Callusing Techniques Under South African Conditions" (PDF). University of the Free State. Archived from the original (PDF) on 7 September 2012. Retrieved 6 March 2011.
  36. ^ a b "Walnuts: Australia - Nuts". Austnuts.com.au. Archived from the original on 29 November 2010. Retrieved 23 August 2012.
  37. ^ "Juglans regia". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Retrieved 6 July 2019.
  38. ^ "USDA Plants Database". USDA Plants Database. Retrieved 8 November 2024.
  39. ^ "English walnuts - profile". Agricultural Marketing Resource Center. Archived from the original on 28 September 2006.
  40. ^ Walter Fox Allen. "How to grow English walnuts". WalnutsWeb. Archived from the original on 25 April 2009.
  41. ^ "Ornamental Tree Photography - NZ Plant Pics Photography ornamental garden trees". Nzplantpics.com. Archived from the original on 2 March 2013. Retrieved 23 August 2012.
  42. ^ Juglans Regia (in Spanish)
edit
 
Wikimedia Commons has media related to Juglans regia.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Juglans_regia&oldid=1259501756"