Juglans regia | |
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Mature walnut tree | |
Scientific 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 | |
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Distribution map | |
Synonyms [ citation needed ] | |
J. duclouxiana Dode Contents |
Juglans regia, the Persian walnut, English walnut, Carpathian walnut, Madeira walnut, [2] or, especially in Great Britain, common walnut, [1] is an Old World walnut tree species native to the region stretching from the Caucasus eastward to the Kashmir region. It is widely cultivated across Asia, Northern America and Europe.
It is the origin of cultivated varieties which produce the edible walnut, consumed around the world. China is the major commercial producer of walnuts.
Juglans regia is a large deciduous tree, attaining heights of 25–35 metres (80–120 feet), and a trunk up to 2 m (6 ft) in diameter, commonly with a short trunk and broad crown.
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 (10 to 16 in) 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 (4 to 7 in) long and 6–8 cm (2 to 3 in) broad; the basal pair of leaflets are much smaller, 5–8 cm (2 to 3 in) long, with the margins of the leaflets entire. The male flowers are in drooping catkins 5–10 cm (2 to 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, 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 flavour.
The Latin name for the walnut was nux Gallica, "Gallic nut"; [3] the Gaulish region of Galatia in Anatolia lies in highlands at the western end of the tree's presumed natural distribution.
For the etymology and meaning of the word in English and other Germanic languages, see "walnut".
"Walnut" does not distinguish the tree from other species of Juglans. Other names include common walnut in Britain; Persian walnut in South Africa [4] and Australia; [5] and English walnut in North America and Great Britain, [6] New Zealand, [7] and Australia, [5] the latter name possibly because English sailors were prominent in Juglans regia nut distribution at one time. [8] Alternatively, Walter Fox Allen stated in his 1912 treatise What You Need to Know About Planting, Cultivating and Harvesting this Most Delicious of Nuts: [9] "In America, it has commonly been known as English walnut to distinguish it from our native species."
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. In Mexico, it is called nogal de Castilla, [10] 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).
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.
One of the centers of origin and diversity of Juglans regia is Iran. [11] [12] 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. [13]
The largest forests are in Kyrgyzstan, where trees occur in extensive forests at 1,000–2,000 metres (3,300–6,600 ft) altitude, [14] notably at Arslanbob in Jalal-Abad Province [ citation needed ].
In the fourth century BC, Alexander the Great introduced this "Persian nut" (Theophrastus' καρυα ή Περσική [15] ) 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 naturalized. Cultivated J. regia was introduced into western and northern Europe very early, in Roman times or earlier, and to the Americas in the 17th century, by English 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. [16] 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 flavored oil; numerous cultivars have been selected for larger nuts with thinner shells.
It tends to grow taller and narrower in dense forest competition. It is a light-demanding species, requiring full sun to grow well.
Juglans regia is infested by Rhagoletis juglandis , commonly known as the walnut husk fly, which lays its eggs in the husks of walnut fruit.
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.
Walnut production (shelled) – 2019 | |
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Country | (millions of tonnes) |
![]() | 2.52 |
![]() | 0.59 |
![]() | 0.32 |
![]() | 0.23 |
![]() | 0.17 |
World | 4.50 |
Source: FAOSTAT of the United Nations [17] |
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. [18] 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.
Walnut cultivars include:
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. [19]
In 2019, world production of shelled walnuts was 4.5 million tonnes, led by China with 56% of the total harvested (table). Secondary producers were the United States and Iran.
Walnuts and other tree nuts are food allergen sources having potential to cause life-threatening, IgE-mediated allergic reactions in some individuals. [20] [21]
Nutritional value per 100 g (3.5 oz) | |
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Energy | 654 kcal (2,740 kJ) |
13.7 g | |
Sugars | 2.6 |
Dietary fiber | 6.7 g |
65.2 g | |
Saturated | 6.1 g |
Monounsaturated | 8.9 g |
Polyunsaturated | 47.2 g 9.1 g 38.1 g |
15.2 g | |
Vitamins | Quantity %DV† |
Thiamine (B1) | 30% 0.34 mg |
Riboflavin (B2) | 13% 0.15 mg |
Niacin (B3) | 7% 1.13 mg |
Pantothenic acid (B5) | 11% 0.57 mg |
Vitamin B6 | 42% 0.54 mg |
Folate (B9) | 25% 98 μg |
Choline | 8% 39.2 mg |
Vitamin C | 1% 1 mg |
Vitamin E | 5% 0.7 mg |
Vitamin K | 3% 2.7 μg |
Minerals | Quantity %DV† |
Calcium | 10% 98 mg |
Copper | 80% 1.6 mg |
Iron | 22% 2.9 mg |
Magnesium | 45% 158 mg |
Manganese | 162% 3.4 mg |
Phosphorus | 49% 346 mg |
Potassium | 15% 441 mg |
Selenium | 7% 4.9 μg |
Sodium | 0% 2 mg |
Zinc | 33% 3.1 mg |
Other constituents | Quantity |
Water | 4.1 g |
†Percentages estimated using US recommendations for adults. [22] |
English walnut kernels are 4% water, 65% fat, 15% protein, and 14% carbohydrates. In a 100 gram reference amount providing 654 calories, the kernels supply several nutrients in "rich" amounts (20% or more of the Daily Value, DV), including the dietary minerals manganese (162% DV), phosphorus (49% DV), magnesium (45% DV), zinc (33% DV), and iron (22% DV), among others; B vitamins B6 (42% DV), thiamine (30% DV), and folate (25% DV); and dietary fiber. [23]
One study of various cultivars of J. regia in Turkey showed the fatty acid composition included about 6% palmitic acid, 3% stearic acid, 30% oleic acid, 50% linoleic acid, and 9% linolenic acid (omega-3 alpha-linolenic acid vs. omega-6 gamma-linolenic acid content not specified). [24]
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.
The Native American Navajo tribe has been documented using the hulls of the nut to create a brown dye. [25]
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. [26] 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. [27]
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 their sabbats 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. [28] 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. [29] The Beneventan liqueur Strega depicts on its label the famous walnut tree with the witches dancing under it. [30]
Cashew is the common name of a tropical evergreen tree Anacardium occidentale, in the family Anacardiaceae. It is native to South America and is the source of the cashew nut and the cashew apple, an accessory fruit. The tree can grow as tall as 14 metres, but the dwarf cultivars, growing up to 6 m (20 ft), prove more profitable, with earlier maturity and greater yields. The cashew nut is edible and is eaten on its own as a snack, used in recipes, or processed into cashew cheese or cashew butter. The nut is often simply called a 'cashew'. Cashew can cause allergies triggered by the proteins found in the nuts.
Walnut trees are any species of tree in the plant genus Juglans, the type genus of the family Juglandaceae, the seeds of which are referred to as walnuts. All species are deciduous trees, 10–40 metres (33–131 ft) tall, with pinnate leaves 200–900 millimetres (7.9–35.4 in), with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya), but not the hickories (Carya) in the same family.
The pecan is a species of hickory native to the southern United States and northern Mexico in the region of the Mississippi River.
The Juglandaceae are a plant family known as the walnut family. They are trees, or sometimes shrubs, in the order Fagales. Members of this family are native to the Americas, Eurasia, and Southeast Asia.
The hazelnut is the fruit of the hazel tree and therefore includes any of the nuts deriving from species of the genus Corylus, especially the nuts of the species Corylus avellana. They are also known as cobnuts or filberts according to species.
Hickory is a common name for trees composing the genus Carya, which includes around 18 species. Five or six species are native to China, Indochina, and India (Assam), as many as twelve are native to the United States, four are found in Mexico, and two to four are native to Canada. A number of hickory species are used for their edible nuts, lumber or other wood and woodcraft products.
Juglans nigra, the eastern American black walnut, is a species of deciduous tree in the walnut family, Juglandaceae, native to North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south to Georgia, northern Florida and southwest to central Texas. Wild trees in the upper Ottawa Valley may be an isolated native population or may have derived from planted trees.
Juglans cinerea, commonly known as butternut or white walnut, is a species of walnut native to the eastern United States and southeast Canada.
Juglans ailantifolia, the Japanese walnut, is a species of walnut native to Japan and Sakhalin. It is a deciduous tree growing to 20 m (66 ft) tall, rarely 30 m (98 ft), and 40–80 cm (16–31 in) stem diameter, with light grey bark. The leaves are pinnate, 50–90 cm (20–35 in) long, with 11–17 leaflets, each leaflet 7–16 cm (2.8–6.3 in) long and 3–5 cm (1.2–2.0 in) broad. The whole leaf is downy-pubescent, and a somewhat brighter, yellower green than many other tree leaves. The male flowers are inconspicuous yellow-green catkins produced in spring at the same time as the new leaves appear. The female flowers have pink/red pistils. The fruit is a nut, produced in bunches of 4–10 together; the nut is spherical, 3–5 cm long and broad, surrounded by a green husk before maturity in mid autumn.
Juglans californica, the California black walnut, also called the California walnut, or the Southern California black walnut, is a large shrub or small tree of the walnut family, Juglandaceae, endemic to the Central Valley and the Coast Range valleys from Northern to Southern California.
Juglans neotropica is a species of plant in the Juglandaceae family. It is found in Colombia, Ecuador, and Peru. It is threatened by habitat loss. Common names include Colombian walnut, Ecuadorian walnut, Andean walnut, nogal, cedro negro, cedro nogal, and nogal Bogotano.
Juglans mandshurica, also known as monkey nuts, or tigernut, is a species of deciduous tree in the walnut family Juglandacea, native to the Eastern Asiatic Region. It grows to about 25 m.
Juglans sigillata, also called iron walnut, is the second most cultivated species of walnut tree after the Persian walnut Juglans regia. Commonly distributed in the eastern Himalayas and western China. The tree has been cultivated for its edible nuts, and there are at least 80 authorised or approved cultivars produced after successful implementation of grafting technology.
Juglans hindsii, commonly called the Northern California black walnut and Hinds's black walnut, is a species of walnut tree native to the western United States. It is commonly called claro walnut by the lumber industry and woodworkers, and is the subject of some confusion over its being the root stock for English walnut orchard stock.
Rhagoletis juglandis, also known as the walnut husk fly, is a species of tephritid or fruit fly in the family Tephritidae. It is closely related to the walnut husk maggot Rhagoletis suavis. This species of fly belongs to the R. suavis group, which has a natural history consistent with allopatric speciation. The flies belonging to this group are morphologically distinguishable.
A walnut is the edible seed of any tree of the genus Juglans, particularly the Persian or English walnut, Juglans regia. They are accessory fruit because the outer covering of the fruit is technically an involucre and thus not morphologically part of the carpel; this means it cannot be a drupe but is instead a drupe-like nut.
Husk in botany is the outer shell or coating of a seed. In the United States, the term husk often refers to the leafy outer covering of an ear of maize (corn) as it grows on the plant. Literally, a husk or hull includes the protective outer covering of a seed, fruit, or vegetable.
Juglans regia 'Zijing' is a cultivar of walnut developed in Beijing, China. IT was developed frommother trees of purple-leaved walnut, which was found in the mountains of Qingshui, Mentougou District, China in 1998.
Xanthomonas campestris pv. juglandis is an anaerobic, Gram negative, rod-shaped bacteria that can affect walnut trees though the flowers, buds, shoots, branches, trunk, and fruit. It can have devastating effects including premature fruit drop and lesions on the plant. This pathogen was first isolated by Newton B. Pierce in California in 1896 and was then named Pseudomonas juglandis. In 1905 it was reclassified as Bacterium juglandis, in 1930 it became Phytomas juglandis, and in 1939 it was named Xanthomas juglandis. The International Standards for Naming Pathovars declared it to be named Xanthomonas campestris pv. juglandis in 1980. There have been recent proposals to change the name once again to Xanthomonas arboricola pv. juglandis, but this has not yet been universally accepted.