Juglans
Juglans | |
---|---|
Juglans major Morton Arboretum acc. 614-47*1 | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Rosids |
Order: | Fagales |
Family: | Juglandaceae |
Subfamily: | Juglandoideae |
Tribe: | Juglandeae |
Subtribe: | Juglandinae |
Genus: | Juglans L. |
Type species | |
Juglans regia | |
Species | |
See text | |
Native ranges of Juglans spp. | |
Synonyms[1] | |
Wallia Alef |
Walnut trees are any species of tree in the plant genus Juglans, the
The 21 species in the genus range across the north temperate Old World from southeast Europe east to Japan, and more widely in the New World from southeast Canada west to California and south to Argentina.
Edible walnuts, which are consumed worldwide, are usually harvested from cultivated varieties of the species Juglans regia. China produces half of the world total of walnuts.
Etymology
The common name walnut derives from
Folklore
Tradition has it that a walnut tree should be beaten. This would have the benefit of removing dead wood and stimulating shoot formation.[4]
Production
Walnut (in shell) production – 2017 | |
---|---|
Country | (tonnes) |
China | 1,925,403 |
United States | 571,526 |
Iran | 349,192 |
Turkey | 210,000 |
Mexico | 147,198 |
Ukraine | 108,660 |
World | 3,829,626 |
Source: FAOSTAT of the United Nations[5]
|
In 2017, world production of walnuts (in shell) was 3.8 million tonnes, led by China with producing half of the world total (table). Other major producers were the United States (15%) and Iran (9%).
Cultivation and uses
The two most commercially important species are J. regia for timber and nuts, and J. nigra for timber. Both species have similar cultivation requirements and are widely grown in temperate zones.
Walnuts are light-demanding species that benefit from protection from wind. Walnuts are also very hardy against drought.
Interplanting walnut plantations with a
When grown for nuts, care must be taken to select cultivars that are compatible for pollination purposes; although some cultivars are marketed as "self fertile", they will generally fruit better with a different pollination partner. Many different cultivars are available for growers, and offer different growth habits, flowering and leafing, kernel flavours and shell thicknesses. A key trait for more northerly latitudes of North America and Europe is phenology, with ‘late flushing’ being particularly important to avoid frost damage in spring. Some cultivars have been developed for novel ‘hedge’ production systems developed in Europe and would not suit more traditional orchard systems.
Flowers
The leaves and blossoms of the walnut tree normally appear in spring. The male cylindrical catkins are developed from leafless shoots from the past year; they are about 10 cm (3.9 in) in length and have a large number of little flowers. Female flowers appear in a cluster at the peak of the current year’s leafy shoots.[6]
Fruit
The fruits of the walnut are a type of
Nuts and kernels
The nut kernels of all the species are edible, but the walnuts most commonly traded are from the J. regia, the only species which has a large nut and thin shell. J. nigra kernels are also produced commercially in the US.
Two-thirds of the world export market[
In some countries, immature nuts in their husks are preserved in
Walnuts are heavily used in India. In Jammu, it is used widely as a prasad (offering) to Mother Goddess Vaisnav Devi and, generally, as a dry food in the season of festivals such as Diwali.
The nuts are rich in
Manos and Stone studied the composition of seed oils from several species of the
Shells
The walnut shell has a wide variety of uses. Eastern black walnut (J. nigra) shell is the hardest of the walnut shells, and therefore has the highest resistance to breakdown.
- Cleansing and polishing
- Walnut shells are mostly used to clean soft metals, fiberglass, plastics, wood and stone. This environmentally friendly and recyclable soft grit abrasive is well suited for air blasting, deburring, descaling, and polishing operations because of its elasticity and resilience. Uses include cleaning automobile and jet engines, electronic circuit boards, and paint and graffiti removal. For example: In the early days of jet transportation, crushed walnut shells were used to scour the compressor airfoils clean, but when engines with air cooled vanes and blades in the turbine started being manufactured, this practice was stopped because the crushed shells tended to plug up the cooling passages to the turbine, resulting in turbine failures due to overheating.
- Oil well drilling
- The shell is used widely in oil well drilling for lost circulation material in making and maintaining seals in fracture zones and unconsolidated formations.
- Flour
- Flour from walnut shells can be used in thermoplastic starch composites to substitute oil derivatives.[13]
- Paint thickener
- Walnut shells are added to paint to give it a thicker consistency for "plaster effect" ranges.
- Explosives
- Used as a filler in dynamite
- Cosmetic cleaner
- Occasionally used in soap and exfoliating cleansers
Husks
Walnut husks are often used to create a rich yellow-brown to dark brown dye used for dyeing fabric, yarn or wood and for other purposes. The dye does not require a mordant and will readily stain the hand if picked without gloves.
Wood
The common walnut, and the black walnut and its allies, are important for their attractive timber, which is hard, dense, tight-grained and polishes to a very smooth finish. The color is dark chocolate or similar in the heartwood changing by a sharp boundary to creamy white in the sapwood. When kiln-dried, walnut wood tends toward a dull brown color, but when air-dried can become a rich purplish-brown. Because of its color, hardness and grain, it is a prized furniture and carving wood.
When walnut vascular cambium is involved in a crotch (a branch fork), it behaves unusually, producing characteristic "crotch figure" in the wood which it makes. The grain figure exposed when a crotch in a walnut log is cut in the plane of its one entering branch and two exiting branches is attractive and sought after.
There are some differences between the wood of the European walnut (Juglans regia) and the wood of the black walnut (Juglans nigra). For example, Juglans regia wood sometimes has patches with a wavy texture.[14] Black walnut wood tends to be darker than European walnut wood, and can suffer from paler sapwood that only really comes to light when the wood has been planed.
Walnut wood has been the timber of choice for gun makers for centuries, including the Gewehr 98 and Lee–Enfield rifles of the First World War. It remains one of the most popular choices for rifle and shotgun stocks, and is generally considered to be the premium – as well as the most traditional – wood for gun stocks, due to its resilience to compression along the grain. Walnut is also used in lutherie and for the body of pipe organs.
Walnut burls (or "burrs" in the rest of the world) are commonly used to create bowls and other turned pieces. Walnut burl veneer is one of the most valuable and highly prized by cabinet makers and prestige car manufacturers.
The wood of the
Freshly sawn walnut heartwood may be greenish in color, but with exposure to air this color quickly changes to brown due to oxidation of the pigment.
In North America, forestry research has been undertaken, mostly on J. nigra, aiming to improve the quality of planting stock and markets. In some areas of the US, black walnut is the most valuable commercial timber species.[15] The Walnut Council[16] is the key body linking growers with scientists. In Europe, various EU-led scientific programmes have studied walnut growing for timber.[17]
The
Parkland and garden trees
Walnuts are very attractive trees in parks and large gardens. Walnut trees are easily propagated from the nuts. Seedlings grow rapidly on good soils.[15] The Japanese walnut in particular is known for its huge leaves, which have a tropical appearance.
As garden trees, they have some drawbacks, in particular the falling nuts, and the releasing of the
Walnut as wildlife food plants
Walnut species are used as food plants by the larvae of some Lepidoptera species. These include[citation needed]:
- Brown-tailmoth (Euproctis chrysorrhoea)
- Coleophora case-bearers (moths) C. laticornella (recorded on J. nigra) and C. pruniella.
- Common emerald (a geometer moth) (Hemithea aestivaria)
- Small emperor moth (Pavonia pavonia)
- The engrailed(a geometer moth) (Ectropis crepuscularia)
- Walnut sphinxmoth (Amorpha juglandis)
- nominate subspecieson butternut and others, C. n. euphemia on Arizona black walnut, perhaps Texas black walnut and others.
The nuts are consumed by other animals, such as mice and squirrels.
In California (US) and Switzerland, crows have been witnessed taking walnuts into their beaks, flying up to 60 feet or so in the air, and dropping them to the ground to crack the shells and eat the nut inside.[24]
Nutritional information
The raw edible seed of walnut is composed of 4% water, 14%
Systematics
Taxonomy
The genus Juglans is divided into four sections.[26]
Sections and species
Section | Description | Image | Name | Common Name | Subspecies | Distribution |
---|---|---|---|---|---|---|
Section Cardiocaryon | Leaves are very large (40–90 cm), with 11–19 broad leaflets, softly downy, margins serrated. The wood is soft, and the fruits borne in racemes of up to 20. The nuts have thick shells. Native to northeast Asia. | J. ailantifolia Carr. (J. cordiformis Maxim., J. sieboldiana Maxim.) | Japanese walnut |
|
Japan and Sakhalin | |
J. mandshurica Maxim. (J. cathayensis Dode, J. formosana Hayata, J. hopeiensis Dode, J. stenocarpa Maxim.) | Manchurian walnut or Chinese walnut | China, Russian Far East, Korea | ||||
Section Juglans | Leaves are large (20–45 cm), with 5–9 broad leaflets, hairless, margins entire. The wood is hard. Native to southeast Europe to central Asia. | J. regia L. (J. duclouxiana Dode, J. fallax Dode, J. orientis Dode) | common walnut, Persian, English, or Carpathian walnut | Balkans eastward to Himalaya, China | ||
J. sigillata Dode | iron walnut (doubtfully distinct from J. regia) | China | ||||
Section Rhysocaryon (black walnuts) | Leaves are large (20–50 cm), with 11–23 slender leaflets, finely pubescent, margins serrated. Native to North America and South America. | J. australis Griseb. (J. brasiliensis Dode) | Argentine walnut, Brazilian walnut | Argentina, Bolivia | ||
J. boliviana (C. DC.) Dode | Bolivian walnut, Peruvian walnut | Andes of Bolivia and Peru | ||||
J. californica S.Wats. | California black walnut | California | ||||
J. hindsii (Jepson) R.E.Smith | Hinds' black walnut | California | ||||
J. hirsuta Manning | Nuevo León walnut | Mexico | ||||
J. jamaicensis C.DC. (J. insularis Griseb.) | West Indies walnut | Cuba, the Dominican Republic, Haiti, and Puerto Rico | ||||
J. major (Torrey) Heller (J. arizonica Dode, J. elaeopyron Dode, J. torreyi Dode) | Arizona black walnut |
|
Mexico, United States | |||
J. microcarpa Berlandier (J. rupestris Engelm.) | Texas black walnut |
|
United States | |||
J. mollis Engelm. | Mexican walnut | Mexico | ||||
J. neotropica Diels (J. honorei Dode) | Andean walnut, cedro negro, cedro nogal, nogal, nogal Bogotano | Colombia, Ecuador, and Peru | ||||
J. nigra L. | Eastern black walnut | Canada, United States | ||||
J. olanchana Standl. & L.O.Williams | cedro negro, nogal, walnut |
|
Central America, Mexico | |||
J. soratensis Manning | Bolivia | |||||
J. steyermarkii Manning | Guatemalan walnut | Guatemala | ||||
J. venezuelensis Manning | Venezuelan walnut | Venezuela | ||||
Section Trachycaryon | Leaves are very large (40–90 cm), with 11–19 broad leaflets, softly downy, margins serrated. The wood is soft. Fruits are borne in clusters of two to three. The nuts have a thick, rough shell bearing distinct, sharp ridges. Native to eastern North America. | J. cinerea L. | Butternut | Canada, United States |
The best-known member of the genus is the Persian walnut (J. regia, literally "royal walnut"), native from the Balkans in southeast Europe, southwest and central Asia to the Himalaya and southwest China. Walnuts are a traditional feature of Iranian cuisine; the nation has extensive orchards which are an important feature of regional economies. In Kyrgyzstan alone, there are 230,700 ha of walnut-fruit forest, where J. regia is the dominant overstory tree (Hemery and Popov 1998). In non-European English-speaking nations, the nut of the J. regia is often called the "English walnut"; in Great Britain, the "common walnut."
The
The Hinds' black walnut (J. hindsii) is native to northern California, where it has been widely used commercially as a rootstock for J. regia trees. Hinds' black walnut shells do not have the deep grooves characteristic of the eastern black walnut.
The
The
Hybrids
- J. × bixbyi Rehd.—J. ailantifolia x J. cinerea
- J. × intermedia Carr.—J. nigra x J. regia
- J. × notha Rehd.—J. ailantifolia x J. regia
- J. × quadrangulata (Carr.) Rehd.—J. cinerea x J. regia
- J. × sinensis (D. C.) Rehd.—J. mandschurica x J. regia
- J. × paradox Burbank—J. hindsii x J. regia
- J. × royal Burbank—J. hindsii x J. nigra
Phylogeny
A study[27] of sequenced nuclear DNA from the external transcribed spacer (ETS) of ribosomal DNA (rDNA), the internal transcribed spacer (ITS) of rDNA, and the second intron of the LEAFY gene taken from at least one individual of most of the species of Juglans has supported several conclusions:
- The genus Juglans is monophyletic;
- Sect. Cardiocaryon is sister to Sect. Trachycaryon;
- Sect. Juglans is sister to Sect. Cardiocaryon and Sect. Trachycaryon together;
- Sect. Rhysocaryon is monophyletic and sister to Sect. Juglans, Sect. Cardiocaryon, and Sect. Trachycaryon together;
- Sect. Rhysocaryon, the black walnuts, contains two clades:
- one comprises the more northerly species J. californica, J. hindsii, J. hirsuta, J. major, J. microcarpa, and J. nigra;
- the other comprises the more southerly species J. australis, J. boliviana, J. jamaicensis, J. molis, J. neotropica, J. olanchana, J. steyermarkii, and J. venezuelensis
- J. olanchana var. standleyi seems to be more closely related to J. steyermarkii than to J. olanchana var. olanchana, suggesting J. olanchana var. standleyi might be better understood as either a separate species or a variety of J. steyermarkii.
The paper presenting these results did not publish any new names for the subdivisions of sect. Rhysocaryon, for any combinations of the other sections, or for J. olanchana var. standleyi.
Paleontological history
Fossils of Juglans nuts have been described from the Tertiary period of North America.[28] The paleontological history of Juglans regia in Europe shows signs of a post-Ice-Age re-expansíon from refugia in the southeast, much influenced by people carrying walnut nuts about after the numbers of humans had been much increased by the start of agriculture.[citation needed]
See also
References
- ^ "Tropicos | Name - Juglans L." www.tropicos.org. Retrieved 29 June 2016.
- Houghton Mifflin. Retrieved 10 February 2014.
- ^ "Online Etymology Dictionary". Etymonline.com. Retrieved 2015-07-16.
- ^ Ursula Buchan (4 October 2003). "Beat them as hard as you can". The Daily Telegraph. Archived from the original on 2022-01-12.
- ^ "Crops/Regions/World list/Production Quantity (pick lists), Walnuts (in shell), 2017". UN Food and Agriculture Organization, Corporate Statistical Database (FAOSTAT). 2019. Retrieved 11 October 2019.
- ^ "Fruit and Nut Trees – Fruit Bearing Plants " Blog Archive " Walnut Tree - Juglans regia – Juglans nigra". Fruitandnuttrees.com. Archived from the original on 2009-04-30. Retrieved 2015-07-16.
- ISBN 9780851997230.
- USDA. Archived from the original(PDF) on October 18, 2012. Retrieved 2015-07-16.
- ^ a b "California Walnut History, Cultivation & Processing | California Walnuts". www.walnuts.org. Archived from the original on August 3, 2009.
- ^ "Frequently Asked Questions | California Walnuts". www.walnuts.org. Archived from the original on August 26, 2009.
- ^ www.padil.gov.au https://web.archive.org/web/20120906054734/http://www.padil.gov.au/viewPestDiagnosticImages.aspx?id=601. Archived from the original on September 6, 2012.
{{cite web}}
: Missing or empty|title=
(help) - ^ Manos, Paul S. and Stone, Donald E.: "Phylogeny and Systematics of the Juglandaceae" Annals of the Missouri Botanical Garden 88(2)231–269 Spring, 2001
- ^ "Physical and mechanical properties of walnut shell flour-filled thermoplastic starch composites :: BioResources".
- ^ Youtube video CURLY WALNUT BEAUTY !!! WOW !!!
- ^ a b "Arquivo.pt". Archived from the original on 2009-07-08. Retrieved 2017-04-07.
{{cite web}}
: CS1 maint: bot: original URL status unknown (link) - ^ "Walnut Council--Growing Walnut and Other Fine Hardwoods". Walnutcouncil.org. Retrieved 2015-07-16.
- ^ "BBC Radio 4 - Open Country". Bbc.co.uk. Retrieved 2015-07-16.
- OCLC 647927893
- ^ Mishnah (Shevi'it 7:3 [p. 47])
- ISBN 978-0-8061-0923-7.
- ^ Ross (1996)
- ^ www.wvu.edu https://web.archive.org/web/20150212041801/http://www.wvu.edu/~agexten/hortcult/fruits/blkwalnt.htm. Archived from the original on February 12, 2015.
{{cite web}}
: Missing or empty|title=
(help) - ^ Rood (2001); Pomogaybin et al. (2002)
- .
- ^ a b c "Nutrition facts: Nuts, walnuts, English, per 100 g". Condé Nast for the US Department of Agriculture National Nutrient Database, Standard Release 21. 2014. Retrieved 4 July 2014.
- ^ Aradhya, M. K., D. Potter, F. Gao, C. J. Simon: "Molecular phylogeny of Juglans (Juglandaceae): a biogeographic perspective",Tree Genetics & Genomes(2007)3:363–378
- ^ D. Stone, S. Oh, E. Tripp, Luis. Gios, P. Manos: "Natural history, distribution, phylogenetic relationships, and conservation of Central American black walnuts (Juglans sect. Rhysocaryon)", Journal of the Torrey Botanical Society 136(1)1–25. 2009.
- S2CID 198410494.
External links
- Juglans species throughout the world
- Rethinking the history of common walnut (Juglans regia L.) in Europe: Its origins and human interactions by Paola Pollegioni et al
- Fossil History of the Juglandaceae
- https://www.ars.usda.gov/ARSUserFiles/31120/walnutsymposium.pdf
- Scientists crack origin of the Persian walnut 4 June 2019
- Notes on the Geological History of the Walnuts and Hickories by Edward W. Berry, The Plant World, Vol. 15, No. 10 (October, 1912), pp. 225–240 (16 pages)
- 16.58-minute Youtube video about making a black walnutwood.