Editing Juglans (section)

==Cultivation and uses==
[[File:Baklava in Bodrum, Turkey (5653812987).jpg|thumb|Walnut is one of the main ingredients of [[Baklava]] and [[Turkish cuisine]].]]
The two most commercially important species are ''[[Juglans regia|J. regia]]'' for timber and nuts, and ''[[Juglans nigra|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 [[nitrogen fixation|nitrogen fixing]] plant, such as ''Elaeagnus × ebbingei'' or ''[[Elaeagnus umbellata]]'', and various ''[[Alnus]]'' species, results in a 30% increase in tree height and girth (Hemery 2001).

When grown for nuts, care must be taken to select [[cultivar]]s 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 {{convert|10|cm|in|abbr=on}} 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.<ref>{{cite web|url=http://fruitandnuttrees.com/walnut-tree-j-regia-j-nigra|title=Fruit and Nut Trees – Fruit Bearing Plants " Blog Archive " Walnut Tree - Juglans regia – Juglans nigra|publisher=Fruitandnuttrees.com|access-date=2015-07-16|archive-url=https://web.archive.org/web/20090430130505/http://fruitandnuttrees.com/walnut-tree-j-regia-j-nigra|archive-date=2009-04-30|url-status=dead}}</ref>

===Fruit===
The fruits of the walnut are a type of [[accessory fruit]] known as a pseudodrupe (or drupe-like nut), the outer covering of the fruit is an [[involucral bract|involucre]] - in a drupe the covering would be derived from the carpel.<ref>{{Cite book|page=250|title=The Encyclopedia of Seeds: Science, Technology and Uses|author1=J. Derek Bewley |author2=Michael Black |author3=Peter Halmer |publisher=CABI|date=2006|isbn=9780851997230}}</ref>

====Nuts and kernels====
[[File:Walnuts by RustedStrings.jpg|thumb|Persian walnut (''Juglans regia'') seeds]]

The nut kernels of all the species are edible, but the walnuts most commonly traded are from the ''J.&nbsp;regia'', the only species which has a large nut and thin shell. ''J.&nbsp;nigra'' kernels are also produced commercially in the US.

Two-thirds of the world export market{{citation needed|date=July 2015}}{{how|date=July 2015}}<ref>{{cite web|url=http://www.fas.usda.gov/htp/Hort_Circular/2004/12-10-04/12-04%20Walnuts.pdf |title=Walnuts |work=[[USDA]] |access-date=2015-07-16 |url-status=dead |archive-url=https://web.archive.org/web/20121018232341/http://www.fas.usda.gov/htp/Hort_Circular/2004/12-10-04/12-04%20Walnuts.pdf |archive-date=October 18, 2012 }}</ref><ref name="walnuts.org">{{cite web |url=http://www.walnuts.org/walnuts101/history_cultivation_processing.php |title= California Walnut History, Cultivation & Processing &#124; California Walnuts|website=www.walnuts.org |archive-url=https://web.archive.org/web/20090803161811/http://www.walnuts.org/walnuts101/history_cultivation_processing.php |archive-date=August 3, 2009}}</ref> and 99% of US walnuts are grown in California's [[Central Valley (California)|Central Valley]] and in Coastal Valleys, from [[Redding, California|Redding]] in the north to [[Bakersfield]] in the south.<ref>{{cite web |url=http://www.walnuts.org/walnuts101/faq.php |title= Frequently Asked Questions &#124; California Walnuts|website=www.walnuts.org |archive-url=https://web.archive.org/web/20090826070300/http://www.walnuts.org/walnuts101/faq.php |archive-date=August 26, 2009}}</ref>  Of the more than 30 varieties of ''J.&nbsp;regia'' grown there, Chandler and Hartley account for over half of total production.<ref name="walnuts.org"/> In California commercial production, the Hinds' black walnut (''J.&nbsp;hindsii'') and the hybrid between ''J.&nbsp;hindsii'' and ''J.&nbsp;regia'', ''Juglans x paradox'', are widely used as [[rootstock]]s for ''J.&nbsp;regia'' cultivars because of their resistance to [[Phytophthora]] and to a very limited degree, the oak root fungus.  However, trees grafted on these rootstocks often succumb to black line.<ref>{{cite web |url=http://www.padil.gov.au/viewPestDiagnosticImages.aspx?id=601 |title= |website=www.padil.gov.au |archive-url=https://web.archive.org/web/20120906054734/http://www.padil.gov.au/viewPestDiagnosticImages.aspx?id=601 |archive-date=September 6, 2012}}</ref>

In some countries, immature nuts in their husks are preserved in [[vinegar]]. In the UK, these are called [[pickled walnuts]] and this is one of the major uses for fresh nuts from the small scale plantings. In [[Armenian cuisine]], unripe walnuts, including husks, are preserved in sugar syrup and eaten whole. In Italy, [[liqueur]]s called [[Nocino]] and [[Nocello]] are flavoured with walnuts, while ''Salsa di Noci'' (walnut sauce) is a pasta sauce originating from [[Liguria]]. In [[Georgian cuisine|Georgia]], walnuts are ground with other ingredients to make [[walnut sauce]].

[[File:Green leaves of a walnut tree with budding walnuts.jpg|thumb|Green leaves of a walnut tree with budding walnuts, in [[Kashmir Valley]].]]

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 [[Walnut oil|oil]], and are widely eaten both fresh and in [[cookery]]. Walnut oil is expensive and consequently is used sparingly; most often in [[salad dressing]]s.  Walnut oil has been used in [[oil paint]], as an effective binding medium, known for its clear, glossy consistency and nontoxicity.

Manos and Stone studied the composition of seed oils from several species of the [[Rhoipteleaceae]] and [[Juglandaceae]] and found the nut oils were generally more unsaturated from species which grow in the [[Temperateness|temperate]] zones and more saturated for species which grow in the [[Tropics|tropical]] zones.<ref>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</ref>  In the northerly-growing section ''Trachycaryon'', ''J.&nbsp;cinerea'' oil was reported to contain 15% [[Alpha-Linolenic acid|linolenate]] (the report did not specify whether the linolenate was the alpha (n-3) or gamma (n-6) isomer, or perhaps a mixture), 2% of saturated [[palmitic acid|palmitate]], and a maximum concentration of 71% [[linoleic acid|linoleate]].  In the section ''Juglans'', ''J.&nbsp;regia'' nut oil was found to contain from 10% to 11% linolenate, 6% to 7% palmitate, and a maximum concentration of  linoleate (62% to 68%).  In the section ''Cardiocaryon'', the nut oils of ''J.&nbsp;ailantifolia'' and ''J.&nbsp;mandshurica'' were reported to contain (respectively) 7% and 5% of linolenate, 2% of palmitate, and maximum concentrations of 74% and 79% linoleate.  Within the section ''Rhysocaryon'', the nut oils of the  U.S. native black walnuts ''J.&nbsp;microcarpa'' and ''J.&nbsp;nigra'' were reported to contain (respectively) 7% and 3% linolenate, 4% and 3% palmitate, and 70% and 69% linoleate.  The remaining results for black walnuts were: ''J.&nbsp;australis'' contained 2% linolenate, 7% palmitate, and 61% linoleate; ''J.&nbsp;boliviana'' contained 4% linolenate, 4% palmitate, and 70% linoleate; ''J.&nbsp;hirsuta'' contained 2% linolenate, 5% palmitate, and 75% linoleate; ''J.&nbsp;mollis'' contained 0% linolenate, 5% palmitate, 46% linoleate, and 49% [[oleic acid|oleate]]; ''J.&nbsp;neotropica'' contained 3% linolenate, 5% palmitate, and 50% linoleate; and  ''J.&nbsp;olanchana'' contained only a trace of linolenate, 9% palmitate, and 73% linoleate;

====Shells====
[[File:Walnuts.JPG|thumb|left|The shells of walnuts]]

The walnut shell has a wide variety of uses. Eastern black walnut (''J.&nbsp;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.<ref>{{cite web | url=https://bioresources.cnr.ncsu.edu/resources/physical-and-mechanical-properties-of-walnut-shell-flour-filled-thermoplastic-starch-composites/ | title=Physical and mechanical properties of walnut shell flour-filled thermoplastic starch composites :: BioResources }}</ref>
;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====
[[Image:Walnut hand stain.jpg|thumb|upright|Staining from handling walnuts with [[husk]]s]]

Walnut husks are often used to create a rich yellow-brown to dark brown [[dye]] used for dyeing [[textile|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===
[[File:Walnut pith.jpg|thumb|left|upright=1.2|Walnut shoot cut longitudinally to show chambered [[pith]], scale in mm]]

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.<ref>[https://www.youtube.com/watch?v=NgDO3dO0MgM&t=1156s Youtube video] CURLY WALNUT BEAUTY !!! WOW !!!</ref> 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 [[Luthier|lutherie]] and for the body of [[pipe organ]]s.

Walnut [[burl]]s (or "burrs" in the rest of the world) are commonly used to create bowls and other turned pieces. Walnut burl [[Wood veneer|veneer]] is one of the most valuable and highly prized by cabinet makers and prestige car manufacturers.

The wood of the [[butternut (tree)|butternut]] and related Asian species is of much lower value, softer, coarser, less strong and heavy, and paler in colour.

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.&nbsp;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.<ref name=ohioline>{{Cite web|url=http://ohioline.osu.edu/b700/b700_22.html|title=Arquivo.pt|access-date=2017-04-07|archive-date=2009-07-08|archive-url=http://arquivo.pt/wayback/20090708061425/http://ohioline.osu.edu/b700/b700_22.html|url-status=bot: unknown}}</ref> The Walnut Council<ref>{{cite web|url=http://www.walnutcouncil.org|title=Walnut Council--Growing Walnut and Other Fine Hardwoods|publisher=Walnutcouncil.org|access-date=2015-07-16}}</ref> is the key body linking growers with scientists. In Europe, various EU-led scientific programmes have studied walnut growing for timber.<ref>{{cite web|url=http://www.bbc.co.uk/radio4/factual/opencountry_20020330.shtml|title=BBC Radio 4 - Open Country|publisher=Bbc.co.uk|access-date=2015-07-16}}</ref>

The [[Cherokee Indians]] would produce a black dye from walnut bark, which they used to dye cloth.<ref>{{Citation |contribution=History of the Cherokees, 1830–1846 |title=Chronicles of Oklahoma |last1=Knight |first1=Oliver |publisher=Oklahoma Historical Society|place=Oklahoma City|year=1956–57|page=164|oclc=647927893 |language=en }}</ref> As early as the 2nd century CE, shells and kernels of the edible walnut were used to make a dye solution in the [[Levant]].<ref>[[Mishnah]] (''Shevi'it'' [https://archive.org/details/DanbyMishnah/page/n76/mode/1up 7:3] [p. 47])</ref><ref>{{cite book |author-last=Foreman |author-first=Grant |title=The Five Civilized Tribes|publisher=University of Oklahoma Press |location=Norman|year=1934|pages=283–284|language=en |url=https://books.google.com/books?id=gGtLnSkqkekC&pg=PA283 |isbn=978-0-8061-0923-7}}</ref>

===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.<ref name=ohioline/>
The Japanese walnut in particular is known for its huge leaves, which have a tropical appearance.
[[File:Diófa.JPG|thumb|Walnut tree in a garden]]
As garden trees, they have some drawbacks, in particular the falling nuts, and the releasing of the [[allelopathic]] compound [[juglone]], though a number of gardeners do grow them.<ref>Ross (1996)</ref><ref>{{cite web |url=http://www.wvu.edu/~agexten/hortcult/fruits/blkwalnt.htm |title= |website=www.wvu.edu |archive-url=https://web.archive.org/web/20150212041801/http://www.wvu.edu/~agexten/hortcult/fruits/blkwalnt.htm |archive-date=February 12, 2015}}</ref> However, different walnut species vary in the amount of juglone they release from the roots and fallen leaves - ''J.&nbsp;nigra'', in particular, is known for its toxicity, both to plants and horses.<ref>Rood (2001); Pomogaybin ''et al.'' (2002)</ref> Juglone is [[allelopathy|toxic to plants]] such as tomato, apple, and [[birch]], and may cause stunting and death of nearby vegetation.  Juglone appears to be one of the walnut's primary defence mechanisms against potential competitors for resources (water, nutrients and sunlight), and its effects are felt most strongly inside the tree's "drip line" (the circle around the tree marked by the horizontal distance of its outermost branches). However, even plants at a seemingly great distance outside the drip line can be affected, and juglone can linger in the soil for several years even after a walnut is removed as its roots slowly decompose and release juglone into the soil.

===Walnut as wildlife food plants===
Walnut species are used as food plants by the [[larva]]e of some [[Lepidoptera]] species. These include{{Citation needed|date=October 2007}}:
* [[Brown-tail]] moth (''Euproctis chrysorrhoea'')
* ''[[Coleophora]]'' case-bearers (moths) ''C. laticornella'' (recorded on ''J. nigra'') and ''C. pruniella''.
* [[Common emerald]] (a geometer moth) (''Hemithea aestivaria'')
* [[Saturnia pavonia|Small emperor moth]] (''Pavonia pavonia'')
* [[The engrailed]] (a geometer moth) (''Ectropis crepuscularia'')
* [[Walnut sphinx]] moth (''Amorpha juglandis'')
* [[Catocala neogama|The bride]] (a moth) (''Catocala neogama'') &ndash; [[nominate subspecies]] on 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.<ref>{{cite journal |last1=Cristol |first1=Daniel A. |last2=Switzer |first2=Paul V. |title=Avian prey-dropping behavior. II. American crows and walnuts |journal=Behavioral Ecology |date=1 May 1999 |volume=10 |issue=3 |pages=220–226 |doi=10.1093/beheco/10.3.220 |doi-access=free }}</ref>