Walnut

Walnut

Overview
Juglans is a plant genus of the family Juglandaceae
Juglandaceae
The Juglandaceae, also known as the Walnut Family, is a family of trees, or sometimes shrubs, in the order Fagales. Various members of this family are native to the Americas, Eurasia, and Southeast Asia....

, the seeds of which are known as walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

s
. They are deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

 tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s, 10–40 meters tall (about 30–130 ft), with pinnate
Pinnate
Pinnate is a term used to describe feather-like or multi-divided features arising from both sides of a common axis in plant or animal structures, and comes from the Latin word pinna meaning "feather", "wing", or "fin". A similar term is pectinate, which refers to a comb-like arrangement of parts...

 leaves 200–900 millimetres long (7–35 in), with 5–25 leaflets; the shoots have chambered pith
Pith
Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In eudicots, pith is located in the center of the stem. In monocots, it extends also into flowering stems and roots...

, a character shared with the wingnuts (Pterocarya), but not the hickories
Hickory
Trees in the genus Carya are commonly known as hickory, derived from the Powhatan language of Virginia. The genus includes 17–19 species of deciduous trees with pinnately compound leaves and big nuts...

 (Carya) in the same family.

The 21 species in the genus range across the north temperate Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

 from southeast Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 east to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, and more widely in the New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

 from southeast Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 west to California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and south to Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

.

The trivial name
Trivial name
In chemistry, a trivial name is a common name or vernacular name; it is a non-systematic name or non-scientific name. That is, the name is not recognised according to the rules of any formal system of nomenclature...

 walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

derives from Old English
Old English language
Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

 wealhhnutu, literally "foreign nut", wealh meaning "foreign" (wealh is akin to the terms Welsh and Vlach; see Walha
Walha
Walhaz is a reconstructed Proto-Germanic word, meaning "foreigner", "stranger", "Roman", "Romance-speaker", or "Celtic-speaker". The adjective derived from this word can be found in , Old High German walhisk, meaning "Romance", in Old English welisċ, wælisċ, wilisċ, meaning "Romano-British" and in...

 and History of the term Vlach
History of the term Vlach
Vlach is a Slavic-derived term , which is used to designate the Romance speaking peoples of South-Eastern Europe: Romanians, Aromanians, Megleno-Romanians and Istro-Romanians....

).
Discussion
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Encyclopedia
Juglans is a plant genus of the family Juglandaceae
Juglandaceae
The Juglandaceae, also known as the Walnut Family, is a family of trees, or sometimes shrubs, in the order Fagales. Various members of this family are native to the Americas, Eurasia, and Southeast Asia....

, the seeds of which are known as walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

s
. They are deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

 tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s, 10–40 meters tall (about 30–130 ft), with pinnate
Pinnate
Pinnate is a term used to describe feather-like or multi-divided features arising from both sides of a common axis in plant or animal structures, and comes from the Latin word pinna meaning "feather", "wing", or "fin". A similar term is pectinate, which refers to a comb-like arrangement of parts...

 leaves 200–900 millimetres long (7–35 in), with 5–25 leaflets; the shoots have chambered pith
Pith
Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In eudicots, pith is located in the center of the stem. In monocots, it extends also into flowering stems and roots...

, a character shared with the wingnuts (Pterocarya), but not the hickories
Hickory
Trees in the genus Carya are commonly known as hickory, derived from the Powhatan language of Virginia. The genus includes 17–19 species of deciduous trees with pinnately compound leaves and big nuts...

 (Carya) in the same family.

The 21 species in the genus range across the north temperate Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

 from southeast Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 east to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, and more widely in the New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

 from southeast Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 west to California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and south to Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

.

Etymology


The trivial name
Trivial name
In chemistry, a trivial name is a common name or vernacular name; it is a non-systematic name or non-scientific name. That is, the name is not recognised according to the rules of any formal system of nomenclature...

 walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

derives from Old English
Old English language
Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

 wealhhnutu, literally "foreign nut", wealh meaning "foreign" (wealh is akin to the terms Welsh and Vlach; see Walha
Walha
Walhaz is a reconstructed Proto-Germanic word, meaning "foreigner", "stranger", "Roman", "Romance-speaker", or "Celtic-speaker". The adjective derived from this word can be found in , Old High German walhisk, meaning "Romance", in Old English welisċ, wælisċ, wilisċ, meaning "Romano-British" and in...

 and History of the term Vlach
History of the term Vlach
Vlach is a Slavic-derived term , which is used to designate the Romance speaking peoples of South-Eastern Europe: Romanians, Aromanians, Megleno-Romanians and Istro-Romanians....

). The walnut was so called because it was introduced from Gaul
Gaul
Gaul was a region of Western Europe during the Iron Age and Roman era, encompassing present day France, Luxembourg and Belgium, most of Switzerland, the western part of Northern Italy, as well as the parts of the Netherlands and Germany on the left bank of the Rhine. The Gauls were the speakers of...

 and Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. The Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 name for the walnut was nux Gallica, "Gallic
Gaul
Gaul was a region of Western Europe during the Iron Age and Roman era, encompassing present day France, Luxembourg and Belgium, most of Switzerland, the western part of Northern Italy, as well as the parts of the Netherlands and Germany on the left bank of the Rhine. The Gauls were the speakers of...

 nut".

Sections and species

  • Juglans sect. 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. The origin is in northeast Asia
    Asia
    Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

    .
    • J. ailantifolia Carr. (J. cordiformis Maxim., J. sieboldiana Maxim.)—Japanese walnut
      • J. ailantifolia var. cordiformis—Heartnut
    • J. mandshurica
      Juglans mandshurica
      Juglans mandshurica, the Manchurian walnut, is a deciduous tree of the genus Juglans , native to the Eastern Asiatic Region...

      Maxim. (J. cathayensis Dode, J. formosana Hayata, J. hopeiensis Dode, J. stenocarpa Maxim.)—Manchurian walnut or Chinese walnut
  • Juglans sect. Juglans. Leaves are large (20–45 cm), with 5–9 broad leaflets, hairless, margins entire. The wood hard. The origin is southeast Europe
    Europe
    Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

     to central Asia
    Asia
    Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

    .
    • J. regia L. (J. duclouxiana Dode, J. fallax Dode, J. orientis Dode)—common walnut, Persian, English, or Carpathian walnut
    • J. sigillata
      Juglans sigillata
      Juglans sigillata, known as the Iron Walnut, is a species of walnut tree. The tree has been cultivated for its edible nuts. The nuts are oval-shaped with bumps and ridges. The tree is also use for its wood. It is commonly found in Yunnan, but are also found in Guizhou, Sichuan and Xizang in China...

      Dode—iron walnut (doubtfully distinct from J. regia)
  • Juglans sect. Rhysocaryon (black walnuts) Leaves are large (20–50 cm), with 11–23 slender leaflets, finely pubescent, margins serrated. The wood can be extremely hard (Brazilian walnut Janka hardness test of 3684). The origins are North America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

     and South America
    South America
    South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

    .
    • J. australis
      Juglans australis
      Juglans australis is a species of plant in the Juglandaceae family. This large, fast-growing tree can grow to 20 m tall at altitudes of 0.5—1.5 km in the "Yungas" or Montane Cloud Forest of Argentina and in Bolivia. It is more frost resistant than the Persian Walnut...

      Griseb. (J. brasiliensis Dode)—Argentine walnut, Brazilian walnut
    • J. boliviana (C. DC.) Dode—Bolivian walnut, Peruvian walnut
    • J. californica
      Juglans californica
      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 Juglandaceae family endemic to California....

      S.Wats.—California black walnut
    • J. hindsii
      Juglans hindsii
      Juglans hindsii, the Hinds' black walnut, also called the Northern California walnut, is a large tree endemic to roughly circular area in California centered near Fresno and reaching the San Francisco Bay area. Some authorities Juglans hindsii, the Hinds' black walnut, also called the Northern...

      (Jepson) R.E.Smith—Hinds' black walnut
    • J. hirsuta Manning—Nuevo León walnut
    • J. jamaicensis
      Juglans jamaicensis
      Juglans jamaicensis is a species of walnut in the Juglandaceae family. It is found in Cuba, the Dominican Republic, Haiti, and Puerto Rico. It is not, in fact, native to Jamaica, as its name would suggest.This is a large tree which can reach 25 meters in height...

      C.DC. (J. insularis Griseb.)—West Indies walnut
    • J. major
      Juglans major
      Juglans major is a walnut tree which grows to with a DBH of up to at elevations of 1000–7000 ft in Texas, Oklahoma, New Mexico, Arizona, and Utah. Common names include Arizona Walnut and Nogal....

      (Torrey) Heller (J. arizonica Dode, J. elaeopyron Dode, J. torreyi Dode)—Arizona black walnut
      • J. major var. glabrata Manning
    • J. microcarpa
      Juglans microcarpa
      Juglans microcarpa, known also as the Texas Walnut and the Little Black Walnut is a large shrub or small tree which grows wild along streams and ravines in Texas, New Mexico, Oklahoma, and Kansas. It produces nuts with a width of 1/2—3/4 in. The pinnately compound leaves bear 7—25 untoothed...

      Berlandier (J. rupestris Engelm.)—Texas walnut or little black walnut
      • J. microcarpa var. microcarpa
      • J. microcarpa var. stewartii (Johnston) Manning
    • J. mollis Engelm.—Mexican walnut
    • J. neotropica Diels (J. honorei Dode)—Andean walnut, cedro negro, cedro nogal, nogal, nogal Bogotano
    • J. nigra L.—Eastern black walnut
    • J. olanchana
      Juglans olanchana
      Juglans olanchana is a semideciduous tree up to 40 m in height and 1.5 m in diameter, which belongs to the Juglandaceae family. It is found in Colombia, Ecuador, Guatemala, El Salvador, Honduras, Mexico, Nicaragua, and Peru. It is commonly called cedro negro or nogal...

      Standl. & L.O.Williams—cedro negro, nogal, walnut
      • J. olanchana var. olanchana
      • J. olanchana var. standleyi
    • J. peruviana
      Juglans peruviana
      Juglans peruviana is a species of plant in the Juglandaceae family. It is endemic to Peru.-Source:* World Conservation Monitoring Centre 1998. . Downloaded on 22 August 2007....

      Dode—Peruvian walnut
    • J. soratensis Manning
    • J. steyermarkii Manning—Guatemalan walnut
    • J. venezuelensis
      Juglans venezuelensis
      Juglans venezuelensis, or Nogal de Caracas, is a species of black walnut endemic to Venezuela. It is a small tree which bears ~1 inch nuts.-References and external links:...

      Manning—Venezuela walnut
  • Juglans sect. 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. Origin is in eastern North America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

    .
    • J. cinerea L.—Butternut


The best-known member of the genus is the Persian walnut (J. regia, literally "royal walnut"), native from the Balkans
Balkans
The Balkans is a geopolitical and cultural region of southeastern Europe...

 in southeast Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, southwest and central Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 to the Himalaya and southwest China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

. Walnuts are a traditional feature of Iranian cuisine
Iranian cuisine
Iranian cuisine is diverse, with each province featuring dishes, culinary traditions and styles distinct to its region.It includes a wide variety of foods ranging from chelo kabab , khoresht Iranian cuisine is diverse, with each province featuring dishes, culinary traditions and styles distinct to...

; the nation has extensive orchards which are an important feature of regional economies. In Kyrgyzstan
Kyrgyzstan
Kyrgyzstan , officially the Kyrgyz Republic is one of the world's six independent Turkic states . Located in Central Asia, landlocked and mountainous, Kyrgyzstan is bordered by Kazakhstan to the north, Uzbekistan to the west, Tajikistan to the southwest and China to the east...

 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 eastern black walnut
Black Walnut
Juglans nigra, the Eastern Black walnut, is a species of flowering tree in the hickory family, Juglandaceae, that is native to eastern 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...

 (J. nigra) is a common species in its native eastern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, and is also widely cultivated elsewhere. The nuts are edible, and though they are often used in expensive baked goods, the Persian walnut is preferred for everyday use because it is easier to extract the nutmeat. The wood is particularly valuable.

The Hinds' black walnut
Juglans hindsii
Juglans hindsii, the Hinds' black walnut, also called the Northern California walnut, is a large tree endemic to roughly circular area in California centered near Fresno and reaching the San Francisco Bay area. Some authorities Juglans hindsii, the Hinds' black walnut, also called the Northern...

 (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 Japanese walnut
Japanese Walnut
Juglans ailantifolia , the Japanese Walnut, is a species of walnut native to Japan and Sakhalin. It is a deciduous tree growing to 20 m tall, rarely 30 m, and 40-80 cm stem diameter, with light grey bark. The leaves are pinnate, 50-90 cm long, with 11-17 leaflets, each leaflet 7-16 cm long and 3-5...

 (J. ailantifolia) is similar to butternut, distinguished by the larger leaves up to 90 cm long, and round (not oval) nuts. The variety cordiformis, often called the heartnut has heart-shaped nuts; the common name of this variety is the source of the sectional name Cardiocaryon.

The butternut
Butternut (tree)
Juglans cinerea, commonly known as Butternut or White Walnut, is a species of walnut native to the eastern United States and southeast Canada. Its range extends east to New Brunswick, and from southern Quebec west to Minnesota, south to northern Alabama and southwest to northern Arkansas...

 (J. cinerea) is also native to eastern North America, where it is currently endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 by an introduced disease, butternut canker, caused by the fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 Sirococcus clavigignenti. Its leaves are 40–60 cm long, the fruits are oval, the shell has very tall, very slender ridges, and the kernel is especially high in fat.

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 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.

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 nitrogen fixing
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...

 plant, such as Elaeagnus × ebbingei or Elaeagnus umbellata
Elaeagnus umbellata
Elaeagnus umbellata, also referred to as Japanese silverberry, umbellate oleaster or autumn-olive, is a species of Elaeagnus native to eastern Asia from the Himalayas east to Japan...

, 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
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

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
Phenology
Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate...

, 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 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.

Fruit


Some fruits are borderline and difficult to categorize. Hickory nuts (Carya) and walnuts (Juglans) in the Juglandaceae
Juglandaceae
The Juglandaceae, also known as the Walnut Family, is a family of trees, or sometimes shrubs, in the order Fagales. Various members of this family are native to the Americas, Eurasia, and Southeast Asia....

 family grow within an outer husk; these fruits are technically drupe
Drupe
In botany, a drupe is a fruit in which an outer fleshy part surrounds a shell of hardened endocarp with a seed inside. These fruits develop from a single carpel, and mostly from flowers with superior ovaries...

s or drupaceous nuts, and thus not true botanical nuts. "Tryma" is a specialized term for such nut-like drupes.

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 and 99% of the US commercial production of English walnuts is grown in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

's Central Valley and in Coastal Valleys, from Redding
Redding
-Places in the United States:*Redding, California*Redding, Iowa*Redding Township, Jackson County, Indiana**Reddington, Indiana, an unincorporated town in Redding Township*Redding Township, Michigan*Redding, Connecticut-Places in Europe:...

 in the north to Bakersfield in the south. Of the more than 30 varieties of J. regia grown there, Chandler and Hartley account for over half of total production. In California commercial production, the Hinds' black walnut (J. hindsii) and the hybrid between J. hindsii and J. regia, Juglans x Paradox, are widely used as rootstock
Rootstock
A rootstock is a plant, and sometimes just the stump, which already has an established, healthy root system, used for grafting a cutting or budding from another plant. The tree part being grafted onto the rootstock is usually called the scion...

s for J. regia cultivars because of their resistance to Phytophthora
Phytophthora
Phytophthora is a genus of plant-damaging Oomycetes , whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems. The genus was first described by Heinrich Anton de Bary in 1875...

 and to a very limited degree, the oak root fungus. However, trees grafted on these rootstocks often succumb to black line.

In some countries, immature nuts in their husks are preserved in vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

. 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
Armenian cuisine
Armenian cuisine includes the foods and cooking techniques of the Armenian people, the Armenian diaspora and traditional Armenian foods and dishes. The cuisine reflects the history and geography where Armenians have lived as well as incorporating outside influences...

, unripe walnuts, including husks, are preserved in sugar syrup and eaten whole. In Italy, liqueur
Liqueur
A liqueur is an alcoholic beverage that has been flavored with fruit, herbs, nuts, spices, flowers, or cream and bottled with added sugar. Liqueurs are typically quite sweet; they are usually not aged for long but may have resting periods during their production to allow flavors to marry.The...

s called Nocino
Nocino
Nocino is a sticky dark brown liqueur from the Emilia-Romagna region in Northern Italy. It is made from unripe green walnuts steeped in spirit. It has an aromatic but bittersweet flavor. It may be homemade, and is also available commercially in bottled form...

 and Nocello
Nocello
Nocello is a walnut- and hazelnut-flavored liqueur from Italy. It is produced by the Toschi Vignola s.r.l. company of Savignano sul Panaro, Province of Modena, Emilia-Romagna, Italy. It is labeled "Imitation Liqueur" in the United States and is 24% alcohol by volume. The liqueur, which is colored...

 are flavoured with walnuts, while Salsa di Noci (walnut sauce) is a pasta sauce originating from Liguria
Liguria
Liguria is a coastal region of north-western Italy, the third smallest of the Italian regions. Its capital is Genoa. It is a popular region with tourists for its beautiful beaches, picturesque little towns, and good food.-Geography:...

. In Georgia, walnuts are ground with other ingredients to make walnut sauce
Walnut sauce
Walnut sauce is a food paste made primarily from walnuts and popular in Georgian cuisine.-Varieties:There are numerous varieties of walnut sauce, and Georgian cuisine itself boasts of dozens of them.-Bazha:...

.

Walnuts are heavily used in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

. In Jammu
Jammu
Jammu , also known as Duggar, is one of the three administrative divisions within Jammu and Kashmir, the northernmost state in India.Jammu city is the largest city in Jammu and the winter capital of Jammu and Kashmir...

, it is used widely as a prasad (offering) to Mother Goddess Vaisnav Devi
Devi
Devī is the Sanskrit word for Goddess, used mostly in Hinduism, its related masculine term is deva. Devi is synonymous with Shakti, the female aspect of the divine, as conceptualized by the Shakta tradition of Hinduism. She is the female counterpart without whom the male aspect, which represents...

 and, generally, as a dry food in the season of festivals such as Diwali
Diwali
Diwali or DeepavaliThe name of the festival in various regional languages include:, , , , , , , , , , , , , popularly known as the "festival of lights," is a festival celebrated between mid-October and mid-December for different reasons...

.

The nuts are rich in oil
Walnut oil
Walnut oil is oil extracted from English walnuts . It is about 50% linoleic acid, an essential omega-6 fatty acid. Walnut oil is also a good source of omega-3 fatty acids which are also essential to human nutrition....

, and are widely eaten both fresh and in cookery. Walnut oil is expensive and consequently is used sparingly; most often in salad dressings. Walnut oil has been used in oil paint
Oil paint
Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnish may be added to increase the glossiness of the...

, 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
Rhoipteleaceae
Rhoiptelea is a monotypic genus of flowering plants in the Juglandaceae family. It contains a single species, Rhoiptelea chiliantha, commonly known as the horsetail tree. This genus was previously recognized in its own family, Rhoipteleaceae, but the APG III system of 2009 placed it in the...

 and Juglandaceae
Juglandaceae
The Juglandaceae, also known as the Walnut Family, is a family of trees, or sometimes shrubs, in the order Fagales. Various members of this family are native to the Americas, Eurasia, and Southeast Asia....

 and found the nut oils were generally more unsaturated from species which grow in the temperate zones and more saturated for species which grow in the tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

 zones. In the northerly-growing section Trachycaryon, J. cinerea oil was reported to contain 15% linolenate
Linolenic acid
Linolenic acid can refer to either of two octadecatrienoic acids:*α-Linolenic acid, an ω-3 fatty acid found in many vegetable oils. The unmodified term linolenic acid most commonly refers to this substance.*γ-Linolenic acid, an ω-6 fatty acid...

 (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 palmitate
Palmitic acid
Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is one of the most common saturated fatty acids found in animals and plants. Its molecular formula is CH314CO2H. As its name indicates, it is a major component of the oil from palm trees . Palmitate is a term for the salts and esters of...

, and a maximum concentration of 71% linoleate
Linoleic acid
Linoleic acid is an unsaturated n-6 fatty acid. It is a colorless liquid at room temperature. In physiological literature, it has a lipid number of 18:2...

. In the section Juglans, J. 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. ailantifolia and J. 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. microcarpa and J. 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. australis contained 2% linolenate, 7% palmitate, and 61% linoleate; J. boliviana contained 4% linolenate, 4% palmitate, and 70% linoleate; J. hirsuta contained 2% linolenate, 5% palmitate, and 75% linoleate; J. mollis contained 0% linolenate, 5% palmitate, 46% linoleate, and 49% oleate
Oleic acid
Oleic acid is a monounsaturated omega-9 fatty acid found in various animal and vegetable fats. It has the formula CH37CH=CH7COOH. It is an odorless, colourless oil, although commercial samples may be yellowish. The trans isomer of oleic acid is called elaidic acid...

; J. neotropica contained 3% linolenate, 5% palmitate, and 50% linoleate; and J. olanchana contained only a trace of linolenate, 9% palmitate, and 73% linoleate;

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 made from walnut shells is widely used in the plastics industry.
  • 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
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

 used for dyeing fabric
Textile
A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...

 and for other purposes. The dye does not require a mordant
Mordant
A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which then attaches to the fabric or tissue. It may be used for dyeing fabrics, or for intensifying stains in cell or tissue preparations. The term mordant comes from the Latin...

 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 colour ranges from creamy white in the sapwood to a dark chocolate colour in the heartwood. When kiln-dried, walnut wood tends toward a dull brown colour, but when air-dried can become a rich purplish-brown. Because of its colour, hardness and grain, it is a prized furniture and carving wood. Walnut burl
Burl
A burl or bur or burr is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from dormant buds.A burl results from a tree undergoing some form of stress. It may be caused...

s (or 'burrs' in Europe) are commonly used to create bowls and other turned pieces. Veneer
Wood veneer
In woodworking, veneer refers to thin slices of wood, usually thinner than 3 mm , that are typically glued onto core panels to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry...

 sliced from walnut burl is one of the most valuable and highly prized by cabinet makers and prestige car manufacturers. Walnut wood has been the timber of choice for gun makers for centuries, including the Gewehr 98
Gewehr 98
The Gewehr 98 is a German bolt action Mauser rifle firing the 8x57mm cartridge from a 5 round internal clip-loaded magazine that was the German service rifle from 1898 to 1935, when it was replaced by the Karabiner 98k. It was hence the main rifle of the German infantry during World War I...

 and Lee Enfield rifles of the First World War. It remains one 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
Luthier
A luthier is someone who makes or repairs lutes and other string instruments. In the United States, the term is used interchangeably with a term for the specialty of each maker, such as violinmaker, guitar maker, lute maker, etc...

. The wood of the butternut and related Asian species is of much lower value, softer, coarser, less strong and heavy, and paler in colour.

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. The Walnut Council is the key body linking growers with scientists. In Europe, various EU-led scientific programs have studied walnut growing for timber.

Traditional Chinese medicinal use



Walnuts are considered to be an herb in traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...

. They are said to tonify kidneys, strengthen the back and knees, warm and hold qi
Qi
In traditional Chinese culture, qì is an active principle forming part of any living thing. Qi is frequently translated as life energy, lifeforce, or energy flow. Qi is the central underlying principle in traditional Chinese medicine and martial arts...

in lungs and help kidneys to grasp the qi, moisten the intestines and move stool. It is believed to stop asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

 and is prescribed to be taken between bouts of asthma, but not for acute asthma. It is also used by the elderly to relieve constipation.

Parkland and garden trees


Walnuts are very attractive trees in park
Park
A park is a protected area, in its natural or semi-natural state, or planted, and set aside for human recreation and enjoyment, or for the protection of wildlife or natural habitats. It may consist of rocks, soil, water, flora and fauna and grass areas. Many parks are legally protected by...

s and large garden
Garden
A garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form today is known as a residential garden, but the term garden has...

s. Walnut trees are easily propagated from the nuts. Seedlings grow rapidly on good soils.
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 allelopathic compound juglone
Juglone
Juglone, also called 5-hydroxy-1,4-naphthalenedione or 5-hydroxynaphthoquinone, is an organic compound with the molecular formula C10H6O3. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500...

, though a number of gardeners do grow them. However, different walnut species vary in the amount of juglone they release from the roots and fallen leaves - J. nigra, in particular, is known for its toxicity, both to plants and horses. Juglone is toxic to plants
Allelopathy
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial or detrimental effects on the target organisms...

 such as tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

, apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

, and birch
Birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...

, 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


Walnuts are used as food plants by the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e of some Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

 species. These include:
  • Brown-tail
    Brown-tail
    The brown-tail is a moth of the family Lymantriidae. It is distributed throughout Europe.The wings of this species are pure white, as is the body, apart from a tuft of brown hairs at the end of the abdomen. The brown coloration extends along most of the back of the abdomen in the male...

     (Euproctis chrysorrhoea)
  • Coleophora
    Coleophora
    Coleophora is a very large genus of moths of the family Coleophoridae. It contains some 1,350 described species. The genus is represented on all continents, but the majority are found in the Nearctic and Palaearctic regions...

    case-bearers C. laticornella (recorded on J. nigra) and C. pruniella.
  • Common emerald
    Common Emerald
    The Common Emerald is a moth of the family Geometridae. The species is found throughout the Nearctic and Palearctic regions and the Near East. In the British Isles it is not found in Scotland but is a common species elsewhere...

     (Hemithea aestivaria)
  • Emperor moth (Pavonia pavonia)
  • The Engrailed
    Engrailed
    The Engrailed and Small Engrailed are moths of the family Geometridae. They are distributed across most of Europe. There is an on-going debate as to whether they make up one species, or whether E. crepuscularia actually refers only to the Small Engrailed, with the Engrailed proper being separable...

     (Ectropis crepuscularia)
  • Walnut sphinx (Amorpha juglandis)


The nuts are consumed by other animals, such as mice and squirrels.

In California and Geneva (Switzerland), ravens 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.

Nutritional information


100g of walnuts contain:
  • Calories : 654
  • Fat: 65 g
  • Carbohydrates: 14 g
  • Fibers: 6.7 g
  • Protein: 15 g

External links



  • Juglans species throughout the world