View source for Juglans

{{SPlantbox
|familia=Juglandaceae
|genus=Juglans
|common_name=Walnuts
|name_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|habit=tree
|habit_ref=Flora - A Gardener's Encyclopedia ISBN 0881925381
|lifespan=perennial
|features=fruit
|Temp Metric=°F
|jumpin=If this plant info box on watering; zones; height; etc. is mostly empty you can click on the edit tab and fill in the blanks!
|image=Juglans major Morton.jpg
|image_width=200
|image_caption=Juglans major
}}
'''Walnuts''' (genus ''Juglans'') are [[plant]]s in the family [[Juglandaceae]]. They are [[deciduous]] [[tree]]s, 10–40 [[meter (unit)|meter]]s tall (about 30–130 [[foot (length)|ft]]), with [[pinnate]] leaves 200–900 millimetres long (7–35 [[inch|in]]), with 5–25 leaflets; the shoots have chambered [[pith]], a character shared with the [[wingnut (plant)|wingnuts]] (''Pterocarya''), but not the [[hickory|hickories]] (''Carya'') in the same family.

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]]. The Latin name, ''Juglans'', derives from ''[[Jupiter (mythology)|Jupiter]] [[glans]]'', "Jupiter's acorn": figuratively, a nut fit for a god.

The word ''walnut'' derives from [[Old English language|Old English]] ''wealhhnutu'', literally "foreign nut", ''wealh'' meaning "foreign" (''wealh'' is akin to the terms [[Wiktionary:Welsh|Welsh]] and [[Vlach]]; see [[Walha]] and [[History of the term Vlach]]).<ref name=OED>[http://www.etymonline.com/index.php?search=walnut&searchmode=none Online Etymology Dictionary - "Walnut"]</ref> The walnut was so called because it was introduced from [[Gaul]] and [[Italy]]. The [[Latin]] name for the walnut was ''nux Gallica'', "[[Gaul|Gallic]] nut".<ref name=OED/>

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.

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. There are many different cultivars available for growers, offering different growth habit, flowering and leafing, kernel flavour and shell thickness.  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.

The leaves and blossoms of the walnut tree normally appear in spring. The male cylindrical catkins of the Walnut tree 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.<ref>http://fruitandnuttrees.com/walnut-tree-j-regia-j-nigra Fruit and Nut Trees</ref>

{{Inc|
Juglans (ancient Latin name from Jovis glans, nut of Jupiter). Juglandaceae. Walnut. Butternut. Plate LX. Woody plants grown for their handsome foliage and some species for their edible nuts.

Deciduous trees, rarely shrubs: branches with lamellate pith: lvs. alternate, without stipules, odd- pinnate, of aromatic fragrance when bruised: staminate fls. with a 2-5-lobed perianth and 6-30 stamens, in slender catkins; pistillate fls. in few- to many-fld. racemes; ovary inferior, 1-celled, with 4 calyx-lobes and included in a 3-lobed involucre: fr. a large drupe with a thick, indehiscent husk; nut 2- or 4-celled at the base, indehiscent or separating at last into 2 valves. —About 15 species in N. and S. Amer. and from S. E. Eu. to E. Asia; 44 species have been distinguished and described in a monograph by Dode (B.S.D. 1906: 67-97; 1909: 22-50, 165-215, with many illustrations).

The walnuts are usually tall broad-headed trees with large leaves, and with small greenish flowers, the staminate in pendulous slender often conspicuous catkins, the pistillate inconspicuous followed by a greenish large drupe containing an edible nut. Most of the species are hardy, and are very valuable park trees, with a massive, straight trunk, and a light and airy broad top, the best being probably J. nigra, one of the noblest trees of the American forest. J. regia, J. rupestris, and J. cathayensis are hardy as far north as Massachusetts, while J. californica is tender in the North. Though many fungi and insects prey on the walnut, none of them does very serious damage, the worst being, perhaps, the hickory-borer. The wood of the walnut, which is easily worked and susceptible of receiving a beautiful polish, is much used for cabinet making and the interior finish of houses, especially that of J. nigra and J. regia, which is heavy, strong and durable, and of dark brown color, while that of J. cinerea and J. Sieboldiana is light and soft. The husks of the nuts are sometimes used for dyeing yellow, and the bark for tanning leather. The husk of J. cinerea has some medicinal properties. The nuts of all species are edible, and are an article of commercial importance, especially those of J. regia, which are the best. This species is extensively grown in the warmer parts of Europe, in California and in the East from Pennsylvania to Georgia. The nuts of the native species are also sold on the market, but mostly gathered in the woods, though a number of improved varieties are in cultivation. J. sieboldiana and var. cordiformis, with nuts superior to those of the native species, and much valued in Japan, will probably become valuable nut trees where J. regia is too tender; also J. regia var. sinensis is hardier than the type.

The walnut grows best in moderately moist, rich soil, but J. cinerea is more moisture-loving and J. regia prefers well-drained hillsides. They are not easily transplanted when older, and therefore the nuts are often planted where the trees are to stand, but they may be safely transplanted when two or three years old, or even later when they have been transplanted in the nursery. Propagation is by seeds, which should be stratified and not allowed to become dry. A light, sandy soil is to be preferred, as the young plants produce more fibrous roots, while in stiff soil they are liable to make a long taproot. The young seedlings are transplanted when about two years old; sometimes the taproot is cut by a long knife. Varieties are often grafted on potted stock in the greenhouse in early spring or are budded in summer, either shield- or flute- budding being employed; even top-grafting of old trees is sometimes practised. For culture and further information, see United States Department of Agriculture, "Nut Culture in the United States," quoted below as U. S. N. C.; see, also, Walnut.

Index.
ailantifolia, 10. 
alata, 12. 
allardiana, 10. 
aspleniifolia, 1. 
bartheriana, 1. 
californica, 4, 5. 
cathayensis, 8. 
cinerea, 7. 
coarctata, 10. 
corcyrensis, 1. 
cordiformis, 10. 
draconis, 8. 
duclouxiana, 1. 
elongata, 1.
fertilis. 1. 
filicifolia, 1. 
fruticosa, 1. 
gibbosa, 11. 
hindsii, 5. 
intermedia, 11, 12. 
laciniata, 1. 
lavallci, 10. 
major, 2. 
mandshurica, 9. 
monophylla, 1. 
nigra, 6. 
ovoidea, 6. 
pendula, 1.
praeparturiens, 1.
pyriformis, 11.
quadrangulata, 12.
quercina, 5.
quercifolia, 5.
regia, 1.
rupestria, 2, 3.
sieboldiana, 10.
sinensis, 1.
subcordiformis, 10.
torreyi, 2.
vilmoreana, 11.
vitmoriniana, 11.

Besides these described above, several other hybrids have been reported. Luther Burbank raised a hybrid between J. hindsii and J. nigra, named "Royal," with large nuts of excellent flavor, and one between J. Hindsii and J. regia, named "Paradox," a very vigorous grower, but a shy bearer. There are supposed hybrids between J. mandschurica X J. regia, J. cinerea XJ. nigra and J. cinerea X J. rupestris; J. longirostris, carr. (R. H. 1878, p. 53), may be a hybrid between J. regia and J. major, which often has a fr. similar in shape to the one figured.—J. australis. Griseb. Allied to J. rupestris. lfts. 13-21, large, ovate-oblong, abruptly acuminate, serrate, viscid- pubescent: nut ovoid, acute, small, slightly grooved. Argentina.— J. collapsa, Dode. Allied to J. mandschurica and probably only a variety, but nut less rugose, less sharply angled, with ovoid depressions. Probably from N. China.—J. kamadnia, Dode (J. regia var. kamaonia, DC.). Allied to J. regi. Lfta. 5-11, oblong-elliptic to oblong-lanceolate, puberulous on both sides, rufous-pubescent on the veins beneath: nut globose, rather hard-shelled. Himalayas. —J. stenocorpa, Maxim. Closely allied to J. mandschurica. Lfts. narrower, more coarsely serrate, more pubescent, the terminal 1ft. very large: fr. more oblong, less strongly ridged. Manchuria.
Alfred Rehder
}}

==Cultivation==
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).

===Propagation===


===Pests and diseases===


==Varieties==
The genus ''Juglans'' is divided into four sections.<ref>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</ref>

Sections and species:
*'''Sect. ''Cardiocaryon'''''. Leaves very large (40–90 cm) with 11–19 broad leaflets, softly downy, margins serrated. Wood soft. Fruits borne in racemes of up to 20.  Nuts have thick shells.  Northeast [[Asia]].
**''[[Juglans ailantifolia|J. ailantifolia]]'' Carr. (''J. cordiformis'' Maxim., ''J. sieboldiana'' Maxim.) — Japanese Walnut
***[[heartnut|''J. ailantifolia'' var. ''cordiformis'']] — Heartnut
**''[[Juglans mandshurica|J. mandshurica]]'' Maxim. (''J. cathayensis'' Dode, ''J. formosana'' Hayata, ''J. hopeiensis'' Dode, ''J. stenocarpa'' Maxim.) — Manchurian Walnut or Chinese Walnut.
*'''Sect. ''Juglans'''''. Leaves large (20–45 cm) with 5–9 broad leaflets, hairless, margins entire. Wood hard. Southeast [[Europe]] to central [[Asia]].
**''[[Juglans regia|J. regia]]'' L. (''J. duclouxiana'' Dode, ''J. fallax'' Dode, ''J. orientis'' Dode) — common walnut, Persian, English, or Carpathian walnut
**''[[Juglans sigillata|J. sigillata]]'' Dode — Iron Walnut (doubtfully distinct from ''J. regia'')
*'''Sect. ''Rhysocaryon'''''.  (The '''black walnuts''') Leaves large (20–50 cm) with 11–23 slender leaflets, finely pubescent, margins serrated. Wood hard. [[North America]], [[South America]].
**''[[Juglans australis|J. australis]]'' Griseb. (''J. brasiliensis'' Dode) — Argentine Walnut, Brazilian Walnut
**''[[Juglans boliviana|J. boliviana]]'' (C. DC.) Dode — Bolivian walnut, Peruvian walnut
**''[[Juglans californica|J. californica]]'' S.Wats. — California Black Walnut
**''[[Juglans hindsii|J. hindsii]]'' (Jepson) R.E.Smith — Hinds' Black Walnut
**''[[Juglans hirsuta|J. hirsuta]]'' Manning — Nuevo León Walnut
**''[[Juglans jamaicensis|J. jamaicensis]]'' C.DC. (''J. insularis'' Griseb.) — West Indies Walnut
**''[[Juglans major|J. major]]'' (Torrey) Heller (''J. arizonica'' Dode, ''J. elaeopyron'' Dode, ''J. torreyi'' Dode) — Arizona Black Walnut
***''J. major'' var. ''glabrata'' Manning
**''[[Juglans microcarpa|J. microcarpa]]'' Berlandier (''J. rupestris'' Engelm.) — Texas Walnut or Little Black Walnut
***''J. microcarpa'' var. ''microcarpa''
***''J. microcarpa'' var. ''stewartii'' (Johnston) Manning
**''[[Juglans mollis|J. mollis]]'' Engelm. — [[Mexican Walnut]]
**''[[Juglans neotropica|J. neotropica]]'' Diels (''J. honorei'' Dode) — Andean Walnut, Cedro Negro , Cedro Nogal , Nogal , Nogal Bogotano
**''[[Juglans nigra|J. nigra]]'' L. — Eastern Black Walnut
**''[[Juglans olanchana|J. olanchana]]'' Standl. & L.O.Williams — Cedro Negro, Nogal , Walnut
***''J. olanchana'' var. ''olanchana''
***''J. olanchana'' var. ''standleyi''
**''[[Juglans boliviana|J. peruviana]]'' Dode — Peruvian Walnut
**''[[Juglans soratensis|J. soratensis]]'' Manning
**''[[Juglans steyermarkii|J. steyermarkii]]'' Manning — [[Guatemalan Walnut]]
**''[[Juglans venezuelensis|J. venezuelensis]]'' Manning — Venezuela Walnut
*'''Sect. ''Trachycaryon'''''.  Leaves very large (40–90 cm) with 11–19 broad leaflets, softly downy, margins serrated. Wood soft.   Fruits borne in clusters of 2-3.  Nuts have a thick, rough shell bearing distinct, sharp ridges. Eastern [[North America]].
**''[[Juglans cinerea|J. cinerea]]'' L. — Butternut

[[File:Juglans ailantifolia.jpg|right|240px|thumb|Japanese Walnut foliage and nuts]]
The best-known member of the genus is the [[Juglans regia|Persian walnut]] (''J. regia'', literally "royal walnut"), native from the [[Balkans]] in southeast [[Europe]], southwest & 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 [[Black Walnut|Eastern Black Walnut]] (''J. nigra'') is a common species in its native eastern [[North America]], and is also widely cultivated elsewhere. The nuts are edible, but have a smaller kernel and an extremely tough shell, and they are not widely grown for nut production.  The wood is particularly valuable.

The [[Juglans hindsii|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 that are characteristic of the eastern black walnut (''J. nigra'').

The [[Japanese Walnut]] (''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 (tree)|Butternut]] (''J. cinerea'') is also native to eastern North America, where it is currently [[endangered species|endangered]] by an introduced disease, [[butternut canker]], caused by the [[fungus]] ''[[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''

==Gallery==

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Image:Upload.png| photo 1
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==References==
<references/>
*[[Standard Cyclopedia of Horticulture]], by L. H. Bailey, MacMillan Co., 1963
<!--- xxxxx  *Flora: The Gardener's Bible, by Sean Hogan. Global Book Publishing, 2003. ISBN 0881925381  -->
<!--- xxxxx  *American Horticultural Society: A-Z Encyclopedia of Garden Plants, by Christopher Brickell, Judith D. Zuk. 1996. ISBN 0789419432  -->
<!--- xxxxx  *Sunset National Garden Book. Sunset Books, Inc., 1997. ISBN 0376038608  -->

==External links==
*{{wplink}}

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