Changes

From Gardenology.org - Plant Encyclopedia and Gardening Wiki
Jump to navigationJump to search
168 bytes added ,  19:07, 24 December 2009
no edit summary
Line 17: Line 17:  
|image_caption=Shoot and nut of ''Juglans regia''
 
|image_caption=Shoot and nut of ''Juglans regia''
 
}}
 
}}
 +
'''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".
 +
 
{{Inc|
 
{{Inc|
 
Walnut (formerly sometimes written wallnut, but the name has no connection with wall, being rather of Anglo-Saxon derivation signifying "foreign nut," as the product came from the continent). A name applied to Juglans regia and its fruit, to us known mostly as English walnut because the supply yearly reached America through England; also, by extension, to other species of the genus Juglans. The name is sometimes, but provincially, given to hickory-nuts.
 
Walnut (formerly sometimes written wallnut, but the name has no connection with wall, being rather of Anglo-Saxon derivation signifying "foreign nut," as the product came from the continent). A name applied to Juglans regia and its fruit, to us known mostly as English walnut because the supply yearly reached America through England; also, by extension, to other species of the genus Juglans. The name is sometimes, but provincially, given to hickory-nuts.
Line 105: Line 111:  
}}
 
}}
   −
[[File:Noyer.JPG|thumb|Walnut tree (Juglans regia)]]
+
==Cultivation==
'''Walnuts''' (genus ''Juglans'') are [[plant]]s in the walnut family [[Juglandaceae]]. They are [[deciduous]] [[tree]]s, 10 - 40 [[metre]]s tall, with [[pinnate]] leaves 200 - 900 millimetres long, with 5 - 25 leaflets; the shoots have chambered [[pith]], a character shared with the [[wingnut]]s (''Pterocarya'') but not the [[hickory|hickories]] (''Carya'') in the same family.  
+
[[Image:2005walnut.PNG|thumb|left|Walnut output in 2005]]
 +
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.
   −
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 ''Jovis glans'', "Jupiter's nuts", the nut fit for a god.
+
Walnuts are light-demanding species that benefit from protection from wind. Walnuts are also very hardy against drought.
   −
Walnuts are used as food plants by the [[larva]]e of some [[Lepidoptera]] species including [[Brown-tail]], [[Common Emerald]], [[Emperor Moth]], [[Engrailed|The Engrailed]] and the ''[[Coleophora]]'' case-bearers ''C. laticornella'' (recorded on ''J. nigra'') and ''C. pruniella''.
+
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).
   −
The word ''walnut'' derives from Old English ''wealhhnutu'', literally "foreign nut". The walnut was so called because it was introduced from [[Gaul]] and [[Italy]]. The Late [[Latin]] name for the walnut was ''nux Gallica'', "[[Gaul|Gallic]] nut".
+
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.
   −
==Species and classification==
+
===Flowers===
*'''Sect. ''Juglans'''''. Leaves large (20-45 cm) with 5-9 broad leaflets, hairless, margins entire. Wood hard. Southeast [[Europe]] to central [[Asia]].
+
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>.
**''Juglans regia'' L. (''J. duclouxiana'' Dode, ''J. fallax'' Dode, ''J. orientis'' Dode) - [[Persian Walnut]]
  −
**''Juglans sigillata'' Dode - [[Iron Walnut]] (doubtfully distinct from ''J. regia'')
  −
*'''Sect. ''Rhysocaryon'''''. Leaves large (20-50 cm) with 11-23 slender leaflets, finely pubescent, margins serrated. Wood hard. [[North America]], [[South America]].
  −
**''Juglans australis'' Griseb. (''J. boliviana'' Dode) - [[Argentine Walnut]]
  −
**''Juglans brasiliensis'' Dode - [[Brazilian Walnut]]
  −
**''Juglans californica'' S.Wats. - [[California Walnut]]
  −
**''Juglans hindsii'' (Jepson) R.E.Smith - [[Juglans hindsii|Hinds' Walnut]]
  −
**''Juglans hirsuta'' Manning - [[Nuevo Leon Walnut]]
  −
**''Juglans jamaicensis'' C.DC. (''J. insularis'' Griseb.) - [[West Indies Walnut]]
  −
**''Juglans major'' (Torrey) Heller (''J. arizonica'' Dode, ''J. elaeopyron'' Dode, ''J. torreyi'' Dode) - [[Arizona Walnut]]
  −
***''Juglans major'' var. ''glabrata'' Manning
  −
**''Juglans microcarpa'' Berlandier (''J. rupestris'' Engelm.) - [[Texas Walnut]] or Little Walnut
  −
***''Juglans microcarpa'' var. ''stewartii'' (Johnston) Manning
  −
**''Juglans mollis'' Engelm. - [[Mexican Walnut]]
  −
**''Juglans neotropica'' Diels (''J. honorei'' Dode) - [[Andean Walnut]]
  −
**''Juglans nigra'' L. - [[Black Walnut]]
  −
**''Juglans olanchana'' Standl. & L.O.Williams -
  −
**''Juglans peruviana'' Dode - [[Peruvian Walnut]]
  −
**''Juglans soratensis'' Manning -
  −
**''Juglans steyermarkii'' Manning - [[Guatemalan Walnut]]
  −
**''Juglans venezuelensis'' Manning - [[Venezuela Walnut]]
  −
*'''Sect. ''Cardiocaryon'''''. Leaves very large (40-90 cm) with 11-19 broad leaflets, softly downy, margins serrated. Wood soft. Northeast [[Asia]], eastern [[North America]].
  −
**''Juglans ailantifolia'' Carr. (''J. cordiformis'' Maxim., ''J. sieboldiana'' Maxim.) - [[Japanese Walnut]]
  −
**''Juglans cinerea'' L. - [[Butternut (tree)|Butternut]]
  −
**''Jugl
  −
ans mandschurica'' Maxim. (''J. cathayensis'' Dode, ''J. formosana'' Hayata, ''J. hopeiensis'' Dode, ''J. stenocarpa'' Maxim.) - [[Chinese Walnut]] or Manchurian Walnut
     −
[[Image:Juglans ailantifolia.jpg|right|240px|thumb|Japanese Walnut foliage and nuts]]
+
====Nuts and Kernels====
The best-known member of the genus is the [[Persian Walnut]] (''Juglans regia''), native from the [[Balkans]] in southeast [[Europe]], southwest & central [[Asia]] to the [[Himalaya]] and southwest [[China]]. In [[Kyrgyzstan]] alone there are 230,700 ha of walnut-fruit forest, where ''J. regia'' is the dominant overstorey (Hemery and Popov 1998). This is the species which is widely cultivated for its delicious [[nut (fruit)|nuts]]. ''J. regia'' is also called English walnut because English merchant marines once controlled its world commerce.
+
[[Image:Walnut03.jpg|thumb|250px|left|Inside of a common walnut nut with green outer layer visible in the top left corner]]
 +
The nut kernels of all the species are edible, but the walnuts most commonly available in shops are from the Persian walnut, the only species which has a large nut and thin shell; black walnut species are more difficult to crack and remove from the shell. One horticultural form selected for thin nut shells and hardiness in temperate zones is sometimes known as the 'Carpathian' walnut.
   −
The [[Black Walnut]] (''Juglans 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.
+
Of the more than 30 varieties of ''J.&nbsp;regia'' grown there, Chandler and Hartley account for over half of total production.[http://www.walnuts.org/walnuts101/history_cultivation_processing.php] 
   −
The [[Butternut]] (''Juglans 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, and the nuts oval.
+
===Propagation===
   −
The [[Japanese Walnut]] (''Juglans ailantifolia'') is similar to Butternut, distinguished by the larger leaves up to 90 cm long, and round (not oval) nuts.
     −
;Hybrids
+
===Pests and diseases===
*''Juglans x bixbyi'' Rehd. - ''J. ailantifolia'' x ''J. cinerea''
+
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>http://www.padil.gov.au/viewPestDiagnosticImages.aspx?id=601</ref>.
*''Juglans x intermedia'' Carr. - ''J. nigra'' x ''J. regia''
  −
*''Juglans x notha'' Rehd. - ''J. ailantifolia'' x ''J. regia''
  −
*''Juglans x quadrangulata'' (Carr.) Rehd. - ''J. cinerea'' x ''J. regia''
  −
*''Juglans x sinensis'' (D. C.) Rehd. - ''J. mandschurica'' x ''J. regia''
  −
*''Juglans x paradox'' Burbank - ''J. hindsii'' x ''J. regia''
  −
*''Juglans x royal'' Burbank - ''J. hindsii'' x ''J. nigra''
     −
==Cultivations==
+
==Varieties==
The two most important species commercially are ''J. regia'' for timber and nuts, and ''J. nigra'' which is grown primarily for timber. Both species have similar cultivation requirements and are widely grown in temperate zones.   
+
[[Image:Walnuts02.jpg|thumb|250px|right|Common walnuts]]
 +
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>:
 +
*'''Sect. ''Juglans'''''. Leaves large (20–45&nbsp;cm) with 5–9 broad leaflets, hairless, margins entire. Wood hard. Southeast [[Europe]] to central [[Asia]].
 +
**''[[Juglans regia|J.&nbsp;regia]]'' L. (''J.&nbsp;duclouxiana'' Dode, ''J.&nbsp;fallax'' Dode, ''J.&nbsp;orientis'' Dode) &mdash; common walnut, Persian, English, or Carpathian walnut
 +
**''[[Juglans sigillata|J.&nbsp;sigillata]]'' Dode &mdash; Iron Walnut (doubtfully distinct from ''J. regia'')
 +
*'''Sect. ''Rhysocaryon'''''. Leaves large (20–50&nbsp;cm) with 11–23 slender leaflets, finely pubescent, margins serrated. Wood hard. [[North America]], [[South America]].
 +
**''[[Juglans australis|J.&nbsp;australis]]'' Griseb. (''J.&nbsp;boliviana'' Dode) &mdash; Argentine Walnut
 +
**''[[Juglans boliviana|J.&nbsp;boliviana]]'' (C. DC.) Dode &mdash; Bolivian walnut, Peruvian walnut
 +
**''[[Juglans brasiliensis|J.&nbsp;brasiliensis]]'' Dode &mdash; Brazilian Walnut
 +
**''[[Juglans californica|J.&nbsp;californica]]'' S.Wats. &mdash; California Black Walnut
 +
**''[[Juglans hindsii|J.&nbsp;hindsii]]'' (Jepson) R.E.Smith &mdash; Hinds' Black Walnut
 +
**''[[Juglans hirsuta|J.&nbsp;hirsuta]]'' Manning &mdash; Nuevo Leon Walnut
 +
**''[[Juglans jamaicensis|J.&nbsp;jamaicensis]]'' C.DC. (''J.&nbsp;insularis'' Griseb.) &mdash; West Indies Walnut
 +
**''[[Juglans major|J.&nbsp;major]]'' (Torrey) Heller (''J.&nbsp;arizonica'' Dode, ''J.&nbsp;elaeopyron'' Dode, ''J.&nbsp;torreyi'' Dode) &mdash; Arizona Black Walnut
 +
***''J.&nbsp;major'' var. ''glabrata'' Manning
 +
**''Juglans microcarpa'' Berlandier (''J.&nbsp;rupestris'' Engelm.) &mdash; [[Texas Walnut]] or Little Black Walnut
 +
***''J.&nbsp;microcarpa'' var. ''microcarpa''
 +
***''J.&nbsp;microcarpa'' var. ''stewartii'' (Johnston) Manning
 +
**''J.&nbsp;mollis'' Engelm. &mdash; [[Mexican Walnut]]
 +
**''J.&nbsp;neotropica'' Diels (''J.&nbsp;honorei'' Dode) &mdash; [[Andean Walnut]], Cedro Negro , Cedro Nogal , Nogal , Nogal Bogotano
 +
**''J.&nbsp;nigra'' L. &mdash; [[Black Walnut|Eastern Black Walnut]]
 +
**''[[Juglans olanchana|J.&nbsp;olanchana]]'' Standl. & L.O.Williams &mdash; Cedro Negro, Nogal , Walnut
 +
**''[[Juglans boliviana|J.&nbsp;peruviana]]'' Dode &mdash; Peruvian Walnut
 +
**''J.&nbsp;soratensis'' Manning
 +
**''J.&nbsp;steyermarkii'' Manning &mdash; [[Guatemalan Walnut]]
 +
**''[[Juglans venezuelensis|J.&nbsp;venezuelensis]]'' Manning &mdash; Venezuela Walnut
 +
*'''Sect. ''Cardiocaryon'''''. Leaves very large (40–90&nbsp;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]].
 +
**''J.&nbsp;ailantifolia'' Carr. (''J.&nbsp;cordiformis'' Maxim., ''J.&nbsp;sieboldiana'' Maxim.) &mdash; [[Japanese Walnut]]
 +
***''J.&nbsp;ailantifolia'' var. cordiformis &mdash; [[Japanese Walnut|Heartnut]]
 +
**''[[Juglans mandshurica|J.&nbsp;mandshurica]]'' Maxim. (''J.&nbsp;cathayensis'' Dode, ''J.&nbsp;formosana'' Hayata, ''J.&nbsp;hopeiensis'' Dode, ''J.&nbsp;stenocarpa'' Maxim.) &mdash; Manchurian Walnut or Chinese Walnut.
 +
*'''Sect. ''Trachycaryon'''''.  Leaves very large (40–90&nbsp;cm) with 11–19 broad leaflets, softly downy, margins serrated. Wood soft.  Fruits borne in clusters of 2-3Nuts have a thick, rough shell bearing distinct, sharp ridges. Eastern [[North America]].
 +
**''J.&nbsp;cinerea'' L. &mdash; [[Butternut (tree)|Butternut]]
   −
Walnuts are light-demanding species but benefit from protection from wind. Research has shown that interplanting walnut plantations with a [[nitrogen fixation|nitrogen fixing]] plant such as ''Elaeagnus × ebbingei'' or ''E. umbellata'', and various ''Alnus'' species can have a dramatic impact on tree height and girth, resulting in a 30% increase according to some studies (Hemery 2001).
+
[[Image: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]]. This species is widely cultivated for its delicious [[nut (fruit)|nuts]]. According to the UN Food and Agriculture Organization (FAO), Shahmirzad orchard in Iran is the largest in the world (700-750 ha). In [[Kyrgyzstan]] alone there are 230,700 ha of walnut-fruit forest, where ''J.&nbsp;regia'' is the dominant overstory tree (Hemery and Popov 1998).  In non-European English-speaking nations, the nut of the ''J.&nbsp;regia'' is often called the "English walnut";  in Great Britain, the "common walnut."  Tuiserkan is the second city in Iran that is famous for the best quality of its walnut.{{Citation needed|date=October 2009}} 
   −
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 thicknessA key trait for more northerly latitudes of N. 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 [[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 productionThe wood is particularly valuable.
   −
;Nuts
+
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&nbsp;cm long, the fruits are oval, the shell has very tall ridges, and the kernel is especially high in fat.
[[Image:Walnut02.jpg|thumb|Persian Walnut nuts]]
  −
[[Image:Walnut03.jpg|thumb|Inside of a Persian Walnut nut with green outer layer visible in the top left corner]]
  −
The [[nut (fruit)|nuts]] of all the species are edible, but the walnuts commonly available in stores are from the Persian Walnut, the only species which has a large nut and thin shell. A horticultural form selected for thin nut shells and hardiness in temperate zones is sometimes known as the 'Carpathian' walnut. The nuts are rich in [[Walnut oil|oil]], and are widely eaten both fresh and in [[cookery]]. [[Oil paint]] often employs walnut oil as an effective binding medium, known for its clear, glossy consistency and non-toxicity
  −
. Walnuts are also an excellent source of [[omega-3 fatty acids]], and have been shown as helpful in lowering [[cholesterol]]. They need to be kept dry and refrigerated to store well; in warm conditions they become rancid in a few weeks, particularly after shelling.
     −
In some countries immature nuts in their husks are preserved in vinegar. In England these are called 'pickled walnuts' and this is one of the major uses for fresh nuts from the small scale plantings.
+
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 black walnut (''J. nigra'').
   −
Walnut nut husks are often used to create a rich yellow-brown to dark brown [[dye]] that is used for dyeing [[textile|fabric]] and for other purposes. When picking walnuts, the husks should be handled wearing rubber gloves, to avoid dyeing one's fingers.
+
The [[Japanese Walnut]] (''J. ailantifolia'') is similar to Butternut, distinguished by the larger leaves up to 90&nbsp;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.
   −
;Wood
+
;Hybrids
The Persian Walnut, and the Black Walnut and its allies, are important for their attractive timber, which (except in young trees) is hard, dense, tight-grained and polishes to a very smooth finish. The color ranges from creamy white in the sapwood to a dark chocolate color in the heartwood. 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. Walnut [[burls]] (or 'burrs' in Europe) are commonly used to create bowls and other turned pieces. [[Veneer]] sliced from walnut burl is one of the most valuable and highly prized by cabinet makers and presitige car manufacturers. Walnut wood has been the timber of choice for gunmakers for centuries, including the [[Lee Enfield]] rifle of the First World War. Today it is used for exclusive sporting guns, by makers such as Purdy of London. The wood of the Butternut and related Asian species is of much lower value, softer, coarser, less strong and heavy, and paler in color.
+
*''Juglans x bixbyi'' Rehd. &mdash; ''J. ailantifolia'' x ''J. cinerea''
 +
*''Juglans x intermedia'' Carr. &mdash; ''J. nigra'' x ''J. regia''
 +
*''Juglans x notha'' Rehd. &mdash; ''J. ailantifolia'' x ''J. regia''
 +
*''Juglans x quadrangulata'' (Carr.) Rehd. &mdash; ''J. cinerea'' x ''J. regia''
 +
*''Juglans x sinensis'' (D. C.) Rehd. &mdash; ''J. mandschurica'' x ''J. regia''
 +
*''Juglans x paradox'' Burbank &mdash; ''J. hindsii'' x ''J. regia''
 +
*''Juglans x royal'' Burbank &mdash; ''J. hindsii'' x ''J. nigra''
   −
In North America research has been undertaken mostly on ''Juglans nigra'' aiming to improve the quality of planting stock and markets.  [http://www.walnutcouncil.org The Walnut Council] is the key body linking growers with scientists. In Europe, various EU-led scientific programs have studied walnut growing for timber (e.g. [http://www.bbc.co.uk/radio4/factual/opencountry_20020330.shtml in the UK]).
+
==Gallery==
   −
;Parkland and garden trees
+
<gallery perrow=5>
Walnuts are very attractive trees in [[park]]s and large [[garden]]s. The Japanese Walnut in particular is grown for its huge leaves, which have a 'tropical' appearance.
+
Image:Upload.png| photo 1
 +
Image:Upload.png| photo 2
 +
Image:Upload.png| photo 3
 +
</gallery>
   −
Walnuts are not particularly well suited to smaller urban gardens. They drop numerous small twigs, leaves, branches or nuts, so are considered "messy" by some people; the falling nuts in late summer and early autumn can be quite dangerous. Both the fallen leaves and the roots secrete a substance called [[juglone]] which kills many popular garden plants, such as [[tomato]], [[apple]] and [[birch]]; all walnuts produce juglone, but Black Walnut produces larger amounts than other species. Juglone appears to be one of the walnut's primary defense 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 many years even after a walnut is removed as its roots slowly decompose and release juglone into the soil.
+
==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  -->
   −
==References==
+
==External links==
 
*{{wplink}}
 
*{{wplink}}
   −
[[Category:Fagales]]
+
{{stub}}
[[Category:Edible nuts and seeds]]
   
__NOTOC__
 
__NOTOC__

Navigation menu