Juglans
Habit | tree
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Lifespan: | ⌛ | perennial |
Features: | ✓ | fruit |
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Juglans > |
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Walnuts (genus Juglans) are plants in the family Juglandaceae. They are deciduous trees, 10–40 meters tall (about 30–130 ft), with pinnate leaves 200–900 millimetres long (7–35 in), with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya), but not the 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 glans, "Jupiter's acorn": figuratively, a nut fit for a god.
The word walnut derives from Old English wealhhnutu, literally "foreign nut", wealh meaning "foreign" (wealh is akin to the terms Welsh and Vlach; see Walha and History of the term Vlach).[1] The walnut was so called because it was introduced from Gaul and Italy. The Latin name for the walnut was nux Gallica, "Gallic nut".[1]
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 cultivars that are compatible for pollination purposes; although some cultivars are marketed as "self fertile" they will generally fruit better with a different pollination partner. 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.[2]
ExpandRead about Juglans in the Standard Cyclopedia of Horticulture
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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 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.[3]
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.
- J. ailantifolia Carr. (J. cordiformis Maxim., J. sieboldiana Maxim.) — Japanese Walnut
- J. ailantifolia var. cordiformis — Heartnut
- J. mandshurica Maxim. (J. cathayensis Dode, J. formosana Hayata, J. hopeiensis Dode, J. stenocarpa Maxim.) — Manchurian Walnut or Chinese Walnut.
- J. ailantifolia Carr. (J. cordiformis Maxim., J. sieboldiana Maxim.) — Japanese Walnut
- Sect. Juglans. Leaves large (20–45 cm) with 5–9 broad leaflets, hairless, margins entire. Wood hard. Southeast Europe to central Asia.
- J. regia L. (J. duclouxiana Dode, J. fallax Dode, J. orientis Dode) — common walnut, Persian, English, or Carpathian walnut
- 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.
- J. australis Griseb. (J. brasiliensis Dode) — Argentine Walnut, Brazilian Walnut
- J. boliviana (C. DC.) Dode — Bolivian walnut, Peruvian walnut
- J. californica S.Wats. — California Black Walnut
- J. hindsii (Jepson) R.E.Smith — Hinds' Black Walnut
- J. hirsuta Manning — Nuevo León Walnut
- J. jamaicensis C.DC. (J. insularis Griseb.) — West Indies Walnut
- J. major (Torrey) Heller (J. arizonica Dode, J. elaeopyron Dode, J. torreyi Dode) — Arizona Black Walnut
- J. major var. glabrata Manning
- J. microcarpa 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 Standl. & L.O.Williams — Cedro Negro, Nogal , Walnut
- J. olanchana var. olanchana
- J. olanchana var. standleyi
- J. peruviana Dode — Peruvian Walnut
- J. soratensis Manning
- J. steyermarkii Manning — Guatemalan Walnut
- 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.
- J. cinerea L. — Butternut
The best-known member of the genus is the 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 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 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 (J. cinerea) is also native to eastern North America, where it is currently 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
References
- ↑ Jump up to: 1.0 1.1 Online Etymology Dictionary - "Walnut"
- ↑ http://fruitandnuttrees.com/walnut-tree-j-regia-j-nigra Fruit and Nut Trees
- ↑ 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
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
External links
- w:Juglans. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
- Juglans QR Code (Size 50, 100, 200, 500)