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Juglans regia L.
Juglandaceae
English walnut, Carpathian or Persian walnut
Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.
- Uses
- Folk Medicine
- Chemistry
- Description
- Germplasm
- Distribution
- Ecology
- Cultivation
- Harvesting
- Yields and Economics
- Energy
- Biotic Factors
- Chemical Analysis of Biomass Fuels
- References
Principal value is an orchard tree for commercial production of nuts. Nuts
consumed fresh, roasted, or salted, used in confectioneries, pastries, and for
flavoring. The shells may be used as antiskid agents for tires, blasting grit,
and in the preparation of activated carbon. (Activated charcoal and fructose
have recently been suggested to foil the alcohol "breathalizer.") Ground nut
shells used as adulterant of spices. Crushed leaves, or a decoction used as
insect repellant and as a tea. Outer fleshy part of fruit very rich in Vitamin
C and produces a yellow dye. Fruit, when dry pressed, yields a valuable oil
used in paints and in soap-making; when cold pressed, a light yellow edible oil
used in foods as flavoring. Young fruits made into pickles, also used as fish
poison. Twigs and leaves lopped for fodder in India. Decoction of leaves,
bark, and husks used with alum for staining wool brown. Wood hard, durable,
close-grained, heavy, used for furniture and gun-stocks. Tree often grown as
ornamental.
According to Hartwell (19671971), the English walnuts are used in folk
remedies for aegilops, cancer, carbuncles, carcinoma, condylomata acuminata,
corns, excrescences, growth, indurations, tumors, warts, and whitlows,
especially cancerous conditions of the breast, epithelium, fauces, groin,
gullet, intestine, kidneys, lip, liver, mammas, mouth, stomach, throat, and
uterus. Reported to be alterative, anodyne, anthelmintic, astringent,
bactericide, cholagogue, depurative, detergent, digestive, diuretic, hemostat,
insecticidal, laxative, lithontryptic, stimulant, tonic, and vermifuge, the
English walnut is a folk remedy for anthrax, asthma, backache, caligo, chancre,
colic, conjunctivitis, cough, dysentery, eczema, ejaculation, favus, heartburn,
impotence, inflammation, intellect, intestine, intoxication, kidney, legs,
leucorrbea, lungs, rheumatism, scrofula, sore, syphilis, and worms (Duke and
Wain, 1981).
Per 100 g, the seed is reported to contain 647657 calories, 2.54.2 g H2O,
13.718.2 g protein, 63.667.2 g fat, 12.615.8 g total carbohydrate, 1.62.1 g
fiber, 1.72.0 g ash, 92106 mg Ca, 326380 mg P, 3.03.3 mg Fe, 23 mg Na,
450536 mg K, 0.50 mg b-carotene equivalent, 0.270.50 mg thiamine,
0.080.51 mg riboflavin, 0.73.0 mg niacin, and 05 mg ascorbic acid. Wealth
of India (C.S.I.R. 19481976) also reports, per 100 g, 2.7 mg Na, 687 mg K, 61
mg Ca, 131 mg Mg, 2.4 mg Fe, 0.3 mg Cu, 510 mg P, 104 mg S, and 23 mg Cl, and
2.8 mg I (as well as Ar, Zn, Co, and Mn). About 42% of the total phosphorus is
in phytic acid; lecithin is also present. The immature fruit is one of the
richest sources of ascorbic acid, the skin with 1,090 mg, 100 g, the pulp with
2,330 mg. The leaves, also rich in ascorbic acid (almost 1% of the weight),
are rich in carotene (ca 0.3% wet weight). Juglone is the active compound in
the leaves; also quercetin, cyanadin, kaempferol, caffeic acid, and traces of
p-coumaric acid, hyperin (0.2%), quercitrin, kaempferol-3-arabinoside,
quercetin-3-arabinoside. The seed oil contains 37% palmitic, 0.53% stearic,
930% oleic, 5776% linoleic, and 216% linolenic acids. The oil cake, with
86.6% dry matter, contains 35.0% protein, 12.2% fatty oil, 27.6% carbohydrates,
6.7% fiber, 5.1% ash (Digestible nutrients: 31.5% crude protein, 11.6% fatty
oil, 23.5% carbohydrates, and 1.7% fiber). The shells contain 92.3% DM, 1.7%
protein, 0.7% fatty oil, 31.9% carbohydrates, 56.6% fiber, and 1.4% ash.
Deciduous, monoecious trees, 1215 m tall (Payne vars.), 1720 m tall (Eureka,
Placentia, Mayette, Franquette), and rarely up to 60 m tall; bark brown or
gray, smooth, fissured; leaf-scars without prominent pubescent band on upper
edge; leaves alternate, foetid, pinnate, without stipules; leaflets to
ovate-lanceolate, acuminate; margin irregularly serrate, glabrescent above,
pubescent and glandular beneath; flowers developing from dormant bud of
previous season's growth; staminate flowers in axillary, pendulous aments 515
cm long, developing 14 million pollen grains each; flowers in axils of scales,
with 2 bracteoles, perianth-segments 14, stamens 340; pistillate flowers in
clusters of 39, developing as many nuts; in selected varieties not only
terminal bud produces fruit, but all lateral buds on previous years growth also
produce; perianth 4-lobed; fruit 3.55 cm in diameter, globose or slightly
ridged, not splitting.
Reported from the Eurosiberian and Central Asian Centers of Diversity, English
walnut, or cvs thereof, is reported to tolerate frost, high pH, heat, insects,
low pH, and slope (Duke, 1978). Cultivars are selected on basis of high heat
tolerance, resistance to walnut blight (Xanthomonas juglandis),
tolerance for winter cold, and yield and quality of kernels. Most promising
cvs are of Carpathian origin and have been introduced from Poland and withstand
temperatures below those recorded in the fruit belt of New York. Recent
superior cvs include: 'Broadview', 'Schafer', 'Littlepage', 'McKinster',
'Metcalfe', 'Jacobs', and 'Colby'. Other cvs widely grown in the world
include: 'Marmot', 'Meylanaise', 'Corne', 'Gourlande', 'Mayette', 'Brantome',
'Ashley', 'Glackner', 'Nugget', 'Poe', 'Franquette', 'Concord', 'Ehrhardt',
'Payne', and 'Waterloo'. Persian walnuts have been hybridized with butternuts,
black walnuts, and other European and Oriental walnuts. Juglans regia
var. orientis (Dode) Kitam. J. orientis Dode; J. regia
var. sinensis sensu auct. (Japan, non DC.) is a widely cultivated
Chinese tree, with glabrous leaves and branchlets, leaflets 39, obtuse,
entire, except in young trees, and nuts relatively thin-shelled. (2n =
32, 36)
Native to the Carpathian Mountains of eastern Europe, but often found growing
wild eastward to Himalayas and China. Widely cultivated throughout this region
and elsewhere in temperate zone of the Old and New World. Thrives in temperate
Himalayas from 1,000 to 3,000 m altitude. In North America, thrives as far
north as New York State. Introduced from Spain by way of Chile to California
about 1867. In 1873 'Kaghazi' was introduced in northern California and a
seedling 'Eureka' has become the important source of our commercial varieties.
Ranging from Cool Temperate Steppe to Wet through Subtropical Thorn to Moist
Forest Life Zones, English walnut is reported to tolerate annual precipitation
of 3.1 to 14.7 dm (mean of 25 cases = 8.4), annual temperature of 7.0 to
21.1°C (mean of 25 cases = 12.0), and pH of 4.5 to 8.2 (mean of 21 cases =
6.4). Thrives on rich, sandy loam, well-drained, slightly acid or neutral.
Responds well to cultivation and fertilization. In areas where hardiness is a
problem, trees should not be forced into excessive vegetative growth. Minimum
temperature should not go below -29°C. One fault of Carpathian walnuts is
that it begins growth early in spring with result that crop and foliage may be
damaged by late frosts. When fully dormant, trees can withstand temperatures
from -24°C to -27°C without serious damage. French cvs are more winter
hardy. 'Eureka' is less hardy than newer cvs being produced for northern
California, Oregon, and higher altitudes. Very high summer temperatures cause
damage to kernels, slightly at 38°C, severe at 40.5 to 43.5°C. Quite
variable resistance to heat among varieties. Reported from areas with pH 4.5
to 8.3 annual rainfall 03 to 15 dm and annual temperature 719°C. Rains in
late spring and summer increase walnut blight infections.
Various methods are used for preparing an area for a walnut orchard, all giving
equally good results, when measured by profitable crop production. Since trees
are deep-rooted, soil should be fertile, well-drained, alluvial, 2 m or more
deep, of medium loam to sandy or silt loam texture, and free of alkali salts,
especially excessive boron. Seedling trees show great variation as to
hardiness, type of fruit and fruitfulness. 'Paradox' hybrids, 'Royal' hybrids
and Juglans hindsii are used as rootstocks for grafting Persian and
Carpathian walnuts. Rootstock of Juglans regia may be used if oak root
fungus (Armillaria mellea) is absent in area. Persian walnuts have been
grafted to Chinese wingnut (Pterocarya stenoptera). Selected varieties
are best whip or bark grafted or patch budded on seedling trees, or top-worked
on existing trees. Persian walnuts are planted in the orchard from 10 to 20 m
each way; however, many spacings are in use depending on the variety and the
cultivation methods to be used. Intercropping young walnut orchard with trees
of a different species may be useful, at least for the first 510 years.
Intercropping may be difficult because of irrigation, spraying, and use of
equipment for cultivation of the intercrop. Holes should be dug amply wide to
accomodate roots, a few m deeper than the roots, and planted no deeper than
they were in the nursery. Roots should never be allowed to dry out during the
transplanting process. Topsoil should be used to fill hole when planting tree,
and firmly tamped around roots. Do not transplant when soil is wet. Nut trees
must have tops reduced or cut back, either before or after planting, usually to
about 1.52 m from ground level. Lower buds should be suppressed so the upper
ones will be forced to grow and make the framework of the tree. Newly planted
trees should be staked, either with a single stake driven close to the tree and
tying it to the stake, or driving three stakes equidistant, fastening tree to
each with stout cord so as not to injure bark. After trees are planted, they
should be watched, and watered during every severe dry spell until they have
become established. When irrigated, total of 2 1/25 acre feet of water per
acre should be applied through-out the year, including normal rainfall. The
modified central leader system of training young walnuts is recommended for
western orchards, in which 4 or 5 main framework branches spaced both
vertically and horizontally are developed; the first branch should be started
no lower than 2 m from the ground. Trend is toward heavier and more consistent
pruning both in young and old trees; very fruitful new cvs respond more readily
than some of the older cvs. Nitrogen and zinc deficiencies in soils are based
on minimum of 100150 kg/ha per year for bearing walnuts; 200 to 250 kg/ha are
used on high-producing orchards. Standard method for applying zinc to walnut
trees is to drive zinc-bearing metal pieces or glazing points into outer
sapwood of trees. Other elements which may show mineral deficiencies in
various soils and hence must be corrected are iron, manganese, boron,
potassium, magnesium, phosphorus, and copper.
Under favorable conditions, the husks of nuts crack open and adhere temporarily
to twigs, allowing nuts to fall to ground, this occurring with most cvs between
September 1 and November 7. First picking up of nuts begins in second week of
September. Hastening of falling of nuts is usually done by shaking the trees
with long poles or a boom shaker. During harvest period, nuts are picked up 3
or 4 times before total crop has matured and dropped. Nuts should not be
allowed to remain on ground too long. After being picked up and sacked, nuts
are washed if dirty, and spread out in shallow trays with bottom slats spaced
1.52 cm apart. Nuts should not be exposed to sun for entire day. Trays are
piled up so as to permit ventilation after nuts have become warm. Too fast
drying causes shell to crack and open. In large orchards, a drying house is
constructed for curing process. After curing and bleaching, nuts are graded
and packed for shipment.
Newer cvs begin producing nuts in 56 years; by 78 years, they produce about
2.5 tons of nuts per hectare. Orchards on relatively poor, unirrigated
mountain soil report 1.52.25 MT/ha; orchards in well cultivated valleys,
6.57.5 MT/ha. According to the Wealth of India, a grown individual can yield
about 185 kg, but 37 kg is more likely. In the United States, California is
the major producing area, with about 129,400 acres producing 77,000 tons nuts
per year; Oregon is second with about 3,500 tons annually; the total valued at
about $32.3 million. About 60% of Persian walnuts are sold shelled. Lumber
from large trees may bring up to $1,500/tree.
If the walnuts yields of 7,500 kg/ha (Duke, 1978) yielded all their 65% (6367%
oil) oil, there is a potential oil yield of nearly 5 MT per year, a very
worthwhile target, if attainable. The green hulls have recoverable ascorbic
acid (content 2.55% of dry weight). Hulls contain 12.2%, bark 7.5%, leaf
blades 911% tannin. After extraction of the vitamin C and tannin, the
residues might be used for fuel or ethanol. Prunings from the trees might
contribute another 5 MT biomass per year.
Pollination is often a problem, as Persian walnuts are monoecious, with
separate staminate and pistillate flowers in different parts of the same tree.
Staminate catkins are 1015 cm long and produce 14 million pollen grains each.
Sometimes freshly picked catkins are put on paper in room at 21°C and the
shed pollen stored in desiccator at 0°C. Then pollen is blown on trees by
fan mounted on truck. Helicopters are sometimes used to blow pollen over
orchard. Seedlings are very susceptible to mushroom root rot, and Walnut
girdle disease 'Blackline' is thought to occur when certain horticulture
varieties of Juglans regia are grafted on rootstocks of Juglans
hindsii and its hybrids, associated with graft incompatibility. Fungi
known to attack Persian walnuts include: Alternaria nucis, Armillaria
mellea, Ascochyta juglandis, Aspergillus flavus, Auricularia auricula-judae,
Auricularia mesenterica, Cerrena unicolor, Cladosporium herbarum, Coniophora
cerebella, Coprinus micaceus, Coriolus tephroleucus, Cribaria violaceae,
Cryptovalsa extorris, Cylindrosporium juglandis, C. juglandis, C.
uljanishchevii, Cytospora juglandina, Cytosporina juglandina, C. juglandicola,
Diplodia juglandis, Dothiorella gregaria, Erysiphe polygoni, Eutypa ludibunda,
Exosporina fawcetti, Fomes fomentarius, F. igniarius, F. ulmarius, Fusarium
avenaceum, F. lateritium, Ganoderma applanatum, Glomerella cingulata, Gnomonia
ceratostyla, G. juglandis, G. leptostyla., Hemitricia leiotyichia, Hypoxylon
mediterraneum, Inonotus hispidus, Laetiporus sulphureus, Lentinus cyathiformis,
Licea tenera, Marsonia juglandis, Melanconis carthusiana, M. juglandis,
Melanconium juglandis, M. oblongum, Melanopus squamosus, Microsphaera alni, M.
juglandis, Microstroma juglandis, Mycosphaerella saccardoana, M. woronowi,
Nectria applanata, N. cinnabarina, N. ditissima, Oxyporus populinus, Phellinus
cryptarum, Phleospora multimaculans, Phoma juglandis, Phomopsis juglandis,
Phyllactinia guttata, Phyllosticta juglandina, P. juglandis, Phymatotrichum
omnivorum, Phytophthora cactorum, P. cinnamomi, P. citrophthora, Pleospora
vulgaris, Pleurotus ostreatus, Polyporus hispidus, P. picipes, P. squamosus,
Polystictus versicolor, Rhizopus nigricans, Stereum hirsutum, Trametes
suaveolens, Tubercularia juglandis, T. vulgaris, Verticillium albo-atrum.
Bacteria attacking Persian walnut include: Agrobacterium tumefaciens,
Bacillus mesentericus, Bacterium juglandis, Pseudomonas juglandis, Xanthomonas
juglandis, Cuscuta pentagona, also parasitized the tree. The
following nematodes have been isolated from Persian walnut: Cacopaurus
pestis, Diplogaster striatus, Diplogaster coronata, Ditylenchus intermedius,
Meloidogyne arenaria, M. javanica, M. sp., Pratylenchus coffeae, P.
pratensis, P. vulnus, Rhabditis debilicauda, R. spiculigera, Tylolaimophorus
rotundicauda. Among the insect pests of this walnut are the following:
Walnut Blister mite (Eriophytes tristriatus), Walnut aphid
(Chromaphis juglandicola), Italian pear scale (Diaspis iricola),
Calico scale (Eulecanium cerasorum), Frosted scale (Parthenolecanium
Pruinosum), Walnut scale (Quadraspidiotus juglansregiae), Codling
moth (Cydia pomonella), Fruit tree leaf-roller (Archips
argyrospila), Indian meal moth (Plodia interpunctella), Walnut
caterpillar (Datana integerrima), Red-humped caterpillar (Schizura
concinna), Walnut span worm (Phigalia plumigeraria), and Walnut husk
fly (Rhagolestis completa).
Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985)
reported a spread of 19.63 to 18.49 MJ/kg, compared to 13.76 for weathered rice
straw to 23.28 MJ/kg for prune pits. On a % DM basis, the orchard prunings
contained 80.82% volatiles, 1.08% ash, 18.10% fixed carbon, 49.72% C, 5.63% H,
43.14% O, 0.37% N, 0.01% S, 0.06% Cl , and undetermined residue.
- C.S.I.R. (Council of Scientific and Industrial Research). 19481976. The wealth
of India. 11 vols. New Delhi.
- Duke, J.A. 1978. The quest for tolerant germplasm. p. 161. In: ASA Special
Symposium 32, Crop tolerance to suboptimal land conditions. Am. Soc. Agron.
Madison, WI.
- Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer index
with more than 85,000 entries. 3 vols.
- Hartwell, J.L. 19671971. Plants used against cancer. A survey. Lloydia 3034.
- Jenkins, B.M. and Ebeling, J.M. 1985. Thermochemical properties of biomass
fuels. Calif. Agric. 39(5/6):1416.
Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw