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 Walnut
N AHMAD, S R SINGH, MEGNA RASHID AND HIDAYATULLAH MIR
Central Institute of Temperate Horticulture, Old Air Field, P.O: Rangreth-190 007, Srinagar

Introduction and Importance among all other nuts. Volatile flavor components of
Walnut (Juglans regia L.) is known by different names walnut constitute about 37 compounds including 6
throughout the world. The most commonly used name aldehydes, 6 alcohals and 5 ketones (Mitra and Bose
is akhrot in hindi, doon in Kashmiri and Gardgani in 1991). Both immature fruits and green hulls of walnut
unani, The trivial name walnut derives from old wealhh are very rich sources of ascorbic acid containing about
nutu, literally foreign nut, wealhh meaning foreign 2.0- 2.5 per cent and 0.4- 0.8 per cent on fresh weight
(wealhh is akin to the terms Welsh and Vlach). The basis, respectively (Table 1).
walnut was so called because it was introduced from
Gaul and Italy. The Latin name for the walnut was Table 1: Nutritional value per serving of 100 g
nux Gallica, Gallic nut. The Latin name Juglans regia
Energy 2,738 kJ Alcohol 0
is derived from the name Jovis glans which translates (654 kcal)
to Jupiter’s Acorn. This description comes from the Carbohydrates 13.71 Caffeine 0
classical golden age when it was said that while ordinary Starch 0.06 Vitamin- A. 1 µg (0%)
men lived on Acorns, Jupiter and his fellow gods feasted Sugars 2.61 Vitamin- A 20 IU
Lactose 0 Beta- carotene 12 µg (0%)
on walnuts. The modern name, however, comes from Dietary fiber 6.7 Lutein and 9 µg
the German Wallnuss which means foreign nut. The Zeaxanthin
growing of walnut groves in Europe took off in the 1500’s, Fat 65.21 Thiamine 0.341 mg (30 %)
however, they are now grown worldwide with California (Vit- B1)
Saturated 6.126 Riboflavin 0.15 mg (13 %)
being the largest producer. (Vit- B2)
Monounsaturated 8.933 Niacin 1.125 mg (8 %)
In India, walnut grows in the northwestern Himalayan (Vit- B3)
belt, expanding up to Darjeeling and Sikkim. The history Polyunsaturated 47.174 Pantothenic 0.570 mg (11 %)
of walnut is lost in antiquity. O. Rourke (1969) records acid (B5)
its spread from Asia Minor to other parts of the world Protein 15.23 Vitamin- B6 0.537 mg (41 %)
Water 4.07 Folate (Vit- B 9) 98 µg (25 %)
while slate (1969) considers it older than man on the Iron 2.91 mg Vitamin B 12 0 ìg (0 %)
basis of fossil testimony. (22 %)
Magnesium 158 mg Vitamin C 1.3 mg (2 %)
Composition and uses: Almost all the parts of the (45 %)
plant are utilized in one way or the other way but the Manganese 3.414 mg Vitamin D 0 IU (0 %)
fruit and timber have been put to maximum use. (163 %)
Phosphorus 346 mg Vitamin E 0.7 mg (5 %)
Kernel: Kernel of walnut, the edible portion, constitutes (49 %)
Potassium 441 mg Vitamin K 2.7 µg (3 %)
about half the total fruit weight and its composition as
(9 %)
reported by Ozakhan (2005) is given in table. Walnut is Sodium 2 mg (0 %) Calcium 98 mg (10 %)
rich in proteins, fats and minerals and is concentrated Zinc 3.09 mg (33 %)
source of energy. It contains a good amount of various
(Ozkhan et al. 2005)
vitamins of B group and is the richest in vitamin B- 6
 662 Fruit Production in India

Leaves: The walnut leaves can be used as an infusion at altitudes of 1500 m and above are considered of
as well as eyewash. It is beneficial for skin disorders superior quality, with a light coloured kernel and a
and irritations in the eyes, and can also be used to characteristic thin shell. At lower elevations, the kernel
stimulate poor appetite. At the same time, infusions usually turns brown because of high temperatures at
prepared from the walnut leaves can be applied for skin the time of ripening. The important walnut growing
diseases like eczema or to heal wounds and scratches. A countries of the world as per area and production are
tincture prepared with the walnut leaves and water is given in Table 2.
useful in treating conjunctivitis as well as blepharitis.
Table 2: Area and production of important walnut growing countries
Outer nut rind: The exterior of the walnut nut crust (2009)
is beneficial for chronic diarrhea when it is taken as a Country Area (ha) Production
tonic. Even people suffering from anemia may use an (MT)
infusion prepared from the outer crust of the walnut China 305000 979366
nuts. The infusion prepared from the outer layer of the
walnut nut is also useful for treating hair loss. People United States of America 90246 376480
Turkey 86533 177298
suffering from baldness may use the infusion as a bathe Iran(Islamic Republic of Iran) 67776 141426
for hair loss for effective results. Ukraine 13400 83890
Mexico 58000 70000
Nut: Oil prepared from the walnut nut is immensely France 17679 41624
beneficial for women suffering from menstrual Romania 1523 38329
dysfunction. Walnut oil is almost colour less or pale India 30800 36000
Egypt 5249 27000
yellow with pleasant aroma. It is used for edible purposes, Chile 12600 26000
artists oil colours, varnishes and soap making. The Serbia 16410 25172
kernals contain about 60- 70 % fat and oil, the major Austria 6709 18937
components of which are lonoleic acid (49.2 %), oleic Morocco 5078 15222
Greece 13951 15000
acid (25.7 %) and linolenic acid (18.2 %). Belarus 5125 13575
1297 12748
Shell: walnut shell flour is extensively used as an
ingredient in plastic fillers, battery cases, moulding resin (FAO, 2011)
forms, industrial tile and as insectide spreader. It is
also used on large scale a diluents for agricultural Taxonomy: Walnuts are members of the family
insectides as lignin and cutin contents of the flour easily Juglandaceae and genus Juglans L. (Manning 1978),
containing about 60 species, 21 of which are placed in
absorb and retain active toxic chemicals.
the genus Juglans. Nuts from all species are edible,
Inner bark: The inner bark of the walnut may be used although none is large and easily cracked as the Persian
both as decoction as well as a tincture. The decoction or English walnut, Juglans regia L. The somatic
may be used to heal constipation, slow digestion, as a chromosome number (2n) of Juglans species is 32. The
stimulant for the liver or even to cure skin diseases. genus is divided into four sections based mainly on the
morphology (Dode 1909a,b; Manning 1978).
Origin, Distribution and Systematics Section a- Juglans: Juglans regia is the only species.
Area and production: Walnut (J. regia) is one of There are two sub species. subsp. turcominica and sub-
important nut fruit of the India being exported to more sps fallax. It is commonly known as English or Persian
than 40 countries with earnings of more than Rs 300 walnut and ranges from south- eastern Europe, Iran to
crore of foreign exchange annually. It is grown mainly the Himalayas, and China.
in Jammu & Kashmir, Himachal Pradesh, and
Section b- Rhysocaryon (Black walnut), it has sixteen
Uttarakhand & Arunachal Pradesh. However Jammu
species viz. Juglans australis, Juglans boliviana,
& Kashmir is the major walnut producing state
Juglans californica, Juglans hindsii, Juglans hirsute,
contributing more than 85 per cent of total production
Juglans jamaicensis, Juglans major, Juglans
of the country. The most important districts for walnut microcarpa, Juglans mollis, Juglans neotrapa, Juglans
cultivation are Anantnag, Pulwana, Kupwara, Budgam, nigra, Juglans olanchana, Juglans pyriformis, Juglans
Baramulla and Srinagar. In Jammu, the largest areas sortensis, Juglans steyermarkii, Juglans venezuelensis.
under walnut cultivation are Doda district, followed by Black walnut is the most important walnut famous for
Poonch and Udhampur, with minor quantities grown its good quality wood. It is a wild tree found most in
in Rajouri and Kathua districts. Major walnut growing south central and south- eastern United States. Nuts
Districts in HP are Kullu, Mandi, Shimla, Kinnaur, are hard and difficult to crack. Its Shell are used in
Sirmour, Chamba and Major walnut growing Districts plastics, glue extends, sand slats cleaners and metal
in Uttarakhand are Nanital, Dehradun, Pauri, Tehri, polishers. Black walnut has indehiscent, thick, adherent
Chamoali, Almora, Pithoragarh. The walnuts produced husks, four celled nuts, and thick shells that are ridged.
Walnut 663

Other important black walnut species are Juglans of shoots. The chilling hour requirement varies with
california (southern California black walnut, Juglans the cultivars as 700 and 1500 hours are needed for Payne
hindsii (northern California black walnut) Juglans and Franquette cultivars, respectively, at or below 70C.
major (Arizona black walnut) Juglans microcarpa
Rainfall: Requires 760- 800 mm rainfall or irrigation
(Texas black walnut) but of these only Juglans hindsii
equivalent. To obtain high yield, avoid planting walnut
and its hybrids are of significances (as root for Persian
in drought prone areas. Spring rainfall is associated
walnut).
with increased problems from walnut blight.
Section c- Cardiocaryon: Juglans ailantifolia var.
Wind tolerance: The plant can grow and crop much
cardiformis, Heartnut is the most popular species in
more slowly if exposed to persistent winds. It is also
the section found oftenly in Japan .They are easily
susceptible to limb breakage. Thus, shelter is essential
cracked nuts. Other species includes J. ailantifolia
to promote good growth during establishment years.
(Japanese walnut) J. Cathayensis (Chinese walnut ) and
J. mandsinuria (Manchurian walnut). In this section, Soil: Walnut requires slightly acidic soils between pH
nuts are two celled with four to eight ridges, has 5.5- 6.5. It is prone to zinc and boron deficiencies, hence
indehiscent and are borne on long claster of several nuts. select a site wherein recent soil analysis show reasonable
The only variant in this group producing easily cracked levels of zinc and a slightly acidic pH. The walnut grows
nuts. Other species include; best on deep, friable loamy soil/ silt loam or clay loam
well supplemented with lime and rich in humus, where
Section d- Trachycaryon: Juglans cineria L.
roots can develop to a depth of 3- 4 m. Besides good top-
Butternut is the only species in the section. They are
soil, the sub- soil should be free of impermeable layers
used to make maple butternut candy in New England,
like clay and rock gravel and anaerobic conditions (clayey
they are very thick shells with eight ridges indehiscent
soil coupled with high rainfall). Walnut cannot tolerate
husks with four ribs and two celled nuts with small
wet soils for any extended period. A few hours of water
fennels that tend to shatter when cracked.
logging can cause severe damage. Gentle slopes are more
easily managed. As walnut plantation is likely to be on
Ecological Requirements
steep slopes in Kashmir, there are two important factors
Altitude: It grows in temperate regions between the to consider:
altitudes of 900- 3500 m above sea level. However,
beyond 2,500 m, commercial walnut production is not a) Choose a site with southerly and south- westerly
recommended as it result to erratic and even total crop facing slopes. This warms up faster in spring and
loss in some year when there is late spring frost. cools down more slowly in the autumn, thus
extending the growing season at higher altitude.
Temperature: It requires cool period in autumn to Northerly and easterly aspects tend to be colder
promote leaf fall and the physiological process of plant and more prone to frost damage at higher altitudes,
hardening and induction of dormancy. The plant can but may allow walnut production at lower altitude.
tolerate as low as -110 C during deep dormancy without
serious damage but late spring frosts are detrimental. b) Choose a site with good frost drainage. Unimpeded
As soon as growth commences after dormancy, the down slope drainage of cold air is important
temperature even two or three degrees below freezing particularly in spring where a build- up of cold
point (00C) kills leaves, shoots and flowers and thus air in pocket behind a line of trees or in a fold in
resulting into crop failure. The tree normally grows well the ground can cause crop loss due to late frosts.
in cool climates that are free from frost during spring
but does not thrive in areas with hot summers. It is not Species and Commercial Varieties
recommended in areas where late spring or early fall Suitable cultivars: Most of walnut plantations are
frost is common as freezing temperature kills the seedling origin and each plant is a genotype being a
growing point of walnut trees and severely affects cross pollinated crop. Walnut varieties developed
production. High temperature at 380C cause sun burning throughout the world are seedling selection. A large
of hulls and shriveling of kernels resulted sometimes number of varieties introduced from abroad or selected
into blank nuts. Severe damages are further aggravated from indigenous material in India include exotic cultivars
if the humidity is low and temperature exceeds 400C. like Lake English, Colby Blackmore, Turtle 16, Turtle
Hence cool or short growing season is a limiting factor 31, Nielson, Orth, Serr and Natra Attiro doing well under
in walnut production. Most other temperate fruits, the Himachal Pradesh conditions (Rathore 1986). In India
walnut require certain amount of chilling period in few seedlings with high Shelling percentage, better
winter to break dormancy in order to make satisfactory Kernal quality and soft Shell has been identified and
vegetative growth and flowering. In the absence of released for cultivation. Gobind, Roopa, Ratna nad
adequate chilling, the bud opening and blossoming are Pratap and Sholding in Himachal Pradesh. Hamdan,
irregular and delayed, resulting into poor and die back Sulaiman, CITH-Walnut-1, 2, 3, 4, 5, 6, 7, 8, 9 and 10
 664 Fruit Production in India

in J & K and Charata No- 2, 4, 6, 13 and 14 in suited to wet and humid areas, but Franquette seems
Uttarakhand (Rathore 1986) are promising. A Quite to have some degree of blight resistance. On the down
number of commercial cultivars of walnut are commonly side, from the home garden viewpoint, the tree is
grown in the countries like USA, France, Spain etc vigorous and spreading, slow to come into bearing, and
having good qualitative traits. Out of which only few Franquette is also a 100 per cent terminal bearer. The
number of exotic cultivar like Opex Culchery, Tutle, nuts are large, and attractive, Kernel weight averages
Nugget, and Chenovo has been introduced and planted 5.2 grams, and crack out is about 46 per cent, alto” it
in the field gene bank of CITH, Srinagar to see their may be lower in some conditions. Franquette reputedly
comparative performance. The salient feature of the also has very high quality timber.
promising exotic walnut cultivars are:
Serr: A Californian cultivar released in the late 60s,
Hartley: Most popular cultivar of California. Tree is
Serr is very vigorous and large, and need to be lightly
medium to large in size, kernels are light in colour,
pruned every year. Serr bears large, well filled, thin
good yielder and tolerance to codling moth and blight.
but strong shelled nuts on laterals as well as tips (nut
The nuts are large with broad flat base and pointed tip.
Shell is light coloured, thin and well sealed. bearing is evenly distributed between terminal and
lateral buds). Its usual crop load is rated as fair. It is an
Payne: A leading cultivar of California; heavy yielder early leafing Californian cultivars it has some resistance
due to fruitfulness of lateral buds. Tree is vigorous, round to bacterial blight infection. On very fertile, well drained
and require heavy pruning for maintaining vigour. soils it tends to be an excessively strong grower and
Susceptible to codling moth and blight difficult to control. Serr comes into bearing quickly once
Ashley: From the breeding program of the pomology planted out. Variable 50– 50 per cent recovery average,
Department University of California at Davis, 90 per larger nuts the kernel weight 7.6 g. Pollinized by Chico
cent of lateral buds produce female (Pistillate) flowers, and Tehama.
and therefore, potentially nuts. Ashley matures its nuts
CITH Walnut-1: Suitable for export as well as domestic
relatively early because it comes into leaf early. For
market, having medium tree vigor, light kernel colour,
this reason, it is not suitable for areas with heavy spring
bold nut (28 g), and large kernel size (14.21 g), good
frosts. Like many early leafing Californian selections,
it is extremely sensitive to being infected with walnut kernel recovery (50.75%), light shell colour, intermediate
blight (Xanthomonas juglandii) if it is rainy in spring shell seal, intermediate shell strength, long trapezoidal
and therefore not so suitable for humid areas. The kernel in shape and very easy to remove kernel halves.
weight average 5.3 g and the recovery average 50 per CITH Walnut-2: Promising walnut genotype with
cent. vigorous plant growth, having medium size nut (16.0 g)
Chico: Many desirable features for the home gardeners and kernel weight (8.0 g) soft shell with shelling
– upright, small, 90 per cent lateral bud potentially nut percentage (50%) with light kernel colour. Nuts are
bearing (makes it possible to prune without losing the large in size, ovate in shape with medium shell texture,
crop), and it is one of the heaviest bearing varieties medium shell colour, strong shell seal, intermediate
available. The nuts mature early in the season. Like shell strength, complete shell integrity, satisfactory
many early leafing Californian selections, it is extremely kernel flavour, and well filled kernel, plumy, easy to
sensitive to being infected with walnut blight if it is remove kernel halves.
rainy in spring, and therefore not so suitable for humid
areas. Chico comes into leaf early, so it is not suitable CITH Walnut- 3: Medium tree vigor, nuts are large,
for areas with heavy spring frosts. The nuts are small long trapezoidal in shape, rough shell texture, medium
(kernel averages 5 grams and the crack out is 47 %), shell colour, strong shell seal, strong shell strength,
but the quality of kernels is good. Pollenized by Payne, complete shell integrity, satisfactory kernel flavour, well
Serr, Vina and Sunland. filled kernel, plumy, difficult to remove kernel halves
and light kernel colour. It gives nut weight (19.3 g) and
Eureka: A very large and spreading tree, and a 100 per
kernel weight (9.8 g) with kernel recovery (50.7%)
cent terminal bearer, so not really suited to the home
gardens situation. CITH Walnut- 4: The tree bears heavily with high tree
vigour, nuts are large, ovate, rough shell texture, light
Franquette – A late leafing old French variety, so it is
good for areas with late spring frosts. Unfortunately, it shell colour, strong shell seal, intermediate shell
is also late flowering which means it misses the pollen strength, complete shell integrity, thin, satisfactory
shed by other varieties, so nut set and yield are often kernel flavour, well filled kernel, moderately plumy,
poor. It may be worth trying Mayrick also late flowering, very easy to remove kernel halves and light kernel
as a pollenizer, or Rex. Most Californian varieties are colour. It gives nut weight of (19.08) and kernel weight
susceptible to walnut blight, and are therefore poorly of (10.09 g) with kernel recovery (50.9%).
Walnut 665

CITH Walnut- 5: High yielder, high tree vigour, having layering have also been reported. Walnut trees can be
extra light kernel colour, suitable for export market, also raised by clonal means. Also present technology
bigger nut (19.5) and kernel (10.16 g), good kernel has improved up tissue culture propagation techniques.
recovery (52.1%), light shell colour, ovate in shape, Propagation of elite varieties may play an important
moderate to remove the full kernel halves. role in improving the precocity and yield and to achieve
this objective production of quality rootstock is a pre-
CITH Walnut-6: Highly desirable from the point of view
requisite.
it is high yielder with superior quality nuts. Intermediate
tree vigour, broad ovate in shape, shell colour light, Clonal propagation: With the use of various plant
intermediate shell seal, weak shell strength, satisfactory regulators, such as IAA, IBA and NAA at high
kernel flavour, well filled kernel, moderate plumy and concentrations in combination, Rashid (1978) obtained
easy to remove kernel halves. It gives in shell nut weight good rooting and establishment of stool layers. He
(24 g), kernel weight (12.2 g) with kernel recovery suggested stooling as a suitable method of walnut
(50.8%). propagation but mother stools of commercials
commercial cultivars will have to be raised by cuttings
CITH Walnut-7: High tree vigour having large nuts,
or layers in the first instance.
elliptic in shape, rough shell texture, medium shell
colour, strong shell seal, strong shell strength, complete Seed propagation: For propagation through seeds soft
shell integrity, satisfactory kernel flavour, well filled shelled nuts of superior quality are sown. Although
kernel, plumy, easy to remove kernel halves and light walnut germinates without stratification under some
amber kernel colour. It gives (23.3 g) nut weight and conditions, yet proper stratification is desirable for good
(11.7 g) kernel weight with kernel recovery (50.2%). germination and growth. The propagation through seed
viz preparation of seed, planting in nursery, and planting
CITH Walnut-8: Intermediate tree vigour, nuts are
in field (pit digging etc) is done in similar way as is done
having light kernel colour, nut weight (20.4 g), and
for vegetative propagation. Walnut plants raised from
kernel weight (11.01g), good kernel recovery (54%), light
seedlings come to fruit at the age of 10- 15 years but
shell colour, long trapezoidal in shape, very easy to
optimum production is not expected until the plant
remove kernel halves, rough shell texture, strong shell
reaches the age of 20- 25 years. These trees may continue
seal and strong shell strength.
to flower until the age of 100 years. Heterozygosity in
CITH-Walnut-9 : High tree vigour having medium plant material coupled with long juvenile period and
size nuts, round in shape, rough shell texture, light greater degree of variability in relation to nut shape,
coloured shell, intermediate shell seal, intermediate shell size, colour, quality and maturity. Plants grow
strength, satisfactory kernel flavour, well filled kernel, unmanageable size which necessitates spars
plumy, easy removal of kernel halves. It gives inshell plantations, leading to low density and ultimately low
nut weight (21.2 g), kernel weight (10.7g) with (50.5%) yield.
kernel recovery.
Raising of root stock: Use the local walnut seedlings
CITH-Walnut-10: High tree vigour having large size as rootstocks. Generally hard shelled, smaller size
nuts,long trapezoid in shape, light in colour, strong shell unmarketable nuts are used for the root stock purpose,
seal, intermediate shell strength, well filled kernel, which give poor germination coupled with inferior
plumy, moderate to remove the kernel halves. It quality root stock, though soft shelled nut germinate
gives in shell nut weight (19.95 g) and kernel weight early and result in better growth but keeping in view
(11.08 g) with kernel recovery (55.5%). the cost of nuts in the market, hard shelled nuts may
be selected. The walnut seeds of medium size (3- 4 cm
Hamdan: The variety is precocious and dwarfing in dia) give higher germination than smaller and larger
nature. Nut weight is 14 g. Smooth shell, larger than size nuts. Though larger size nuts result into vigorous
width of nut. The shelling percentage is 54 with good seedlings but are not cost effective. Thus well sealed
quality kernels. It has been released by SKUAST-K. medium sized nuts (3- 4 cm long) from current season
Sulaiman: Cultivar also released by SKUAST- K, is crop should be used for raising of walnut seedlings.
precocious and semi- dwarfing in nature, average nut Collect the walnut in September to October from the
weight is 20 gm, shell surface is smooth. Nut shape is plant. Hull the seeds and air dry in the open shed.
somewhat round. Shelling percentage is 50 with good Though walnut germinates without stratification under
kernel characters. some conditions, however, for good germination and
better growth, stratification is desirable. For
Propagation and Planting
stratification, nuts are placed in alternate layers with
Plant propagation: Generally walnut is propagated suitable moist medium such as sand, vermiculite or
through sexual (seed) and asexual methods viz grafting, peat moss in the container which is then subjected to
budding and rarely propagation through cutting and cold treatment (3-50) for period of two-three months.
 666 Fruit Production in India

During this period the nuts should be prevented from desired temperature around the union, wrapped graft
drying and should get proper aeration. Stratify walnut is covered by aluminum foil. The thermostat is connected
seeds either by early fall planting (planting in December with the sensor which is inserted between the cables.
where natural stratification occurs) or by moist cold When the temperature in the cables rises above the fixed
stratification for spring planting (end of February). (26+2ºC) the thermostat become active and supply of
Rodent’s damage should be protected. After stratification electricity is automatically cut off. This system
walnut seeds soaked for 24 hours in 125 to 250 ppm GA3 maintains only temperature, however, the maintenance
or 30 minutes in 10 per cent H2SO4 germinate better. of desired humidity (80- 90%) is not possible.
At higher elevation, there is no need to stratify as they
Whip grafting is the best method to graft walnut if the
are naturally stratified by exposure to outside winter
size of stock and scion are same. For the large size stock,
temperatures in a cold room or shady open area. Dip
used modified whip grafting. Scion is a short piece of
the seeds for one minute in hot water (that is, almost
shoot containing dormant buds that is united to the
boiling condition) before fall planting or stratification.
rootstock on the upper portion of the graft and form the
Sowing: For fall or spring planting prepare the nursery shoot system of the composite plant. The procedure is
carefully. Plant the seed in about 4 -10 cm deep. The as follows: The materials require for grafting are sharp
distance between the seeds and rows for sowing depend knife, grafting tape, wax and aluminum vessel, burner
upon the period for which the seedlings are to be left in (to melt wax), and plant materials (scion and rootstock).
nursery. Following spacing is opted. Use 1- 2 year old healthy rootstocks of Juglans regia
and freshly collected scions of known cultivars for
Seed to seed Row to row
grafting. Use only dormant scion and active rootstock
1. For one year 25 x 25 cm 75 x 75cm
for grafting. Make a slanting cut (about 5 cm) with a
2. For two year 30 x 30 cm 100x 100cm.
sharp knife at the base of the scion and at the top of
Undercut the seedlings when it is about 30 cm tall. rootstock. For the stock, make the cut in the bark portion
Irrigate the seedlings thereafter. It takes more than or lesser cut on wood portion depending on scion size.
two months for the seed to germinate in the nursery for Fit the cut sections of stock and scion together making
fall planting without stratification while for spring sure that the cambial layers of both stock and scion fit
planting (after cold stratification), the seeds germinate perfectly. Tie the fitting (graft union) with a grafting
within 1-2 weeks after planting. Thin the seedlings, if tape. Dip the scion portion of the grafted plant into the
required, a few days after undercutting. Make sure that hot wax to prevent scion desiccation. Grow the grafted
the nursery is free of weeds. Irrigate frequently and walnut in the nursery or in pots with a growing medium
fertilize the seedlings to correct soil deficiencies. Areas prepared as 1:1:1 ratio of sand, Farm Yard Manure
devoid of rain during the summer should be mulched to (FYM), and soil. Add basal fertilizers. Remove the
conserve moisture. Mulching also control weeds, suckers or shoots growth from the stock as and when it
enhance germination and boost the growth of the plants. appears. Irrigate the nursery 1-3 times a week depending
If nursery is properly managed, seedlings attend grafting upon the weather condition and soil types. Take note if
size within a year time. In order to ensure better bleeding occurs during grafting, that is, sap flow due to
establishment of grafts after the transplanting, the tap root pressure, as it kills the grafts. Control the bleeding
root of seedlings should be cut off 20- 25 cm below ground by either cutting off the rootstock 5-8 cm above the
level in dormant season, a year before the actual grafting site about two weeks beforehand or make few
transplanting. 2-3 year old seedlings under open slanting cuts in the rootstock through the bark into the
conditions and 1-2 year old under controlled conditions wood as low as possible below the grafting point, if latter
give higher graft success. any bleeding occurs, it occurs through this cuts. You
can also stop irrigation for about two weeks prior to
Grafting: The ideal rootstock thickness get maximum
grafting. In zero energy high humid polyhouse system,
graft success is 1.5-2 cm, at 15-20 cm above the ground
an indigenous system, higher success has been recorded.
level. For higher success bench grafting should be done
Construction is also cheaper.
15 cm above ground level during mid- February to mid-
March; however, the best time for budding is mid June Top- working: For walnut orchard establishment, plant
to mid July. The most suitable time to graft walnut the walnut seedlings directly in the production field
under ambient condition is towards the end of dormancy without nursery grafting and top-worked two years later.
or early spring season (mid- March) especially in areas This is the best method of orchard development in. To
of 700-2100 meters above sea level. If the nursery is avoid sap bleeding, either head back the stock before
located at higher altitude, use grafting cable or hot two weeks before actual operation or make few slanting
callusing technique to maintain suitable temperature cuts on the stock through the bark into the wood just
for walnut grafting. In this technique an insulated cable below the grafting point so that if any bleeding occur
which is covered by adhesive strips increase the latter, it occurs though these cuts. Select disease free
temperature around the graft union. To maintain the young trees for top- working. Cut the dormant scion
Walnut 667

wood from the parent tree in advance. Wax the scion, on the tree type and vigour. For small and compact
pack properly, and store in the refrigerator at 40C. Do tree, use initial spacing of 5 x 5 m and adjust this to 10
bark grafting for top- working in late spring (end of x 10 m at maturity (high density planting). For highly
March to April) or when new growth has taken place. fruitful lateral bearing but vigorous cultivars and
Wrap the graft union with thick plastic sheet paint the terminal- bearing vigorous cultivars, maintain an initial
stem portion with white wash. Remove the shoots other spacing of 6 x 6 m and finally adjust to 12 x 12 m. As a
than the scion growing on the plant. general guide, use the following spacing: Seedling trees
12 x 12 m, grafted on Juglans regia 10 x 10 m, grafted
Micro- propagation: Great variation has been
Juglans nigra 8 x 8 m, when pollinizer are required,
observed, in morphological and biochemical characters
place them in permanent position to avoid their
among distinct geographic ecotypes. At present,
elimination during the temporary tree removal. Every
although, the tree improvement programmes for Juglans
eight row, a pollinizer variety is planted perpendicular
species have made some progress (eg. new promising
to the usual direction of the wind.
clones and varieties have been produced) problems in
vegetative propagation of selected walnut trees are Pit digging and filling: On clayey or not very fertile
holding back the improvement of the species and thereby soil, dig a pit 1 m deep and 1 m in diameter. For loamy
their wider use (Zobel and Talbert 1984). Generally, the soil, dig a pit 0.3 m deep and 0.3 m in diameter. Break
most popular way of walnut vegetative propagation is the hard layer on any side of the pit. Keep the top surface
that of grafting which is, however, labour intensive, soil from the subsoil separate. Fill the pit with mixture
time consuming and costly. On the other hand, of rotten FYM and top surface soil at the ratio of 1:2.
propagation by cuttings is very difficult due to their low
Planting: Order for purchase planting materials in
rooting ability (Mcgranahan et al. 1988, Land and
advance before planting. If planting is delayed lay the
Cunningham 1994). In the last decade, other more
seedlings in a trench. Cover the root portion with moist
sophisticated techniques (micro-propagation,
soil. Do not allow the seedlings to dry. Prepare a hole
embryogenesis etc.) have been investigated for the
just enough to accommodate the entire root system.
successful large scale propagation of walnut. Rodriguez
Spread the roots around in all sides and cover with soil.
and Sanchez- Tames (1981) and Rodriguez (1982a,b)
Make sure that the graft union is above the soil zone.
were among the first to report establishment of walnut
Plant the seedlings in late dormant/ early spring season.
cultures in vitro and to describe the development of
Irrigate immediately. In the first year prune the young
shoots or roots from cultured walnut embryos. Later, a
tree by cutting the top above the graft union but leaving
large amount of work was conducted on different walnut
5- 6 buds. Paint the trunk with whitewash. Stake the
species using different types of explants, media, culture
young tree in the windy area. As the tree leaf out and
conditions and rooting techniques, with encouraging
growth occurs, pinch the growing tip from the shoots
results (Jay- Allemand and Cornu 1986, Gruselle et al.
other than the one selected as a main trunk.
1987, Cornu and Jay- Allemand 1989). Most of the above
work was based on a medium developed by Driver and Tree Architecture and Pruning
Kuniyuki (1984) (DKW medium) for the in vitro culture
Training: Train the walnut after the first year using
of Juglans spp. Research with Juglans spp. has focused
the modified central leader system (delayed open centre).
on several different biotechnological approaches and
After the 1st years’ growth, head back to 2 m of its
initial explant material for the purpose of clonal mass
height. Remove all the lateral shoots on the leader,
propagation and subsequent genetic improvement
leaving one or two shoots at lower level on the trunk to
(Preece et al. 1989, Rodriguez et al. 1989). Progress in
provide shade on trunk’s south and west sides. To avoid
developing techniques for in vitro culture of about five
narrow crotches, remove all primary buds above 1.5 m
Juglans spp and hybrids has been very successful over
from the ground to force secondary buds to grow. Select
the past 10 years (Pijut 1997).
main scaffold limb 1.6 m above ground. Choose primary
scaffold limbs in all directions on the trunk. Ensure
Planting and layout that limbs have wider angles, more than 30 cm apart
Layout and tree density: Layout the orchard in vertically on the main trunk. Remove the rest of the
square or quincunx (diamond) design in gentle slope vigorous branches leaving small branches undisturbed
and flat valley. Use contour planting for hilly and steep for fruiting. Head back all the selected limbs on terminal
slope. Consider the number of trees to plant per unit fruiting cultivars but not for lateral fruiting ones. In
area in terms of both short- and long-term productivity the later (after 2-3 years), allow the secondary scaffold
of an orchard. The short-term objective is to have limbs on primary scaffolds to grow by removing the extra
maximum numbers of trees to obtain the earliest vigorous branches. Head back all scaffold limbs every
economic production potential per unit area. If the initial year in terminal fruiting cultivars. For cultivars that
tree density is too high, remove specific number of trees are highly fruitful on lateral buds, head back a large
8-10 years after planting. Space the plants depending number of new shoots on the periphery to reduce fruiting
 668 Fruit Production in India

and increase vigorous shoot growth throughout the with a vibratool or other device. Each catkin may
trees’ periphery. On terminal bearing cultivars, head produce 2 million pollen grains.
back selected branches and thin out limbs completely.
Early nut breeder (Crane et al. 1973) concluded that
Pruning: Carry- out pruning operation in the dormant sub- freezing temperatures would kill walnut pollen.
season but early spring is preferable. Further delay This idea persisted until recently. Walnut pollen
causes excess bleeding. For young tree (16-17 year old) seems to lose its viability in a week or less at room
and middle aged trees (34-35 year-old) cut back 3- year temperature. Forde and Griggs (1975) showed that J.
old shoots. For mature trees (40 year- old), cut back 4-5 regia pollen remains viable for at least 1 year in a freezer
year-old shoots. Initiate selective thinning out of limbs at -190C. Recent work by Luza and Polito (1987) showed
in the top and sides of the tree before overcrowding that fresh J. regia pollen ranges from 4.6 to 12.1 per
becomes serious. Do not remove more than 25 per cent cent moisture and that germination declines as pollen
of the branch structure at any time. Treat all the cut moisture falls below 5 per cent, but if the dry pollen is
surfaces with a tree wound dressing with copper held in a water saturated environment it remains its
oxychloride or Bordeaux paste. ability to germinate in vitro.
Flowering and fruiting: Usually new leaves sprout
Flowering Physiology
and flowers blossom on the walnut tree in April. The
Pollination: Walnuts are similar to pecans in that pendulum like staminate male organ of the plant, catkins
the time of pollen shedding does not always overlap well grow individually from the top of the leafless stems of
with the time of female flower receptivity to pollen. Hence, the previous season. The cylinder shaped catkin of the
although most are self- fertile, they sometimes require walnut grows to about three inches long and three-
another cultivar for pollination, since the timing of the quarters of an inch in width. The walnut catkin
function of male and female flowers is different. This comprises of a large number of closely packed and
condition is referred to as dichogamy. Two possible forms minute flowers of a plain arrangement. Each of these
of dichogamy are protandry (meaning first male) in tiny flowers has a short shoot, a supporting bract, two
which the pollen is shed before the female flower become tangential bracteoles, and a perianth of six leaves
receptive and protogyny meaning first female, in which surrounding an indefinite number of nearly stamens
the female flower becomes receptive to pollen before pollen that are directly attached to the base without any stem.
is shed. Most walnut are protandrous, some cultivars, The walnut bears female flowers in a collection of four
such as Payne are only slightly dichogamous and can to eight flowers at the top of the green stems that grow
be planted in solid blocks because they are self– on the same year. Each of these female flowers comprises
pollinating. Furthermore, the situation is aggravated a supportive perianth made up of four leaves in two
by short periods of both pollen viability and stigma pairs each. In addition, their bracteoles and the twin
receptivity (Polito 1985). Pollen is normally released 10- disposition of the fruit is suggested by comparatively
12 days after bud burst; full bloom of female flowers is large plump stigmas.
usually 15- 18 days later although this varies between
cultivars. Nutrition, Water Management and
Walnut flowers are anemophilous representing all the Abiotic Stresses
characteristics of wind pollination ie. non- sticky, light Manures and fertilizer: For the accurate diagnosis
pollen is produced in abundance and stigma is protruded, of nutritional needs of the plant soil sampling or leaf
feathery and remains receptive for few days. Effective tissue sampling should be done. The leaf samples are
pollination, however, can be assured by planting the taken in the month of July to August and then analyzed
early and late cultivars whose pollen shedding overlaps in laboratory for the formulation of nutrient guide. The
each other. following guide can be used as a indicative amount of
Pollen collection and storage: Walnuts are self- NPK for the walnut in the absence of plant and soil
fruitful and cross– compatible and in majority of the nutrients analysis information (Table 3).
cultivars, since catkins develop very little after they
Table 3: Fertilizer schedule for walnut:
are removed from the tree, they must be ready or almost
ready to shed pollen when gathered. Probably the best Age in years Fertilizer/ tree (g)
catkin for pollen production is one that has already had
Urea DAP MOP
a few of its anthers dehisce. Most of the anthers will
dehisce in about 24 h the catkins are spread thin on 1 20 65 30
paper or on fine–screen trays over paper, at room 2 30 65 40
3 40 65 50
temperature. The pollen can then be separated from 4 60 65 65
the rest of the catkin by sieving through cheesecloth or 5 85 65 80
fine screen. Sieving is most rapid if the screen is vibrated 6 136 65 125
Walnut 669

7 190 65 165 walnut green aphid (Chromaphis juglandicola Kalt).

8 290 70 250 Among the different pests prevalent in the walnut
9 390 110 330
10 490 130 415 producing areas, of India (especially Jammu and
11 585 160 500 Kashmir) walnut weevil is considered serious in some
12 780 215 665 places. Defoliation due to Chaetopractus odata has
13 980 270 830 occasionally been observed in some areas. Among the
14 1175 325 995
15 1565 435 995 common diseases, leaf spot, powdery mildew and gall
16 1960 540 1245 canker are of some significance.
17 2460 650 1995
18 2950 760 1825 Diseases
19 3415 975 2155
Walnut blight (Xanthomanas campestris
20 and onwards 3915 1085 2400
pv.jugalandis): Also known as bacterial blight, it is
caused by Pseudomonas juglandis or Xanthomonas
Full dose of P and K and ½ dose of N should be applied
campestris pv juglandis. It usually causes black spots
two weeks before expected bloom. Rest ½ of N should be
on leaves, holes and blotches on fruit, and possibly
split into two equal doses, which should be applied three
dieback of shoots. Fruits are usually damaged
weeks after fruit set and during early July.
extensively, especially when the male catkins are
Inter- cropping: Inter- crop walnut trees with legume affected walnut blight affects mainly young growth and
fodders in areas traditionally under pasture farming nuts, and is the most damaging when it occurs during
system. For other farming systems, use low growing cool and wet periods, around flowering time (so it is
and non-competitive vegetables such as non- climbing most dangerous to species which leaf early). The bacteria
beans and other legumes, tomato, and onion and more will overwinter in seemingly healthy buds, launching a
competitive vegetables such as chili and asparagus. new attack when new growth is at hand. Treatment
Inter- crop during the first 4- 6 years after planting consists of cutting out damaged parts (cutting too much
only. If sustained inter- cropping is planned from the is better than cutting too little) and burning them.
establishment of the orchard, modify the spacing, that Bordeaux mixture may help too. Prevention may be
is, much wider between rows of mature trees. attained by using a soil with a pH above 6, avoiding
excessive nitrogen, excessive wetness and allowing for
Irrigation: At least 760 mm of rain is required and
good aeration by pruning. The most effective rate of
irrigation will benefit trees in drier areas. Deficit
irrigation (where a mild water stress is applied mid metallic copper is 4.5 Kg/ ha (Teviotdale et al. 1985).
season after flowering but before the plant has strong Walnut Leaf Blotch: This disease also goes by the
carbohydrate demand for nut fill) may improve flowering name of Walnut anthracnose, its scientific names being
and nut production and reduce vegetative growth. Gnomonia leptostyla, Marssonina juglandis or
Supplemental irrigation in dry spring and early summer Marssoniella juglandis. This widespread fungus, it
before the start of monsoon period i.e. from April to June causes nuts to turn black and then fall, as well as brown
is beneficial. No irrigation is needed from June onwards blotches on leaves and fruits. It also causes a great
until harvest in areas receiving monsoon. Wet weather number of leaves to fall. This disease spreads well in
at harvest cause shell and kernel stain. Trees can be wet weather, usually during May and early June and
damaged by high water table and needs drainage to at will overwinter on leaf litter. The only treatment consists
least 3 m. The plants are susceptible to fungal root rots of burning fallen leaves and maybe using a Bordeaux
under prolonged exposure to wet soil. The plant dislikes mixture. The disease has been reported from Kashmir
cool and wet weather in spring. This predisposes the valley and other walnut cultivating regions (Parihar et
tree to bacterial blight which can be a serious disease in al. 1980). Other diseases are common to several plants,
wetter climates. including walnut trees, and the most common are:
Weed control: the use of chemicals has become Blackline: This is a dangerous disease caused by a
prevalent in controlling weeds instead of cultivation. virus (a strain of the cherry leaf roll virus - CLRV-W),
The herbicides, simazine and diuron have been
and it only affects non- regia rootstocks. Plants affected
successfully used in weed control of young and
by blackline suffer yellow drooping leaves; stunted
established walnut groves for four months.
growth and early leaf fall. The name of the disease comes
from the typical dark line between the stock and grafted
Major Diseases, Insect- pests and their
tissue. The tree may suffer dieback and death. The virus
Management spreads through pollen, seed, and infected grafts, so it
Walnut trees are susceptible to pests and disease such tends to spread fast
as walnut weevil (Alcides porrectirostris Marsha),
walnut blue beetle (Monolepta erythrecephale), Nectria: Walnuts are affected mainly by two types of
Sanjosescale (Quadraspidiotus perniciosus Comst), and Nectria, namely Nectria galligena (Nectria canker) and
 670 Fruit Production in India

Nectria cinnabarina (Coral spot). N. cinnabarina is the of the kernel and feed in the husk. They may also
more dangerous, since it can lead to rot, wilting and stain the fruits.
dieback, while N. galligena causes cankers. Any
Disease and pest resistance: Disease and pest
infection should be cut and burned.
resistant traits in fruit trees are essential to realize
Insect-pests the full yield potential augmenting the profit of the
Pest and disease management is a problem in walnut grower. Resistance in walnut will, therefore be
because of giant trees. Planting of grafted trees, using desirable against anthracnose, Indian gypsy moth and
dwarfing rootstock, training and pruning and choice blister mite. In the process of incorporating the pest
of lateral bearing cultivars altogether help in reducing and disease resistant genes, the commercial
the size of walnut trees considerably making them characteristics should not be overlooked because,
amenable to spraying and harvesting. In controlling however, a resistant cultivar is evolved, it would not
pests and disease, the sanitary measures can play an be accepted by the growers unless it gives good yield
effective role but are often overlooked. Sanitary of high quality fruits. PI 159569, an introduction from
measures involve the planting of healthy trees, Afghanistan had never shown symptoms of bacterial
precautions against the transfer of disease and insects blight (Xanthomonas juglandis) in California but could
through tools used in pruning and cultivation, removed not be grown for commercial cultivation due to its shy
of diseased branches and leaves by pruning and bearing habit (Forde 1975).
destroying these by burning (Johnson1969).
Harvesting of Fruits
Walnut weevil: (Alicides porrectirostris Marsha): The
plant parts affected are leaves and fruits. The eggs are Walnut trees from seedling bear nuts in 10-12 years
laid on fruits which on hatching bore deeper into the and full commercial production 18-20 years from
fruits and fed on kernels causing premature fruit drop. planting. Grafted walnut starts production from 4-5
After the emergence, adults feed on petioles and tender years after planting and it takes 8-10 years for
shoots. The grub is more destructive because it kills commercial production. A fully grown, big size tree
new shoots upto old wood the grubs are 12-16 mm produces as high as 100-150 kg nuts but the average
long creamy white in colour. The adults are 9-12 mm yield is 40 kg per tree. Maturity and harvesting of fruits
long, black brown in colour. It has two generations. start from August- October depending on the elevation
One comes in April-July and second comes in June- and cultivars. Delay in harvesting causes deterioration
September. First generation is more damaging as it in the nut and kernel quality (brown colour kernel).
feeds on developing kernels while second generation The lightest kernel colour commands higher price in
often feed on rind. Kernels turn into black mass. It is the international market. The nuts are mature when
only serious in some places. It can be controlled by the nut dehisce and fall. In higher altitude, kernel
collection and destruction of fallen nuts. Proper matures earlier to hull dehiscence while in the lower
sanitation is maintained which is very important for altitude, hull dehiscence take place prior to kernel
its control. Smaller and medium plants are sprayed maturity. The walnut kernels are mature when the
with 0.05 per cent quinalphos during the month of May. packing tissue between and around the kernel halves
has just turned brown (this stage is known as PTB
Walnut leaf gall mite: Aceria erinoea, previously
stage i.e. packing tissue turns brown) and crop can be
known as Eriophyes erineus. This disease causes raised
harvested if 80 per cent of the nut can be removed
bumps (around 1.3cm/ 0.5 inch long) on the leaves
with 95 per cent of them hullable. Harvest the
resembling a caterpillar’s body. The mites are only
remaining nuts few days after the first harvest. Some
0.1mm wide, lurking in the winter in young buds and
nuts fall on the ground after splitting of the hull in
damaging them before they even develop the leaves.
natural way while others are forced to drop down by
It is difficult to get rid of this pest, but fortunately the
beating with long poles (mechanical harvesting). The
damage dealt is usually small and not life threatening
fallen nuts are collected in huge heaps in the orchard
for the plant.
and covered with leaves and grass for hull fermentation
Walnut tree minor pest: These pests are not taking about 9- 15 days. Dehulling, washing and
encountered frequently, but it might be useful for you cleaning are done manually which causes staining of
to know them Panonychius ulmi - red spider mite hands. The nuts are spread on a sheet or floor to dry
Lecanium coni-European fruit Lecanium, Pratylenchus them up to 8 per cent moisture level. Sometimes to
vulnus- root lesion nematode, Chromaphis juglandicola- improve the appearance of nut, theses are bleached
walnut aphid. The following pests are (usually) found with alkali or acid solution. Grade the nuts according
in north America, Conotrachelus juglandis- walnut to size, colour, and variety. Store the nuts in gunny
weevil, Amyelous transitella- Navel orange worm, bags in small well ventilated rooms free from excessive
Datuna integerrima- walnut caterpillar, husk flies- are humidity. Nuts have long shelf- life and it can be sold
found in the USA and Canada: they may spoil the flavor in extended marketing season.
Walnut 671

In- shell walnuts for export are graded and sold under Jay-Allemand C and Cornu D 1986. Culture in vitro d’embryons
marketing rules set in 1966 in J & K. Those of a isoles de noyer commun ( Juglans regia L.). Ann Sci For
43: 189–198.
minimum size of 32 mm, a good cracking rate of over
90 per cent and the fewest internal defects are assigned Johnson WT 1969. In: Handbook of North America Nut trees.
(ed RA Jaynes), The WF Humphery Press Inc Geneva
the grade designation of India Super-special. Nuts with New York, Pp: 67-156.
a minimum size of 30 mm are designated India- special
Land SB and Cunningham M 1994. Rooted cutting macro-
and nuts of 24-26 mm are graded India- I and India- B
propagation of hardwoods. In: Applications of vegetative
grade. The kernels of the Juglans regia produced in propagation in forestry’. Proc of the Southern Regional
India are assigned the grade designation of India light Information Exchange Group Biennial Symposium on
half; they have a light creamy and light golden colour. Forest Genetics. Foster GS and AM Diner (eds). Published
by Southern Forest Experiment Station New Orleans,
The other designations used for the halves that have
Louisiana. Pp: 75–96.
cotyledons of fully developed kernels are known as: India-
special light half, Indian Light broken, Indian Light Leslie C, McGranahan G, Hackett W, Manterola N, Dandekar A,
Escobar M, Bennett A, Haroldsen V, Burchell T, Beede B,
pieces, Indian Light crumbs, Indian light-my-fire, Indian Olson B, Anderson K Ke, Grant J, Caprile J, Coates B
light amber halves, Indian light amber broken, Indian Buchner R, Hasey J, Sudarshana M 2009. Walnut
light amber pieces, depending upon the colour of the Improvement Program . Walnut Research Reports Pp: 32
kernel. Manning WE1978. The classification within the Juglan
dandaceae. Annals of Missouri Botanical 59: 1058-1087.
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rrr

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