Associated Forest Cover
provided by Silvics of North America
Black walnut grows in many of the mixed mesophytic forests but is
seldom abundant (43). Usually it is found scattered among other
trees; pure stands are rare, small, and usually located on the
forest edge. Black walnut is a common associate in five forest
cover types (16): Sugar Maple (Society of
American Foresters Type 27) in the central hardwood zone and the
Appalachian highlands, Yellow-Poplar (Type 57) at lower
elevations of the Appalachians, Yellow-Poplar-White Oak-Northern
Red Oak (Type 59) at lower elevations, Beech-Sugar Maple (Type
60) in the Midwest, and Silver Maple-American Elm (Type 62) in
southern Ontario washboard swamps where high and low ground
intermingle.
It is also found as an occasional associated species in four cover
types: Chestnut Oak (Type 44), White Oak-Black Oak-Northern Red
Oak (Type 52), Northern Red Oak (Type 55) on moist sites, and
Sassafras-Persimmon (Type 64) in older stands.
Chief associated species include yellow-poplar (Liriodendron
tulipifera), white ash (Fraxinus americana), black
cherry (Prunus serotina), basswood (Tilia americana),
beech (Fagus grandifolia), sugar Maple (Acer
saccharum), oaks Quercus spp.), and hickories (Carya
spp.). Near the western edge of its range, black walnut may
be confined to floodplains, where it grows either with American
elm (Ulmus americana), hackberry (Celtis
occidentalis), green ash (Fraxinus pennsylvanica), and
boxelder (Acer negundo), or with basswood and red oak
Quercus rubra) on lower slopes and other favorable sites
(10).
No universal vegetative indicator of a good walnut site is known,
but the presence of Kentucky coffeetree (Gymnocladus dioicus)
seems to indicate such a site (10,43). In general, where
yellow-poplar, white ash, red oak, basswood, sugar maple, or
slippery elm (Ulmus rubra) grow well, black walnut
thrives also.
An antagonism between black walnut and many other plants growing
within its root zone has been recognized and is attributed to
juglone, a toxic substance found in the leaves, bark, nut husks,
and roots of walnut trees (32,42). Some tree species apparently
are immune, but others, such as paper birch (Betula
Papyrifera), red pine (Pinus resinosa), white pine
(P. strobus), Scotch pine (P. sylvestris),
and apple (Malus spp.), reportedly are sensitive.
Tomatoes are especially susceptible. In a laboratory study,
juglone at high concentrations was lethal to four coniferous
species, but seedling growth was actually promoted when exposed
to minute concentrations (19). Although tomatoes are especially
susceptible to juglone, black walnut trees may be compatible with
some agricultural crops and might even improve the growth of
bluegrass (Poa spp.).
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Climate
provided by Silvics of North America
The growing season within the range of black walnut ranges from
140 days in the north to 280 days in western Florida (10,43).
Annual precipitation is less than 640 mm (25 in) in northern
Nebraska and 1780 mm. (70 in) or more in the Appalachians of
Tennessee and North Carolina. Mean annual temperatures range from
about 7° C (45° F) in the north to 19° C (67°
F) in the south. Temperatures as low as -43° C (-45° F)
have occurred where walnut grows, but few races of black walnut
can tolerate such low temperature. Within black walnut's optimum
range, the average annual temperature is about 13° C (55°
F), the frost-free season is at least 170 days, and the average
annual precipitation is at least 890 min (35 in).
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Damaging Agents
provided by Silvics of North America
Black walnut is damaged by a number of
insects. In southern Illinois more than 300 insect species were
found on black walnut (49). Even though many insects feed on
black walnut, only a few are considered serious pests. Two of the
most common defoliating insects are the walnut caterpillar (Datana
integerrima) and the fall webworm (Hyphantria cunea).
They are commonly found eating the leaves beginning in
midsummer and continuing until September. Important boring
insects are the ambrosia beetle (Xylosandrus germanus), which
may introduce a Fusarium fungus into the tree, causing
dieback and resprouting from the base of the tree; the flatheaded
apple tree borer (Chrysobothris femorata), which feeds in
the phloem and outer sapwood area as larvae and on the foliage as
adults; the walnut curculio (Conotrachelus retentus), which
damages developing nuts when the larvae bore into them and cause
great losses during the so-called "June drop" of
walnuts; and the walnut shoot moth (Acrobasis demotella),
which damages the terminal buds in early spring when the
larvae bore into the still unexpanded bud, causing multiple forks
and crooks in the main stem. The pecan leaf casebearer (Acrobasis
juglandis) is closely related to the walnut shoot moth but is
a much less damaging pest of black walnut. Important sucking
insects are aphids or plant lice (Monellia spp. and Monelliopsis
spp.), which suck the juices from leaves and often deposit a
sticky substance called "honey-dew" on the leaf surface
that may turn black and prevent photosynthesis; and the walnut
lace bug (Corythucha juglandis), which causes damage when
the adults and nymphs suck the sap from the lower surfaces of
walnut leaflets.
Black walnut is susceptible to only a few serious diseases, but
their impact is significant. Two serious root rot diseases found
in seedling nurseries are caused by the fungi Phytophthora
citricola and Cylindrocladium spp. An important mold
of stored seed and seedlings is associated with Penicillia
and other normally saprophytic fungi (24). Walnut
anthracnose, caused by the fungus Gnomonia leptostyla, is
a leaf spot disease that begins during wet spring weather,
although symptoms may not become visible until June or July (49).
Another important foliage disease is target leafspot which is
caused by the fungus Cristulariella pryamidalis and is
responsible for premature defoliation (38). A newly discovered,
serious leaf spot disease is caused by the fungus Mycosphaerella
juglandis (24).
Important stem diseases caused by fungi are the Fusarium cankers
caused by several species of Fusarium and the perennial
target canker (Nectria galligena) commonly known as
Nectria canker (49). Cankers usually occur on the main stem where
a branch broke off and left an open wound.
Animals damage black walnut in several ways. Deer browse on buds
and rub antlers against young trees. Mice and rabbits gnaw on the
stems of young trees during the winter, and squirrels dig up and
eat direct-seeded nuts and feed on green and mature nuts still on
the trees. Perching birds break the terminal or new branches from
the tree, and the yellow-bellied sapsucker drills holes through
the bark during late winter or early spring (49). Some trees may
be nearly girdled with peck holes.
Decay, dieback, and frost also cause damage. At times dieback and
frost damage may be extensive. Late spring frosts kill succulent
new growth and thus reduce height growth and destroy desirable
form. Late winter warming periods sometimes cause walnut trees to
break dormancy prematurely, resulting in freezing injury to the
stem tissue (13,37).
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Flowering and Fruiting
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Depending on latitude, black
walnut flowers generally begin to appear about mid-April in the
South and progressively later until early June in the northern
part of the natural range. Flowering and leafing out occur at
approximately the same time and always early enough for possible
damage by late spring frosts (18,27).
Walnut is monoecious; male flowers, which are slender catkins,
develop from axillary buds on the previous year's outer nodes,
while female flowers occur in short terminal spikes, ranging from
a few to many, home on the current year's shoots. Flowering is
dichogamous, and protogyny (the female flowers appearing first)
is more common than protandry (male flowers appearing first)
(33,34). Because of its dichogamous flowering habit,
self-pollination is unlikely. However, individual trees usually
are not self-sterile; if they are not pollinated by neighboring
trees, they may set self-fertilized seeds (3). Fertilization
follows 2 to 5 days after pollination, succeeded by development
of the husk, the shell, and finally by the seed itself (18).
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Genetics
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Population Differences
Black walnut contains great genetic variation for growth and
survival, and an important part of this variation is related to
geographic origin (8). Preliminary seed collection zones have
been recommended (15). Geographic variation among stands is three
to five times greater than local (within stands) variation for
characteristics such as growth rate, dates of foliation and leaf
drop, twig maturation, and degree of winter dieback (17). Genetic
gains can be made through selection within a designated seed
collection zone. Generally, trees from seed collected south of
the planting site grow as fast or faster in height and diameter
than trees from local or northern sources (7,9). Both duration
and rate of growth are responsible for the growth differences. In
1969, trees from Mississippi and Texas seed sources planted in a
southern Illinois plantation grew in height for 134 days compared
to 93 days for trees from northern Illinois and Iowa sources (5).
On the average, height growth continued 1 day longer for every 24
miles south of the planting site that seed was collected (6).
Duration of diameter growth was less closely related. However,
trees of southern origin grew fastest.
Flowering phenology, seed weight, kernel percent, nut
crackability, foliage characteristics, grafting and budding
compatibility, rooting capacity of layered trees in stool beds,
autumn leaf retention, cold resistance, and growth rates vary
widely among black walnut families (17).
More than 400 black walnut cultivars have been named and released
during the past century. Twenty of the most popular, including
origin and nut evaluations, are listed by Funk (18). Three
timber-type walnut clones chosen for outstanding straightness,
anthracnose resistance, or late spring foliation have been
patented by Purdue University.
Hybrids
Wright (54) has pointed out that species that can cross within a
genus usually have distinct (often adjacent) ranges, while
species that occupy the same sites in the same regions develop
barriers to hybridization. Juglans seems to follow this
pattern; J. nigra and J. cinerea often grow
together but apparently never cross naturally, while all other
walnut species (at least in the western hemisphere) are almost
completely isolated. Thus, easy crossing might be expected among
the morphologically similar North America Rhysocaryon walnuts.
One example is the "Royal" hybrid between J.
nigra and J. hindsii produced by Burbank in about
1888. This hybrid begins to bear viable seed by age 5 and
produces exceptionally large nuts (50). The hybrids are vigorous
and have been recommended for timber areas. Black walnut has been
crossed with other species of Juglans in attempts to
increase nut production, to produce a thin-shelled nut, or to
produce a faster growing tree. Juglans can be divided
into three sections: the black walnuts, the butternuts, and the
Persian/Carpathians. A somatic chromosome number of 32 is
consistent for all the species reported to date (18).
Crossing between the black walnut and butternut sections is
difficult or impossible. A cross between J. nigra and
J. ailantifolia is the only one recognized between the
black walnut and butternut sections. However, J. regia can
hybridize with species in both the other sections, although the
crosses are not always easy.
Artificial hybridization is simple but time consuming. Each
pollination may yield two or three nuts and a season's work only
a few thousand nuts.
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Growth and Yield
provided by Silvics of North America
On the best sites, young black walnut
trees may grow 91 to 122 cm (36 to 48 in) in height per year
(28). The best tree in a southern Indiana plantation at age 7 was
11.9 cm (4.7 in) d.b.h. and 7.6 in (25 ft) in height (9). In a
southern Illinois plantation (site index 24.4 m or 80 ft at base
age 50 years), the best tree was 21 cm (8.3 in) d.b.h. and 12 m
(40 ft) tall at age 14 (1). However, the average size tree in the
plantation was 12 cm (4.8 in) d.b.h. and 7 m (24 ft) tall. Even
on less favorable sites (site index 21.3 m or 70 ft), trees reach
heights of 12 to 15 rn (40 to 50 ft) and diameters of 15 to 25 cm
(6 to 10 in) in 20 years (28). In contrast, diameter growth of
black walnut planted on Kansas strip mine spoil banks averaged
only 6 mm (0.25 in) per year and height growth averaged only 33.5
cm (13.2 in) per year during the first 10 to 12 years (10). On
Illinois spoil banks trees grew best on the lower slopes, on
areas formed from limestone parent material and containing a high
percentage of fine soil, or if underplanted with black locust
(Robinia pseudoacacia). In two 10-year-old southern
Illinois plantations, walnut trees in mixture with autumn-olive
(Elaeagnus umbellata), a nitrogen-fixing species, were 89
percent taller and 104 percent larger in diameter than walnut
trees in pure walnut plots (41). In an Indiana study, 10 years
after autumn-olive was interplanted into 2-year-old black walnut,
the walnut in the interplanted plots were 2.6 rn (8.4 ft) taller
than those in the pure plots (14).
Mature black walnut trees on good sites may reach 30 to 37 m (100
to 120 ft) in height and 76 to 102 cm (30 to 40 in) in d.b.h.
(28). Trees 40 m (130 ft) tall and more than 244 cm (96 in) in
d.b.h. have been reported in Wisconsin. In Indiana, black walnut
trees were 46 m (150 ft) tall and 183 cm (72 in) in d.b.h. on the
most favorable sites (43). Research and experience indicate that
with proper care it may be possible to produce 41-cm (16-in) saw
logs in 30 to 35 years, and by planting on good sites it may be
possible to produce 51 cm (20 in) veneer logs in 40 to 50 years.
By applying some basic cultural practices, such as release and
pruning, to established trees, growth and quality can be greatly
increased in only a few years.
Board-foot volume growth rate was correlated with site quality in
midwestern plantations. According to Kellogg's yield tables (23),
predicted yield for site index 21.3 rn (70 ft) at age 75 is 10
times that of site index 12.2 m (40 ft), and yields for site
index 18.3 m (60 ft) are twice those for site index 15.2 m (50
ft). The yield tables also show that periodic annual growth rate
is not constant: maximum growth occurs between ages 40 and 50
years on the better sites.
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Reaction to Competition
provided by Silvics of North America
Black walnut is classed as
intolerant of shade (2). In mixed forest stands it must be
dominant or codominant to survive, although it has survived and
grown in the light shade of black locust. In a mixed hardwood
stand in Indiana, pole-size black walnut responded to crown
release by more than doubling diameter growth over a 10-year
period (39,40). Trees only partially released grew about 50
percent more than unreleased trees. Controlling understory growth
had little effect on growth of the walnut trees. Following
release, dominant and codominant trees continue to grow more
rapidly than those in intermediate or suppressed crown classes,
but strong intermediates often respond most to release (in terms
of growth rate increase). A walnut tree should be considered for
release if it is healthy, has a bole with potential to make a
veneer or high quality saw log, and is small enough that it can
reasonably be left for at least 10 more years. To be effective,
release must be thorough. A rule of thumb is that at least
threefourths of the crown of the released tree should be at least
1.5 m (5 ft) from the crowns of adjacent trees 60 to 100 percent
as tall, and at least 3 m (10 ft) from the crowns of taller
trees. Subsequent releases will be required at intervals of 6 to
10 years to maintain free growing space.
Some bole sprouting can be expected on forest-grown trees that are
released for the first time. Bole sprouts developed on almost
half of the unreleased trees and on almost two-thirds of the
released trees during an Indiana study (39). Sprouts were more
numerous on the unreleased trees (16.1 sprouts per tree) than on
the partially (12.2 sprouts per tree) and completely released
trees (9.2 sprouts per tree), but the sprouts were much larger on
the released trees. The intermediate and suppressed trees had
more sprouts than dominant or codominate trees. Most of the bole
sprouts were above the butt log, and more were on the south side
than on the north side of the trees.
Control of competing vegetation is especially important in new
plantations. In an Indiana study, walnut seedlings established on
formerly cultivated fields and given 3 years of weed control were
100 cm (39 in) taller at 10 years of age, and 15 mm (0.6 in)
larger d.b.h. than trees given 2 years of control (53). Trees
with vegetation controlled 2 years were 40 cm (15.7 in) taller
and 5 mm (0.2 in) larger in diameter than those where weeds were
controlled only 1 year. Broadcast weed control is neither
necessary nor desirable because it aggravates erosion problems.
In a southern Illinois experiment, seventh-year survival of black
walnut planted on a cleared forest site was 94 to 99 percent
regardless of weed control treatment (25). The young trees grew
better, however, when all vegetation or only forbs and grasses
were controlled than when only woody vegetation was controlled or
when no vegetation control was used. Biennial control was no
better than triennial, but annual control was superior. When only
woody vegetation was controlled, frequency of treatment had no
effect.
Pruning lateral branches helps to produce knot-free wood under
open growing conditions that would normally permit most of the
lower branches to persist. The objective of pruning is to produce
a clear bole while minimizing damage to the tree and growth loss.
When needed, pruning should be begun early in the life of the
tree and continued as needed. To minimize damage and promote
rapid healing, branches should be pruned before they are 5 cm (2
in) d.b.h. A neat, clean cut should be made, being careful not to
be cut into the branch collar (44). Ring shakes and dark bands of
discolored wood were associated with 14 of 17 stubs that were "flush
cut" (branch collar removed) 13 years earlier. Pruning young
trees eliminates these problems, but if older trees are pruned,
care must be taken not to remove the branch collars that form
around the bases of dying and dead branches.
When trees are pruned during the dormant season (early spring just
before the leaves appear is best), wounds tend to heal more
rapidly and completely and sprouts from dormant buds near the
wound are less likely to develop. If sprouts do develop, they
should be removed promptly. No more than 25 percent of the live
crown should be released in a single year, and at least 50
percent of the total tree height should be maintained in live
crown (10).
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Rooting Habit
provided by Silvics of North America
The root system of mature black walnut has
been described as combining the deep taproot of more xeric trees,
such as the oaks, with the strong laterals characteristic of more
mesic ones, such as maple. The rooting configuration of
individual trees depends on soil texture and moisture conditions
(47).
The root system is deep and wide spreading, with a definite
taproot, at least in early life. The taproot of a 9-year-old
walnut tree excavated from an Indiana plantation was 2.3 rn (7.5
ft) long and the lateral roots extended more than 2.4 m (8 ft)
from the taproot (11). One-year-old walnut seedlings lifted from
nursery seedbeds have well-developed taproots (51). The mass of
fibrous roots varies with the soil type; the more fibrous-rooted
seedlings develop in the more sandy-textured soils.
Early growth of the seedling root system is rapid. Vertical
taproot extension during the first growing season is great,
especially on drier soils. One researcher reported a taproot
penetration of more than 1.2 rn (4 ft) for 1-year-old walnut
seedlings on a prairie silt loam soil. Another reported 64 to 69
cm (25 to 27 in) for 1-year-old walnut on a more moist site (47).
In the second year of root growth, the taproot continues to
extend and many lateral roots develop.
The depth of walnut lateral roots may vary in response to root
competition with its associates. In one study, lateral roots of
walnut occupied a much shallower position in pure walnut stands
than in mixed walnut-ash stands. This was explained by theorizing
that the ash, having a strongly developed surface root system,
forced the walnut roots into deeper soil layers. Root competition
with Norway maple (Acer platanoides), on the other hand,
was not as intense (47).
Black walnut is moderately tolerant of flooding. Mature trees are
generally killed after 90 days of continuous inundation during
the growing season, although some individuals may survive for 150
days or more. Black walnut is more flood-tolerant than black
cherry, shortleaf pine (Pinus echinata), basswood, and
shagbark hickory (Carya ovata) (47).
The initial root form of black walnut, with its rapidly growing
juvenile taproot and wide spreading laterals, is characteristic
of species that grow on deep, fine-textured soils in regions with
well-distributed summer rains. Such soils maintain a fairly
uniform available water content to considerable depth, and walnut
growing on these soils are able to draw their moisture and
nutrients largely from the more fertile shallow soil while still
being able to rely on the deeper soil layers for survival during
times of drought.
Black walnut forms endomycorrhizae of the vesicular-arbuscular
type. One study revealed that 100 percent of the walnut seedlings
grown in a southern Michigan nursery had endomycorrhizae, but
seedlings grown in a southern Indiana nursery had no mycorrhizae.
A recent study shows that several Glomus species form a symbiotic
relation with black walnut seedlings. Some Glomus, species and
combinations of species increased growth of black walnut (36).
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Seed Production and Dissemination
provided by Silvics of North America
The large edible nut
ripens in September or October of the same year and drops shortly
after the leaves fall. Good seed crops are produced irregularly,
perhaps twice in 5 years. Open-grown trees may produce some seed
when only 4 to 6 years old, but large seed crops do not occur
until the trees are 20 to 30 years old (28). For example, at 10
years of age, a midwest plantation produced 28 kg of hulled nuts
per hectare (25 lbs/acre), and by age 12 production had increased
to 112 kg/ha (100 lb/acre). Best seed production begins when the
trees are about 30 years old and continues for another 100 years.
Seed is disseminated only short distances by gravity and animals.
In a Missouri study, seed production of trees about 28 years old
and 19.3 cm (7.6 in) in d.b.h. was nearly doubled by release and
fertilization (40). Trees released but not fertilized produced 13
percent more nuts than nonreleased trees.
Stratification for 90 to 120 days is required for optimum seed
germination but the necessity and duration of stratification may
vary by seed source (46). In Canada, 69 to 81 percent of nuts
stratified 19 months germinated within 3 weeks of seeding, while
10 to 25 percent of nuts stratified 7 months germinated after 12
weeks (48). When nuts that had not germinated after 12 weeks in
the seedbed following 7 months stratification were stratified for
an additional 9 months, 81 percent germinated within 3 weeks.
Many of the nuts stratified for 31 months germinated while in
storage.
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Seedling Development
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Germination is hypogeal (46). Young
black walnut seedlings are intolerant of shade and are seldom
found under dense tree canopies. Regeneration develops primarily
from seed that squirrels bury and fail to recover. Normal winter
temperatures usually cause the buried seeds to break dormancy the
following spring, but germination is sometimes delayed until the
second year.
Seedlings emerge in April or May the first or second spring after
the seed is planted (46). On deep, rich, moist soils in coves or
well-drained bottom land, seedlings may grow 91 cm (36 in) the
first year and even more the second growing season. Although
black walnut does not make as rapid height growth as
yellow-poplar and white ash on good sites, it generally surpasses
the oaks. In eastern Nebraska, near the western edge of its
range, walnut made much better height growth than oaks or
basswood on a prairie site (10). Walnut developed an excellent
root system and was several times taller than the other tree
species.
Height growth begins slowly in the spring, reaches a peak rate in
late April and May, and is complete by the middle of July or the
first of August. Black walnut loses its leaves somewhat earlier
than other trees and has a growing period of from 115 to 135 days
(10).
Because of its large taproot, planted walnut seedlings typically
survive well. However, they require weed control during the first
2 or 3 years to grow well (26).
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Soils and Topography
provided by Silvics of North America
Black walnut is sensitive to soil conditions and develops best on
deep, well-drained, nearly neutral soils that are generally moist
and fertile (10). These soils are in the orders Alfisols and
Entisols. Although an Ohio study indicated that site index for
black walnut was not significantly related to pH values between
4.6 and 8.2, site index was highest on limestone derived soils
even though some of the soils were acid. Walnut grows best on
sandy loam, loam, or silt loam textured soils but also grows well
on silty clay loam soils (31). Soils with these textures hold a
large amount of water that is available to the tree during dry
periods of the growing season. Internal drainage and depth to
gravel are especially important site characteristics for black
walnut. On well-drained soils, 76 cm (30 in) or more to mottling,
25-year-old trees were 6.6 cm (2.6 in) larger in d.b.h. than
trees growing on imperfectly drained soils, 15 to 76 cm (6 to 30
in) to mottling. Twenty-five-year-old trees on deep soils, more
than 102 cm (40 in) from surface to gravel, were 5.2 m (17 ft)
taller and 6.4 cm (2.5 in) larger in d.b.h. than trees on shallow
soils less than 102 cm (40 in) from surface to gravel (30).
Walnut is common on limestone soils and grows especially well on
deep loams, loess soils, and fertile alluvial deposits. It also
grows well on good agricultural soils that do not have fragipans.
Walnut grows slowly on wet bottom land and on sandy or dry ridges
and slopes. Throughout its range, walnut generally reaches its
greatest size and value along streams and on the lower portion of
north- or east-facing slopes. This is particularly true near the
limits of its natural range. In northeastern Kansas, site index
on alluvial soils was 2.4 rn (8 ft) greater than on residual
soils and 2.7 in (9 ft) greater on northeast than on southwest
aspects (20).
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Special Uses
provided by Silvics of North America
The best known use of black walnut is for its lumber and veneer.
The wood is used for fine furniture of all kinds, interior
paneling, specialty products, and gunstocks.
The nuts of black walnut serve many purposes. The kernels provide
food for wildlife and humans (45,52). Ground shells provide
special products (12). During World War II, airplane pistons were
cleaned with a "nut shell" blaster and this idea was
carried into the auto industry; manufacturers used shells to
deburr precision gears. Ground shell products are also used to
clean jet engines, as additives to drilling mud for oil drilling
operations, as filler in dynamite, as a nonslip agent in
automobile tires, as an air-pressured propellant to strip paints,
as a filter agent for scrubbers in smokestacks, and as a
flourlike carrying agent in various insecticides.
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Vegetative Reproduction
provided by Silvics of North America
If small black walnut trees are
cut or killed back by fire, the stumps usually sprout. Sprouts
originating near the root collar generally are free from defect
but sprouts originating high on older stumps often develop heart
rot or other decay from the parent stump.
Within the last few years the success of grafting and budding of
walnut has increased substantially. From 80 to 100 percent
success has been achieved by three grafting methods done in the
greenhouse and growth chamber (35). In the field the success rate
for inlay grafting, the best method tested, ranged from 33 to 83
percent. A consistent field survival of 70 to 90 percent for the
outplantings of grafted stock is predicted if tested procedures
are followed (4). Black walnut is compatible with several other
Juglans species, either as a root stock or scion (22).
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Distribution
provided by Silvics of North America
Black walnut typically grows as scattered individual trees or in
small groups throughout the central and eastern parts of the
United States. Although it is found on a variety of sites, black
walnut grows best on good sites in coves and well-drained bottoms
in the Appalachians and the Midwest. Its natural range extends
from western Vermont and Massachusetts west through New York to
southern Ontario, central Michigan, southern Minnesota, eastern
South Dakota and northeastern Nebraska; south to western Oklahoma
and central Texas; excluding the Mississippi River Valley and
Delta, it ranges east to northwestern Florida and Georgia
(28,29). On the western fringe of its range in Kansas, walnut is
fairly abundant and frequently makes up 50 percent or more of the
basal area in stands of several hectares (21).
-The native range of black walnut.
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Brief Summary
provided by Silvics of North America
Juglandaceae -- Walnut family
Robert D. Williams
Black walnut (Juglans nigra), also called eastern black
walnut and American walnut, is one of the scarcest and most
coveted native hardwoods. Small natural groves frequently found
in mixed forests on moist alluvial soils have been heavily
logged. The fine straight-grained wood made prize pieces of solid
furniture and gunstocks. As the supply diminishes, the remaining
quality black walnut is used primarily for veneer. The
distinctive tasting nuts are in demand for baked goods and ice
cream, but people must be quick to harvest them before the
squirrels. The shells are ground for use in many products.
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- copyright
- USDA, Forest Service