Black walnut is one of the Midwest's most valuable trees for wood products. Often called black gold, walnut also produces edible nuts and wildlife food while contributing to biological diversity. This program describes how to grow and manage black walnut - PowerPoint PPT Presentation


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Black walnut is one of the Midwest's most valuable trees for wood products. Often called black gold, walnut also produces edible nuts and wildlife food while contributing to biological diversity. This program describes how to grow and manage black walnut


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Title: Black walnut is one of the Midwest's most valuable trees for wood products. Often called black gold, walnut also produces edible nuts and wildlife food while contributing to biological diversity. This program describes how to grow and manage black walnut

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Black walnut is one of the Midwest's most
valuable trees for wood products. Often called
black gold, walnut also produces edible nuts and
wildlife food while contributing to biological
diversity. This program describes how to grow and
manage black walnut trees for wood and nuts.
A tree's value for wood products depends on its
stem size and quality. Major defects that reduce
the total volume of useable wood, include crooked
stems and low forks.
Cracks, decay, and fence wire also reduce useable
Less serious defects reduce wood quality.
Examples are dead limbs, live limbs, knots, and
small holes made by birds or insects.
Top quality logs, with only minor defects, are
sliced into veneer for doors, wall panels,
furniture, and cabinets. Veneer often is cut from
the first log on trees at least 16 inches in
diameter and 8-½ feet long.
Logs with more significant defects are sawn into
lumber or gunstock blanks. Sawlog quality trees
usually must be at least 12 inches diameter and
8-½ feet long.
Portions of trees not suitable for lumber, may be
cut for novelty items.
The size at which a walnut tree should be
harvested depends on its log quality and growing
site quality. A high quality tree on a good site
may be left to grow larger than 24 inches
A low quality tree or one on a poor site, may be
harvested when it's less than 16 inches diameter.
Contact a forester for advice before harvesting
or marketing walnut trees!
Rich nut meats from black walnuts are used
primarily in retail sale and in commercial
production of ice cream, baked goods, and candy.
Black walnut's natural range is in the central
and eastern states. Large scale plantings for
timber and nut production are discouraged beyond
this range.
In natural woodlands, walnut trees grow primarily
in small groups or scattered among elm,
hackberry, boxelder, maple, ash, basswood, oak,
and hickory.
Walnut requires annual precipitation of at least
25 inches, but prefers more than 35 inches. It
needs a frost-free growing season of at least 140
days, but prefers more than 170 days.
Soil should be at least 30 inches deep, fertile,
and moist but well-drained. Soil texture should
be sandy loam, loam, silt loam, or silty clay
loam. Avoid soils that are shallow, dry, sandy,
gravelly, or rocky.
Walnut is often found along streams where
periodic flooding occurs in the dormant season.
However, do not grow walnut where soils are wet
during the growing season or where flooding and
ice damage occur frequently.
Walnut grows well on river terraces, hillside
benches, and in coves in hilly terrain facing
north or east. It will not grow well on steep
slopes facing south or west--such sites are too
hot and dry.
When planting walnut, choose sites with some air
flow, but not windy sites. Exposed upland sites
can be used if walnut is mixed with other species
for wind protection.
Walnut trees have never been abundant because nut
crops are small compared to other trees, and most
nuts are eaten by animals or damaged by insects.
Walnut can stump sprout after being cut, but
sprouting vigor declines greatly when trees are
more than 30 years old.
Because natural regeneration is unreliable,
planting nuts or seedlings is the best way to
start walnut trees. Walnuts don't tolerate shade,
so plant them only in forest openings or open
fields. When your objective is timber, plant
trees 7 to 10 feet apart. This close spacing
encourages trees to grow straight and to
self-prune as lower branches become shaded and
die. It also allows you to be more selective
about which trees to let grow and which to remove
during thinnings.
Planting walnut in pure rather than mixed stands
helps to maximize tree value and simplify
planting and management. However, mixed stands
reduce pest and environmental problems, have more
aesthetic appeal, increase biodiversity, and may
have less expensive seedling costs. Different
tree species may be planted in alternate rows or
mixed within a row. Pines help control weeds by
shading the ground, and they encourage walnut
stems to grow straight.
Walnuts also can be mixed with hardwood trees
that have a similar growth rate, such as red oak,
and white or green ash. Nitrogen- fixing shrubs,
notably autumn olive, can stimulate walnut growth.
Some people grow walnut trees primarily for their
nuts. Trees begin producing large quantities of
nuts when they are about 30 years old. Good nut
crops occur in about two out of five years.
Open-grown trees with large crowns produce more
nuts than woods-grown trees with small crowns.
But the number of nuts, frequency of nut crops,
and size of kernel varies greatly from tree to
tree. Find trees that have large nuts with a high
percentage of kernel. Use these nuts as your
planting stock.
Good nut-producing trees usually have low timber
value because of their short logs, numerous
knots, wide growth rings, and high percentage of
light-colored sapwood. However, nut plantations
can be grown on poorer quality sites than timber
Plant nut trees 12 to 15 feet apart. Gradually
thin to about half this density as trees mature.
Keep other trees and shrubs from invading. Sod
reduces nut production, but also reduces soil
erosion and may discourage other plants from
invading that would make nut collection difficult.
Agroforestry refers to growing trees at a wide
spacing with agricultural crops or shrubs between
tree rows. Walnut trees usually are grown for
their nuts because wide spacing can lead to poor
timber quality. Crops grown between tree rows
provide annual income while the nut trees mature.
Consider growing corn, soybeans, winter wheat,
forage, vegetables, berries, or Christmas trees
between tree rows. Continue growing these crops
until nut trees take over the site.
Plant trees 7 to 10 feet apart within a row, but
space tree rows 30 to 40 feet apart or at least 4
feet wider than the equipment used to maintain
Agroforest plantations are not easy to manage
because the cultivation, harvest, and pest
control activities needed to grow agricultural
crops may damage the trees.
Site preparation will increase tree survival,
growth rate, and quality. Begin controlling weeds
and brush before planting and continue at least
three years or until tree crowns close together
and shade out the weeds.
If the planting site has been cropped recently,
leave stubble for moisture retention, weed
suppression, and erosion control. But, remove
excess stubble that will interfere with machine
planting of walnuts chisel-plow if there is a
plow pan or disk to loosen compacted soil.
Sod strongly competes with walnut trees. Mowing
will not control it. Before planting, remove sod
in strips or patches by rototilling, disking, or
using herbicides. Clear at least a 1½ to 2-foot
radius around each seedling.
If you cultivate, keep rototillers and disks away
from tree stems and till no more than 6 inches
Where chemicals are used, always read and follow
label directions. Pre-emergent chemicals are less
likely to damage walnut seedlings than chemicals
applied to foliage.
Mulches suppress weeds and retain soil moisture.
Woodchips, straw, sawdust, bark, shredded corn
cobs, plastic sheets, or fabric mats can be used.
Keep mulches 1 to 2 inches away from tree stems
to avoid heat buildup. Because organic mulches
use nitrogen when they decompose, you may need to
add fertilizer around trees. Some mulches may
attract small rodents that build nests and then
feed on tree seedlings in fall and winter.
Forest openings and clearcuts provide an
excellent environment for walnut, but brush,
weeds, and grasses must be controlled in a 2- to
3-foot radius around each seedling. Plant walnuts
where natural regeneration of other desirable
tree species is not adequate.
If the site has not yet been harvested, first,
spray small understory trees and shrubs with a
herbicide in late summer. Second, harvest
merchantable trees during the winter. Third, cut
down or girdle all nonmerchantable trees and
spray herbicide on their stumps or girdles to
prevent resprouting. And fourth, plant walnuts in
the spring.
If the planting site has been harvested and is
stump free, rototill or disk to uproot small
woody stems, herbaceous plants, and grasses. Or,
for more reliable results, apply herbicides late
in the growing season. Plant walnuts the
following spring.
If the site already has been harvested, but there
are too many stumps for mechanical site
preparation, let woody and herbaceous plants
resprout. Spray them with a herbicide in late
summer. Then plant walnuts the following spring.
Be very cautious when using herbicides where
walnut trees grow or will be planted. Walnuts are
easily damaged when some herbicides are applied
nearby and drift through the air or wash onto the
ground where walnuts can absorb it.
Mark each seedling with a wire flag or ribbon to
help you relocate it for follow-up weed control.
Your planting stock should come from nuts on
trees growing not more than 200 miles south or 50
miles north of the planting site.
The most reliable way to start walnut trees is to
plant seedlings. One-year-old seedlings usually
are adequate, but they must be at least 1/4 inch
and preferably 3/8 inch in diameter, 1 inch above
the root collar. Plant bareroot seedlings before
Containerized seedlings are much more expensive,
but they are used occasionally when it's
necessary to plant later in the growing season
and when soil is drier.
To plant a seedling, make a hole deep enough to
hold the root system without significant bending.
Use a planting bar, shovel, or auger, depending
on seedling size and soil texture.
After planting, press soil firmly around the
roots to eliminate air pockets. Then water
seedlings if possible.
A tree planting machine pulled by a tractor can
be used for large open-field plantings.
Tree shelters increase planting costs, but also
protect trees from animal damage and herbicides,
and encourage rapid height growth. Tree shelters
must be raised slightly in the fall to allow air
flow that helps harden off the trees. Remove
shelters after seedlings emerge from the top.
Although planting seedlings is more reliable, you
may want to plant nuts to save the expense of
seedlings, to grow your own seedlings, or to grow
walnuts from a parent tree with characteristics
that you like.
For timber production, collect nuts from trees
with good stem form and quality. For nut
production, collect large nuts with a high
percentage of kernel.
Walnuts can be planted with husks, but they're
easier to handle and sort for viability if husks
are removed. Collect nuts as soon as they fall
and immediately remove husks using one of these
Place nuts in a bucket of water to soften and
then peel the husks by hand. Or place nuts in a
small cement mixer along with gravel, cover with
water, and rotate for 20 to 30 minutes. Wear
clothing and gloves for protection from stain in
the husks.
After removing husks, rinse the nuts in water.
Discard nuts that float those that sink have
full kernels and are more likely to germinate.
Walnut seeds require cold treatment before they
will germinate. To prepare nuts for spring
planting, dig a pit, spread a layer of nuts in
the bottom, and cover them with 1 to 2 feet of
sand, leaves, or mulch. Cover the pit with
screening to keep out rodents.
When the ground thaws in spring, dig up the nuts
and plant them 1 to 2 inches deep in the prepared
site. Plant two nuts at each planting spot. About
half the nuts will germinate in four to five
weeks. Additional nuts may germinate the
following year. Remove excess seedlings to allow
adequate growing space.
To reduce predation by squirrels and other
rodents, plant nuts in the spring, in an open
field at least 330 feet from a woodland. When
nuts will be planted closer to a woodlot with
squirrels, rodent protection may be needed.
Tin cans, such as soup cans, may be used to
protect small plantings. Burn the cans so they
will rust and disintegrate within a few years.
Remove one end of each can and cut an X into the
other end using a chisel. Pry up the cut ends.
Grasping the can with the open end up, place 1 to
2 inches of soil into the can, drop in a walnut,
then fill the can with soil. Plant the entire can
with the sharp points facing up and buried about
1 inch below the soil surface. A seedling will
grow out of the can.
When trees are spaced close together, their stems
grow straight and their lower limbs become
shaded, die, and fall off, creating a clear stem.
Dense stands need to be thinned, however, to
maintain diameter growth. Thinning also lets you
remove undesirable tree species and poorly formed
trees, providing more growing space to trees with
greater potential value. Start thinning when
crowns slightly overlap and continue at roughly
10-year intervals.
Begin by locating a potential crop tree with a
straight stem, dominant leader, average or larger
stem diameter, small lateral branches, and no
significant damage.
Cut down or deaden surrounding trees to provide
at least 5 feet of clear space around
three-fourths of the walnut's crown. If
surrounding trees are taller than the crop tree,
remove them to create at least 10 feet of clear
space around three-fourths of the walnut's crown.
Then find another crop tree and release it in the
same manner. Do not over-thin a stand. Heavy
thinning may stimulate sprouts to grow out of
tree stems.
Corrective pruning on seedlings and saplings
encourages straight stems, but do this only on
potential crop trees. Many trees will straighten
on their own and others will be removed during
thinnings. Bend the dominant shoot so its tip is
over the central axis of the main stem. Hold it
in place by bending another shoot or two close to
the dominant shoot and fastening the shoots
together with three wraps of 1-inch masking tape.
Cut off the tip of the supporting shoot, just
above the wrapping, to eliminate potentially
competing new growth. Small crooks in branches
will fill and not cause problems as tree diameter
If a sapling has multiple stems, leave the best
and remove the others.
A badly deformed sapling should be cut off 1-inch
above ground and allowed to resprout.
Clear-stem pruning develops knot-free lumber and
veneer. Although you can begin when trees are
only 12 feet tall, it's more efficient to prune
trees that are 3 to 4 inches in stem diameter.
Trees up to 10 inches in diameter may benefit
from clear-stem pruning. Prune only 25 to 150
potential crop trees per acre. Select crop trees
with straight stems, dominant leaders, average or
larger stem diameters, small lateral branches,
and no significant stem or branch damage.
Prune at least 9 feet high, but if possible,
prune up to 17 feet in two or more stages. Stem
forks, crooks, or large branches may restrict
pruning height. Do not remove more than 25
percent of the live crown or prune higher than 50
percent of total tree height.
Prune only branches less than 2 inches in
diameter. Larger pruning cuts heal slowly and may
lead to decay and tree ring separation. Prune
only during the dormant season. Do not apply
paint or other sealants to pruning cuts.
Walnut trees have few pest problems, but extreme
cold can severely damage branches and kill trees.
Damaged trees then can be infected by canker
diseases. To avoid frost damage, do not plant
walnut in narrow valleys with steep adjacent side
slopes, or on bottomland sites that are frost
pockets. Your seed source should originate no
more than 200 miles south of the planting site.
Canker diseases can kill trees. Do not prune or
wound trees in the summer.
Leaf diseases may look unsightly but are seldom
Leaf feeding insects cause noticeable damage, but
they usually are active late in the growing
season after trees have accomplished most of
their growth.
Insects that bore into twigs can disfigure
saplings, but will not kill trees.
Keep livestock out of woodlands. They compact
soil, rub bark, break branches, and eat twigs and
foliage. Such damage can severely reduce growth
of seedlings and saplings and lead to wood stain
or decay.
Growing trees requires energy, enthusiasm, money,
and a long time commitment. Although walnut
timber value has increased over time, changes in
supply and demand, land prices, and tax
consequences of growing trees make it difficult
to predict the long-term financial outlook.
However, black walnut has been and continues to
be a premier hardwood that is marketed throughout
the world. Some uses of walnut have decreased,
while new uses for the wood, nuts, and byproducts
continue to expand. Walnuts also provide benefits
to wildlife, nuts for human consumption,
aesthetic qualities, improved biodiversity, and
much more. Whether you plant just a few trees or
many acres, the rewards can be very satisfying.
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