living plants, whether the plant is in leaf and growing or is dormant.
Growing plants, and dormant plants under normal conditions, are able to
replace this moisture by absorption through the roots. In climates where
newly planted trees may obtain sufficient soil water to replace these
losses by drying, fall planting is best. Where the plants are unable to
get sufficient winter moisture, planting would better be done only in the
spring. Where the soil freezes to a depth greater than that to which the
plant roots extend, the supply of water is cut off from the roots and the
tree will be killed by drying out through evaporation from the top. Where
winter winds are very drying and the soil moisture is limited, evaporation
from the top is likely to be in excess of that supplied by the roots and
the tree is killed in the same way.
[Illustration: Fig. 33.--Setting a tree: _A_, Measuring from the curb to
get the tree in line; _B_, filling the hole: _C_, placing the box; _D_,
fastening the box.]
In regions normally adapted to fall planting, newly set trees may be
killed by a dry autumn followed by a dry winter with, high winds or by a
cold winter with so little snow that the ground freezes below the roots.
On the other hand, trees may often be successfully planted in the fall
where such practice is not usually successful by thoroughly mulching the
soil if freezing is the sole cause of the difficulty, or by drenching the
soil thoroughly and then mulching well if lack of moisture and high winds
are the causes of the trouble. Protection from the wind by wrapping the
trunk and large limbs with burlap or some other protecting material is
also desirable.
After a liberal opening has been made in the specially prepared soil the
tree should be brought, preferably from the city's own nursery (fig. 32),
but if such a nursery has not been provided, then from among the newly
received trees that have been "heeled in" as already described.
If the tree has been well handled and the roots carefully protected it is
ready for setting. It is desirable to immerse the roots in a thin mixture
of clay and water just before putting it in the hole if there is suspicion
that the roots have been exposed. This can be done before leaving the
nursery or "heeling in" ground, but the roots must be properly protected.
Any mutilated ends of roots should be removed, the top should be severely
pruned, as described later, and the tree should be placed in the hole in
line with the other trees (fig. 33, _A_) and at such a height that after
the filling is completed it will be about an inch deeper in the ground
than it was before transplanting. The roots should be spread out in as
near their original position as practicable, and soil should be carefully
worked in about them with the fingers, so that each rootlet may come in
contact with soil and not be crowded against other rootlets. When all the
roots have been placed and covered the soil should be thoroughly trampled
or tamped to bring the roots into as close contact as possible with it.
Then more soil should be put in and the ground again tamped. Of course, in
order to get satisfactory results the soil used for planting must not be
too wet or too dry. If the soil is in such a state as to hold together in
soggy masses and not spring apart again when squeezed in the hand, it is
too wet for planting. If the soil is too dry, it will not stay in contact
with the roots during the planting operations. A soil that is too dry may
be well-watered a day or two in advance of the planting, or if excessive
dryness does not make it difficult to handle, the tree may be planted and
then be thoroughly watered. After the watering 3 or 4 inches of loose
soil should be spread over the wet ground in order to prevent undue
evaporation. It should not be trampled or pounded in any way after the
water is applied. If trees planted in moist retentive soils are watered
after planting they should be provided with a mulch of similar earth. East
of the Missouri River trees planted in soil that is in good condition
usually do not need watering at the time of planting.
Trees planted from pots, cans, or boxes should have the ball of earth
taken from the receptacle handled with care, so as not to break it further
than to loosen some of the roots on the outside of the ball; then the soil
should be as carefully placed about this ball and the loosened roots as
about the roots of trees without balls. Trees planted with balls need no
root pruning and little top pruning.
[Illustration: P20367HP
Fig. 34.--A pin oak trimmed for planting. Note the bad stubs (_A, A_) on
the left-hand side of the tree.]
[Illustration: P20368HP
Fig. 35.--A sycamore trimmed for planting. Well primed, without bad stubs.]
PRUNING.
At planting time the trees should be so pruned as to remove from one-half
to three-fourths of the leaf buds. The head should be formed in the
nursery, so that at planting time the only problem is how to reduce the
amount of prospective growth the first season without destroying the form
of the head. Specific directions are difficult, because different species
of trees are so different in their character of growth. A species that
is naturally compact in growth (fig. 34) should be pruned by removing
whole branches rather than by having the ends of branches removed. One
that is open and spreading (fig. 35) will probably need the shortening
of the longer limbs as well as the removal of interior branches. The
first pruning should be the removal of such branches as can be spared.
If enough buds can not be removed in this way without leaving the head
too open, then the shortening of the branches must follow. It is usually
necessary to remove three-fourths of the limbs to accomplish this. An
expert can do this pruning or most of it more easily before the tree is
planted than afterwards. Some additional pruning may be necessary after
the tree is set.
In addition to the pruning of the top the roots may need some cutting.
Any broken pieces or ends should be removed, making a clean cut with a
sharp knife, as new rootlets put out more readily from a cleanly cut fresh
surface than from ragged breaks. If the roots are very long, without
branches or rootlets, it sometimes makes planting easier to cut off some
of the ends. As roots are the braces by which a tree is supported in the
ground, it is undesirable to reduce their length unless some positive good
is to be gained by it.
[Illustration: P20372HP
Fig. 36.--Types of tree guards.]
The best implement for cutting small limbs is a sharp knife, and for
larger limbs a fine-toothed saw. Pruning shears are sometimes used, but
they are likely to bruise the wood. If used at all, the blade should
always be turned toward the tree so that the bruise made by the supporting
bar will be on the portion cut off. Where branches are taken off, the cut
should be close to the remaining limb, so that no suggestion of a stub
will remain. (Figs. 34 and 35.) Where ends are cut from branches the cut
should be just above a bud, and the remaining bud should point in the
direction that it is desired the limb should grow.
STAKES AND GUARDS.
Under city conditions young trees need the support of a strong stake as
well as protection for the trunk. Boys like to swing around small trees
or see the tops fly up if bent to the ground. Men find them convenient
hitching posts for their horses, and horses frequently like the taste of
the bark or tear it off for the sake of having something to do.
Guards are of many forms (fig. 36), from stakes 2-1/2 inches square set 3
feet in the ground and extending 6 feet above, with heavy-netting placed
about the tree and stapled to the stake, to heavy wooden cribs of four
stakes and intermediate slats and wrought-iron patterns of many forms.
The trees should be firmly secured to the tops of the guards so that they
will not swing against them in the wind and be rubbed. This is best done
by securing the tree in place in the guard by two loops of pieces of old
garden hose, soft leather, or rope, in such a way as not to bind the tree
too tightly while keeping it from swinging much or rubbing. The essentials
are a firm support for the tree while young with reasonable protection of
the trunk from careless depredations until the tree has reached a diameter
of 6 inches or more.
LATER CARE.
If after planting, the season is dry and it becomes necessary to apply
water, the ground should be soaked thoroughly, and as soon as it has dried
sufficiently to work up loosely it should be hoed or raked to make a good
earth mulch. A mulch of strawy manure or litter may be used in place of
the earth mulch if desired. The watering should not require repeating for
a week or more.
If the weather becomes warm soon after planting and the trees come into
leaf, wither, and droop, further pruning may save them. The reason for the
difficulty is probably that the growth of the top has been greater than
the newly formed roots can support; therefore the additional pruning is
likely to restore the balance between the top growth and root growth. At
least three-fourths of the remaining young wood should be removed. This
may leave the tree looking almost like a bean pole, but if it induces a
vigorous root growth the top can easily be re-formed.
Young trees should have an annual inspection, and all crossing branches
and any that are not well placed to form a good head should be removed.
Attention should be given also to all forks, and where two branches start
almost parallel to one another or at a small angle, making a fork liable
to split apart as the tree grows, one branch should be removed. Where
three branches start from almost the same point there is little likelihood
of their splitting apart, but with only two growing at a less angle than
30° there is liable to be trouble in the case of most kinds of trees. On
trees on which few but long shoots form, it may be well to remove the ends
of such shoots. As a rule, it is undesirable to use for street planting
trees with this kind of growth. Young trees should be trained into a
desirable shape by the use of a pruning knife each year, so that a saw
will not be necessary later. Some trees have a tendency to form too dense
a head. The interior branches of these should be removed and the head made
as open as possible while the work can be done with a knife. No attempt
should be made to alter the natural form of a tree but only to insure its
best development. A skillfully pruned young tree will show no evidences of
the pruning after three or four years.
CARE OF MATURE TREES.
PRUNING.
It is very little trouble to train a tree into a good shape by using the
pruning knife while the limbs are small, but it is usually difficult
to re-form a tree after it has grown to maturity. One who understands
tree growth, however, can often reshape the top of a neglected tree to
advantage, though many who make a business of tree trimming know so little
about it that they do more harm than good. More mature trees have been
hurt by severe pruning than have been helped. Of course, dead or dying
wood should be removed whenever it is found, no matter what the age of
the tree. This should be done by cutting off the limb back to the nearest
healthy crotch. A limb should not be cut off square across (fig. 21)
unless the tree is apparently in a dying condition and the whole top is
treated thus in an attempt to save its life. In such a case, a second
pruning should follow within two years, at which time the stubs left at
the first trimming should be cut off in a proper manner near the newly
started limbs. Healthy silver maples and willows are frequently cut in
this way, but the maples in particular would better be cut down at once
than to subject the public to the dangers of the insidious decay that
almost always follows such an operation on these trees and completes their
destruction promptly.
Trees that have been neglected a long time frequently have interfering
or crossing branches, or are too low headed or too densely headed for
the place where they are growing. Defects of this kind may be at least
partially remedied. The removal of limbs by cutting them off at a crotch
in such a manner that the wound is parallel with the remaining branch
(fig. 37) inflicts the least possible damage. Such a wound in a healthy
tree will soon heal over if the cut is made through the slight collar or
ring that is nearly always present at the base of a branch. The closer
this cut can be made to the trunk the better the appearance when the cut
is healed. The closer the cut the larger the wound, but the difference
is unimportant if the wood is well protected until it is healed. These
operations are entirely different in purpose and result from the "heading
in" or "heading back" so often practiced under the guise of tree pruning,
either from a false notion of forming a top or for the passage of wires.
Changing the form of a tree by pruning should not be attempted. Each
species has its own form or forms, and no attempt should be made to
change or distort a tree from its normal habit of growth. Successful
pruning will accentuate rather than disguise a tree's characteristics.
[Illustration: P20371HP
Fig. 37.--Part of a tree trunk showing proper and improper methods of
removing old limbs. Although healing has started on the stub (at the
right) it is likely to proceed very slowly. The nearer the cut is to the
tree the larger the wound but the less conspicuous the stub will be when
healed.]
All cuts should be made so that no stubs or protuberances are left to
prevent quick healing. Small wounds need no after treatment if the cut
is well made. Large wounds should have the wood of the center of the
cut well protected to prevent decay until the new growth has had an
opportunity to heal over the cut. An application made to the center of the
cut to preserve the wood should not be permitted to come near the cambium
layer or inner bark, especially of soft-wooded trees like the tulip and
magnolia, as the oil or other substances contained in the paint, tar, or
other covering may spread to the cambium layer and kill it. It is well not
to make any application within half an inch of the outside of the wound
unless the coating has been thoroughly tested.
Dead wood should be entirely removed, the cut being made through good live
tissue. Removing such wood frequently exposes decayed cavities, usually
from bad stubs or injuries which have started decay that has followed back
to the main limbs or the trunk. The treatment of such cavities is the
province of tree surgery and is discussed in another publication.[87]
[87] Collins, J. F. Practical tree surgery. _In_ U. S. Dept. Agr.
Yearbook, 1913, pp. 163-190, pl. 16-22. Published as Yearbook Separate
622, obtainable from the Superintendent of Documents for 10 cents in coin.
One source of trouble with a large tree that has developed with two trunks
or branches instead of three or more is the liability of their splitting
apart in the crotch. This is especially characteristic of the elm. Careful
attention to the early pruning of trees may eliminate this defect, but
when it exists in mature trees it is frequently advisable to connect the
branches by a strong chain (fig. 18) in order to prevent the limbs from
being torn apart.
FEEDING.
It is difficult to do anything to stimulate the growth of street trees
after they are once started, because usually the only uncovered area over
the roots is the small opening immediately about the tree; hence, the
importance of supplying the best of soil well enriched at the time of
planting. Sometimes a stimulation is desirable, which can be accomplished
by dissolving one-half to 1 pound of nitrate of soda in 50 gallons of
water and applying from 1 to 25 gallons of the liquid, depending on the
size of the tree. Unless the soil is damp at the time of application water
will be needed immediately afterward. This material should be applied only
when the tree is in full leaf and growing. If applied when the tree is
dormant it is likely to be leached from the soil before it is absorbed.
If applied late in the season, that is, within three months of freezing
weather, it would likely stimulate a late growth that would be liable
to be killed the following winter and might make the whole tree more
susceptible to injury from cold.
Water is one of the great needs of city trees, as the ground surface is
often almost completely roofed over with water-tight coverings. It is
usually a help for the pavement washings to drain into the parking space
where the tree is planted. If a curb is placed about the parking space,
frequent, regular watering is necessary where the ground is thoroughly
covered with water-tight pavements.
Where growing under suburban conditions, that is, with streets partially
pervious to water, liberal parking spaces, and adjoining lawns, street
trees will respond to all extra care given the near-by open spaces,
whether parkings, lawns, or gardens. If these are well cared for the trees
should have ample sustenance from them without any direct applications.
In order to prevent the soil about a tree from being packed too hard by
trampling it is frequently desirable on business streets to cover the soil
about it with an iron grating.
SPRAYING.
Street trees, like all other forms of vegetation, are subject to attacks
of insects and diseases. Because of the unfavorable conditions under which
they grow, spraying for biting and sucking insects and suitable treatment
for borers or other burrowing insects require especially careful attention.
In addition to a number of troubles common to street trees in general,
each species is liable to troubles of its own; hence, the need of
competent supervision by a trained man with an efficient outfit rather
than leaving; the work to individual initiative.
Because of the height which many street trees attain a powerful outfit is
required to spray them properly. One capable of maintaining a pressure
of 200 pounds per square inch is desirable. The type of spray required
for tall trees is different from that used on fruit trees and other
low plants. For low trees the ideal spray is a mist within a few feet
of the nozzle, application being accomplished by having the nozzles
near the foliage to be treated. For tall trees it is desirable that the
liquid should leave the nozzle in a solid stream, which is broken into
spray as it passes through the air. The material has to be projected
with sufficient force to reach the highest trees before being entirely
converted into mist, as it is impracticable to extend the nozzles into
the trees to reach the farthest portions, as is done with fruit and other
low trees. The spray can not be applied as uniformly as a mist, but it
is impracticable to climb into the tops of shade trees to cover every
part with a cloudlike spray. On the other hand, the mist spray is better
for small trees, as much injury may be done to low trees or to the lower
branches of high trees by the force of the stream from high-pressure
outfits.
It is estimated that in practice up to 95 per cent of the attacking
insects can be killed with insecticides carefully applied by the stream
method under high pressure.
In addition to the mechanical problem of satisfactorily covering high
trees with insecticides or fungicides there is the problem of selecting
materials that will be effective against the insects and diseases and
at the same time will not disfigure the paint or stone work of adjacent
buildings with which the materials must inevitably come in contact in
street tree spraying. It frequently happens that the most effective
remedies must be rejected because of the damage they would do to buildings
and that less efficient materials must be used.
Whitewashing the trunks of trees is a useless and unsightly
practice--useless, as it does not prevent the attacks of insects, and
unsightly, because it makes the trunks of the trees obtrusive when they
should be inconspicuous.
Banding with cotton or proprietary preparations may occasionally be
useful, but because such applications are so seldom helpful and because
some of the preparations result in injury due to constriction of the
trunks, it should not be resorted to except upon special recommendation of
an entomologist familiar with the existing conditions.
Details as to enemies to be expected, methods of treatment, and materials
to be used may be found in other publications[88] or may be obtained by
correspondence with the nearest State agricultural experiment station or
with the United States Department of Agriculture.
[88] See list on following pages.
* * * * *
PUBLICATIONS OF THE UNITED STATES DEPARTMENT OF AGRICULTURE
RELATING TO DISEASES AND INSECTS AFFECTING SHADE AND ORNAMENTAL TREES.
=AVAILABLE FOR FREE DISTRIBUTION.=
Control of Root-Knot. (Farmers' Bulletin 648.)
The San Jose Scale and Its Control. (Farmers' Bulletin 650.)
The Bagworm, an Injurious Shade-Tree Insect. (Farmers' Bulletin 701.)
The Catalpa Sphinx. (Farmers' Bulletin 705.)
The Leopard Moth: A Dangerous Imported Enemy of Shade Trees.
(Farmers' Bulletin 708.)
The Oyster-Shell Scale and the Scurfy Scale. (Farmers' Bulletin 723.)
The White-Pine Blister Rust. (Farmers' Bulletin 742.)
Carbon Disulphid as an Insecticide. (Farmers' Bulletin 799.)
The Gipsy Moth and the Brown-Tail Moth and Their Control. (Farmers'
Bulletin 845.)
Common White Grubs. (Farmers' Bulletin 940.)
The Blights of Coniferous Nursery Stock. (Department Bulletin 44.)
Forest Disease Surveys. (Department Bulletin 658.)
=FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS,
GOVERNMENT PRINTING OFFICE,
WASHINGTON, D. C.=
The Mistletoe Pest in the Southwest. (Bureau of Plant Industry
Bulletin 166.) Price, 10 cents.
The Death of Chestnuts and Oaks Due to Armillaria mellea.
(Department Bulletin 89.) Price, 5 cents.
New Facts Concerning the White-Pine Blister Rust. (Department
Bulletin 116.) Price, 5 cents.
The Huisache Girdler. (Department Bulletin 184.) Price, 5 cents.
Report on the Gipsy Moth Work in New England. (Department Bulletin
204.) Price, 30 cents.
A Disease of Pines Caused by Cronartium pyriforme. (Department
Bulletin 247.) Price, 5 cents.
Food Plants of the Gipsy Moth in America. (Department Bulletin 250.)
Price, 10 cents.
Dispersion of Gipsy Moth Larvæ by the Wind. (Department Bulletin
273.) Price, 15 cents.
The Cottonwood Borer. (Department Bulletin 424.) Price, 5 cents.
Solid-Stream Spraying against the Gipsy Moth and the Brown-Tail Moth
in New England. (Department Bulletin 4.80.) Price, 15 cents.
Protection from the Locust Borer. (Department Bulletin 787.) Price,
5 cents.
Principal Insects Liable to be Distributed on Nursery Stock.
(Entomology Bulletin 34, n. s.) Price, 5 cents.
The Locust Borer. (Entomology Bulletin 58, part 1.) Price, 5 cents.
Additional Data on the Locust Borer. (Entomology Bulletin 58, part
3.) Price, 5 cents.
The San Jose or Chinese Scale. (Entomology Bulletin 62.) Price, 25
cents.
Report on Field Work against the Gipsy Moth and the Brown-Tail Moth.
(Entomology Bulletin 87.) Price, 35 cents.
The Importation into the United States of the Parasites of the Gipsy
Moth and the Brown-Tail Moth. (Entomology Bulletin 91.) Price, 65
cents.
The Dispersion of the Gipsy Moth. (Entomology Bulletin 119.) Price,
20 cents.
The Green-Striped Maple Worm. (Entomology Circular 110.) Price, 5
cents.
The Oak Pruner. (Entomology Circular 130.) Price, 5 cents.
The Dying Hickory Trees: Cause and Remedy. (Entomology Circular
144.) Price, 5 cents.
Flour Paste as a Control for Red Spiders and as a Spreader for
Contact Insecticides. (Entomology Circular 166.) Price, 5 cents.
Three Undescribed Heart-Rots of Hardwood Trees, Especially of Oak.
(Journal of Agricultural Research, vol. 1, No. 2.) Price, 25
cents.
A Serious Disease in Forest Nurseries Caused by Peridermium
filamentosum. (Journal of Agricultural Research, vol. v, No. 17.)
Price, 10 cents.
The Chestnut Bark Disease. (Separate 598, from Yearbook of the
Department of Agriculture for 1918.) Price, 10 cents.
Practical Tree Surgery. (Separate 622, from Yearbook of the
Department of Agriculture for 1913.) Price, 10 cents.
Forest Tree Diseases Common in California and Nevada. (Forest
Service Unnumbered Publication.) Price, 25 cents.
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Transcriber Notes
Illustrations were moved so as to not split paragraphs.