BRACING AND REPAIRING TREES
Though occasionally resorted to in olden times, particularly in the
case of orchard trees, it is only of late years that the systematic
treatment of tree wounds and diseases has been generally adopted. Even
at the present time, the filling of hollow trunks, bracing of heavy and
diseased branches and attention to insect and fungoid pests are rarely
engaged in and but imperfectly understood.
When the value of old trees in an ornamental or utilitarian sense is
taken into account, it is remarkable what a small amount of attention
they receive when subjected to accident or disease. As a general rule,
cavities or hollows in a tree stem, if left to themselves, gradually
increase in size until the ascending sap is entirely cut off, when the
crumbling stem either falls to pieces or is broken over by the wind. A
branch requires to be braced or strengthened when from its weight and
shape it is likely to get wrenched from the main stem during stormy
weather and so injure the tree or man its natural beauty.
Both insect and fungoid pests do a considerable amount of damage to
trees, both young and old, but as special chapters are devoted to their
depredations they need only receive a passing notice here.
=Hollow Trunks and their Treatment.=—However desirable it may be to
repair hollow trunks, yet a great deal of discrimination is necessary
in deciding which trees should be operated upon, especially in the case
of such as are reduced to mere shells and are not likely to derive any
benefit commensurate with the labour and cost of materials involved in
bracing and filling.
Young, healthy, vigorous growing trees, that have become damaged or
diseased, should in the majority of instances be attended to; but in
the case of old specimens on which a great amount of labour and money
would necessarily have to be expended, several important bearings must
be considered before works of repair are taken in hand. Historic and
valuable trees, those occupying prominent positions on a lawn or park,
town trees where vegetation is scarce, and such as are not too old and
fragile, may be dealt with within certain bounds, but to doctor all
diseased and hollow trees on the most approved principle in such places
as Epping Forest or Burnham Beeches would be highly imprudent, whether
in view of the little benefit which in many instances would accrue by
so doing or of the great expense involved in such an operation.
The filling, too, must be adapted to circumstances, and to deal with
the entire trunk of a hollow tree is in most cases quite out of the
question, both from the point of utility and expense. Short-lived
trees, such as the Alder, Birch and Poplar, or such as are liable
to sudden attacks of insect and fungoid pests, and those that are
unfavourably situated in mining and chemical areas, should be scantily
dealt with, but the practical woodman will see at a glance which trees
are best worthy of his attention and treatment.
Probably the simplest, and certainly the cheapest method of dealing
with diseased and hollow trunks is to clean out thoroughly all dead
and decaying matter, the interior being scraped and swept with a
rough brush, so that the loose rotting wood and bark is removed. When
quite dry, the interior of the trunk should be painted with one, or
preferably with two coats of creosote or carbolineum, and filled up
with a composition of one part of Portland cement to three of clean
gravel and sand, the surface coating at the orifice containing the
largest quantity of cement. A coat of coal tar on top of the dry
creosote goes far in making the concrete adhere firmly to the wood.
When a fairly healthy tree is being operated upon, and when the bark
is likely to grow over the exposed surface, the concrete should only
be brought up on a level with the underside of the living bark; in
other words, the cambium should be left free for expansion. Sometimes,
brickbats, broken small, are used instead of gravel, but for various
reasons concrete is preferable. The concrete surface may be prevented
from cracking by applying annually a coat of paint, which, for
appearance sake, may be of a similar colour to that of the bark of the
tree.
In the case of a large tree in which the trunk is quite hollow, usually
with a basal and top opening, the amount of cement required to fill the
cavity precludes the possibility of it being employed on the score of
economy, but where the hollow only extends for a comparatively short
distance upwards and inwards the composition is to be recommended. When
a large amount of material is required to fill a hollow stem, clean
bricks broken to about the size of a golf ball may be used, but they
must be packed firmly and the surface, wherever it comes in contact
with the weather, glazed over with cement in order to effectually shut
out dampness. Asphalt has of late years been employed in the filling of
hollow stems, and is to be recommended on account of its elasticity and
lasting properties.
Sometimes, the interior of a large, hollow tree stem is strengthened
by crossbeams of timber, any holes which extend to the outside being
carefully covered with sheet lead or zinc so as to prevent the ingress
of water. A sheet of lead or zinc is, however, only a superficial
remedy and should be dispensed with where filling the cavity is at all
practicable. Lead, in some cases, is preferable to zinc for covering
wounds in trees, as it fits into position more readily and is easily
fixed.
The treatment of hollow stems without filling the cavity is in certain
instances quite permissible, and can be carried out at a comparatively
small cost. Broadly speaking, this method consists in cleaning out all
decayed and decaying matter, painting the interior with carbolineum
or tar, and, where possible, bracing the trunk from the interior by
means of stout crossbars of wood and covering surface holes with lead,
zinc or sheet copper. When a tree trunk is hollow from top to bottom
this method is to be recommended, and stout struts placed within the
cavity at various of the weaker points will go far towards preserving
many an aged specimen. When the cavity in a hollow stem is so large
that a person can enter it, the work of either filling with a suitable
composition or supporting with wooden struts is greatly simplified.
Recent experiments have proved the value of a mixture of sawdust and
asphalt for filling cavities. It is particularly valuable in cases
where concrete is too rigid and unyielding, such as in dealing with
trunks and branches that are apt to be swayed about in stormy weather.
The materials are dry sawdust, that of Oak, Chestnut and Beech being
preferable, and solid asphalt derived from the refining of petroleum,
which is at present in use for filling the interstices of street
pavements in various parts of the metropolis.
For filling cavities in heavy, swaying branches, one part of asphalt
to four of clean, dry sawdust will form a mixture that is non-rigid
and yields with the motion of the branch in which it is inserted.
In dealing with the trunk, which is more rigid and less affected in
stormy weather, a larger quantity of sawdust should be used. The
filling is made by stirring dry sawdust into boiling asphalt until
the desired consistency is reached, and before the composition has
cooled, it should be inserted in the previously prepared cavity. As in
cement filling, the preparation of cavities to be filled with sawdust
and asphalt should be carefully attended to, the decayed wood and
all soft and rotten material being removed, and the interior surface
rendered sterile by an application of carbolineum or kerosene. For
wound dressings, gas tar and liquid asphalt is to be recommended, this
combination forming a more continuous and elastic covering than is the
case when tar or paint alone is used.
Where the cavity is small and, as is often the case, filled with water
and decayed and decaying vegetable matter, the following course is
recommended:—When only a few inches deep, the water can usually be
got rid of by mopping it out with a sponge attached to a convenient
handle, but when the hole is too deep for this method the water may be
extracted by tapping, that is by boring a hole with an auger through
the trunk to the bottom of the hole. A half-inch auger will suffice,
and the correct spot to bore can usually be ascertained by measuring
the depth of the hole. After the water has been removed the cavity
must be thoroughly cleared of all decaying tissue and accumulated
vegetable matter, and in order that this may be done effectually, it
may sometimes be necessary to enlarge the opening so that a suitable
tool can be inserted.
When the cavity has become quite dry—a matter of considerable
importance—it should be treated with creosote or carbolineum and
afterwards filled with concrete in the proportion of one part of cement
to four of clean gravel. Ram the concrete firm so that the cavity is
perfectly filled, and finish off at the orifice with pure cement in
such a way that the cambium may be induced to form a growth over the
edge of the filling.
A cheap but temporary method of dealing with small hollows and cavities
in fruit and other trees, is to fill these with a mixture of clay and
cow-dung in the proportion of two of the former to one of the latter.
Knead well and apply when in the consistency of putty, cleaning and
disinfecting the hollows before filling.
=Supporting Heavy and Diseased Branches.=—A limb requires to be braced
or strengthened when from its weight and shape it is likely to get
wrenched from the main stem during stormy weather, when the weight of
the minor branches and foliage is too great for the strength of the
limb, when the wood of the tree is unusually brittle, when trunk or
limb is decayed, and when, from accident, the tree has become one-sided
and lost its natural appearance.
Forked trees often require staying, as also do such as have suddenly
become exposed to storms to which they have hitherto been unaccustomed.
But probably in the matter of bracing and strengthening, the most
important of all trees are those in our public parks and such as are
contiguous to or overshadow dwelling-houses. Park trees should receive
special attention in the way of making sure that limbs are secure and
not likely to cause injury to visitors; while in the case of heavy
branches hanging over dwelling-houses these should be carefully and
periodically examined and made secure whenever it is found necessary.
Should there be any doubt as to whether a limb is insecure and
dangerous, a decision should be made in favour of bracing or reducing
the weight by pruning.
Unwieldy and heavy limbs are most commonly to be found on isolated
trees, or such as have had plenty of room for the perfect development
of stem and branch. As the loss of one or more of the larger branches
often mars the ornamental appearance of a specimen tree, every
reasonable means should be employed to prevent such a disfigurement.
By reducing the weight of a branch by pruning, or by giving support to
any that are heavy and diseased by means of wires, chains or light iron
bands and connecting-rods, the trouble may be averted. In all cases
the object should be to unite the branches in such a way that they
may offer the greatest amount of resistance to the storm, and at the
same time be neither conspicuous nor clumsy in appearance owing to the
operation.
Chains, though often used, probably owing to their being readily
obtainable and cheap, are for various reasons to be avoided, the flat
iron band lined with leather or rubber being preferable, more readily
adjusted, and less likely to cut into the bark and wood. The bands,
which can be made by any blacksmith, are usually 2½ in. wide, and of
the shape of the branch to be encircled, each being in two parts to
facilitate fixing and to allow of slackening at any future time should
the necessity arise. The band is made of a larger size than the branch
to be encircled, so as to allow of the insertion of a leather or rubber
collar between it and the wood, the purpose of the packing being to
prevent undue friction and chafing of the bark owing to the movement of
the tree. The bands, whether placed around two opposite branches or the
main stem and a branch, are connected together by a light iron rod and,
according to the strain, may be from one-half to three-quarters of an
inch in diameter. This rod, like the bands, is divided into two parts,
which are connected by a swivel and screw for convenience in loosening
or tightening.
[Illustration: BRACING A TREE]
Great care is necessary in choosing the point at which a band should
be placed, and in deciding which branches or branch and stem should be
joined together, so that the greatest resistance may be obtained and in
order that the one may act as a support to the other. The shape of the
tree and disposition of the stem and branches can alone be the guides
in this matter. In comparison with the use of a chain, the advantages
of this method of supporting heavy branches are principally ease of
fixing, greater rigidity, less friction, adaptability for loosening or
tightening as may be required, and better results.
Accurate measurements as to the size and shape of the limb to be
operated upon must be taken and the girdling hoops made accordingly.
The best way to take these is to ascend the tree, and, after deciding
as to the points where bracing is to take place, encircle each branch
with a strip of hoop-iron, which will not only give the size but shape
of the particular limb, a most important point where neatness is
studied and after-chafing of the bark and wood is to be avoided.
[Illustration: BAND AND CONNECTING-ROD]
In the case of old trees, or such as are not likely to greatly increase
in size, the bands need not be much larger than the actual size of
the branches to which they are to be affixed, but where the tree is
young and vigorous, room for expansion should be provided. Fixing the
bands and connecting-rods is readily accomplished either by the use
of ladders or by climbing the trunk and slinging the portions into
position by means of ropes. The exigencies of each case will point out
the best means of carrying out the work, as also the height at which
the supports can most effectively be placed. When damaged or diseased
branches are being dealt with, great care is necessary to ensure that
the bands are placed in such positions that the greatest leverage
against wind is afforded, and so as to minimize the risk of the branch
being broken across at the weakened point during stormy weather.
Frequently, where the main trunk divides into two or more portions near
ground level, it will be found that a split or crack has been caused by
the swaying of the divided stems. In such cases the split between the
stems should be carefully cleaned out, treated with an antiseptic and
filled with asphalt. The limbs should then be braced together by means
of a band and connecting-rod, and, as the asphalt becomes set, the
brace may be tightened up as may be found necessary.
Rarely is it found necessary to place a band around the stem of a
tree to prevent splitting. Where, however, appearances point to the
likelihood of this taking place, as in the case of forked trees,
especially when the stem divides abruptly into two or three heavy
limbs, it is a wise precaution to encircle the bole with a wide band
of iron. This band should be placed at such a height that the greatest
possible resistance to splitting of the stem is afforded. Such bands
are usually proportionate to the strain of the stem to which they are
to act as support. A band of leather or rubber between the iron and
bark of the tree to allow for expansion of the stem is necessary.
Supporting tree branches by chains is not to be recommended, for the
simple reason that, however carefully they may be adjusted, friction
and chafing of the bark and wood is sooner or later bound to ensue.
Connecting the flat iron bands, already referred to, by means of chains
or strand wire, is, however, not so open to objection nor attended
with such ill effects as is the case when the chain or wire is placed
in direct contact with the branch, for even with the most careful
adjusting and packing, the uneven surface of a chain, with its saw-like
action during stormy weather, soon renders the belting useless for the
purpose intended, and both bark and wood suffer in consequence.
Occasionally we see holes bored through the live branch or trunk in
order to fix the binding rod or chain—a most reprehensible practice
that, fortunately, has few supporters amongst those who have even had a
cursory knowledge of trees and their growth.
It is, however, generally admitted that there are several disadvantages
connected with bracing trees with iron rods that pass through holes
bored in the trunk or branch. However carefully this operation may be
performed, there are grave risks from insect and fungoid attacks in
holes that have been made in living wood, as the friction caused by the
movement of the tree renders healing of the wound quite problematical.
Further, the movement of an embedded iron rod is not only apt to cause
friction with the wood but the strain must often be in an opposite
direction to that which was intended, this increasing with the diameter
of the stem or branch.
Another untidy, slipshod and most objectionable method of staying a
tree is by using wire as a band around the trunk. This certainly has
the virtue of cheapness, but in so far as efficiency is concerned, and
especially in the case of old trees, it is to be deprecated.
In the repairing and strengthening of tree limbs it should consistently
be borne in mind that any girdle or band that either partially or
wholly constricts the growth of a branch defeats its own object
by preventing the uninterrupted flow of sap and impairing the
strength of the limb. With care in forming the band and a proper
method of adjusting it, there is no reason why the desired object
of strengthening a stem or branch may not be attained. On the other
hand, a badly formed, narrow band, too tightly applied and without
the requisite packing, may in a short space of time be productive of
the most unsatisfactory results, particularly in the case of young
and fast-growing trees. The main point is that the bands should be
fixed in such a way that friction to the bark is avoided and the flow
of sap uninterrupted. Unfortunately in the past this has not in all
cases been carefully provided against, with the result that the bands,
owing to their being too small, gradually became embedded in the wood
and, by injuring the cambium and preventing the flow of sap, defeated
the object for which they were intended. For fuller information on
doctoring trees, the reader is referred to my book on _Tree Wounds and
Diseases_.