GRAFTING
(Continued)
“There are three principal kinds of grafting, namely: grafting by
approach (also called simply ‘approaching’ or ‘inarching’), grafting by
shoots or scions, and grafting by buds (commonly known as ‘budding’).
The form given to the two cut ends that are brought together and the
disposition of the parts thus placed in contact give rise, in practice,
to numerous subdivisions that need not be mentioned here. We will
confine ourselves to the essentials.
“Grafting by approach is analogous to layering, with this difference,
that the tree to be grafted takes the place of the soil that receives
the layer. In layering we induce the growth of adventitious roots by
partly burying in the ground a branch or shoot still adhering to the
stock that nourishes it. When, acted upon by the soil, roots have
started in sufficient number, the shoot is gradually cut loose until at
last it is quite severed from the parent stock. In grafting by approach
it is also proposed to make a branch, a shoot, a tree-top, while still
united to its own stem or stock, take root, so to speak, not in the
ground, but in the substance of a neighboring tree.
“Let us suppose that two shrubs are growing close together and that we
wish to engraft on one of them a twig or shoot of the other. The parts
to be placed in contact receive each a longitudinal gash that
penetrates to the marrow, or even deeper, and the two gashes are made
of equal length. These parts are then brought together, care being
taken to make the young and growing portions in the one exactly meet
those in the other; that is to say, the inner layer of bark in each,
with the channel traversed by the elaborated sap, is carefully fitted
to the corresponding part in its neighbor. The whole is thereupon made
fast with a ligature, and the two wounds are left to the slow operation
of vital forces. Fed by its own stem or trunk, from which it is not yet
separated, the shoot to be transplanted mingles its sap with the sap of
its neighbor; on both sides there are new growths to cicatrize the
wounds, while the two parts gradually coalesce until, sooner or later,
the graft becomes incorporated with its future support. And now the
graft must be weaned; that is, it must, little by little, be deprived
of the sustenance furnished by its own stock. This is accomplished as
in simple layering, by gradually cutting through the shoot below the
point of union. As soon as the graft is thought to be getting all its
nourishment from the new stem, it is completely severed from the mother
tree. This mode of grafting, the most elementary of all, sometimes
takes place accidentally and unassisted. In a hedge or any dense growth
of bushes, if two branches chance to come into close and prolonged
contact, there will be at this point, first, a slight abrasion and then
a complete wearing away of the bark until the two raw surfaces end, it
may be, in growing together. It is not improbable that natural
occurrences of this kind furnished man with his first notions of
grafting.
“Grafting by approach is an excellent method to apply whenever in the
arrangement of a fruit-tree’s branches there is a vacant space that
needs filling. Regular distribution, symmetry of arrangement, is a
condition demanded if only to satisfy the eye, which is always offended
by disorder; but there is another and still more convincing reason for
this regularity. The more evenly a tree’s branches are distributed, so
that each shall receive an equal share of sap, sunlight, and heat, so
much the more fruit will it bear. Suppose, then, there is a lack of
branches in some part. To fill this gap and thus restore the tree’s
symmetry, grafting by approach offers a ready means. From a branch near
the vacant space and itself sufficiently supplied with twigs or shoots,
one of these latter, of good length, is selected; then it is properly
cut or gashed and the gash is brought into contact with a similar gash
at the point where it is desired to start a new growth; and, finally, a
ligature is applied to hold the two parts together. As soon as
coalescence is complete the graft is severed below the point of union,
and the lower section, after being straightened up again, is ready to
serve once more as branch to the limb that bears it. In this way, with
no loss to themselves, the more abundant branches furnish offshoots to
the poorer ones.
“Grafting by means of shoots or scions cut from the parent stock at the
outset is analogous to slipping. It consists in transplanting on to a
new stock a shoot detached from its mother branch. The most common
method is cleft-grafting. It is done in the spring when the buds begin
to open. Shoots of the preceding year are chosen for grafts, care being
taken to select those that are vigorous and that have attained no later
than August the hard and woody condition necessary for resistance to
the severities of winter. One precaution at the very outset must be
taken. When the graft is put in place it will be of the utmost
importance that it shall find in its new position nourishment
proportionate to its needs. It would infallibly perish if it should
prove to be in a more advanced state of vegetation than the stock
selected to nourish it. The latter, therefore, ought to be rather ahead
of than behind the former in this respect. To secure this result,
between one and two months before the operation is to be carried out it
is well to cut the grafts and place them in the ground on the north
side of a wall, where they will remain quiescent while the branches to
which they are to be transferred will make progress and their sap will
start.
“We will suppose there is a worthless pear-tree in our garden, grown
from a pip or transplanted from its native wood, and we propose to make
it bear good pears. The course to pursue is as follows. We cut off
entirely the upper part of the wild pear tree, trimming the cut with
our pruning-knife so that there are no ragged edges, since these would
not scar over readily and might become the seat of a far-reaching
decay. If the trunk is of moderate size and is to receive but one
graft, it is cut a little obliquely with a small level surface on the
upper edge, as shown in the picture. In the middle of this horizontal
facet a split is made to the depth of about six centimeters. That done,
we take one of the grafts set aside as already indicated, and we cut it
so as to leave only two or three buds, of which the topmost one should
be at the tip of the branch. Then, just under the lowest bud we whittle
the end of the graft into the shape of a knife-blade, letting the bud
stand just above the back or dull edge of the blade. For greater
stability when the graft is put in place, a narrow inverted ledge is
cut at the top of the blade on both sides. A glance at the picture will
show you all these little details. Finally, the graft is slipped into
the cleft of the stock, bark exactly meeting bark, wood meeting wood.
The whole is brought tightly together by binding, and the wounds are
covered with grafting mastic, which may be bought already prepared. If
this mastic is lacking we can use what is known in the country as Saint
Fiacre’s ointment, a sort of paste made of clay, or rather a mixture of
clay and cows’ dung, the fibrous nature of the latter preventing the
former from cracking. A winding of rags holds the ointment in place.
Thus wound, the stump does not suffer from exposure to the air, which
would dry it up. In course of time the wounds cicatrize, and the bark
and wood of the graft coalesce with the bark and wood of the severed
trunk. Finally the buds of the graft, nourished by the stock, develop
into branches and at the end of a few years the top of the wild pear
tree is replaced by that of a cultivated pear tree bearing pears equal
to those of the tree that furnished the graft.
“The operation of cutting back a branch or trunk to receive the graft
always promotes the growth of numerous buds. What is to be done with
the shoots that spring from these? Evidently they must be suppressed,
for they would appropriate, to no good end, the sap intended for the
graft. Nevertheless the suppression must be done cautiously. Let us not
forget that what primarily causes the sap to ascend is the evaporation
of moisture from the leaves. As long as the graft has not opened its
buds and spread its leaves, it is well to let the young shoots of the
stock remain untouched. They act as helpers, in that their foliage
draws upward the juices extracted from the soil by the roots; so that,
far from having an injurious effect at this time, their presence is
most useful. But the day will come when the graft alone will suffice
for this work of pumping up the sap, and then it is best to get rid of
these messmates which, of heartier appetite than the graft, would soon
starve it out. First the lower shoots of the stock are suppressed, then
gradually those higher up, care being taken not to destroy the top ones
until the graft has developed shoots two or three decimeters long.”