GRAFTING
“Grafting is the process by which a twig or a bud [5] is transplanted
from one branch to another, or from one tree to another. That which is
to serve as support and sustenance to the transferred part is known as
the stock, while the twig or bud received by it is called the graft.
“One absolutely necessary condition must be fulfilled if this operation
is to be successful: the transferred part must find on its new
nursing-branch nutriment to its taste, that is to say, a sap like its
own. This requires that the two plants, the stock and the one that
furnishes the graft, should be of the same species or at least belong
to closely related species, since likeness of sap and its products can
result only from likeness of organization. It would be a mere waste of
time to try to engraft the lilac upon the rose, or the rose upon the
willow, for there is nothing in common between these three species
either in leaves, flowers, or fruit. This difference in structure is
invariably accompanied by a marked difference in respect to nutrition.
Hence the rose-bud would starve to death on a lilac-branch, and the
lilac-bud would meet with the same sad fate on a rose-bush. But lilac
can very well be grafted on lilac, rose-bush on rose-bush, vine on
vine. And one can even go further than this: a peach-bud will flourish
on an apricot-tree, a cherry-bud on a plum-tree, and vice versa; for
between the members of each of these pairs there is a close and easily
discernible analogy. In short, there must be the closest possible
resemblance between the two plants if grafting is to succeed.
“The ancients were far from having any clear idea on this absolute need
of likeness in organization. They tell us of grafting the holly with
the rose to obtain green roses, the walnut tree with the grape to
produce enormous grapes as large as walnuts. In our own time has not
the project been seriously considered of grafting a vine shoot on to a
mulberry tree in order to restore vigor to the grape whose roots an
underground grub has attacked? Such graftings and others between plants
completely unlike have never been successfully undertaken except in the
imagination of those who dreamt them.
“We have already seen that, grown from seed, our various fruit trees do
not, as a rule, reproduce the quality of fruit of the parent stock; an
invincible tendency to revert to the wild state causes the fruit to
lose, little by little, from one generation to another, the improvement
it had acquired through cultivation. Thus the pear, through repeated
plantings of the seed, would become increasingly sour, small, and hard,
until it had at last returned to the sorry state of the wild pear
growing on the edge of the woods. But this defect attending growth from
the seed is redeemed by one very desirable quality: the tree thus grown
regains more or less the robustness of its wild type; it is
incomparably more vigorous, healthier, longer-lived, than the
artificially perfected tree whose strength is compromised by the very
excess of its fructification. One has vigor, the other fine fruit. The
two attributes cannot go together; if one increases, the other
decreases. Well then, these robust specimens reared from the seed are
just what we require for grafting. Used as stocks, they supply the
quality inherent in them, namely, vigor; and the cutting engrafted upon
them furnishes the other quality, excellence of fruit.
“Accordingly it is the practice to plant the pips of pears and apples,
and the stones of apricots and peaches; and on the trees thus obtained
to graft cuttings from pear, apple, apricot, and peach trees that bear
fruit of recognized superiority. In this way there are united in the
same tree the root and trunk of the robust and almost wild kind with
the leaves and blossoms of the weak but artificially improved kind.
Every variety of pear tree is by nature fitted to receive a pear graft,
every variety of peach tree to receive a peach graft, and so on with
all fruit-trees. There is no objection to selecting as stock any wild
pear, cherry, or plum tree that may have sprung up of itself in hedge
or thicket. It is thus for example that the cherry is grafted on two
others of like sort, the wild cherry and the cherry of Saint Lucia,
both frequenters of uncultivated hillsides. The first bears fruit
hardly as large as a pea, black, round, and full of a very dark and
rather bitter juice; the second has still smaller fruit with scarcely
any pulp and uneatable. No matter: with grafts from a suitably chosen
source they will cover themselves with the finest cherries. In like
manner our superb garden roses can be grown on the wild rose stock, the
common dog rose of the hedges, whose modest blossoms have only five
petals of a pale carnation color and are well-nigh odorless. Sometimes,
again, two species of similar characteristics are chosen for grafting
purposes. Thus the pear grafts well on the quince-tree, the fruit of
the latter being, after all, a sort of big pear; the apricot can be
grafted on the plum; the peach on the plum and, still better, on the
almond, so like the peach in its foliage, its early blossoming, and the
structure of its fruit.
“As a curiosity let us mention the mixing of several kinds of fruit on
the same stock. By means of grafting the same tree can bear, all at one
time, almonds, apricots, peaches, plums, and cherries, because these
five kinds admit of reciprocal grafting; another tree may be covered
simultaneously with pears, quinces, berries of the mountain ash,
medlars, and service-berries. These are very odd instances, certainly,
but of no practical interest. It would be a waste of time to dwell
longer on them did they not teach a useful lesson. They demonstrate
that however many fresh grafts are added to a tree, the new-comers
exert no influence outside their own sphere. Whether offshoots of the
tree itself or aliens, the grafts develop, blossom, and fructify, each
after its own kind, without contracting any of its neighbor’s habits.
Among the curious phenomena observed in this artificial juxtaposition
of mutually independent grafts, we will mention a pear-tree on which
were represented, by means of grafting, all the different varieties of
cultivated pears. Sour or sweet, dry or juicy, large or small, green or
bright-colored, round or long, hard or mellow, each and all ripened on
the same tree and grew again year after year without change, faithful
to the specific character, not of the supporting tree, but of the
various grafts planted on this common stock.
“The mere bringing together of analogous plants does not suffice for
the success of the operation of grafting; there must be a considerable
extent of contact between those parts of the graft and the stock that
have the most vitality and are consequently best fitted to coalesce.
This contact should be in the inner layers of the bark and in the seat
of plant-growth situated between the wood and the bark. The vital
activity of the plant, in fact, resides especially in this region. It
is between the wood and the bark that the elaborated sap descends;
there is where new cells and new fibers are organized, to form on one
side a sheet of bark and on the other a layer of wood. Hence it is
there and only there that coalescence is possible between the graft and
the stock.”