SLIPPING
“Propagation by means of a slip or scion cut from the parent tree and
so placed that it will develop adventitious roots we may for
convenience speak of as slipping. The cut end of the slip is set in the
ground in some cool, moist, shady spot where evaporation is slow and
the temperature mild. For delicate slips the shelter of a bell-glass is
often necessary in order to insure the requisite moisture in the
atmosphere and thus prevent the slip from drying up before it has sent
down roots to make good its losses. For greater surety, if the slip has
many leaves, most of the lower ones are removed in order to reduce the
evaporating surface as much as possible without compromising the
plant’s vitality, which resides especially in the upper part. But in
many cases these precautions are needless; thus, to propagate the
grape-vine, willow, and poplar, it suffices merely to thrust the
detached scion into the ground.
“Trees whose wood is soft and well filled with sap are the ones best
fitted for slipping; to this class belongs the willow, with its notably
tender fiber. On the other hand, wood that is dense and hard gives us
sure warning that this mode of propagation will be found very difficult
or even impossible. Thus it would invariably fail with the oak, the
olive, the box-tree, and a great many more hard-wood trees.
Furthermore, slipping offers far less certainty of success than
layering, since the layer remains in communication with the parent
stock and is thus supplied with nourishment until it has acquired roots
of its own, whereas the slip, all such communication being abruptly cut
off, is obliged from the outset to rely on its own resources and pass
without help through the difficult period of rootlessness. Among
fruit-bearers there are scarcely any except the grape-vine, the
currant-bush, the quince-tree, and a few varieties of plum and apple
trees, that lend themselves to this method of propagation. Among the
larger trees the willow and the poplar take root with no difficulty
whatever when started from the slip. Finally, a great many ornamental
species, herbaceous plants or bushes like the rose, jasmine, and
honeysuckle, multiply easily by this method, the usual one adopted with
them by the flower-gardener.
“Let us go back now to the very simplest case, the one calling for the
fewest precautions. A damp piece of ground on the water’s edge is to be
planted with poplars or willows. Toward the end of winter the forester
in charge cuts a sufficient number of vigorous young branches as large
around as a stout cane or even a man’s fist, or perhaps larger, and
from one to four meters long. He removes all the lower twigs, clips the
intermediate ones to half their length, and leaves the upper ones
intact if the tree is to be pyramid-shaped; otherwise he gives the top
a truncate form. Finally the lower end is cut to a point with the
hatchet, to make it easier to thrust into the ground. Now the slip is
ready for planting, and all that is necessary is to push it well down
into the earth by its pointed end and leave it to itself. Without any
further attention, if the ground is sufficiently damp, adventitious
roots will start, and each of the stakes thus rudely hacked will become
a poplar or a willow.
“But other forms of vegetation are far from manifesting this facility
in rooting which makes possible the growth of a tree from a stake
driven into the ground, it may be with the blow of a club; therefore
delicate precautions are necessary for success if these obdurate
subjects are to be propagated by slips. Let us take the grape-vine as
an example. Its slips for planting are shoots of the same year’s
growth. These are tied in a bundle and their cut ends placed in water
to soak for a week or more. Why this long immersion of the part that
later is to be planted in the ground? Because the outside bark is dry
and tough, difficult for tender roots to pierce, especially if the soil
is dry. Accordingly the bark is softened by soaking for some time in
water; and also, when the slips are taken out of the water, they are
lightly scraped where they are to be in the earth, but left untouched
where they are to be in the air. In this way the outer layer of bark is
removed after being softened in water, and there is so much the less
resistance offered to the growing roots; but the inner layers, where
the vine’s vital activities go on, are scrupulously spared. The slight
wounds inflicted by this scraping, let it be further noted, favor the
starting of roots by arresting the sap. After being prepared in this
manner the slips are set out. In soil that has been well worked so that
the young roots may push downward without hindrance, vertical holes are
made with a long iron or wooden dibble, and in each of these holes a
slip is inserted to the depth of about half a meter. Fine earth is then
sifted into the hole and well rammed down to insure perfect contact
with the slip, and the operation is finished.
“Just as the process of layering is facilitated by the formation of a
ring-shaped swelling where the descending sap is arrested in its course
either by a ligature or by the removal of a ring of bark, so the same
artifice can be advantageously employed in propagating by means of
slips. Around the shoot selected as slip for the next year’s planting
an iron wire is tightly bound; or, instead of this, a ring of bark is
cut away. By autumn a swelling will have formed all about the stem,
whereupon the shoot is detached and placed in the ground for the winter
in order that the swelling may become a little further enlarged and
somewhat softened. In the spring the shoot is taken up again, trimmed
so that it shall have only four or five buds left, and planted like an
ordinary slip. From the ring-shaped swelling caused by the accumulation
of sap roots will start.
“All the advantages offered by the ring-shaped swelling may be secured
with no expenditure of ingenuity on our part. Take hold of a small
branch and pull it down so as to split it off from the main stem. Thus
torn away it will bring with it a sort of spur or splinter from the
trunk directly under the severed branch. This spur, trimmed with a
knife to give it a less ragged outline, will render the same service as
the ring-shaped swelling: the descending sap will be stopped in its
course at this point, will accumulate, and will foster the growth of
adventitious roots.
“Instead of breaking off the branch by tearing it away at its base, one
can, with a stroke of the pruning-knife above this base and another
below it, cut the older limb bearing this branch so that the latter
carries with it a piece of the former. With this piece as a sort of
natural bourrelet or swelling, success is rendered more assured than in
any other way.
“To conclude, let us say a few words about slipping by means of buds, a
kind of planting that uses buds instead of seeds. This method, which
requires the nicest care of any, is adopted only in exceptional cases.
Let us suppose we have a very few shoots, or only one, from some
extremely rare variety of grape-vine, and we wish to obtain from this
single shoot the greatest possible number of slips. To this end the
shoot is cut into small pieces about five centimeters long, each
bearing a bud midway of its length. These pieces are then each split in
two lengthwise, and the part with the bud is retained, the other thrown
away. Thus prepared, the pieces are planted in fertile soil with the
split surface underneath and the bud just peeping out of the earth. But
to insure any likelihood of success with this method, certain special
conditions not called for in ordinary planting must be observed, as
will be readily understood. The delicate slips are arranged with care
in an earthen pan or pot, and covered with a bell-glass to assure them
a moist and warm atmosphere. After roots have started the slips are
transplanted, each being placed in a separate pot where it gains
strength and awaits the proper time for planting in the ground.”