LAYERING
“Some plants, and among them the pink, send out from the base of the
mother stalk straight, pliant shoots which can be used for obtaining so
many new plants. These shoots are bedded by being bent elbow-wise and
having the angle stuck into the ground and fastened there with a
crotch; then the end is raised upright and held so by means of a stake.
Sooner or later the buried elbow sends down adventitious roots, but
until then nourishment is drawn from the parent stock. When the buried
parts have sent down enough roots, the connections are cut between the
old plant and the new ones, and each of these latter, set out by
itself, is thenceforth a distinct plant. This operation is called
layering, and the several shoots used in obtaining new plants are
called layers.
“Let us now put into practice the method we have just been studying in
theory. In a vineyard, we will suppose, a number of the vines have died
from some cause or other, and it is necessary to replace them. Layering
offers us the readiest means and will occasion least delay to the
harvest. Near the place occupied by the dead vine we select a stock
provided with a vigorous shoot of sufficient length and conveniently
situated. Then we dig down where the old vine stands and pull up all of
the lifeless stalk as well as the roots, since these are seats of decay
that might infect the whole neighborhood. Finally, in the soil thus
stirred we dig a ditch two or three decimeters deep, and in this we lay
the shoot we have selected, taking care in bending it down not to break
or splinter it. The part thus put into the ground is then covered with
a tolerably thick layer of earth, and on this, to complete the filling
of the ditch, is thrown a basketful of manure. The tip of the shoot is
raised upright, tied to a stake, and trimmed in such a manner as to
retain only two eyes or buds above ground. As to the eyes on the part
extending from the mother stem to the point where the shoot plunges
into the ground, they are nipped off because they would needlessly
appropriate a part of the sap. This operation is called vine-layering,
and the shoot bent down and placed in the ground we speak of as a
vine-layer. The best time for this work is the beginning of winter,
because the long rest enjoyed by the shoot in the ground throughout the
season when vegetation slumbers disposes it to sprout with more vigor
upon the renewal of sap-circulation in the spring.
“Let us now watch the behavior of the partly buried vine-shoot. If it
had remained all in the open air, it would have borne fruit; it would
have had its three or four bunches of grapes. Why should it not do so
under the conditions imposed by the vine-dresser, conditions that have
altered nothing in its relations to the mother stem? It still remains
in uninterrupted communication with the vine that sustains it; it
receives its share of ascending sap drawn from the soil by the roots of
this vine; the buds remaining to it will develop leaves which, with the
help of sunlight, will convert this crude sap into elaborated sap; in
short, it lacks nothing to enable it to function almost as it would
have done had it not been partly buried. And in fact the vine-layer
does bear that same year; if well cared for, it bears several bunches
of grapes. So the proverb says: The vine-layer pays its owner from the
very first year. Meanwhile, acted on by the coolness and moisture of
the soil and the stimulus of fertilization, it puts forth adventitious
roots where it has been placed underground, and these roots grow in
number and vigor until the time comes when they suffice to nourish the
young vine without the help of the mother stem. It is in the third year
that the rooting is far enough advanced for the young offshoot’s
independent existence. Weaning is then undertaken, and the nursling is
deprived of its nurse; that is to say, a stroke of the pruning-knife
close to the ground and on the side toward the parent stock separates
the latter from the vine-layer, which becomes henceforth
self-supporting.
“With its long shoots so near the ground the vine offers every
convenience for carrying out the operation just described; but as a
general rule shrubs and trees are far less favorably situated: their
branches are not long enough or flexible enough or (a prime essential)
near enough to the ground to be bent down and laid in the trench dug
for receiving the layer. How is this difficulty to be overcome? The way
is very simple. We have already observed the effect of cutting back; we
know that a stem cut back, that is to say cut off close to the ground,
develops around the border of its wound numerous adventitious buds
which grow into so many shoots. They are precisely the sort of shoots
we need, long, flexible, and starting from the level of the ground.
Each of them, if treated as a layer, partly buried in a trench where it
is fixed with a crotch, and held, above ground, in a vertical position
by means of a prop, takes root sooner or later according to its
species, and can then be transferred as an independent plant to any
desired spot. Such is the simple method known both as layering and as
arching, because it is essentially the same as ordinary layering and at
the same time necessitates the bending of the young shoot so as to
describe an arch.
“The following method dispenses with this bending, which is
impracticable when the wood is too brittle. In the spring the stalk or
trunk that is to furnish the layers is cut back. All around this
cross-section young shoots soon make their appearance, after which it
is only necessary to wait until they are long enough but have not yet
lost their tenderness, a state most conducive to the growth of
adventitious buds; then the parent trunk is earthed up, or in other
words light soil is heaped all about the stump so as to cover the lower
part of each shoot. The earth is piled up in the shape of a truncated
cone with a cup-shaped hollow at the top to receive water from time to
time and thus maintain the necessary degree of moisture and coolness.
Kept damp and cool in this manner, the young shoots will before long
send down adventitious roots, and the following year there will be a
cluster of rooted plants that can easily be detached with a knife. That
is what is called layering by earthing up or by sprouting.
“If it is found undesirable to cut back the parent stem in order to
obtain shoots for layering, and if at the same time the shoot that we
wish to root is too high to be bent down and inserted in the ground,
the following expedient may be employed. A flower-pot broken in two
lengthwise or a leaden cornucopia is hung on the tree, and the branch
to be rooted is placed lengthwise in the pot or cornucopia. The pot is
then filled with mold or moss kept damp by frequent watering, and the
result, sooner or later, is the growth of adventitious roots. When
these are suitably developed, gradual weaning is next in order; that is
to say, underneath the pot a slight cut is made, and this is deepened
day by day. The end here in view is to accustom the layer little by
little to do without the mother stem and support itself. At last the
separation is complete. This gradual weaning is no less advantageous
when the layers are placed in the ground: it assures the success of the
operation.
“If the wood is tender, adventitious roots spring without difficulty
from the interred part, and the methods already described suffice for
the success of the layering; but woods of dense structure are more or
less obstinate about taking root, and might remain in the ground
indefinitely without yielding. In such cases our art must intervene,
based on the plant’s manner of living. Let us recall the effect of a
band drawn tightly about a stalk or trunk. Above this line of
strangulation the descending sap accumulates more and more, since it
can no longer continue on its course between the wood and the bark,
this latter being compressed by the ligature. It accumulates and
produces a ring-shaped swelling where the plant tries to discharge on
the outside the superabundance of matter arrested in its passage. Let
this protuberance be heaped about with fresh earth, and adventitious
roots will speedily be developed to allow the sap to continue its
descent. A tiny streamlet, running free, follows its channel without
effort and without any undermining of obstacles. But if we obstruct its
passage the accumulating body of water will gain power to open new
vents for itself through the dam. Sap does likewise. Circulating freely
in its natural channel, it is not diverted from its course by any
allurements on its way; and unless the conditions present in wood and
bark favor the growth of new roots, no sap will be expended for this
purpose. But if its usual passage is barred, the sap devotes its
energies to the formation of adventitious roots in order that it may,
through them, resume its interrupted course. A like result follows if a
ring of bark is removed from the buried part of the branch or shoot
that we wish to take root. The arrested sap produces a ring-shaped
swelling on the upper edge of the wound, and from this swelling spring
roots.
“Now let us apply these theoretical principles. If the wood is compact
and for that reason rebels against the laws of simple layering, we will
take a piece of wire and strangle (that is the word) the branch we are
operating upon; that is to say, we will bind it tight, but without
breaking the bark. The compression should be made just below a bud or
eye, and about midway of the part that is to be underground. This
process is called layering by strangulation.
“Or again, still midway of the part to be bedded in the earth, and
immediately under a bud, we cut the bark all around the branch without
injuring the wood; a second incision is made a centimeter and a half
lower down; then tearing off the strip of bark between the two
circumcisions, we remove it all in one piece. This method is known as
annular incision from the ring of bark thus taken away.
“Or as a third expedient, still midway of the part to be bedded in the
trench, we make with a sharp instrument an oblique incision from below
upward, cutting into the wood as far as the marrow. In this way we are
enabled to raise a tongue comprising half the thickness of the shoot,
and this tongue is held in its lifted position by a small pebble
inserted in the slit. This is what we call a Y-shaped incision, because
the raised tongue forms with the rest of the stem an opening like that
between the two branches of the letter Y. Through the half that remains
intact communication with the mother stem is maintained and the needed
share of crude sap is received, while from the cut and upraised half
adventitious roots are put forth because the course of the descending
sap is arrested there.
“In order to bring into contact with the damp soil a greater extent of
wounded fiber fit for putting forth adventitious roots, it is customary
to split the upraised tongue in two and keep the two parts gaping by
interposing a small pebble. This method of double incision is used for
trees that offer the greatest resistance to successful layering.
“To sum up, all these methods and others derived from them have for
their object the fostering of adventitious roots by arresting the
course of the descending sap at a certain point beneath the soil.”