PRUNING THE GRAPE IN EASTERN AMERICA
The inexperienced look on pruning as a difficult operation in
grape-growing. But once a few fundamentals are grasped, grape-pruning
is not difficult. There is much less perplexity in pruning the grape
than in pruning tree-fruits. Pruning follows accepted patterns in
every grape region, and when the pattern is learned the difficulties
are easily overcome. The inexperienced are confused by the array of
"principles," "types," "methods," "systems" and the many technical
terms that enter into discussions of grape-pruning. Some of the
technicalities come from European practices, and others originated in
the infancy of grape-growing in this country when there was great
diversity in pruning. Divested of much that is but jargon, an
inexperienced man can easily learn in a few lessons, from word of
mouth or printed page, how to prune grapes.
The simplicity of pruning has led to slighting the work in commercial
vineyards, by too often trusting it to unskilled hands. Then, too, in
this age of power-propelled tools, pride in hand labor has been left
behind, and few grape-growers now take time and trouble to become
expert in pruning. Simple as the work may seem to those long
accustomed to it, he who wants to put into his pruning painstaking
intelligence and to taste the joy of a task well done finds in this
vineyard operation an ample field for pleasure and for the development
of greater profits. The price to be paid by those who would thus
attempt perfection in pruning the vine is forward vision, the
mechanic's eye, the gardener's touch, patience, and pride in
handicraft.
Simple as pruning is, the pruner soon learns that it is an art in
which perfection is better known in mind than followed in deed. The
theory is easy but there are some stumbling blocks to make its
consummation difficult. It is an art in which rules do not suffice,
for no two vineyards can be pruned alike in amount or method, and
every grape-grower finds his vineyard a proper field for the
gratification of his taste in pruning. Happily, however, enlightened
theory and sound practice are in perfect accord in grape-pruning, so
that specific advice is well founded on governing principles.
One cannot, of course, learn to prune unless he understands the habit
of the grape-vine and is familiar with the terms applied to the
different parts of the vine. As a preliminary to this chapter,
therefore, knowledge of Chapter XVII, in which the structure of the
grape-vine is discussed, is necessary. The next step is to distinguish
between pruning and training.
PRUNING AND TRAINING DISTINGUISHED
The grape is pruned to increase in various ways the economic value of
the plant by increasing the quantity and value of the crop. This is
pruning proper. Or grapes are pruned to make well-proportioned plants
with the parts so disposed that the vines are to the highest degree
manageable in the vineyard. This is training. To repeat, the
grape-plant is pruned to regulate the crop; it is trained to regulate
the vine. Grape-growers usually speak of both operations as "pruning,"
but it is better to keep in mind the two conceptions. The distinctions
between pruning and training must be made more apparent by setting
forth in greater detail the results attained by the two operations.
_Results attained in pruning to regulate the crop._
Proper pruning of vines in their first year in the vineyard, which, as
we have seen, consists of cutting the young plants back severely,
brings the vines in productive bearing a year or two years earlier
than they would have borne had the pruning been neglected. This early
pruning, since it is done with an eye to the vigor of each vine,
insures greater uniformity in the growth and productiveness of the
vineyard. Uniformity thus brought about is important not only for the
time being, but for the future development of the vines, since weak
vines, if unpruned, are stunted and may require years to overtake more
vigorous vines in the vineyard.
The quality of the crop may be regulated by pruning. When vines bear
too heavily, the grapes are small, and wine-makers have found that
they seldom develop sugar and flavor as do grapes on vines not
over-bearing. Grapes on vines too heavily laden seldom ripen or color
well. Not only are the grapes on poorly pruned and unpruned vines poor
in quality but the grapes on such vines are usually not well
distributed and therefore ripen and color unevenly. The results just
mentioned follow because the bunches in a poorly distributed crop
receive varying amounts of light and heat depending on the distance
from the ground, the distance from the trunk and on the amount of
shade.
Pruning may be used to regulate the quantity of grapes borne in a
vineyard and so be made somewhat helpful in preventing alternate
bearing. Abnormally large crops are usually followed by partial crop
failure and biennial bearing sometimes sets in, but the large crop may
be reduced by pruning and the evil consequences wholly or partly
avoided. It follows that pruning must depend much on the vigor of the
vine; for a weak vine may be so pruned as to cause it to overbear;
and, on the other hand, a vigorous vine pruned in the same way might
not bear at all.
_Results attained in pruning to regulate the vine._
It is necessary to regulate the shape of the vine by training so that
tilling, spraying, pruning and harvesting can be easily performed and
the crop be kept off the ground. The cost of production is always less
in a well-pruned vineyard because all vineyard operations are more
easily carried out.
The life of a vineyard is lengthened when the vines are well trained,
because when the parts of a vine are properly disposed on trellis or
stake the plants are less often injured in vineyard operations.
Moreover, not infrequently vines die from over-production and
consequent breaking of canes or trunks which might have been prevented
by pruning to shape the vine. Suckers and water-sprouts are less
common on well-trained vines. It is necessary, too, by training to
keep the bunches away from trunk, canes and other bunches and so
prevent injury to the grapes.
Lastly, fashion, taste or a more or less abnormal use of the grapes,
may prescribe the form in which a vine is trained. Fashion and taste
run from very simple or natural styles to exceedingly complex, formal
ones, depending, often, on the variety, the environment or other
condition, but just as often on the whim of the grape-grower. The
grape is a favorite ornamental for fences, arbors and to cover
buildings; for all of these purposes the vines must be trained as
occasion calls.
SOME PRINCIPLES OF PRUNING
Leaving the shaping of the plant out of consideration and having in
mind pruning proper, all efforts in pruning are directed toward two
objects: (1) The production of leafy shoots to increase the vigor of
the plant. (2) The promotion of the formation of fruit-buds. The
first, in common parlance, is pruning for wood; the second, pruning
for fruit.
_Pruning for wood._
Some grapes, in common with varieties of all fruits, produce excessive
crops of fruit so that the plants exhaust themselves, to their
permanent injury and to the detriment of the crop. Something must be
done to restore and increase vegetative vigor. The most natural
procedure is to lessen the struggle for existence among the parts of
the plant. The richer and the more abundant the supply of the food
solution, the greater the vegetative activity, the larger the leaves
and the larger and stouter the internodes. Obviously, the supply of
food solution for each bud may be increased by decreasing the number
of buds. The weaker the plants, therefore, the more the vine should be
cut. The severe pruning in the first two years of the vine's existence
is an example of pruning for wood. The vine is pruned for wood in the
resting period between the fall of leaf and the swelling of buds the
following spring.
_Pruning for fruit._
Growers of all fruits soon learn that excessive vegetative vigor is
not usually accompanied by fruitfulness. Too great vigor is indicated
by long, leafy, unbranching shoots. Some fruit-growers go so far as to
say that fruitfulness is inversely proportionate to vegetative vigor.
There are several methods of diminishing the vigor of the vine; as,
withholding water and fertilizers, stopping tillage, the method of
training and by pruning. Pruning is used to decrease the vigor of the
vine, in theory at least, for the practice is not always so
successful, by pruning the roots or by summer-pruning the shoots.
Root-pruning the grape at intervals of several years is a regular
practice with some varieties in warm countries, Europe more
especially, but is seldom or never practiced in America except when
planting and when roots arise from the cion above the union of stock
and cion.
Summer-pruning to induce fruitfulness consists in removing new shoots
with newly developed leaves. These young shoots have been developed
from reserve material stored up the preceding season, and until they
are so far developed that they can perform the functions of leaves
they are to be counted as parasites. When, therefore, these shoots are
pruned or pinched away, the plant is robbed of the material used by
the lusty shoot which up to this time has given nothing in return. The
vigor of the plant is thus checked and fruitfulness increased.
Summer-pruning may become harmful if delayed too long. The time to
prune is past with the grape when the leaves have passed from the
light green color of new growth to the dark green of mature leaves.
Fruit-bearing may be augmented by bending, twisting or ringing the
canes, since all of these operations diminish vegetative vigor.
Ringing is the only one of these methods in general use, and this only
for some special variety or special purpose, and usually with the
result that the vigor of the vine is diminished too much for the good
of the plant. Ringing is discussed more fully in Chapter XVI.
_The manner of fruit-bearing in the grape._
Before attempting to prune, the pruner must understand precisely how
the grape bears its crop. The fruit is borne near the base of the
shoots of the current season, and the shoots are borne on the wood of
the previous year's growth coming from a dormant bud. Here is
manifested one of Nature's energy-saving devices, shoot, leaves,
flowers and fruit spring in a short season from a single bud. In the
light of this fact, pruning should be looked on as a simple problem to
be solved mathematically and not as a puzzle to be untangled, as so
many regard it. For an example, a problem in pruning is here stated
and solved.
A thrifty grape-vine should yield, let us say, fifteen pounds of
grapes, a fair average for the mainstay varieties. Each bunch will
weigh from a quarter to a half pound. To produce fifteen pounds on a
vine, therefore, will require from thirty to sixty bunches. As each
shoot will bear two or three bunches, from fifteen to thirty buds must
be left on the canes of the preceding year. These buds are selected in
pruning on one or more canes distributed on one or two main stems in
such manner as the pruner may choose, but usually in accordance with
one or another of several well-developed methods of training. Pruning,
then, consists in calculating the number of bunches and buds necessary
and removing the remainder. In essence pruning is thinning.
_Horizontal_ versus _perpendicular canes._
An old dictum of viticulture is that the nearer the growing parts of
the vine approach the perpendicular, the more vigorous the parts. The
terminal buds, as every grape-grower knows, grow very rapidly and
probably absorb, unless checked, more than their share of the energy
of the vine. This tendency can be checked somewhat by removing the
terminal buds, which also helps to keep the plants within manageable
limits, but is better controlled by training the canes to horizontal
positions. Grape canes are tied horizontally to wires to make the
vines more manageable and to reduce their vigor and so induce
fruitfulness; they are trained vertically to increase the vigor of the
vine.
_Winter-pruning._
Winter-pruning of the vineyard may be done at any time from the
dropping of the leaves in the autumn to the swelling of the buds in
the spring. The sap begins to circulate actively in the grape early in
the spring, even to the extremities of the vine, and most
grape-growers believe this sap to be a "vital stream" and that, if the
vine is pruned during its flow, the plant will bleed to death. The
vine, however, is at this season of so dropsical a constitution that
the loss of sap is better denominated "weeping" than "bleeding." It is
doubtful whether serious injury results from pruning after the sap
begins to flow, but it is a safe practice to prune earlier and the
work is certainly pleasanter. The vine should not be pruned when the
wood is frozen, since at this time the canes are brittle and easily
broken in handling. On the other hand, it is well to delay pruning in
northern climates until after a heavy freeze in the autumn, to
winterkill and wither immature wood so that it can be removed in
pruning.
[Illustration: PLATE IX.--Campbell Early (x2/3).]
_Summer-pruning._
There are three kinds of summer-pruning, the removal of superfluous
shoots, heading-in canes to keep the vines in manageable limits and
the pruning to induce fruitfulness discussed on a foregoing page,
which need not have further consideration. It is very essential that
the grower keep these three purposes in mind, especially as there is
much dispute as to the necessity of two of these operations.
All agree that the vine usually bears superfluous shoots that should
be removed. These are such as spring from small, weak buds or from
buds on the arms and trunk of the vine. These shoots are useless,
devitalize the vine, and hinder vineyard operations. A good practice
is to rub off the buds from which these shoots grow as they are
detected, but in most vineyards the vines must be gone over from time
to time as the shoots appear. Still another kind of superfluous
shoots, which ought to be removed as they appear, are those which grow
from the base of the season's shoots, the so-called secondary or
axillary shoots. These are usually "broken out" at the time the shoots
from weak buds are removed.
While there is doubt as to the value of heading-back the vine in the
summer for the sole purpose of inducing fruitfulness, there can be no
doubt that it is desirable for the purpose of keeping some varieties
within bounds. Heading-back is not now the major operation it once
was, the need of severe cutting being obviated by putting the vines
farther apart, by training high on three or even four wires and by
adopting one of the drooping systems of training. The objections to
heading-back in the summer are that it often unduly weakens the vines,
that it may induce a growth of laterals which thicken the vines too
much, and that it delays the maturing of the wood. These bad effects,
however, can be overcome by pruning lightly and doing the work so late
in the season that lateral growths will not start. Most vineyardists
who keep their plantations up find it necessary to head back more or
less, depending on the season and the variety. The work is usually
done when the over-luxuriant shoots begin to touch the ground. The
shoots are then topped off with a sickle, corn-cutter or similar tool.
RENEWING FRUITING WOOD
There are two ways of renewing the fruiting wood on a grape-vine, by
canes and from spurs. The manner of renewing refers to pruning and not
to training, for either can be used in any method of training.
_Cane renewals._
Renewal by canes is made each year by taking one or more canes, cut to
the desired number of buds, to supply bearing shoots. By this method
the most of the bearing wood is removed each year, new canes taking
the place of the old. These renewal canes may be taken either from the
head of the vine or from the ground, though the latter is little used
except where vines must be laid down for winter protection. Canes may
be renewed indefinitely, if care is exercised in keeping the stubs
short, without enlarging the head from which the canes are taken out
of proportion to the size of the trunk. Renewing by canes is a more
common method than renewal by spurs, as will be found in the
discussion of methods of training.
[Illustration: FIG. 13. Vine ready for pruning; _i_, the stem; _g_,
arms; _d_, canes; _s_, shoots; _b_, spurs. The faint lines near the
bases of the canes indicate the points where they should be pruned off
in the winter, leaving spurs for the production of shoots the
following season.]
_Spur renewal._
In renewing by spurs, a permanent arm is established to right and left
on the canes. Shoots on this arm are not permitted to remain as canes
but are cut back to spurs in the dormant pruning. Two buds are left at
this pruning, both of which will produce bearing shoots; the lower
one, however, is not suffered to do so but is kept to furnish the spur
for the next season. The shoot from the upper bud is cut away
entirely. When this process is carried on from year to year, the spurs
become longer and longer until they become unwieldy. Occasionally,
however, happy chance permits the selection of a shoot on the old wood
for a new spur. Failing in this, a new arm must be laid down and the
spurring goes on as before. The objections to renewing by spurs are:
it is often difficult to replace spurs with new wood, and the bearing
portion of the vine gets farther and farther from the trunk. For these
reasons, spur-renewing is generally in disfavor with commercial
grape-growers, though it is still used in one or two prominent
methods of training, as will be discovered in this discussion. Figure
13 shows a vine ready for pruning.
THE WORK OF PRUNING
The pruner may take his choice between several styles of hand
pruning-shears with which to do his work. The knife is seldom used
except in summer-pruning, and here, more often, the shoots are broken
out or pinched out. In winter-pruning, the cane is cut an inch or
thereabout beyond the last bud it is desired to leave; otherwise the
bud may die from the drying out of the cane. The canes are usually
allowed to remain tied to the wires until the pruning is done, though
growers who use the Kniffin method of training may cut them loose
before they prune. Two men working together do the work of pruning
best. The more skilled of the two severs the wood from the bearing
vine, leaving just the number of buds desired for the next season's
crop. The less skilled man cuts tendrils and severs the cut canes from
each other so that the prunings may be moved from the vineyard without
trouble by the "stripper."
Not the least of the tasks of pruning is "stripping" the brush and
getting it out of the vineyard. The prunings cling to the trellis with
considerable tenacity and must be pulled loose with a peculiar jerk,
learned by practice, and placed on the ground between the rows.
Stripping is done, usually by cheap labor, at any time after the
pruning until spring, but must not be delayed until growth starts or
the young buds may suffer as the cut wood is torn from the trellis.
The brush is hauled to the end of the row by hand or by horse-power
applied to any one of a dozen devices used in the several grape
regions. One of the best is the device in common use in the Chautauqua
vineyards of western New York. A pole, twelve feet long, four inches
in diameter at the butt and two at the top, is bored with an inch
hole four feet from the butt. A horse is hitched to this pole by a
rope drawn through the hole, and the pole, butt to the ground, is then
pulled between rows, the small end being held in the right hand. The
pole, when skillfully used, collects the brush, which is dumped at the
end of the row by letting the small end fly over towards the horse.
The "go-devil," shown in Fig. 14, is another common device for
collecting prunings.
[Illustration: FIG. 14. A "go-devil" for collecting prunings.]
THE TRELLIS
The trellis is a considerable item in the grape-grower's budget, since
it must be renewed every fifteen years or thereabouts. Wires are
strung in the North at the end of the second season after planting,
but in the South the growth is often so great that the wires must be
put up at the end of the first season. Trellises are of the same
general style for commercial vineyards; namely, two or three wires
tautly stretched on firmly set posts. Occasionally slat trellises are
put up in gardens but these are not to be recommended for any but
ornamental purposes.
_Posts._
Strong, durable posts of chestnut, locust, cedar, oak or reenforced
cement are placed at such distance apart that two or three vines can
be set between each two posts. The distance apart depends on the
distance between vines, although the tendency now is to have three
vines between two posts. The posts are from six to eight feet in
length, the heaviest being used as end posts. In hard stony soils it
may be necessary to set the end posts with a spade, but usually
sharpened posts can be driven into holes made with a crowbar. In
driving, the operator stands on a wagon hauled by a horse and uses a
ten- or twelve-pound maul. The posts are driven to a depth of eighteen
or twenty-four inches for the end posts. However set, the posts must
stand firm to hold the load of vines and fruit. The end posts must be
braced. As good a brace as any is made from a four-by-four timber,
notched to fit the post halfway up from the ground, and extending
obliquely to the ground, where it is held by a four-by-four stake. A
two-wire trellis and a common method of bracing end posts are shown in
Fig. 15. The posts on hillsides must lean slightly up-hill, otherwise
they will almost certainly sooner or later tilt down the slope. The
posts are usually permitted to stand a little higher at first than
necessary so that they may be driven down should occasion call;
driving is usually done in the early spring.
[Illustration: FIG. 15. A trellis and a common method of bracing end
posts.]
_Wire for the trellis._
Four sizes of wire are in common use for vineyard trellises; nos. 9,
10, 11 and 12. Number 9, the heaviest, is often used for the top wire
with lighter wires lower. The following figures show the length of
wire in a ton:
No. 9, 34,483 ft.
No. 10, 41,408 ft.
No. 11, 52,352 ft.
No. 12, 68,493 ft.
From these figures the number of pounds required to the acre is easily
calculated. Common annealed wire makes a durable trellis, but many
growers prefer the more durable galvanized wire, the cost of which is
slightly greater. The wires are fastened to the end posts by winding
once around the post, and then each wire is firmly looped about
itself; they are secured to the intervening posts by ordinary fence
staples so driven that the wire cannot pull through of its own weight
but with space enough to permit tightening from season to season. The
size and length of the staples depend on whether the posts are hard or
soft wood. The longest and largest staples are used with soft woods,
as cedar or chestnut. An acre requires from nine to twelve pounds of
staples. The wires should be placed on the windward sides of posts and
on the up-hill side in hillside vineyards. The distance between wires
depends on the method of pruning.
The wires must be stretched taut on the posts, for which purpose any
one of a half-dozen good wire stretchers may be purchased at hardware
stores. Some growers loosen the wires after harvest to allow for the
contraction in cold weather and others use some one of several devices
to relieve the strain. Most growers, however, find it necessary to go
over the vineyard each spring to drive down loosened posts and stretch
sagging wires, and so take no precautions to release wires in the
fall. All agree that the wires must be kept tight during the growing
season to protect buds, foliage and fruit from being injured from
whipping.
_Tying._
The canes are tied to the trellis in early spring, and under most
systems of pruning the growing shoots are tied in the summer. This
work is done by cheap men, women, boys and girls. A great variety of
material is used to make the tie, as raffia, wooltwine, willow, inner
bark of the linden or basswood, green rye straw, corn husks,
carpet-rags and wire. The same materials are not usually employed for
both canes and shoots, since the canes are tied firmly to hold them
steady and the work is done early before there is danger of breaking
swelling buds, while the summer shoots are tied to hold for a shorter
time and more loosely to permit growth in diameter. Tying usually
follows accepted patterns in one region but varies greatly in
different regions. There is a knack to be learned in the use of each
one of the materials named, but with none is it difficult, and an
ingenious person can easily contrive a tie of his own to suit fancy or
conditions.
[Illustration: PLATE X.--Clinton (x2/3).]