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Ringing Grape Vines

The ringing of woody plants is a well-known horticultural practice.
Three objects may be attained by ringing: unproductive plants may be
brought into bearing by ringing; the size of the fruits may be
increased and thereby the plants be made more productive; and the
maturity of the fruit may be hastened. In European countries, ringing
has long been practiced with all tree-fruits and the grape, but in
America the operation is recommended only for the apple and the grape
and with neither fruit is ringing widely practiced. Experiments
carried on at the New York Agricultural Experiment Station by Paddock,
as reported in Bulletin 151 from this Station, show that ringing may
well be practiced by grape-growers under some conditions. Since
Paddock's experiments, and possibly to some extent before, the grape
has been ringed to produce exhibition fruits or a fancy product for
the market.

Ringing consists in taking from the vine a layer of bark around the
vine through the cortex and bast of the plant. The width of the wound
varies from that of a simple cut made with a knife to a band of bark
an inch in diameter. The operation is performed during that period of
growth in which the bark peels most readily from the vine, the period
of greatest cambial activity. The term "ringing" is preferred to
"girdling," a word sometimes used, since the latter properly
designates a wound which extends into and usually kills the plant.

The theory of ringing is simple. Unassimilated sap passes from the
roots of the plant to the leaves through the outer layer of the woody
cylinder. In the leaves this raw material is acted on by various
agents, after which it is distributed to the several organs of the
plant through vessels in the inner bark. When plants are ringed, the
upward flow of sap is continued as before the operation, but the newly
made food compounds cannot pass beyond the injury, and therefore the
top of the plant is supplied with an extra amount of food at the
expense of the parts below the ring. The extra food produces the
results noted.

It turns out in practice that ringing is usually harmful to the plant,
as one might expect from so unnatural an operation. Injury to the
plant arises from the fact that parts of the vine are starved at the
expense of other parts; and because, when the bark is removed, the
outer layers of the woody cylinder dry out very quickly and thus check
to some extent the upward flow of sap through evaporation from the
exposed wood. Thus, not infrequently, the plant's vitality is
seriously drained. Nevertheless, vineyards may be found in which
ringing has been extensively practiced many seasons in succession and
which continue to yield profitable crops, the growers having learned
to perform the work of ringing so as to injure the vines but little.

Ringing without harm to the plant depends much on the way in which the
vines have been pruned. For instance, if the vines are pruned to the
two-arm Kniffin method, the ringing of bark should be done from both
arms just beyond the fifth bud. Thus, the ten buds left on the vine
produce enough leaf surface to supply the food necessary to keep the
vine in vigorous condition. When the four-arm Kniffin method is used,
the two top arms only are ringed, and even so three or four buds must
be left on each for renewals. Whatever the method of training, it will
be seen from these examples that some unringed wood must be left to
the vine with which to supply leafy shoots to support the vine. Some
growers ring their vines only every other year, thus giving them an
opportunity to recover from whatever loss of vigor they may have
sustained in the season of ringing.

Several other considerations are important in ringing: First, the
vines must not be permitted to carry too large a crop. Again, the
amount of fruit on the ringed portion of the vine must depend on the
amount of leaf surface not only of the plant but of the ringed arms,
each ringed arm acting somewhat independently so far as its crop is
concerned. If too many clusters are left on the ringed arms, it always
follows that the fruit is inferior and often worthless. Lastly, all
fruit between the rings and the trunk must be removed, for it does not
mature properly and so adds only to the drain on the plant's vitality.

As to the results, it is certain from the experiments that have been
conducted and from the experience of grape-growers, that the maturity
of the fruit is hastened, and berries and bunches are larger when the
ringing has been done intelligently. Many growers hold that fruit
produced on ringed vines is never quite up to the mark in quality and
in firmness of fruit. There seems to be a difference in opinion about
this falling off in quality, however, although unquestionably, choice
sorts, as Delaware, Iona and Dutchess, suffer more or less in quality.
It is commonly agreed, also, that varieties, the fruits of which crack
badly, as the Worden, suffer more from cracking on ringed than on
unringed vines.

Experiment and experience prove that the best results of ringing are
obtained if the work is done when the grapes are about one-third
grown. Of course the exact time depends on the season and on the
variety. The operation is variously performed and is easily done with
a sharp knife, but when large vineyards are to be ringed the grower
ought to provide himself with some simple tool. Paddock, in the
bulletin previously mentioned, pictures two of these tools and these
are reproduced in Fig. 52.

1 and 2; while 3 and 4 show ringed vines at the beginning and the
close of the season.]

In conclusion it must be said that it is doubtful whether the gains
attained by ringing offset the losses. The practice is chiefly of
value only when exhibition clusters of grapes are wanted or when it is
necessary to hasten the maturity of the crop. Always, however, the
work must be performed with intelligence and judgment or the losses
will offset the gains.

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