Grape Trellis and Training Systems

Grapevines can be grown to conform to numerous shapes. Arbors,
fences, and decorative trellises are only a few of the possibilities.
Since many home gardeners may opt for less traditional training
systems, a few general principles should be kept in mind, when pruning
and training your grapevines. As with any fruit crops, this primary
pruning should be done in the dormant season.1. The grapevines
should be trained to reasonably fill the structure but not become
overgrown. This is easier said than done, since initially the vine
grows fairly slowly, but as it matures, it may become a monster of
vegetation. One to two layers of leaves for any area on the canopy is
best for flower bud and fruit development.2. Mature grapevines,
by their nature, produce much more wood than they can support. Think
of the wild grapevine growing in the forest: it produces a huge amount
of wood just to climb up to the sunlight. Your garden grapevine will
not need to do that, but they still produce much more wood than is
necessary or desirable. Typically, during dormant pruning you need to
remove as much as 90 percent of the new growth on a mature grapevine.
Plan on leaving about three or four buds per foot of cordon (the
horizontal trunk on a grapevine) length. Dormant pruning is usually
done in late winter or early spring.3. Grapes bear their fruit
on one-year-old wood.4. Different grape cultivars have different
growth habits. The canes of American cultivars tend to grow in a
willowy, downward direction, whereas those of the European cultivars
and many French-American hybrids tend to grow directly up. Choose your
training system with this in mind.5. Grapevines vary
considerably in their vigor, due to both genetic and environmental
factors. Because of this variation, it is difficult to make exact
recommendations as to how many buds, or how large a crop, to leave on
the vine in any given year. Vigorous vines can support and ripen a
larger load of fruit than less vigorous vines. In other words, you can
leave more buds for next year's fruit development on a big and robust
vine than you can on a little waif of a thing. Therefore, you need to
a judgment about how many buds to leave during pruning based on how
much growth the plant achieved in the previous growing season, which
can be estimated by the amount of wood you have to remove during
dormant pruning. As a general rule, plants that are relatively weak
growing should have two buds per foot of cordon (row) or 30 buds per
plant retained, whereas vigorous vines should have 3 to 4 buds per
foot of cordon or 40 to 45 buds per plants retained. This concept is
called "balanced pruning" because it balances the crop for next season
with last season's growth.Remember that although our methods of
pruning and training are based on science and experimentation, much of
grape pruning relies on experience and, for lack of a better word,
art. These instructions seem a little befuddling at first glance, but
as you engage in the process of pruning, you will understand them more
fully and come to appreciate the time spent in your vineyard in
winter, in sweet anticipation of the summer to come.By way of
guidance, some traditional training systems employed by commercial and
backyard growers are described here. All the various trellis systems
refer to a vine in the early spring after dormant pruning.High-Wire
CordonAmerican cultivars such as 'Concord' or 'Niagara' tend to
produce shoots that grow in a downward direction, so it generally
makes sense to put the permanent horizontal branch on a high wire and
let the plant drape toward the ground. In the high-wire cordon system,
also known as the Hudson River Umbrella, a single horizontal wire is
secured at a height of 6 feet, and another is placed at a 3-foot
height. The lower wire will be used to hold the vine up during early
training, and later, after the plant is trained, it will only be used
to secure the trunk in place.In training a vine to this system, select
two strong canes and train them up to the top wire; then, as the canes
grow, place them along the top wire, in opposite directions. Be
careful not to wrap the canes around the wire, since they will expand
in girth over time and can girdle themselves on the wire. It's better
to tie the canes to the top wire at first. They will eventually send
out tendrils to secure themselves to the wire, but they will need a
little help initially. Make sure that you keep an eye on the string
that is securing the canes to the wire, since the string can also
girdle the canes as they grow. Cordons from one vine should not
overlap with those of adjacent vines. Ideally, you would like to train
up the first two canes in the first year of growth, but realistically
it often takes two years to get the cordons trained to the upper wire.
Have patience; they will eventually get there, provided they are in
the appropriate climate. As in the case with growing many other
perennial small- fruit crops your training and patience in the first
years will pay off in future decades.Once the cordons are established,
they should be pruned so that you are left with several shoots or
spurs that are five to seven buds long, for a total of 30 to 45 buds
per plant, depending on the vigor of the plant, as discussed earlier.
These spurs should be spaced 6 to 12 inches apart on the cordon. In
addition, for each seven-bud spur, leave one two-bud renewal spur. The
smaller spurs will provide the shoots for the following year.The
fruiting shoots will hang like a curtain in groups from the spurs that
originate from the arms along the top wire. Shoots should be carefully
separated and placed vertically downward from the top wire for a
distance of 18 to 24 inches. Positioning should be carried out as soon
as the shoots have toughened, usually 2 to 3 weeks after peak bloom
(when 50 percent of the fused petals have fallen). Extreme care must
be exercised during shoot positioning, as any shoot lost at this time
can result in a poorly filled trellis.In subsequent years, select new
canes and leave new renewal spurs from the shoots that developed from
the previous year's buds. Remember to balance the number of buds with
the vigor of the plant: a high number of buds should be left on
vigorous plants than on weaker ones.Low-Wire CordonThe idea behind the
low- wire, or low-bilateral, cordon training system is similar to that
of the Hudson River system just described. The low-wire system,
however, is used for grapevines that have a tendency to grow up rather
than down, as is the case with the European grapes and most of the
French-American hybrids. If you put these forms on a Hudson River
system, the shoots would grow up from the top, 6-foot high wire- not a
good thing. The low-wire cordon system takes advantage of the plant's
natural tendency to grow up, allowing the shoots from the permanent
cordons on the lower, 3-foot high wire to fill in the trellis from the
bottom up. Of course, gravity tends to work against you, so as the
shoots grow up, you need to help them by using catch wires that
sandwich the new shoots between them as they grow up. Usually, two
sets of catch wires are adequate.Umbrella Kniffen SystemIn the
Umbrella Kniffen system, the plant's trunk is brought up and tied to a
6-foot high wire, with four or more canes left near the top of the
trunk bearing a total of 50 to 60 buds. All other wood except for two
renewal spurs is removed from near the head. After pruning to the
desired number of buds, retie the trunk to the top wire. The canes
should be bent rather sharply over the top wire so that the other
outer bark cracks, and the tips are tied to the lower, 3-foot high
wire. The renewal buds will develop into shoots that probably will not
be fruitful but should be allowed to grow. They are there to be used
for next year's fruiting canes. The buds on the main canes will form
fruiting shoots that do not need to be tied because the vine has
already been trained. Some of those shoots may be well located and can
replace the original canes the following season, in which case the
renewal shoots are not needed.Four-Cane Kniffen SystemThe Four-cane
Kniffen system is a variation on the Umbrella Kniffen system in which
the canes are selected from both the top and the middle of the trunk.
It is often used on low- vigor cultivars. The lower canes are shaded
by the upper canes, and the lower ones often produce later-maturing
fruit that may be lower in quantity and/or quality than that on the
cordons trained on the top wire.Other Training SystemsThe production
of 'Thompson Seedless' grapes in California and similar climates
requires cane-pruning systems, since the buds closest to the base are
not fruitful, yet those are the only buds that are left on the vine in
cordon systems. If you trained 'Thompson Seedless' to a low -wire
cordon, you would get a lot of leaves and no fruit. The most commonly
employed training system for this cultivar is head training. Head
training involves tying the main trunk to a vertical post.Another
common training system is the Geneva Double Curtain. This system is
good for extremely vigorous vines since it allows the plant to achieve
its potential yield in a relatively small space. Weaker growing vines
would not fill such a large trellis system.