Pruning Grapes
(The following material is excerpted from the pruning chapter in "The Grape Grower". The material is copyrighted and may not be used without permission from the publisher)
Probably nothing scares people away from growing grapes more than having to prune. At least with fruit trees, the tree doesn't have to be guided to actually be a tree - it just grows that way. But leave a grape vine alone and it becomes a tangle of growth that doesn't give the inexperienced pruner any idea of where to start.
Too many novice growers have seen old, untended vines growing in trees, apparently producing good looking clusters of grapes year after year. After seeing that, it's easy to think "If such an old vine does so well, do other grapes really need to be pruned?" Certainly they don't - if you don't mind using a tall stepladder to pick, while fighting your way through a mass of tangled, dead vines to get straggly clusters of fruit not half as big or as sweet as they could be.
Proper pruning gives you grapes that bear reliable crops of consistently good quality fruit on a vine that is easy to manage, year after year. The basic principles of pruning grapes are easy to learn, just as easy to apply, and have enough flexibility to allow for error and inexperience, and STILL give you a good chance for a decent crop.
Before we go any farther, the pruning we are talking about here is pruning of the DORMANT vine. The times and reasons for pruning green, growing vines will be covered later.
TOOLS FOR PRUNING
For most grape vines you will need just one tool, a good pair of secaturs (hand-held pruning shears). Get a GOOD brand, not just a cheap knock-off from the local multi-store. If possible, order from a professional nursery supply company. My personal favorite is Felco.
The advantages of their pruners are: 1.) The type of action of a blade sliding past an opposing surface. When the blade is sharp, cuts are clean with no ragged or crushed ends, such as can happen with the type where a blade strkes an anvil. 2.) All parts are replaceable and the blade can be taken off for easier sharpening. Also, the steel is hard
enough to hold an edge well. 3.) Felco has several styles, including one for left handed people, and my personal favorite, the type with a rotating handle that reduces strain of cutting. When larger cuts are needed, use a short pair of lopping shears, or a small folding pruning saw.
REASONS FOR PRUNING
.
The first, most basic
reason for pruning of grapes is to regulate the amount of the crop. This, in turn affects the quality and insures uniform, annual production. A vine produces it's crop from buds laid down in the previous year's new
growth. That means that in the winter, all the buds on all the new canes already carry flower buds which can bloom and become clusters of grapes. If you carefully open and dissect a bud, you will actually find a tiny little
compressed shoot and flower bud clusters. Leave a lot of buds and there will be a large crop, but too many buds means more fruit than the vine can handle properly. Here's what happens when you leave a vine unpruned or prune it
too little:
First, at bloom time, if there are too many flower clusters, available food (carbohydrates) is spread among too many flowers. This means fewer flowers in each cluster get the energy needed to allow them to set
and start developing into berries, or they get only enough to develop into undersized berries.. With fewer berries per cluster the clusters are straggly or loose instead of well-filled or even compact.
Additionally, there
are many more clusters than usual, so the overall weight of fruit is still higher than normal. This fruit is competing with new shoots and undeveloped leaves for the food stored in the vine, that being the only source the vine
has until the new leaves have matured enough to make carbohydrates. This means the fruit has to wait until there are sufficient mature leaves to make all the carbohydrates needed by both the new growth and the fruit. But by
then, it is too late to improve the fruit set, and there isn't enough growing season left for the new shoots to develop size and vigor, and the berries get don't get needed sugar to ripen until much later than normal, if they
get enough at all.
If the variety ripens late normally, overcropping can make it so late it won't ripen before frost. Even if the fruit does ripen, it may taste flat, because the acid in the berries keeps decreasing as part
of the ripening process, no matter how long it takes for the sugar to build up. This means that on an overloaded vine, it can take so long
for the sugar to build up that by the time it is high enough, the acid has dropped
too low and the fruit tastes flat and insipid. Finally, the fruit color on an overcropped vine usually doesn't develop well, making it both unattractive and lacking pigment for wine, juice or jelly.
Meanwhile, because the
new shoots got little food, they developed fewer buds with smaller flower clusters in them, setting up the vine for a sparse crop the next year.
In short, an unpruned vine may have more fruit, but it's quality is likely to
be so poor it's hardly worth using, and it insures that the next year's crop will be quite small.
Even more important, when the fruit has to stay on the vine longer than usual to ripen, the energy it takes is diverted from
helping the new growth harden off and get ready for winter. This can mean more dieback of the vine and it's canes, possibly leaving the vine in a weakened state or even killing it, by the time spring arrives. Even in mild
winters, poorly ripened wood is apt to fall prey to disease and die back to older wood.
The year after a vine is overcropped, it produces very few clusters, though thier quality of may be surprisingly good. That's because so
few fruit buds were laid down the year before, due to the overcropping of the vine. Now, with so few clustrs, the ratio of leaves to fruit is higher and the few clusters there are get sweeter, the berries get bigger, and the
crop ripens earlier. Trouble is, with a smaller crop, the vine also has energy enough to produce more new growth, inlcuding more fruitful buds, which means another large crop looms ahead for the following year. And because
there is also more food to allow the wood to harden off better, the odds of all the new growth surviving are increased. In other words, the stage is set to repeat the boom-bust
cycle again.
Unpruned vines can reach a
sort of equilibrium and stop the up and down cycle, but the fruit rarely as good as on a pruned vine, since it still doesn't get the amount of light or air circulation it might, due to the mass of old growth surrounding it.
If all you wanted to do was keep crop production regular each year, you could do it without pruning, by picking off flower clusters early in the season, before bloom. This would adjust the crop so the vine wouldn't be
overloaded, keeping the fruit quality high.
Of course after a few years of doing it this way, the vine would be an enormous tangled mess - pruning is needed to keep the vine under control at the same time it adjusts the
crop.
Let's stop and explain a little of what is happening here. The same buds which produce fruit also produce shoots that bear leaves. On a pruned vine the smaller number of buds means a much smaller number of new shoots
to start growth in the spring, and until the leaves on the new shoots are mature enough to produce food, the vine is living off stored reserves. Even then it takes a while before there are enough mature leaves to offset the
drain on the stored food. For instance, a vine pruned to have only 24 fruit buds on it will have to grow for several weeks before the first new leaves are ready to produce food.
Meanwhile an unpruned vine will have at least
ten times that many shoots, or 240 leaves producing food at the same time the pruned vine has only 24. Now, if the crop on the unpruned vine had been thinned so it has the same number of flower clusters as the pruned vine, each
flower cluster will have at least ten times as many leaves feeding it, early in the season, right at bloom time. This gives the unpruned vine a big jump on the pruned one early in the season. Eventually the shoots on the pruned
vine get long enough to have as many productive leaves total as the unpruned vine, especially since the unpruned vine's shoots don't elongate much. So while the unpruned vine has the edge early in the season, but the pruned
vine catches up. That is, the energies of the unpruned vine are divided among many more shoots, so each one may grow only a foot or so, while the pruned vine thrusts it's energy into fewer shoots, pushing them to much greater
ultimate size. But the unpruned vine has the edge for the first part of the season, if the number of clusters is adjusted, giving it a much higher percentage of leaves to fruit early on. If regulating the size and quality of
the vine's crop was the only reason for pruning grapes, the chapter would end right there, but other factors weigh against the advantages of leaving a vine unpruned. After crop regulation, the next most important reason to
prune is to make the vine manageable and the fruit accessible. Unpruned vines can give good crops by just adjusting the ratio of flower clusters to shoots, but given room enough, plus sufficient nutrients, water and light, a
vine can cover a large fraction of an acre. Letting a vineyard grow that way could be more than a little difficult to deal with.
You can do a lot with grape vines - they can be trained or guided to grow in a greater variety
of forms, sizes and situations than any fruit tree or bush. Grapes can be grown in pots and kept to tiny sizes that bear no more than one or two clusters of fruit per year. At other end of the scale, at the University of
California at Davis, a vine of the
"Mission" variety of Vitis vinifera has been allowed to reach a size to cover a massive trellis of around a tenth of an acre and it produces at least a half ton of fruit per
year. The vine could potentially grow to cover a quarter acre or more, but is restrained by pruning. IT is by no means the largest of it's kind, either. There are records of old
vines of "Mission" grapes in
California that reached massive sizes. A vine planted in Carpenteria, California in 1842 produced eight tons in 1893 and had a trunk circumference of 9 feet. In England, the "Hampton Court" vine, the vinifera variety
"Black Hamburg", has attained amazing size and production for being grown in a greenhouse, often yielding 2500 clusters a year. The form of a vine can be anything the grower dictates, from a single trunk growing in
one direction, as the English sometimes use in greenhouse growing of grapes, to multiple trunks fanning out to all points of the compass, on arbors. Vine height can range from many feet high, as with the Italian "marriage
of the tree and the vine" in which vines are trained into trees, down to methods of spreading a vine flat on the ground to take advantage of heat radiated from soil and rocks. In the latter case, this can be done to both
protect grapes from late frost and to allow them to get enough heat to ripen in cold northern summers. In between are numerous forms that range from using the vine's own shade to protect the fruit from sun in hot climates, to
systems used in high latitudes where sunlight has low intensity, where vines are spread out in ways to catch all available light. More on this further on.
Pruning helps the grower adjust the vine to the environment in other
ways. Proper pruning can improve air circulation in the vine to cut down the likelyhood of disease. Vines can be pruned so they will bloom later than usual, to escape frost. The right pruning and training system can make it
possible to grow vines so they can be better
protected from winter so that a variety that wouldn't survive a harsh climate on it's own can instead produce and bear where Nature would otherwise say "No".In short,
pruning controls the size and form of the vine both for the convenience of the grower and for the vine to best adapt to it's environment.
One serious misconception is that there is a single "one-size-fits-all"
system of pruning and training for all grapes in all situations. While some principles apply to the pruning and training of all grapes, trying to make one system fit every variety in every situation is a sure way to fail,
wholly or partly.
How a vine is best pruned depends on two main factors: the system used to train the vine and the variety of grape, with each factor having an effect on the other. But no matter what system is used, they all
are based on variations of two basic methods, spur pruning and cane pruning. The one thing all pruning and training systems have in common is that they all use one or the other (or rarely, both) of the same basic structures to
carry the fruit buds. That is, fruit buds are borne on shoots that grew the previous summer, and those shoots, a.k.a. "canes" are pruned to different lengths to either become fruiting spurs or fruiting canes. A spur
is generally recognized as a cane or shoot that has been shortened so it has from one to four buds, with 2 to 3 being the most common.
Fruiting canes may have from 5 to as many as 15 buds, with 10 to 12 the most common
number.
The difference between training systems is largely a matter of how long the spurs or canes are and how they are positioned, in relation to both the vine and to the trellis. The spurs or canes are replaced every year,
while the older wood of the vine is basically unchanged, once trained into it's permanent form early in the vine's life.
SPUR Pruning is done on a vine trained to a permanent framework of two year or older wood with the fruit bearing
wood - spurs with one to four buds each on them - spaced along the framework. The buds on the spurs produce the fruit bearing shoots every summer. In turn, most of those shoots are removed every winter with one of the lowest
shoots on the old spur being cut back to become a new spur.(see illustrations). Spur pruning is probably the easiest system for the novice to prune. Once the spur positions have been established, pruning is little more than
removal of unwanted canes, plus cutting back of the remaining shoots at the spur positions, and the old spurs help serve as a guide. In other words, just repeat what has been done the year before.
The common training systems using spur pruning are head-trained,
spur-pruned vines (HTSP) and cordon trained
vines. A HTSP vine is nothing more than a vertical trunk, usually tied to a post, with spurs radiating around the top 1/2 to 1/3 of the trunk, making the vine look something like a bush or dwarf tree. The system is easy and cheap to establish because untreated wooden posts can be used as supports and by the time the wood rots away, the vine's trunk has become rigid enough to support itself. However, vines trained this way tend to yield less because they are restrained to a smaller size than they are capable of reaching, so they don't carry as many fruiting spurs as they could.
The clusters are all produced near the trunk and tend to get tangled in the shoots, making them harder to pick and more prone to damage. And the dense tangle of growth reduces air circulation and makes the interior of the
vine a good place for disease to start, as well as making it hard to get spray into the area for treatment.
In the past, HTSP vines were common in the wine vineyards of California, but the system lost favor because of
difficulties in caring for the vine and harvesting the fruit. The system is only suited to low to moderate vigor wine grapes with an open growth habit that keeps picking from being too difficult. Table grapes grown with this
system
may have poor appearance due to difficulty controlling disease, and tangling of the clusters in the vine that can crush and deform berries and make it difficult to pick them without damage.
The other important
system using fruiting spurs is the cordon system. In this method, fruit spurs are carried on permanent, horizontal arms extending from the trunk. Usually there are two arms, giving the vine a "T" shape, though
other arrangements are possible. Each arm is usually three to four feet long and has up to six spur positions. While each position may strt out with only one spur, as the vine matures and gains vigor, it may be able to carry
more fruit and it's possible to add
additonal spurs at each position.
How to add a new spur: When pruning spurs, there are usually at least two shoots coming out of the previous year's spur, assuming it was a two bud
spur. If you were pruning the regular way, you would cut off the upper half of the old spur, and the attached shoot, then make a new spur by cutting back the remaing shoot to two buds. To get a new spur, simply leave both
shoots, and cut each one back to become a new
spur. Or, if you are lucky, there are often suckers near the base of the old spur and one of those can be cut back to become a new spur itself. Don't be in a hurry to add new
spurs at every location - it's usually better to add only three or four spurs to the vine at first, then wait and see how it performs. If the vine carries the new crop load well with no sign of overcrop, more spurs can be left
the next pruning season. Eventually, instead of a row of straight spurs lined up on the cordon arms, there may be two spurs at each location, arranged in a "V" shape.
While vines trained to cordons need full
trellising, with wires, posts, wire anchors, etc., compared to HTSP vines, which need only untreated wood posts to start them out, the difference in production and fruit quality, espcially with table grapes, is worth it. On
cordon trained vines, clusters are spaced evenly and regularly, usually hanging just below the cordon arms where they can be harvested easily, and where they are protected by the foliage from sunburn. Growth is spread evenly
along the wires, so air circulates through the vine well, and spray penetrates more uniformly than with HTSP vines. A vine properly trained to cordons is very easy to prune and even novice
pruners can handle it with only a
bit of instruction. This is because the pruner can see how the vine was pruned the previous year by the appearance and location of the spurs and just has to simply repeat the process, while removing excess shoots that have
arisen outside the spurs.
There are several variations of the cordon system. including th Geneva Double Curtain
and forms that have up to four arms vertically - two upper and two lower. The Geneva Double Curtain (illustration) is an extremely productive system, though it has some disadvantages. If the variety is a vigorous one, the double "curtains" may be so dense as to create a "dead air" space between them where air circulation is
restricted and spray doesn't penetrate readily.
There are so many different training systems that have been developed for commercial wine vineyards that it isn't possible to cover them here. Each is designed to make best
use of light, help develop fruit buds, help ripen fruit, give better air circulation for disease control, etc. in a specific climate, site, and situation. Because of
that, a would-be commercial grower should seek out
systems from others in similar types of climate and site. A good place to start is to find out if your state has a grape grower's association. Ask at extension offices, or at your state land-grant college (state university,
like Oregon State U., Iowa State U., etc.)
Remember, when pruning spurs, prune weak spurs heavily, vigorous ones very little -just the reverse of fruit trees. Try not to leave large wounds - vines don't heal over like fruit
trees, and disease can enter large wounds more readily. It's sometimes better to leave stubs sticking out, which may eventuatly rot, than to cut a cordon arm or large spur off flush with the old wood and leave a big wound that
won't heal over at all.
Systems like the Geneva Double Curtain are very efficient at producing large crop loads for the area they cover because the way the system allows the new shoots to hang downward, exposing the bases of
the shoots to full sun, which increases the fruitfulness of developing fruit buds. Experiments at U.C. Davis showed that buds fully exposed to the sun became more fruitful (larger flower clusters and more clusters) so that the
same number of buds gave a larger crop than similar vines whose developing fruit buds were shaded. More interesting, the extra crop didn't overload the vines - they were able to mature their crop as well as the vines with
shaded buds. The drawback of the Geneva Double Curtain in some cases is that the "curtain" creates a dead air space in the center of the vine that fosters disease. Use of the system in Oregon with vigorous vinifera
wine grapes increased yield, but powdery mildew became rampant and the accompanying decrease in fruit quality offset any gain in crop size.
In cold climates, one variation of the cordon trained vine is a straight trunk
trained diagonally, with spurs on the upper half of the trunk. By being trained diagonally, the vine is easier to lower to the ground to be covered up for winter protection. (see section on cold climate viticulture for more)
CANE pruning.
Additional notes: I've had people ask if they should cut the shoots off beyond the clusters to make the vine put energy in the clusters.
Illustrations Coming Soon...
Various forms of this type of system are used extensively in modern
commercial wine vineyards for a number of reasons, covered further on.
The version most home growers will recognize is the old "Kniffen"
system, both the two cane "umbrella" Kniffen and the four cane Kniffen.
Cane pruning, as the name indicates, relies on canes rather than
spurs, to produce the fruit. Canes may have as few as 5 buds to as many
as 15. Cane systems often require more wires or other supports than
spur systems, and pruning them takes more experience and decision
making. However, canes are a more flexible system than spur pruning and
they allow more year-to-year variation in the amount of fruit buds left
on the vine. If you want to increase the number of fruit buds on spurs
for greater crop, you can usually only add about 12 or so per season.
With cane pruning you can add as many canes as there are available,
possibly even doubling the amount of fruit buds over the previous year.
The main difficulty with cane pruning is that it takes more experience
to learn how to choose which canes to cut back to become the
replacement spurs and which to leave as fruiting canes, as well as
deciding how many canes to leave. New growers often fail to remove
enough wood, letting the vine overcrop, with the results discussed
earlier. 90 to 95% of the previous season's growth should be removed in
proper pruning.
Several systems have been developed to help a grower determine if
enough wood is being removed at pruning time. One method is to weigh
the wood removed from the vine. Pruning a vine this way, based on
its growth in terms of the amount of one year old wood it produced the
previous growing season, is called balanced pruning. It is used to
determine the fruiting capacity of a vine for the coming season season
by
weighing the wood removed at pruning time. Common balanced pruning formulas include: Vitis Vinifera - 20 buds for the first pound. of
prunings, plus another 20 buds for each additional pound. of prunings,
up to a maximum of 60 buds. For French or American hybrids - 20 buds
(for the first pound), plus another 10 buds/ additional lbs. of
prunings, up to a max of 50 buds. Native American varieties -30 buds
(for the first pound) plus another 10 buds per each additional pound of
prunings, up to a max of 60 buds.
Another is to count the buds on the pruned vine. Both methods depend
on how well the grower knows the vines. Weight of wood depends a lot
on health of the vines, soil, climate, growing year, crop load, and
more. A novic setting pruning standards based on weight of wood may
find it awkward as it is necessary to prune the vine and weigh cuttings
a little at a time or you may find that when you get the total weight
of the prunings, you haven't left enough wood on the vine to leave
enough fruit buds by the formula. Of course it also means more work as
you have to take time to cut up the wood and either carry it to a
scale, or set one up in the vineyard. Either way adds time and work to
the job.
Pruning by counting the number of fruiting buds is the easier method
for home growers or anyone who stays close to their vines. When you
have started from a cutting or a new vine and followed it through
training and into bearing, you get to know it well enough to tell if
you have left too many buds, or not enough, by the quality of the fruit
and how the vine grows.
How many buds SHOULD you leave? That is mainly a matter of your
climate, soil, the age of the vine, and the variety of the grape(s) you
are growing. A good basic rule is: First bearing year. Leave 24 buds
(two
cordon arms with 6 spurs each, or two canes with twelve buds each) for the first bearing year, and remove at least half the crop, just
after fruit set. Second bearing year - still 24 buds, but leave the
full crop. Third bearing year, leave 36 buds (three canes or an extra
bud at each spur on the cordon), etc. In other words, if the vine is
growing well, ripening it's crop well, and seems healthy, add another
12
buds each pruning season, up to a maximum of about 60. The two main exceptions to the 60 bud limit is if the variety is extremely vigorous and can clearly carry more crop, or if the clusters of the variety are small and the
only way to get a reasonable weight of crop is to leave more buds to get more clusters. Some of the French Hybrid wine grapes, such as Marechal Foch, for example, often have small clusters and the only way to get a reasonable
crop is to leave as many as six canes with 12 to 15 buds each per vine. Though even in that case, the vines must be on fertile soil. Vines on poor soil may not be able to carry large crops, or the fruit quality may be lowered
with too large a crop.
It should be noted that while lower fruit quality is a sign of
overcropping, it is possible to have the quality of wine grapes
decreased by too much crop, without actually overloading the vine.
That is, the fruit ripens well enough, and on time, but subtlties of
flavor and character in the wine can be lost. A friend with a vineyard
did such an experiment in which he left three canes on some vines and
two canes on others. The fruit on both ripened well, and on time, but
the wine from the two-cane vines had flavor that was more intense, with
extra subtle undertones to it. These are the sorts of results that are
personal and each grower must try different crop levels to find what is
best in a given area, and what suits a particular taste.
When you have selected the canes you want to leave for fruit,
PRUNING TO ESCAPE FROST
While you are at the mercy of Nature with respect to frost on most
fruit bearing plants, the right pruning can give leeway with grapes.
Here is the method.
Delayed pruning to delay budbreak.
If a grape cane is left unpruned, the buds at the ends will push
before the ones farther down and the upper buds will delay the lower
buds by a few days to as much as a week or more. Taking advantage of
this is just a matter of timing your pruning.
1. At the usual winter pruning time, remove only those canes that will
not be used for fruiting or as a source of spurs - suckers, undersized
canes, etc. Leave everything else unpruned.
2. In the spring, when buds are starting to push, wait until the buds
on the ends of the canes you left are swelling enough that the new
leaves become visible just opening out from the bud. At this point, go
through and pruned those remaining shoots back to fruiting canes or
spurs.
If you compare these late pruned vines to ones that were pruned
completely at the usual time in winter, you will see that the buds on
the winter pruned vines are visibly farther along, at least a week
ahead of the ones on the spring pruned vines. But the buds on the
spring pruned vines are still tight enough to be able to withstand
frost that can kill the unfurling buds on the winter-pruned vines. And
though the late-pruned vines will open their buds later, they will
ripen their crop at the same time as vines that were pruned completely
at one time, in winter.
NEGLECTED OR OVERGROWN VINES.
Eventually, you are going to have to prune a neglected arbor or vines
that weren't trained right to start with, or have been left unpruned
for a long time. The vines will have a mass of dead and tangled shoots
with most of the new growth being too small to be of any use as new
fruiting canes, and in the wrong place to be pruned as fruiting spurs.
Chances are good the arbor or trellis will be in disrepair and need
work, as well. Here are some options.
If you see a useable vine structure or a good trunk under all the
growth, you may wish to take the time to sort it out. In most cases,
though, you will spend a long time cutting out masses of old growth
while hunting for the few shoots usable as new fruiting wood. At best,
you will probably get a partial crop that year. And it will likely
take at least two more winters of redirecting new shoots until you have
something that works. At that, the new fruiting wood is apt to be
badly located and probably convoluted at best.
If the trunk of the vine is straight, or is otherwise healthy, you may
be able to shortcut the process by cutting everything off back to the
head of the trunk - the point at the top of he trunk where the canes or
cordonts originate. You will have no crop that season, but you can
easily train the new shoots that come out as canes or new cordons to
bear a full crop the following year.
In many cases, however, the vine will likely be such a mess of old
growth and oversized wood, combined with the twisted, multiple trunks
that result from amateur training attempts, that the simplest way to
prune it is with one quick cut, through the base of the trunk(s), one
to two inches from the ground.
No, that doesn't mean you should kill the vine, or will have even
harmed it by doing that.
Unless the vine was sick in the first place, it will sprout back and
refill the arbor/trellis in one season, given the chance. The new
growth will usually resume bearing the very next year. Indeed, this is
one of the advantages grapes have over fruit trees. If a tree is killed
by cold weather, it may well be lost altogether, or if it isn't it will
take at least two or three years to re-grow sufficiently to resume
production. An otherwise-healthy vine killed to the ground by cold will
usually re-grow completely in one season, able to resume full
production the following year.
With the vine cut off, you can now make necessary repairs to the
arbor/trellis without having to work around a tangled vine and you will
have the chance to train the vine up in a better form than it had to
begin with, as though you were training a new vine (which is what it
is, from the ground up).
The only time this may present a problem is if the vine was grafted to
a rootstock, but the odds of such a vine being planted to an arbor are
small. Grafted vines are usually encountered only in commercial
vineyards. Even there, the union between the fruiting variety and the
rootstock is usually easy to spot as the rootstock will have different
bark than the top, and there will be a distinct juncture between the
two, usually a visible swelling or knob. Further, the vines in a
commercial vineyard, even when neglected will very likely still have a
good basic structure and can be brought back to fruitfulness without
having to resort to such drastic pruning.
After an own-rooted vine has been cut off so drastically, soil should
be mounded around the base of the shoots as they grow. Because grapes
are not able to heal large cuts the way trees do, growing new bark over
the wound, a large cut-off stump may rot out in a few years. By putting
earth over the base of the new shoots, they will root and establish a
separate root system long before the stump rots down into the old
roots.
Just be sure that if you are doing the work for someone else, you
explain it in advance, or at least be sure the person isn't fanatical
about the vine, doesn't have a weak heart and isn't prone to being a
homicidal maniac - they'll think you MUST have killed the vine when you hack it
off next to the ground.
SUMMER PRUNING."The shoots on my vines grow out where I don't want
them in the summer. Can I cut them off?"
Removing green growth from a vine should be taken on a case-by-case
basis. That green, new growth is often producing food the vine needs
to help the fruit ripen and to mature the wood for winter. Further,
cutting the shoots may stimulate shoots at the end of the cut cane to
start growing, keeping the vine active late in the season when it
should be getting ready for cold weather.
Additionally, if a vine is growing so much late into the summer that
you do have a big mass of green growth that seems to be excessive,
enough to make you WANT to do some summer pruning, it's likely the vine is getting
water and fertilizer too late into the season. Better to
cut off the water and fertilizer to make the vine slow down than to cut
it.
Finally, if you prune shoots in the summer too much, you may find your
self short of good, long canes at dormant pruning time - they were
shortened prematurely.
Of course, there ARE times when the vine is just too big, either
because it's a very vigorous variety, like "Niagara", or you have no
control over the moisture or fertility of the location where it is
growing, and you have to do something to keep it from overrunning it's
space.
If you must cut green shoots, a compromise is to cut them back to the
point on the shoot where the leaves are half the size of mature size.
Until a leaf reaches that size, it isn't producing food for the vine,
so it will be missed less than mature leaves that are feeding the vine.
In general, however, it's safest not to cut or remove green shoots from
the main structure of the vine. This insures the vine will have it's
food-producing capacity unimpaired. The exception is in the removal of suckers from the trunk, which should be taken off as early as possible.
Definitely NOT. This not only doesn't put extra energy into the clusters, it
reduces the amount of foliage that the vine would otherwise use to make food FOR the clusters. Plus stimulating too much vegetative growth at what might be the wrong time.
Should I clip back leaves, to allow nutrients
and sunlight to get to the grapes? NO. The vine takes care of getting nutrients to the fruit, and most varieties don't need to be in full sun to develop color. More sun on the fruit may improve the color in some cases -
make white grapes more golden, for instance, but for that you only need to remove a few leaves that are directly shading the cluster, and don't do it until ripening has started.
In a small home
vineyard, it is often simplest to collect the prunings and chip or shred them, especially if you feel there is disease in them. They can then be composted to kill the disease and the compost returned to the vineyard later.
In my own vineyard, I find it easiest to leave the prunings in the row middles and go over them with a flail mower. By setting the tractor on low speed, the mower runs fast enough with enough power to grind most canes up
completely. By early summer, there is little or no sign of anything left. With a very few vines, it's possible to cut the canes up into short pieces with a hand pruner and leave them in the row to break down.
HOME - Pruning - Profile - Projects - Publications - Links - Grape Varieties - Scions - Order Form - Cutting Information - Books - Mycorrhiza - Products
Copyright © 2001 - 2008 Lon J. Rombough - All rights reserved worldwide.
Rate this website @ Vitisearch.com Grape Growing Directory and Community
For grape growing questions, please ask them at the Vitisearch Forums
Site built and maintained by Grape Grower Solutions 874 Webpages Link to Bunchgrapes.com July 13th, 2007