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How to Prune Grapevines

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So you have planted grapes and you are wondering how in the world to prune them. The first step is learning how they grow and fruit.

Grapevines always produce fruit on last years growth; any wood that is older than 2 years wont produce.  2nd year growth could have up to 300 buds with potential to produce, but if left alone, the excessive amount could be too much for the vine to handle and you could end up with vines of ripened or immature fruit. Over production can also cause stress to the vine leaving little nutrients for it's vegetative growth. Pruning grapevines is EXTREMELY important if you want to get a good crop. You want to have high quality grapes as well as good vegetative growth to allow for a nice crop the following year.

Training the Vines

To get the most out of your vines, training them to grow in such a way that the entire vine can get adequate sun is very important. The 2 most common methods of training are the four-cane Kniffin and six-cane Kniffin.

  • The Four-Cane Kniffin is the simplest and most common way to train your grapevines. This method is identified by having 2 canes on each side of the trunk that are trained onto two trellis wires. The grapevine also has 4 renewal spurs, which are just very short canes that have one or two buds on them.  These buds are what produce the canes for next years grapes.
  • The Six-Cane Kniffen is very much like the four-can kniffin.  In this system you have 3 canes on both side of the trunk that are trained on 3 trellis wires. For this method you keep 6 renewal spurs instead of 4, to give you next years crop.

When to Prune Grape Vines

The best time to prune your vines is very late winter or early spring.  Depending on where your hardiness zone is, this could be anywhere between late December to early April.  I live in Minnesota so I try to get started in late February and am certain to do it before the second week in April.  The grapevines may bleed heavily after pruning, but this will not harm the vines. They will heal nicely on their own.

What You Will Need

The tools you will need for proper pruning are a saw, hand shears, a small scale for weighing pruned material and lopping shears. Yarn, cloth or ribbons that are a bright color, can be a great help when trying to identify fruiting canes.

Pruning Directions by Richard Jauron, Department of Horticulture Iowa State University

The degree or extent of pruning is dictated by vine vigor. Vine vigor is determined by estimating the amount of the previous season's growth. The concept of pruning grapevines based on plant vigor is called "balanced pruning."
The first step in balanced pruning of grapevines is to study the vine and estimate the amount of one-year-old wood in pounds. Start by selecting and retaining the appropriate number of fruiting canes per vine. To aid identification, some gardeners tie brightly colored ribbons or cloth strips on those canes they wish to retain. Leave equal numbers of renewal spurs (canes pruned back to one or two buds). Completely remove all remaining one-year-old canes. Next, weigh the pruned canes. The weight of the canes is used to determine the number of buds to retain on the grapevine.
To determine the number of buds to leave, use the following balanced pruning formula: "30 plus 10." For the first pound of canes removed, leave 30 buds. For each additional pound, leave an additional 10 buds. When counting the buds to be retained on the grapevine, include both the buds on the fruiting canes and those on the renewal spurs.
The balanced pruning concept is illustrated in the following examples. If a grapevine had two pounds of canes removed at dormant pruning, the gardener would leave 30 buds for the first pound of canes, plus an additional 10 buds for a total of 40 buds. Using the four-cane Kniffin system, the four fruiting canes would each have eight or nine buds. There should also be 4 one- or two-bud renewal spurs. The total number of buds should equal 40. If a vine had three pounds of canes removed, the gardener should leave 30 buds for the first pound of canes, 10 for the second pound, plus a final 10 buds for the third pound, or a total of 50 buds.
For the training systems most common, the maximum number of retained buds on a grapevine is 60. If too many buds are present after the initial pruning and weighing, remove as many as needed to obtain the desired bud number.

So now that we know exactly how to do it, let's hope we have a speedy winter so we can watch our grapevines start to fruit!

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