Pruning the Backyard Grapevine
Proper pruning of your backyard grapevines is essential to maintain vine size, shape, and yield of the grapes. If you don't prune your vines, they will become unruly, tangled messes. Fruit ripeness will suffer. Overproduction of the vine may lead to premature death. It is also one of the harder things to visualize but one of the easier things to accomplish for the home gardener.
Pruning is performed in the early spring while the vine is still dormant. This is done in February, March, or early April depending upon when the grapevines generally come out of dormancy and bud out.
Pruning the grapevine and training the vine go hand-in-hand. You must decide the way you want to train the vine in order to prune it correctly. Vines that "droop" should be trained to a top wire of about 6 feet. Canes are then pruned and trained outward from the middle on each side of the trunk. As the new shoots grow, they droop on each side of this high pruned wire, naturally, taking in account of their habit of growth. Concord, and other native American varieties are typical of those varieties that droop downward naturally.
Varieties that grow upright are trained to a low wire of about 3 feet and allowed to grow upward according to their natural growth habit. These varieties need several wires above the trained canes in order that the upright growing shoots have something to attach to. Often, you will need to tie the growing shoots to these wires to keep the grown going up and to prevent wind damage. European grapes, V. vinifera, and many hybrid varieties (crosses between the European grape and American species) fall into this category.
Whether trained to a high wire or to a low wire, the pruning techniques are the same. The amount of one-year old, fruitful wood to be left after pruning is dependent upon the amount of vegetation produced during the previous growing season. Usually, around 90-95% of last year's growth is pruned off. The wood left is dependent upon the variety, how vigorous last years growth was, whether the variety over produces or under produces, and how old the vine is all enter into how you will prune it.
Grapes bear fruit on one year old wood. Thus when you prune the vine you will be leaving one year old buds to produce the fruit clusters this year. Much of what will be removed is two year wood with attached canes from last year's growth (that won't be needed this year) and excess one year old canes. When pruning you will be trying to balance the growth of the vine based upon how it grew and bore fruit last year.
Excessively vigorous vines that overbore their fruit last year will be pruned with more buds as this will de vigor the growth and balance the vine's growth this year. Low vigor vines will be left with fewer buds to invigorate their growth this year.
The two methods of pruning grapevines are short "spurs" and long "canes". The idea behind spur and cane pruning is the same. They differ in which of the buds are the most fruitful on the particular variety you are pruning. Varieties where the bottom buds are fruitful are spur pruned. Varieties where the bottom buds aren't fruitful are generally cane pruned.
Spur pruned vines are trained to heads and cordons. The difference here is that head trained vines are pruned to a couple to several spurs close in to the main trunk of the vine. Cordon trained vines have arms extending out from the trunk, on each side, with several spurs generated along the main frame of the arms. Either way of training has spurs of two to three buds each.
Cane pruning involves leaving at least one long cane of one-year old wood on each side of the trunk. The number of buds to leave depends on the variety and how much growth of the vine occurred during the last growing season. Usually, 7-12 buds are left on each cane. But this is relative. And that's where pruning becomes an art. After several years you will gain a "feel" of how many buds to leave based upon its performance in the prior growing season.
Besides the cane that is left, a small, two-bud spur is left for next year's cane and spur. That's why this method is often referred to as cane and spur pruning. The spur that is left at pruning time is known as a renewal spur. It gives rise to next year's cane and renewal spur.
Each year the job of pruning will become easier. You will soon begin to understand what is happening as you watch your vine grow during the summer. Your visualization of how the vine is supposed to look each year will grow. This will make the pruning each spring go smoothly.
The tools used to prune your grapevines are hand pruners, loppers, and small handsaws. Select the appropriate pruning tool to remove the wood as cleanly as possible and reduce unnecessary injury to the vine. Hand pruners are used to remove one year old wood. Older wood requires the use of loppers. Sometimes old, unfruitful trunks need to be removed. This is where the handsaw comes in.
Learning the art of grapevine pruning takes time and practice. You can contact your local county Ag Extension agent or Agricultural University for bulletins on grapevine pruning. These grapevine pruning bulletins have drawings and pictures of what you are trying to accomplish and will make your pruning easier. Just make sure that you prune your grapevines every year to maintain their size and shape, and to maximize the fruit production and overall fruit quality.
Jim Bruce has been growing grapes since the mid-seventies under a range of growing conditions. His Rist Canyon Vineyards is a research project to aid others in growing grapes. More information can be found at www.ristcanyonvineyards.com">http://www.ristcanyonvineyards.com