A Discussion of Grapevine Pruning and Training
Presented by Rist Canyon Vineyards
Much has been written about pruning and training grapes. I just want to put in my two cents worth on this subject as it concerns grape growing in short season, cool climate areas.
Pruning and training of grapevines is one of the most important cultural practices to maintaining the health and vigor of the vineyard. This is especially true in northern range of grape growing and at the higher elevations where the growing season is short. Proper training and pruning insure the health of the vine and maximum hardening off for winter protection.
For those that are just starting to grow grapes under these conditions, training is the first consideration. The grower wants to train two shoots to become the trunks of future years. You want to use a multiple trunk system to limit winter damage in the winters. This may mean two or more trunks. But for the first years, I suggest starting with two. Chose the two strongest shoots and elimate any others after the possibility of frost is past.
I use grow tubes during the first (and sometimes the second), year. I have found that these aid in trunk formation and speed up the time to first harvest. They also are handy to keep herbicide sprays off the sensitive green portions of the developing vine. One caution with the grow tubes is that they should be removed after the shoots grow out of them. I have found that tubes should be removed late in the day (nice to do on a cloudy day) to prevent serious sunburning. The leaves then have time to adapt to their new surroundings over night and early the next morning. Remember, they've been in a greenhouse up until now.
If the tubes are not removed, the vines may not harden off properly in the fall. Removal should be no later than the 1st of August. Grow tubes are not needed after the first year unless a vine has to be pruned back to two buds or death during the winter to the ground level. Those vines are then treated as first year vines.
I pinch laterals forming during the first growing season to encourage growth of the shoots I have chosen to be future trunks. If you pinch them too early, they will proliferate. I usually allow 6-8 inches of growth before I pinch. In a large vineyard this is quite time comsuming and you may not need to do this as extensively as I do. But the thing is to encourage two shoots to become the future trunks. Pinching also helps the chosen shoots to better harden off, in my experience, by directing photosynthates into the main shoot. But after mid summer, this becomes less important.
Hopefully the vines have gone through their first winter with flying colors. It's at this point that you need to think about which trellising system you're going to use. I'm not going to go into details of the kinds of trellis systems that you can do. Information on them can be found through the various publications listed on the Rist Canyon Vineyards information links page. But, I do have my 2-cents worth and here it is:
Maximum photosynthetic area is all important.
This is achieved through canopy management. I find that upright, and semi-upright growing varieties do well on the vertical shoot positioning (VSP) system. Those grape varieties with a more vinifera, upright growth respond to this system because they naturally grow upwards. It is up to the grower to train, or position the shoots to distribute evenly to the sunlight as the shoots grow up. The bunches of grapes all hang at the same level. Leaf removal late in the growing season is facilitated with this system.
Varieties with American descent having a trailing habit may be easier to contain and train using a single curtain system where the shoots descend from the upper wire, just as vines flowing out of the trees in the wild. Shoots can be easily "combed" to separate them as they grow and just allowed to hang on either side of the trellis, naturally. With many varieties with this type of growth habit, the basal buds are the most productive (provided they get light). This type of training system allows the most basal buds the most sunlight. The grapes hang under the canopy and can make harvest more difficult.
I do two prunings:
Depending upon the system, you will be training the shoots to; either the top or the bottom wire. Some of the vines meant to be trained to the top wire may have to be trained to the bottom this year. This is your first year of pruning. As it is here at Rist Canyon Vineyards this year for a lot of vines.
I do two prunings. The first one is early in the year on a nice warm day. Usually in March. During this first pruning, I remove all of the laterals and unwanted wood, leaving only the canes that I want to form the structure of my system. Those canes that are chosen to form the mainframe are cut back, node by node, until green wood is reached. That's where I leave it at this time.
Laterals that were pruned can be used to determine the bud health. See Evaluating Bud Damage and Vine Recovery
The second time I prune is after the first bud break. If you leave the main canes long, the apical buds usually burst out before the basal ones. This makes long-pruning a method of frost control. (See Frost Tolerance) If you wait until the apical buds break (and the frost is over with), then prune the second time, the basal, more fruitful buds will survive and produce the crop that you want. This is very important to producing a crop in short-season, marginal areas.
Everything you do, pruning or training, is done for maximum winterhardiness
Frost tolerance comes in a close second for reasons to prune a certain way, or what training system you use. The grower should keep in mind the intention of maximum productivity, balanced with winterhardiness and frost control. Utilize multiple trunks to insure at least one makes it through the winter. Double prune to insure a crop. Train your vines to insure maximum sunlight and penetration. Ways to succeed!
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