Pruning grape vines can be a mystery. But if you remember that all grapes produce fruit on one-year old wood, you have taken the first step towards viticulture! Here's how to prune a grapevine.
Allow the grape vine to grow any-which-way the first year it is in the ground. Having abundant stems and leaves will help develop a strong root system on immature grape vines. No pruning at all for the first year.
Select the strongest and most vigorous-looking stem during the winter of the first year. Using bypass pruners, remove all the other stems at the base of the plant or as close to the trunk on the main stem as possible. Stake the remaining stem which will become the trunk of the plant. Use a grape stake or secure the vine along a fence with wire.
Allow stems to grow from the main trunk. In the spring of the second year, begin removing all but two of the very best side shoots that grow from the trunk. If the vine isn't branching where you want it too, pinch the top of the main trunk to encourage side branching.
Cut back the top of the trunk during midsummer of the second year, when the vine reaches the desired height. The process of tip pruning will force new growth along the main trunk. Remove any new branches that don't fit your plan.
Cut back all but the desired side branches and the main trunk during the second winter. What you have now is the basic frame for the plant - an upright stem with two sets of side branches.
Allow the vine to grow during the third spring and summer, removing anything that grows from the trunk. You want to retain the basic framework of the vine.
Leave 12 buds along each of the arms during the third winter. Pruning during the third winter is crucial to future fruit production. These 12 are the buds that will produce fruit during the 4th summer. Each of the 12 should have 1-2 leaf joints so that the vine looks like a stubby hat rack when you are finished pruning. These are called 'renewal buds' and will remain on the plant forever.
Prune the 12 renewal buds so that there is always one more bud growing from the tip. This practice will continue from the fourth winter onward. What you are doing is allowing the renewal buds to extend and grow one bud length every season. During the summer, the fruit develops on the new growth that springs from the renewal bud. Keeping them short during the dormant season keeps the plants under control.
Keep pruning tools sharp and clean.
Be careful not to cut off the newest year's growth from the renewal bud. You only need one bud from that growth, but if you loose it by careless pruning, you will loose your harvest for next summer.