Question: How do you prune a grape vine?
Answer: Many varieties of grapes grow well in Indiana, and pruning is a vital part of successful grape production. Below is a general introduction to pruning and some resources for more detailed descriptions of the process.
You should start pruning your grape vine in its very first year. You want to create a T-shaped vine, with one trunk and two canes trained along each horizontal wire of the trellis. So, if you are starting a new vine, trim so that there is one primary vertical shoot – the trunk of the vine. As it reaches the horizontal wires of the trellis, you will want one main shoot, or cane, for each direction of the horizontal wires you are using to train the vine.
Pruning an established vine is essential for grape production, since grapes grow on one-year-old canes. Your goal is to prune the old wood to make room for the new wood, and to limit the number of buds so that the vine produces quality bunches of grapes. Common pruning errors include pruning at the wrong time and not pruning enough.
Prune grapes each year in late winter. Pruning too early can cause damage from freezing, so wait until the worst of the freezing temperatures are over. In Indiana, this might mean around the middle of February. For each side of each horizontal wire on your trellis, choose one new shoot, or cane, from last year, and cut off the rest. The cane should be about the thickness of your little finger. If there are more than 8-10 buds on the cane, trim off the excess buds. It may feel like you are leaving only a skeleton of your grape vine, but that will give you the best grape production. Remember: grape vines grow quickly, so if you make a mistake, you can fix it next year!
For photos and descriptions of all aspects of grape vine care, see “How to Prune Grape Vines” from Gardening Wizards at https://gardeningwizards.com/prune-grape-vines/.
More advanced pruning techniques involve the concept of “balanced” pruning; that is, leaving a number of buds appropriate to the cane size. For details, see “Growing Grapes in Indiana” from Purdue University Extension at https://ag.purdue.edu/hla/pubs/HO/HO-45.pdf.
For a detailed description of pruning for a number of varieties see “Principles and Practices of Pruning Grape Vines,” also from Purdue University Extension, at http://www.foodsci.purdue.edu/research/labs/enology/Pruninggrapes08.pdf.