Grape Vines in Summer.
image by Courtesy of Jason Schiffer, stock.xchng
It is important to prune grapevines for winter so next year's growth produces a quality harvest. Pruning also gives you the chance to remove any unwanted vines or old growth that is no longer productive. Although the grapevines may look like a tangled mess, they will soon tame down when you start removing the old stuff.
Remove all fruit and excess foliage. This opens up the vines, so you can see them clearly to prune the grapevines for winter. This helps eliminate unnecessary work when the vines are prominently exposed.
Examine the main trunk of the grapevines for any damage or disease. If everything appears acceptable, then proceed with pruning the grapevines for winter. Should you discover problems, treat the disease or damage before pruning. In some cases another trunk may be forming which can replace the existing one. Train new cordons to the trellis or support system for next season, and remove the old trunk.
Mark the new growth with the colored tape. Choose another color to mark second-year growth and a third color for older vines. This allows you to prune the grapevines for winter in stages, making the job easier.
Remove any dead vines or weeds growing around the grapevines. Inspect the fasteners used to secure the vines to the trellis or support system. Replace any that are worn or broken. At this time, it is acceptable to cut back some of the older vines which did not produce any grapes this past growing season. Clear away the debris so the work area is easier to maneuver.
Choose any new cordons (the horizontal vines that grow the fruit-producing shoots) for next year's harvest, and wire them to the trellis in such a fashion that air and sunlight will be able to circulate through the foliage when it grows back. Trim the ends of the cordons to prevent new shoots forming off the ends.
Trim the existing cordons back to 15 to 18 buds. Keeping the new shoots to a minimum allows the grapevines to concentrate on forming the grapes and not growing excessive foliage. The second year shoots also need to be pruned until there are only about 40 or 50 buds remaining. These buds will produce next year's grapes.