Grape vines left to grow on their own may or may not develop an abundance of juicy grapes, but careful pruning of the vines will almost certainly produce the fruit you want. Trimming of grape vines starts right away and continues as the plant branches out, with select pruning being the key to continued fruit production year after year.
Decide on a training system within the first year of growth. One common system is the four-cane Kniffin, which develops vines along a two-tiered trellis. One vine on each side of the main cane grows out at a mid-point trellis line, and another two vines grow along a top trellis line.
Allow the main cane to grow after planting in order to reach past the first tier line on the trellis.
Snip the tip of the main vine in late winter to force buds along the cane to grow.
Select two of the side vines near the first tier line during the second growing season, and attach them to the line on either side of the main cane. Use twine to loosely tie the vines. Snip all other side vines back along the first tier line.
Snip the main stem back again during the next winter to force vine buds to develop shoots, or spurs, along the second tier. Also, snip the ends or the two shoots along the first tier line of the trellis to force buds along these spurs to produce fruiting vines. Cut them back so that there are no more than five nodes along the vine.
Wait until the third growing season to select two vines from the second tier line of the trellis, and tie them to the second tier. Cut any other vines back along the second tier.
Snip the ends of the second tier vines back to five nodes to force fruiting vines to grow off the spurs during the next winter. Trim back fruiting vines along the first tier, leaving three to five nodes.
Maintain a process from here on out of trimming back the fruiting vines to within three to five nodes of the side vines of the plant. This will force fruiting each growing season.