Later in the year, the grapes will look something like this:
So what happens to a vine that does not get pruned back at the end of the growing season?
Here’s a good example: The picture above is a enlarged section of the picture below:
When a vine goes un-pruned, clusters form all over the vine. The above vine was not pruned because this block of vines is scheduled for removal. There are too many clusters for the vine to carry them all uniformly to full maturity during a regular growing season. The resulting crop is out of control and would not produce the quality of fruit used in most high end wines.
These are obviously “Grapes Gone Wild”