Thinning grapes, grudgingly

Two clusters were too close together. I thinned one of them; can't recall which.

I've heard another voice of advice urging me to thin grape clusters from vines. The reasons for doing so are set forth succinctly in a Ohio State University Extension bulletin:

• Balance the amount of fruit with the growth of foliage.
• Assure that each shoot will be capable of maturing the fruit retained.
• Avoid allowing vines to overproduce and lose vigor.

I have encountered several rules of thumb for thinning. The one I have followed is:

• Remove any clusters on shoots of 8 inches or less.
• Allow one cluster on shoots up to 15 inches.
• Allow two clusters on longer shoots.

However, I became easily confused as to what constitutes a shoot. I understand a trunk and a cane, and anything running off a cane must be a shoot. 

But what about sub-shoots running off of a shoot that's sturdy, almost woody in strength? I ran into a bunch of those and thinned to one cluster per sub-shoot. However, it's possible that I should have thinned the entire group of sub-shoots down to a couple of clusters total. Hard to say.

In any case, I thinned grudgingly and, it turns out, sparingly — but I did thin.