The book "General Viticulture" suggests that red wine grapes need 20 - 26
leaves per cluster to ripen effectively.

Question: are the number of leaves per cluster limited to the shoot the
cluster is growing on (what if there are two clusters growing on one shoot.
Does there need to be 40+ leaves on one shoot to contribute to those two
clusters?)? If one wanted to be meticulous and count leaves on a single
vine, could the number for the whole vine be averaged for X amount of
clusters?

Jeff