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
Good question. I just recently read an article in "Practical Winery & Vineyard" - May / June 2005 by Eben Archer and J.J. Hunter (page 45) that stated among a lot of other things that leaves that are 80 to 90 days old no longer contribute much to the vine. They state that it is the younger leaves higher in the canopy and on laterals that contribute to ripening. To me this means count the leaves in the laterals. It also makes me feel better about pulling the older basal leaves around the clusters to permit more air circulation and exposure of the buds on the lower shoot to sunlight for next years crop. I suggest reading the whole article and derive your own conclusions.
I think just that shoot contributes. I need to put more fruit on, I think, which I believe slows the vegetative growth. I've noticed some Frontenac shoots with mega clusters that seem to put out much fewer leaves. Getting that balance right is a trick. Keeping the birds away will be the next trick :)
I'd guess the real ratio is the weight of the grapes to the surface area of the leaves (instead of cluster number to number of leaves), and as someone else mentioned, the older darker leaves seem to be less efficient.
Bill
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