defoliation, loss of leaves, of a vine can be caused by various agents. If extensive and badly timed, it inevitably adversely affects fruit ripening and wine quality, although the precise effects depend on the time of the year. Defoliation is, of course, a natural process and happens at the end of each growing season in the autumn. Normally it is caused by the first frost, but it may also be through mechanical damage or merely senescence. By this time the vines have lost most of the green colour from their leaves anyway and they are no longer effective at photosynthesis. Providing the vine’s reserves of carbohydrates are topped up by late-season photosynthesis, there is no negative effect of defoliation.
