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COULURE (French) or SHATTER (English) is the consequence of metabolic and weather conditions that cause either the grapevine flowers to not pollinate, so they do not becomes berries, or the tiny berries to fall off soon after they form. This means a poor fruit set. Depending upon the severity, the net result is low or poor quantity, or even no crop at all.

This condition occurs in vines that have too little sugar content in their tissue. It manifests in the Spring blooming period of the vintage year and is triggered by periods of cold, cloudy, rainy weather, or unseasonably high temperatures, both of which may interrupt or retard photosynthesis.

Shatter may occur in any variety. Certain varieties, however, have a high proclivity, including grenache, malbec, merlot, and muscat Ottonel. Vineyard conditions and practices can also cause the condition; pruning that is too early or too severe, excessively fertile soils or overuse of fertilizers, and improper selection of rootstocks or clones may bring aboout shatter.

Page created June 10, 2010; updated October 4, 2014
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