Coulure

The failure of grapes to develop after flowering occurs. Poor weather conditions during the spring, such as overcast skies, very cold or very hot temperatures, wind, and rain can cause the flowers to stay closed or drop off the vine altogether, therefore remaining unfertilized. Each flower represents a potential grape, and vines that experience coulure (pronounced co-LURE), sometimes called “shatter” in English, have irregular bunches that are missing grapes.