A dormant vine bud is fertile as soon as it buds and consists of one or more flower clusters.
The fertility of a vineyard is determined by the budburst. A dormant bud is seen as fertile as soon as it buds and consists of one or more flower clusters. These clusters are already formed inside the bud 15 months before the current harvest, October to January, if conditions are favourable. Favourable conditions include enough nutrients, direct sunlight, temperatures above 20°C and a ground temperature above 10°C.
Although a bud can be very fertile it means nothing if there is no budburst. The best budburst percentage is obtained by spur pruning but in some instances it is necessary to use chemical rest-breaking agents to initiate budburst.