In June, the vineyards are bursting with energy and life. Vines can grow as much as two inches per day. As the new canes grow, flowers that resemble miniature grape bunches start to develop. The vine typically enters the bloom period, which, depending on the accumulated heat units, occurs from mid to late June. By late June, growers begin planting their cover crops – annual rye grass or oil radish, for example – to incorporate more organic matter into the soil structure and provide footing for the harvesters in the fall.
Growers fertilize their crops in early July. What was once the developing flowers on the grapevine in June have now become bunches of grapes. Growers are busy removing the excess bunches to enhance and ensure premium quality. (This can be done either before or after fertilization). Crop removal is one of several cultural practices done to enhance grape quality.
This is a time of grape berry enlargement. To further enhance grape quality, growers remove the vine’s basal leaves to expose the grapes to more sunlight and air movement. This is important to enhance the quality of grapes and to control disease, because exposed grapes dry out sooner and are less susceptible to fungal attack. Growers also position the young shoots to maximize air and sun distribution. By the end of August, there is rapid increase in sugar levels in the vines. This is also the beginning of the grape maturation process. White grapes are transformed from a solid to translucent green, while red or blue grapes start to develop skin pigmentation. This process is called verasion. After verasion and as maturation proceeds, sugars increase and total acids start to decrease in the grapes. The whole complexion of the vineyard changes.