For many the annual life cycle of the vineyard begins in the fall, immediately after the previous year’s harvest. During this time, vines lose their leaves and begin to go dormant. The vineyard manager’s primary concerns are pruning the vines and ensuring that they are protected from cold temperatures. Depending on the severity of the climate, vineyards are normally pruned sometime within three months after harvest. In very cold climates pruning is delayed to the end of this time frame.
As temperatures begin to warm in the spring, canes begin to grow and bud break approaches. In California, this usually occurs in April or May. The start of this cycle is signaled by a “bleeding” of the vine, which occurs when the soil begins to warm and water is pushed up from the root system of the vine and out from the cuts or wounds left from pruning.
After bleeding, tiny buds on the vine start to swell or “break” and eventually shoots begin to grow from the buds. After bud break, the young shoots are very vulnerable to frost damage and vineyard managers may go to great lengths to protect the fragile shoots from damage due to freezing. This may be the most hazardous time of the vineyard cycle, as the return of cold winter weather can hurt vines during this vulnerable stage. Assuming no damage, in time the shoots begin to sprout leaves.
In California, flowers begin to form in late spring, depending on temperatures. Small flower clusters looking like buttons appear on the tips of the shoots. A few weeks after the initial clusters appears, the flowers start to grow in size with individual flowers becoming observable. It is during this time of flowering that the pollination and fertilization of the grapevine takes place with the resulting product being a grape berry containing 1-4 seeds.
Immediately following flowering fruit set occurs, when the fertilized flower begins to develop a seed and a grape “berry” is formed to protect the seed. In California, fruit set occurs and grape clusters develop usually in June – July. This is very critical for wine production since it determines the potential crop yield. Not every flower on the vine gets fertilized, and unfertilized flowers eventually fall off the vine without grapes being formed.
Following fruit set, the grape berries are green and hard. They have very little sugar, are high in acids and taste sour, and have grown to about half their final size when they enter veraison. Veraison (a French word meaning “onset of ripening”) occurs in California around August and signals the beginning of the ripening process. During this stage as the grapes ripen, the colors of the grape take form – red/black or yellow/green depending on the grape varieties. Within just a few days of the start of veraison, the berries grow dramatically as they accumulate sugar and acids begin to fall.
The final event in the vineyard is the harvest in which the grapes are removed from the vine and taken to the winery to begin the wine making process. Although tradition dictates that harvest will occur 100 days after flowering, the decision to begin is ultimately the vineyard manager’s. Harvest normally occurs in California in late September or early October. The exact date is selected based on the varietal as well as sugar (“brix”) and acid levels. Testing for sugar and acid is frequent in the final weeks and days. Weather can dramatically affect grapes at this stage either positively or negatively. Late rains can dilute sugar levels and high temperatures can detrimentally lower acidity, making wines either flat and boring or overly alcoholic. The risks of leaving grapes on the vine for too long must be weighed against the need to develop varietal characteristics.
After the vineyard manager accounts for all of the variables and decides that the time is right, harvest begins, grapes are picked and the annual life cycle starts over again.