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| Grape growing, winemaking and wine maturation |
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| The life of the vine |
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The growth cycle begins with dormancy, which is the end of one cycle and the beginning of another. Dormancy begins with leaf fall and ends with budbreak, when the average daily temperature reaches approximately 50ºF (8 - 10º C), although the temperature is lower in cooler regions.
 At the end of dormancy sap begins to rise from the roots and flow through the vine, causing the buds to swell. Most but not all buds will burst – some will remain dormant. There are two types of buds, leaf buds and fruit buds, which are identical at budbreak. The growth of the shoots or leaves depends on the reserves of carbohydrate in the vine. Growth is slow at first and then accelerates, reaching its peak just before flowering. The growth of the shoots drops off rapidly at flowering, but continues through the growing season, stopping only at veraison. Shoot growth at this stage begins photosynthesis.
Fruit buds contain the beginnings of flower clusters. The length of time between leafing out and flowering is about eight weeks. The quantity of fruit buds formed (and thus yield) depends on many factors, include carbohydrate accumulation in the vine, the supply of nitrogen and water available to the vine, and the climate – temperature and light intensity are both important.
 Flower caps covering the stamens fall after flowering, and the stigma receives the pollen. The fertilization of the flowers leads to berry set. Most flowers self-pollinate, with all flowers having both stamens and pistils. Weather at this stage is crucial because poor weather can stop the fertilization from occurring, reducing the amount of clusters that each vine carries. In a successful flowering, about 30% of the flowers become grape clusters. If flowering is disrupted by poor weather, yield is reduced and the result is known as shatter or coulure. If the unfertilized flowers do not drop off the vine, they form small hard berries with no seeds called shot berries (millerandage). If the vine lacks carbohydrates because of low photosynthesis or excessive shoot growth, it can cause the flowers to fall off more easily, leading to this condition. It can also be caused by mineral deficiency, viral infection or old age.
 Approximately 40-50 days after fruit set, the berries turn color in the veraison process. At this point, the berries begin to ripen. They soften as the volume of the grape increases. As ripening continues, the acidity of the grapes decreases. The growth of the shoots stops, allowing the vine to concentrate on ripening the fruit. Mature, ripe fruit has a good balance between the sugars in the ripe fruit and the acidity. This balance is a personal decision made by each grower as he watches his crop.
In addition to this balance, though, ripeness also depends on maturity of the phenolic compounds in the grape. These are the tannins and coloring agents present in the skin, seeds and stems. If harvest occurs before they are ripe, the tannins will be hard and unyielding and the wine will have green, unripe flavors. After harvest, the leaves fall and the vine enters dormancy once again.
 All vineyard treatments must stop long enough before harvest to ensure that residue from pesticides does not find its way into the wine. This is the period when growers sample the grapes in the vineyard continually in order to ensure that the desired level of ripeness is achieved. As detailed in the chapter on grapes, the grower decides the balance that he seeks between sugar, acid and phenolic ripeness, and thus decides picking time.
Harvesting can be done in most regions either manually by pickers with shears cutting individual bunches and laying them in small baskets or through the use of a machine. Hand harvesting is mandatory in Champagne because it is dictated by the traditional method of pressing the whole clusters as is done in Champagne and sometimes in other regions such as Burgundy and California.
Hand harvesting is gentler, but it is slower and more expensive. In general it gives superior results because the grapes suffer less damage during the harvest. In cases where the harvest needs to be completed quickly, however, machine harvesting can be preferable. This may be the case if poor weather threatens, or if acidity is falling rapidly due to hot weather.
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Wine Regions of the World
