Growing Wine Grapes

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describe the vine cycle. include dates of key imprtance

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THE VINE CYCLE: In California the vine cycle begins around April 1, when new shoots emerge from the dormant bud. The shoots elongate during April and May and the vine flowers around May 15. Tiny berries begin to grow but remain green and hard until about July 15. Veraison, the onset of ripening, begins then and the berries begin to develop color and to soften. Fruit is usually harvested around September 15, but this date varies with the variety, the location, and the weather. In November or December, the vine loses its leaves and enters dormancy. Pruning usually takes place between December and February.

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When do dormant buds start to develop why are they so important

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DORMANT BUDS: Because these buds contain the developing flower clusters that will produce the next year's fruit, the environmental conditions that exist this year and the farming practices used this year will greatly influence next year's crop. The dormant bud begins to develop near the end of the summer.

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Describe how berry composition changes beyween veraison and harvest

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BERRY COMPOSITION: Between veraison and harvest, the composition of the berry changes markedly. The sugar concentration rises from about 4% to 20–28% as sugar is transported into the fruit from the leaves. Several different scales are used to express sugar concentration. In the U.S. the °Brix scale is used, equivalent to % sugar by weight. Other scales are used in Europe and elsewhere. Ripeness or maturity is a matter of taste, but grapes for wine production are usually harvested between 19° and 24° Brix (compared to 16° to 18° Brix for table grapes).

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What changes occur to acid levels as the grapes mature?

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Between veraison and harvest, the acid concentration (largely malic and tartaric acids) decreases from around 3% to less than 1%. Most of this decrease is due to dilution because the berry is increasing in size and water content. Some of the malic acid is also lost by respiration (the conversion of malic acid to CO2). During this time, pigments develop in the skin of red varieties, flavor compounds develop and the tannins in the seeds also increase.

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What key factors determine harvest time?

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HARVEST: The decision to harvest wine grapes is typically made on the basis of sugar and acid concentrations. The sugar must be high enough to produce the desired alcohol concentration in the wine and the acid must be high enough to maintain the desired tartness. However, winemakers are also interested in varietal character. Key flavor compounds may not always reach their optimum concentrations at the same time as the sugar and acid, so the winemaker must carefully monitor the development of the fruit as it nears maturity, often by tasting the fruit in the vineyard.

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What are heating degree days

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TEMPERATURE: Environmental conditions greatly affect the grapevine and its fruit. The date at which the vine leafs out in the spring is determined by temperature, as is the rate at which the vine progresses through its growing season. Varieties differ in the amount of heat they require to mature their fruit. The cumulative amount of heat typically available over the course of a season can be expressed in degree days which are calculated by summing, for each day over the course of the season, the number of degrees by which the average temperature exceeds 50°F (the temperature above which the vine is physiologically active).

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On average how many heating degree days to california vinyards accumulate in a growing season

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Most wine grape regions in California have 2,000 to 4,000

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Desribe how heating degree days define california wine regions

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Generally, mature grapes cannot be produced with less than 1,700 degree days. Most wine grape regions in California have 2,000 to 4,000 degree days. In the 1940’s UC Davis researchers classified California grape growing areas into 5 regions based on average degree day accumulation. Varieties are recommended for different locations within California based on their heat requirements. Varieties with low heat requirements, like Pinot noir and Chardonnay, are usually recommended for the cooler areas (such as the cool southern end of the Napa and Sonoma Valleys and the cooler parts of Mendocino County). Varieties with higher heat requirements, like Cabernet Sauvignon or Zinfandel, will not ripen in very cool locations, and are therefore recommended for Regions II and III (such as the middle and northern parts of Napa and Sonoma Counties) and IV (northern Sacramento Valley). Davis is Region IV. The northern and southern ends of the Central Valley are Region V.

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Wine map of california

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wine map california

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Front 11

Describe how a hotter climate affects the garape characteristics.
Include changes in sugar content, acid levels, color intensity, grape volume (yield) and fruit flavors.

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HOTTER AREAS: In hotter areas, grapes can reach very high sugar concentrations but the acidity is lower because of increased loss of malic acid by respiration. Color and flavor intensity are also usually lower in fruit produced in hot regions. Yield (the amount of fruit produced) is higher. Extreme heat, however, can result in shriveled fruit and arrested sugar accumulation. Grapes for premium wine are not usually grown in very hot locations because they will lack distinctive varietal flavors.

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What kind of wines are produced from hotter grape growing regions

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Hot areas are ideal for the production of dessert wines, however, because high sugar is desirable in order to achieve the high alcohol concentrations of these wines and varietal distinctiveness is not as important.

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How do cooler growing regions affect the characteristics of the wine produced?

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COOLER AREAS: In cooler regions, sugar accumulation is slower and yield is lower. In very cool areas, the grapes may not even reach maturity. Acidity is generally higher in cool areas because respiration is reduced. Color and flavor intensity are increased and maximum varietal distinctiveness is achieved in cool areas. The vineyards from which California's premium wines are produced are in relatively cool areas, notably the coastal valleys. Wine grapes produced in these areas are typically 10 times as valuable as those produced in the hottest areas of California, but this differential is partially offset by the 2 to 3-fold higher yields obtained in the hotter areas.

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Describe how weather during various parts of the growing season may affect the vineyard.

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WATER: Winter rainfall is ideal for grapevines because their deep roots can extract stored moisture from the soil throughout the growing season. Rain at the time of flowering interferes with fruit set and summer rain encourages bunch rot and other fungal diseases. Rain at harvest can also result in swollen berries and reduced sugar. So places that have wet winters and dry summers, like California, are well suited to viticulture. Most traditional vineyards in Europe are not irrigated, but irrigation is common in California and the rest of the New World. While excessive irrigation can result in overly vigorous vines and reduced fruit quality, the proper use of irrigation can result in consistent yields of high quality wine grapes.

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How does soil affect the vines and grape

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SOIL: Soil supports the vine and is a reservoir for nutrients and water. Many of the differences in wine flavor that are attributed to soil are due to the different water holding capacities of various soil types.

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Describe the parts of a grape vine. When do new vines start to produce fruit. how long does a vinyard last?

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PROPAGATION: Grapevine plants are usually purchased from commercial nurseries as grafted plants. The scion variety has already been grafted to the rootstock in the nursery. New vines do not produce much fruit until the third or fourth year after planting. Because vineyard establishment is very expensive and because a significant crop is not obtained for several years, great consideration must be given to rootstock and variety choices. A vineyard in California typically has a life of about 20 years, after which time the vines are removed because they are diseased or because the grower wishes to plant a different variety or to use a different spacing or trellising system.
Grafted grapevine

Front 17

describe some general considerations of pruning. include over pruning leaving too few buds and under pruning resulting in too many buds

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PRUNING: Pruning is one of the most important tools for controlling a grapevine. It not only controls the size of the vine but, because it establishes the number of dormant buds the vine will have, it also determines the total number of clusters and thus the total amount of fruit the vine can produce the following year. A vine left with too few buds may be excessively vigorous with a resulting reduction in fruit quality. Conversely, a vine left with too many buds will be overcropped—it will not be able to produce enough sugar to fully ripen its fruit clusters. The ratio of fruit to foliage and the amount of light that reaches both leaves and fruit are critical to the development of high quality wine grapes. It is the increasing appreciation for these principles that is leading winemakers to further manipulate the foliage of wine grapes by summer pruning and leaf removal around fruit clusters.

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What is meant by canopy management

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CANOPY MANAGEMENT: The total foliage of the grapevine is called the canopy. Good grape growers know that the way they manage the canopy affects the flavor of the resulting wine. They aim to balance the amount of fruit and foliage, to avoid both overcropping and excess vigor. They also try to maximize the amount of light that reaches all the leaves. In addition to pruning during the winter, they may also trim the vines during the summer (summer pruning) and remove leaves in the vicinity of the fruit clusters. Leaf removal not only affects fruit flavor but also can help minimize fungal disease problems.
Most winemakers spend a lot of time in the vineyard. They know that vineyard factors usually have more influence on wine flavor than anything they can do in the winery.