Growing Grapes in EL Dorado County

 Growing Grapes in El Dorado County

     It is a well-known fact that from region to region wine varies in character and quality. The factors that determine why grapes exhibit such a wide range in flavor and quality are elusive and still poorly understood, but it is generally agreed that soils and climate both play essential roles. In past years the role of climate was deemed paramount by many California vintners, but now the critical role of soils is more widely appreciated, as it has been in France for centuries. These two features -climate and soils- working together produce what viticulturists call terroir - a French term signifying a summa­tion of all the subtle climatic and soils attributes that impart to wine from a particular vineyard or region a special character found nowhere else. Terroir connotes a sense of place, and grapes from El Dorado, per­haps more strongly than elsewhere in California, express fully this concept. In this section, we explore some of the physical reasons why El Dorado is such a special place for growing grapes and producing fine wines.

     The growing importance of terroir can be seen in the widespread use of geographic designations, or Appellations, that denote specific growing regions ("Napa Valley" is the best known Appellation in California. "El Dorado" is also an appellation, (see figure 1) but it has only recently been identified as pro­ducing wine of special character. All such geographic terms must be registered with and approved by the U.S. Department of Agriculture). Another rapidly growing usage that signifies terroir is the designation on the label of the specific vineyard in which all the grapes were grown. The term "Estate Bottled" on a wine label carries a similar connotation in that all the grapes in that particular bottling were produced by, or un­der the direction of, the winery that produced the wine. Some appellations are so large (e.g., "California") that the concept of terroir becomes meaningless. That is not to say that such wines blended from grapes grown in several different areas are inferior wines. They do, however, generally lack the unique character­istics that identify the wine's homeland. The trend in California wine production during the past ten years or so has been to more clearly differentiate and promote these various growing regions and this trend is likely to intensify as each region attempts to gain recognition of their own special characteristics.

• Three separate appellations can be applied to EL Dorado grapes (see figure 1): Sierra foothills; 2) El Dorado; and 3) Fair Play
• Sierra foothills is appropriate for wine blended from grapes grown in two or more foothills ap­pellations (e.g., Amador and El Dorado). For all appellations, 95% of the grapes processed to make a particular wine must have been grown within the designated area..

     All El Dorado vineyards are in a mountain setting at elevations above the valley and coastal fog belts. The mountainous topography imparts complexity and variety to our growing conditions that are not found in valley settings. Three critical aspects - elevation, complex topographic, and lack of fog, make El Dorado appellation unique and impart a special character to our grapes. No other grape growing region in North America possesses this special set of physical parameters, which is why El Dorado wines are rap­idly gaining recognition in world-wide markets.

     "Climate" is a term that refers to the long-term temperature, humidity, and rainfall characteristics of a region. "Weather" signifies the short-term, daily, weekly, or yearly variations that typify any climatic re­gion. Climate changes slowly, whereas weather is changeable from day to day. For the grape grower, un­derstanding both the long-term and short-term conditions is vital. The long-term climatic conditions stipu­late whether or not growing grapes is feasible, and if so, which kind of grapes may be grown successfully. Critical climatic data include: average maximum and minimum temperatures during the growing season^., average rainfall and yearly rainfall distribution; average relative humidity, and average date of the last kill­ing frost in the spring. The longer the duration of weather data that is available, the more meaningful these kinds of measurements may be. Short term, daily to monthly weather data is useful for proper crop man­agement, for spraying programs, and for efficient irrigation schedules. Freezing weather following bud break (early to mid April) is a local hazard that can severely damage young shoots and drastically decrease grape production in affected vineyards. A frost warning system and overhead sprinklers or a misting sys­tem may ameliorate this problem under favorable conditions.

Daily weather conditions are modulated by topography. Air changes density as it is warmed or cooled, so that warm air rises and cold air sinks and flows over the topography much like water. During freezing weather, cold air will flow downhill from regions of higher elevation and may pond in valleys or depressions if the natural drainage way is blocked, resulting in a thick blanket of frosty air that can freeze the entire grape vine. Good air drainage is essential for avoiding frost problems. In general, ridges tend to be cooler than valleys during the day, and warmer during the night. For this reason, hillsides are preferred sites for planting grapes because they exhibit more dynamic microclimates. South and west-facing slopes are warmer than east and north-facing slopes, so these differences must be taken into account for proper positioning of selected grape varieties

Climate Zones:

Various methods have been proposed to categorize and compare the climatic conditions within and between various regions. The two most widely used are native plant communities, and degree-day heat summations. Neither method tells us all we would like to know about the climate, but both are useful. De­gree-day summations are easiest to understand as they are based on physical measurements (temperature), but as they utilize only average daily temperature measurements during the growing season (April 1 through October 31), the maximum and minimum peak values as well as winter-time values are not consid­ered. Plant communities, on the other hand, record the response of flora to the entire spectrum of climatic conditions throughout the year, but the climatic conditions during the growing period may not be uniquely specified.

Native Plant Communities: Three climatic zones defined by plant communities have been identified as being suitable for wine grape growing in El Dorado County. These are roughly delimited by elevation, as follows:

• Region II - Elevation ranges from 2,200 to 3,200 feet; Black Oak and Madrona are the best in­dicator trees. Other diagnostic species include: Douglas Fir, Ponderosa Pine, and Incense Cedar.
• Region III - Elevation ranges from 1,200 to 2,200 feet; Live Oak, Grey ("Digger") Pine, Pon­derosa Pine, Toyon, and poison oak thrive in this environment.

Region IV - Elevation ranges from 800 to 1,200 feet; Blue Oak is the best indicator species ac­companied by Live Oak, Grey Pine, and brushy species (chaparral). The purported link between this zonation and elevation must be treated cautiously, because  variation in soil character as well as topography can modify local plant communities. Special plant communities that lack temperature (or elevation) control exist on soils derived from weathered gabbro and serpentinite (rocks rich in magnesium and iron); likewise, thin, rocky volcanic soils on ridge tops above 2,200 feet may support plant communities characteristic of much lower elevations. In addition, cool and damp north-facing slopes have markedly different vegetation than do warm and dry south-facing slopes. Plant climatic Zone II is the preferred zone for planting grapes as it is more amenable to wider range of grape varieties.