St. Helena Growing Conditions

Climate

Climate is an important factor in wine grape growing, and the St. Helena Appellation has the perfect climate for growing Cabernet Sauvignon and many other red varietals.

St. Helena is at the northern end of Napa Valley, away from San Pablo Bay (part of what many people think of as San Francisco Bay). For that reason, during the day the St. Helena Appellation is one of the warmest sub-appellations of Napa Valley. Cabernet Sauvignon vines need warm weather to properly ripen and to develop the flavors most Cabernet drinkers like.

But it is important that the temperature not be constantly high. Growing wine grapes in a warm climate like St. Helena requires balancing physiological ripeness (taste) with sugar ripeness. If the temperature was always high, the grapes would tend to develop excessive sugar before they were ripe from a winemaking standpoint. The result would be a wine very high in alcohol. Cool nights are just as important as warm days, because they allow the grapes to continue to ripen without developing excessive sugar.

Because of its location at the narrowest point of Napa Valley, at night cool air from San Pablo Bay is funneled through St. Helena, causing a difference between nighttime temperatures and daytime temperatures of about 40°F. This allows for perfect ripening without exceptionally high alcohol.

Soil

Unlike food products (for example, table grapes), the best wine grapes tend to result from soils in which the vines must struggle to get the water and nutrients they need.

Well-drained low-fertility soil causes the vine's roots to grow deep in search of nutrients. With a deep root structure, the vines can generally find enough water to sustain themselves even through Napa Valley's normal summer drought. The result is that the vines produce small berries with complexity and deep flavor.

Many Napa Valley growers and winemakers believe that the best soil types are the volcanic rock soils along the valley's sides and alluvial fans (cone-shaped deposits of sediments formed where mountain streams discharge onto the valley floor). Both types of soil have good drainage and are not particularly fertile.

Because of its location in the narrowest part of Napa Valley, much of the the St. Helena Appellation is located near the bases of surrounding mountains. This means that most of the soil is volcanic in origin. In addition, the Appellation is covered by many alluvial fans. In the diagram to the right, the colored areas show the approximate location of some of the more important alluvial fans in the St. Helena Appellation.