Howell Mountain: A Perfect Environment
Spence Vineyards is located in the Napa Valley’s sub appellation of Howell Mountain. The Howell Mountain designation was the first sub appellation in Napa Valley to be recognized as an American Viticulture Area (AVA).
It was defined by a group of early Howell Mountain vintners and it begins where the fog line in the valley ends: 1400 feet above sea level. At 1900 feet, our vineyard is midway between the 1400 foot bottom and the 2200 foot top of Howell Mountain, an area highly regarded for its ability to produce rich, full bodied Cabernets. Compared to the valley floor, the cooler days and warmer nights on the mountain allow for photosynthesis to start very early in the day. Additionally, the soils of Howell Mountain are very well suited for producing superb grapes; they are volcanic, well drained and not particularly fertile. The combination of these conditions stresses the grapes and provides for a longer maturation time, allowing the fruit to develop deep color and intense flavors.
Spence Vineyards: Two Discriminating Factors
The location of Spence Vineyards’ is unique – we are on the knoll of a hill above a canyon that opens to the Napa Valley floor. First, the temperature inversion that occurs, as the valley warms, generates a consistent but gentle breeze that blows from early afternoon until dusk. A warm breeze creates a convection effect that bathes the grapes in circulating air that is not felt a few hundred yards to either side of our vineyard. This consistent breeze thickens the skins to better prevent evaporation which leads to a higher skin to pulp ratio for extraction of more color and intensity. The cooler days extend hang time (typically a month longer than the valley floor) to allow grapes to achieve fully structured ripe tannins.
The second factor is the surface layer of red volcanic soil. Known to be rather shallow on most of Howell Mountain, in our vineyards it is actually quite deep and laced with rocks. This condition drains the soil rapidly forcing the vines to chase the water deeper into the ground and develop a large root system, thus extracting more intensity from the soil.