In the stressful soils and on the steep slopes of the Spring Mountain Estate grape vines struggle to survive, let alone bear and ripen a grape crop. Spring Mountain found that a significant percentage of their reds had excessive color and tannin. Though dazzling in their power; too many lots were too heavy to develop the elegance they sought in their wine. In the early years they sold up to fifty percent of the inky and intense reds to other wineries, selecting only the sumptuous and elegant lots for bottling.
While the old saying refers to "a scrawny vine making great wine" this can be carried to an extreme. Classically on the deeper soils of valley floor vineyards a winegrower seeks to stress the vines to increase the color and flavor in the grapes. Often this takes the form of a huge grape vine carrying fifteen to twenty pounds of fruit planted in wide rows. While this may work in these growing conditions the Napa Valley has a wide range of soil conditions and microclimates.
On Spring Mountain the winemaker is faced with a situation exactly opposite to conditions one finds on the valley floor. His soils are shallow, steep and rocky. To make better wine, the estate's winemaker wants reduce vine stress and he wants to build a healthier vine. The Spring Mountain winemaker believes he will optimize wine quality by minimizing the amount of crop each grape vine has to carry and ripen.
The average weight of a Cabernet Sauvignon cluster on Spring Mountain is about a quarter pound. A pound of Cabernet would then be about 4 clusters. In a wide spacing of 566 vines per acre one would ask each vine to ripen 44 clusters (11 pounds) to achieve a 3.1 ton yield per acre. However, in a dense spacing of 2,723 vines per acre you would ask each vine to ripen only 9 fruit clusters to achieve the same yield per acre.
In replanting of the estate the estate's winemaker chose to plant vines a meter apart within the rows. Depending on the other conditions like the soil, slope, rootstock, and grape variety, he varied the distance between the rows from one meter to the width of a terrace. This gave him vine densities of 4,050 to 2,050 vines per acre, respectively.
At 4,050 vines per acre, he will ask each Cabernet vine to ripen 6 or fewer grape clusters each year (quite a difference from the 42 clusters per vine mentioned earlier for wide spacing). With this light crop the winemaker expects to have healthier grape vines and make more elegant wines.
However, it is not easy to plant and farm a flat, valley floor vineyard at 4,050 vines per acre. On steep hillsides, such a dense planting is a heroic effort. To accomplish plantings of this density Spring Mountain Vineyard had to fall back to a thousand year old method of planting and training the grape vine called the Vertical Gobelet