Issue link: http://winesandvines.uberflip.com/i/101495
GRAPEGROWING William A. Fuchs Important rock types from Napa hillside vineyards (left to right) basalt-basaltic andesite from Darms Lane, dacite from Darms Lane and andesite-dacite from Shifflett Estate Vineyards. behind establishing the Oak Knoll District of the Napa Valley AVA. Although the district is most noted for Merlot in the reds category, two out of the three vineyards I mapped have an emphasis on Cabernet Sauvignon (with Shifflett having about equal emphasis on Merlot and Cabernet Sauvignon.) The Trefethen Hillspring Vineyard contains 25 planted acres plus 15 fallow acres within a much larger block of ground. However, the hillside has relatively small production compared to the nearby Trefethen main ranch on the valley floor. 92 W in es & V i ne s JANUARY 20 13 Nevertheless, premium wines come off this smaller acreage, and Trefethen 2005 Reserve Cabernet Sauvignon was named No. 1 Cellar Selection in 2010 by Wine Enthusiast (61% sourced from the Hillspring Vineyard.) Jon Ruel is the director of viticulture & winemaking, COO of Trefethen and my source for information about the performance of various vineyard blocks. (Read more about Ruel���s steps for improving wine quality on page 50.) Trefethen is a large operation with 100 SEE US AT UNIFIED, BOOTH #306 full-time employees. Peter Luthi was the winemaker prior to 2009, and Zeke Neeley has been Trefethen���s winemaker in the years since. All the best vineyard plots at Trefethen���s Hillspring Vineyard are planted in Cabernet Sauvignon, just as at Darms Lane and Shifflett. Ruel singled out block 807CS as Trefethen���s best vineyard plot. (See map on page 87.) This lies on the same basaltbasaltic andesite unit that represents the best and second best vineyard blocks at Darms Lane. As the Shifflett ground does not have outcrops of this unit (and hence no ranking here), this appears to be a star geologic unit. I attribute this to the chemistry and mineralogy of the rock type, which is geologically considered somewhat mafic but not ultramafic���the latter being universally considered bad from an agricultural viewpoint. Higher calcium, magnesium and iron are likely the ���agriculturally critical��� elemental characteristics of basaltbasaltic andesite that distinguish this rock as a viticultural superstar, but it seems to weather into a nice soil as well. Second best for Ruel are the small contiguous vineyard plots designated 803PV (planted with Petit Verdot), 803CF