DIAMOND MOUNTAIN VITICULTURAL DISTRICT
Area
The viticulture area of the Diamond Mountain District is located in Napa County, California. The northeastern boundary follows the 400-foot contour line from Ritchey Creek northwest to the Petrified Forest Road and the northern boundary follows the Petrified Forest Road west from the 400-foot contour line to the Napa-Sonoma county line. The southwestern boundary follows the official boundary line between Napa and Sonoma counties southeast from Petrified Forest Road to the east-west boundary between Sections 18 and 19 in Township 8 North, Range 6 West, Mount Diablo Range and Meridian. The southern boundary follows the boundary between Sections 18 and 19, Sections 17 and 20 and Ritchey creek east from the Napa-Sonoma county line to the 400-foot elevation line. It also corresponds with the Northern Boundary of the Spring Mountain District viticulture area.
The Diamond Mountain region is situated in the Napa Valley on the eastern slope of the Mayacamas Mountains. The region consists entirely of residual upland soils derived from volcanic parent material. These soils are very different from the alluvial soils on the floor of the Napa Valley to the east and northeast and are also significantly different from the sedimentary upland soils prevalent in the Spring Mountain viticulture area to the south. These soils are significantly different from the shallow, dry soils in the Sonoma County to the west and southwest.
The viticulture area's topography and aspect contribute to a special microclimate. Hillside topography and valley temperature inversions combine to give the region an unusually moderate temperate regime during a growing season, with lower maximum temperatures and higher minimum temperatures than nearby locations on the floor of Napa Valley. The microclimate of the Diamond Mountain region is clearly distinctive when compared to the surrounding areas. The region's microclimate is slightly warmer than that of the Spring Mountain District to the south but somewhat similar due to comparable upland locations, northeastern (eastern, in Spring Mountain's case) aspects, and cooling influence of marine breezes from the Pacific Ocean. The microclimate is significantly cooler than the floor of the Napa Valley to its northwest and north, due to various tempering influences primarily associated with its upland location. So too is it cooler than adjacent land t the west in Sonoma County, due to its predominantly northeastern aspect which provides oblique sun and shade in the afternoon, while the western aspect of the Mayacamas Mountains adjacent to the region in Sonoma County is clearly hotter and drier.
Graeser Winery 255 Petrified Forest Rd., Calistoga, CA. 94515 707-942-4437
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