Napa Valley Wine Appellations
During the early decades of winemaking in the Napa Valley, grapes were often planted in patchwork pattern vineyards in which many varieties were mixed. But experience has since shown the wisdom of matching grapes with locations whose microclimates and soils are best suited to particular grape varieties.
Within the Napa Valley, regions have emerged that possess distinct microclimates and terrains, imprinting recognizable characteristics on the grapes grown within them. Vintners and growers within these regions delineate the boundaries of these growing areas, giving them names that reflect their regional designations, or appellations.
Data supporting a proposed American Viticultural Area, or AVA, is submitted to the government, which decides whether the proposed appellation designation will be granted.
The Napa Valley is itself an appellation. Within the Napa Valley appellation exists a number of other appellations, or AVAs, including:
Atlas Peak AVA
Climate: Cool, mountain-influenced, with temperatures about 10 to 15°F cooler than the Valley floor in summer. Above the fog line, there is a low diurnal change, with summer temperatures rarely above 90°F (30°).
Elevation: Atlas Peak: 1100 to 1800 ft (338 to 550m)
Rainfall: 35 inches (94 cm) annually
Soils: Volcanic in origin, with basaltic red color, shallow with limited water retention, so irrigation is often essential.
Principal varieties & characteristics: Cabernet Sauvignon, Sangiovese: Bright berry and cherry fruit, and more acidity than wines from Stags Leap District. Chardonnay: Crisp, flora, aromatic, with distinctive pear-mineral flavors and bright acidity.
Chiles Valley District AVA
Climate: Fairly warmer summer days (mid-80°F plus), but due to higher elevation and summer fog at night, quite chilly at night (below 50°F). With colder winters and spring, as well as strong winds, harvest comes later than on valley floor at Oakville.
Elevation: 800 to 1300 ft. (242 to 394m)
Rainfall: 35 inches (88cm) annually
Soils: On the valley floor, primarily alluvial soils with silty-clay composition of marine origin, with good fertility. Hillsides show more clay-loam and stony-clay composition, mostly marine in origin, with some volcanic outcropping, and less fertility.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot, Cabernet Franc: Cabernets usually reveal a lush yet firm texture with good acidity, firm tannin and distinctive cherry-blackberry flavors. Merlot typically has vibrant black cherry flavors mixed with a touch of cocoa.
Diamond Mountain District AVA
Climate: Moderately warm temperatures with lower maximum temperatures and higher minimum temperatures than north Napa Valley floor, due to topography and altitude. Significantly cooler than valley floor near Calistoga, 50 to 95°F in growing season (10 to 32°C).
Elevation: 400 to 1800 ft. (130 to 530 m)
Rainfall: 40 to 55 inches (135cm) annually
Soils: Residual uplifted soils of volcanic origin, often reddish and very fine-grained, even gritty in texture, composed of both weathered sedimentary and volcanic origin.
Principal varieties & characteristics: Cabernet Sauvignon, Cabernet Franc: firmly structured, rich and fairly tannic when young, with strong blackcurrant, mineral, and cedary flavors. Less supple and fleshy than valley or benchland wines, with good aging potential. Chardonnay: Full-bodied, yet revealing mineral, green apple-peach aromas with fairly firm acidity; less richly textured than valley floor wines.