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, and it has been since it received its own AVA designation in 1981. It is California's first recognized AVA and the second in the United States. Within the Napa Valley appellation exists 15 subappellations, including: Atlas Peak, Calistoga, Chiles Valley District, Diamond Mountain District, Howell Mountain, Los Carneros, Mt. Veeder, Oak Knoll District of Napa Valley, Oakville, Rutherford, St. Helena, Spring Mountain District, Stags Leap District, Yountville and Wild Horse Valley.
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 (32.2°C).
Elevation: 760 to 2600 ft (231m to 792m).
Rainfall: 38 inches (96cm) annually.
Soils: Volcanic in origin, with basaltic red color, shallow with limited water retention, so irrigation is often essential.
Principal varieties & characteristics: Cabernet Sauvignon: Bright berry and cherry fruit, and more acidity than wines from Stags Leap District. Chardonnay: Crisp, floral, aromatic, with distinctive pear-mineral flavors and bright acidity.
Calistoga AVA
Climate: Warm to hot, depending upon time of year; lower humidity; summer temperatures peak to 90°F (32.2°C) and fall to low 50s°F (11°C), the result of marine air from the northwest; cool afternoon and evening breezes
Elevation: 300 to 1200 ft (92 to 370m)
Rainfall: 38 to 60 inches (96.5 to 150cm) annually
Soils: Almost completely of volcanic origin, soils range from rocky, stony loam on the hillsides, to gravelly or cobbly loams on the alluvial fans, to heavier clay-silt soils in the valley center areas.
Principal varieties: Cabernet Sauvignon, Zinfandel, Syrah, Petite Sirah
Chiles Valley District AVA
Climate: Fairly warmer summer days (mid-80°F plus/28.8 to 31°C), but due to higher elevation and summer fog at night, quite chilly at night (below 50°F/10°C). 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.
Coombsville AVA
Climate: Temperate climate moderated by near-proximity to the San Francisco Bay and the influences of marine air
Elevation: Most vineyards are in the 100-500 foot (30-150 m) zone, though a small portion tops 1000 feet (300 m)
Rainfall: Average rainfall is 24.6 inches (62 cm) per year over the last 100 years
Soils: Primarily weathered volcanic rock and alluvial deposits from the Vaca Range that surrounds the region
Principal varieties: Dominated by Cabernet Sauvignon on the hillsides with Merlot, Chardonnay, Syrah and Pinot Noir in the lower, cooler sites
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 2200 ft. (130 to 530m)
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.
Howell Mountain AVA
Climate: Similar to the facing Spring Mountain AVA, however slightly warmer and dryer overall due to strong afternoon sun influence. Fairly cool nights in both ranges and higher elevations help maintain good acidity.
Elevation: 600 to 2200 ft (184 to 675m).
Rainfall: 40 to 50 inches (125cm) annually.
Soils: Predominantly volcanic, shallow and infertile. Drainage is high, fertility low.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot, Zinfandel: Powerful, firm, blackberry-currant flavors and often richly tannic, with excellent acidity for aging. Chardonnay, Viognier: Sinewy, firm and not as fruity as those of the valley floor, revealing more citrus and stone fruit flavors.
Los Carneros AVA
Climate: Cool, with prevailing marine winds from the San Pablo Bay and through the Petaluma Gap to the west. High temperatures during summer rarely exceed 80°F (27°C) with less diurnal range variation.
Elevation: 15 to 400 ft. (4.6 to124 m)
Rainfall: Lowest in Napa Valley: 18 to 24 inches (7.2 to 9.6cm) annually.
Soils: Clay dominated, very shallow in general, with more loam and hillside alluvials in the northern section. Yields typically are restrained by the hard claypan subsoil, which prevents deep-rooting.
Principal varieties & characteristics: Chardonnay: minerally pear-apple and spice flavors. Merlot: sinewy and lightly herbal, with fine tannins and sleek structure. Pinot Noir: ripe cherry-cinnamon spice flavors with earthy notes.
Mount Veeder AVA
Climate: Cool to moderate, with most vineyards above the fog-line, meaning warmer nights and cooler days and less diurnal range than the valley floor. Typical mid-summer high temperatures about 85°F (30°C).
Elevation: 600 to 2100 ft. (183 to 650m).
Rainfall: 35 inches (87.5cm) annually.
Soils: Sedimentary based, former seabed, shallow and generally well drained, as well as more acidic, with low fertility. Most have a sandy or sandy-loam texture.
Principal varieties & characteristics: Ageability is a hallmark of Mt. Veeder wines. Cabernet Sauvignon, Merlot, Zinfandel: Low yields give red wines a firm, tannic structure with strong earth-berry aromas and rich, but powerful flavors. Chardonnay: minerally, appley, even citrus flavors with good acidity.
Oak Knoll District of Napa Valley AVA
Climate: Moderate to cool: marine air and fog can remain until mid-morning. Late afternoon breezes frequently occur, maintaining slightly cooler temperatures than upper valley. Mid-summer temperatures may reach 92° F (33.3°C) and drop to around 50°F (10°C) at night.
Elevation: sea level to 800 feet (244m)
Rainfall: 36 inches (90cm) annually.
Soils: The valley's largest alluvial fan formed by Dry Creek creates the defining feature of the district. The northwest area is composed of volcanically derived soils, with stony or gravelly consistency. South and east areas are transitional from gravel to silty clay loam.
Principal varieties & characteristics: Merlot, Chardonnay and Cabernet Sauvignon. Merlot and Cabernet Sauvignon benefit from a longer growing season with slightly cooler temperature, though crop size is typically less than in other AVAs. Elegant style is the common note with fruit flavors of cassis, tobacco and spice typical to Bordeaux-style reds. Chardonnay showcases flavors of crisp apple, mineral notes and tropical fruit with fine acidity.
Oakville AVA
Climate: Moderately warm, with temperatures commonly in the mid-90°F (34-35.5°C) range in high summer, but also still strongly affected by night and early morning fog which helps keep acidity levels good. East side of the AVA receives more of warmer afternoon sun.
Elevation: 75 to 500 ft (23 to 150m).
Rainfall: 35 inches (87.5cm) annually.
Soils: Primarily sedimentary gravelly alluvial loams on the western side, with more volcanic but heavier soils on the eastern side. Low to moderate fertility and fairly deep, with average water retention.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot: Ripe currant and mint flavors, rich texture and full, firm structure tempered by rich fruit. Sauvignon Blanc: Full, steely, yet very fleshy.
Rutherford AVA
Climate: Moderately warm, still marginally influenced by early morning fog. Western bench area is cooler, with less late afternoon sun, tempered by afternoon marine winds. (This AVA averages a bit warmer than Oakville and Stags Leap District). Usual summer peak temperatures are mid-90°F (34-35.5°C) with good diurnal range.
Elevation: 100 to 500 ft. (33 to 150m).
Rainfall: 38 inches (95cm) annually.
Soils: Western benchland is sedimentary, gravelly-sandy and alluvial, with good water retention and moderate fertility. The eastern side has more volcanic soils, moderately deep and more fertile.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot, Cabernet Franc, Zinfandel: Quite intense cherry and mineral, almost earthy aromas. Flavors are full, ripe, and notably currant with firm, but supple tannins for extended aging.
Spring Mountain District AVA
Climate: Similar to Mt. Veeder AVA, with cool weather prevailing and smaller diurnal changes. Fairly cool nights and higher elevations help maintain good acidity.
Elevation: 600 to 2200 ft (184 to 675m).
Rainfall: 40 to 50 inches (125cm) annually.
Soils: Primarily sedimentary; weathered sandstone/shale, loamy and friable in texture. Drainage is high, fertility low.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot, Zinfandel: Powerful, firm, blackberry-currant flavors and often richly tannic, with excellent acidity for aging. Chardonnay, Viognier: Sinewy, firm and not as fruity as those of the valley floor, revealing more citrus and stone fruit flavors.
St. Helena AVA
Climate: Warm, due to greater protection from western hills, with less fog or wind incursions. This narrowest part of the Napa Valley floor floor provides more heat reflection off the hillsides. Mid-summer temperature peak is often in the 85 -90°F range (30 to 35°C).
Elevation: 150 to 5 00 ft. (46 to 152 m).
Rainfall: 38 to 40 inches (95 to 101 cm) annually.
Soils: South and west borders are more sedimentary, gravel-clay soils, with lower fertility and moderate water retention. Further north and to the east soils are prevalently volcanic in origin and are deeper and more fertile.
Principal varieties and characteristics: Cabernet Sauvignon, Cabernet Franc, Merlot: deep, ripe, often jammy flavors, with firm tannins for structure and acid for long cellaring. Appealing aromas of currant and black fruit. Syrah, Viognier: Fleshy, supple and slightly earthy. Zinfandel: Blackberry-like, well-structured. Sauvignon Blanc, fresh and forward, passion fruit and lemon, crisp and fresh, not “grassy.â€
Stags Leap District AVA
Climate: Moderately warm, with afternoon marine winds acting as an 'air-conditioner' to cool the warmer air radiating off the bare rocks of Stags Leap itself and the surrounding hillsides. This AVA is often up to 10°F warmer than in Yountville AVA. Mid-summer temperatures can reach 100°F (37.7°C), but more regularly are in mid-90° range (32-34°C).
Elevation: 66 to 400 ft. (20 to 123m).
Rainfall: 30 inches (75cm) annually.
Soils: Volcanic gravel-loams on the floor of the valley, with rocky hillsides, and low to moderate fertility due to hard clay bedrock subsoils 2 to 6 feet down.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot, Sangiovese: Distinguished by lush, velvety textures and fine perfumed cherry and red berry flavors, supported by soft tannins. Chardonnay, Sauvignon Blanc: Round and ripe, especially Sauvignon Blanc, yet retain excellent citrus and apple flavors.
Wild Horse Valley AVA
Climate: A warmer area well to the east of Napa Valley proper, but still moderated by both altitude and prevailing winds coming off Suisun Bay to the southeast.
Elevation: Wild Horse Valley 400 to 1500 ft. (123 to 460m).
Rainfall: 35 inches (94cm) 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, floral, aromatic, with distinctive pear-mineral flavors and bright acidity.
Yountville
Climate: Moderate, with definite cool marine influence and fog contributing to cool summer mornings and the marine breeze keeping afternoons more comfortable than further up valley. Mid-summer peak temperatures may reach 90°F (32.2°C), with noticeable diurnal fluctuation to the mid-50°F range (13°C).
Elevation: 20 to 200 ft (6 to 61m).
Rainfall: 32 inches (80cm) annually.
Soils: Principally gravelly silt loams, sedimentary in origin, and gravelly alluvial soils with rock, moderately fertile.
Principal varieties & characteristics: Cabernet Sauvignon, Merlot: Yountville favors Cabernet and Merlot with ripe, violety aromas and rich, but supple flavors and firm tannins.
+ Information courtesy of www.napavintners.com
Napa Valley AVA
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