EXPLORING NAPA VALLEY: A WONDERLAND OF TERROIR

Napa Valley enjoys some of the finest and most varied terroir in the world

Napa Valley is widely regarded as the finest grape growing region in North American. Despite its diminutive size there is nothing "same-ish" about the wines produced here. The region is most famous for its , but an array of premium grapes thrive here, notably Merlot, Pinot Noir, Chardonnay, Sauvignon Blanc, and . An incredible mix of climates, and elevations combine to produce some of the most diverse and rich grape-growing conditions in the world, providing wonderful insight into the elusive notion of "terroir", or sense of place. In this report we investigate the geological and climatic influences that explain the wonderland that is Napa Valley and hone in on the characteristics of each of Napa Valley's various sub-appellations.

A compact wonderland of 16 sub-appellations

Napa Valley is just 30 miles long and five miles wide at its widest point. There are 18,200 hectares under vine here, accounting for approximately one-tenth of the area. This compares with 26,500 hectares under cultivation in Burgundy and 120,000 in Bordeaux. Yields are very low - just 3.3 million cases of wine are produced annually, compared with 15 million in Burgundy and 70 million in Bordeaux - due to sometimes challenging terrain and a laser focus on quality. Within the Napa Valley appellation there are 16 sub- appellations, each with its own distinctive microclimate and terrain. Before examining the details of each of these sub-appellations, here is a brief overview of the main geological and climatic themes that span the valley.

Climatic and geological influences are key

 Climate: To understand the climate of Napa Valley, one has to understand its landscape and location. The valley is nestled between two relatively high mountain ranges. To the west and north, the shield the valley from the cool ocean breezes and summer fog that dominate in other parts of Northern . To the east, the protect the valley from the searing heat of the Central Valley. As a result, Napa Valley enjoys a dry, warm Mediterranean climate. The proximity of the to the south gives an added twist to the weather. Cooling marine breezes gradually move up the valley in the late afternoons, lowering evening and nighttime temperatures. The exact weather in any particular site depends on its elevation, exposure and location. The main valley floor rises from sea level at the southern end to 362 ft above sea level in the north. Vineyards range in elevation from sea level to 2,600 ft above sea level. Due to its closer proximity to the bay, the southern end of the valley is noticeably cooler than the north. Average summer highs in Carneros in the south are typically 10- 15°F lower than in the north in Calistoga. In general, Napa Valley's benign climate ensures great consistency from one vintage to the next.

 Geology: Violent geologic forces and the passing of time have created an agricultural paradise in Napa Valley. A vast number of soils of volcanic and marine origin exists here, created by geological events that occurred over the last 150 million years. The valley was formed by tectonic plate movement and volcanic activity during the formation of the San Andreas fault, and the erosion and subsequent mixing of these materials have formed complex and varied compositions. The periodic encroachment of San Pablo Bay, which once reached as far as present-day Yountville, and the flooding and shifting of the along the valley floor, have added to the geological mix. The result is a tapestry of volcanic and marine bedrock, the creation of several valleys-within-a-valley and a treasure chest of soils. Napa Valley today possesses 33 soil series and half of the world's soil orders. Valley floor soils tend to be deeper, more fertile and produce vigorous growth, whereas hillside vines fight to survive in the spare, rocky soils and naturally produce smaller, highly concentrated crops.

The AVA system

In 1981, Napa Valley became the first region in California to earn American Viticultural Area (AVA) status. To qualify for AVA status, a region must demonstrate that its growing conditions such as climate, soil, elevation, and physical features are distinctive. For a wine to reference an AVA on its label, at least 85% of the grapes used to make the wine must be grown within the boundaries of that AVA. (Note that unlike the French AOC appellation system, the American system does not define which grape varietals and winemaking practices can be used within an AVA.) Starting in 1983, regions within the Napa Valley began to earn their own AVA status, such that today Napa Valley possesses 16 sub-appellations. Perhaps the most famous region within Napa Valley not to have obtained AVA status is Pritchard Hill, high in the Vaca Mountains and home to such prestigious brands as Brand, Bryant, Colgin, Continuum and Ovid. The 1971 trademark for Pritchard Hill is owned by Donn Chappellet who is adamant that it will not become an AVA.

Napa Valley's 16 sub-appellations

AVA Date designated Los Carneros 1983 Howell Mountain 1983 Wild Horse Valley 1988 Stags Leap District 1989 Mt. Veeder 1990 Atlas Peak 1992 Spring Mountain District 1993 Oakville 1993 Rutherford 1993 St. Helena 1995 Chiles Valley 1999 Yountville 1999 Diamond Mountain District 2001 Oak Knoll District of Napa Valley 2004 Calistoga 2009 Coombsville 2011 Source: Wikipedia

The sub-appellations of Napa Valley in detail

AVA Elevation Size Description Los Carneros Sea level-700 ft TBD Straddling both Napa and Sonoma Counties and located just north of the (6,500 under vine) San Pablo Bay, this AVA is the coolest and windiest in Napa Valley, with temperatures rarely exceeding 80 degrees, providing ideal conditions for cool-climate varietals, namely Pinot Noir, Merlot and Chardonnay. The soils here are predominantly clay and very thin and yields are low. The wines, which benefit from a long growing season, have crisp acidity, tight structure and moderate sugar levels. Coombsville 100-1,000 ft 11,000 acres At the southeast corner of Napa Valley, tucked up against the foothills of (1,370 under vine) the Vaca Mountains, Coombsville's close proximity to the San Pablo Bay ensures cooling, marine influences. Most vineyards sit between 100-500 ft, although small plots sit over 1,000 ft. The soils are dominated by volcanic , with abundant rock and gravel. Cabernet Sauvignon is grown on the hillsides, with Merlot, Pinot Noir, Chardonnay and grown at cooler, lower elevations. The wines are known for their soft feel, good structure and earthy flavors. Wild Horse Valley 600-1,900 ft 3,300 acres One of Napa Valley's least known sub-appellations, Wild Horse Valley is (45 under vine) diminutive in size with only 45 acres under vine. The region enjoys a lot of sunshine and sits above the fog line, but its southerly location exposes it to some cool ocean winds. Cabernet Sauvignon, Pinot Noir and Chardonnay are grown here. Mount Veeder 500-2,600 ft 15,000 acres Nestled in the Mayacamas Mountains, the region is known for its colossal (1,700 under vine) wines. Most vineyards sit above the fog line, creating warmer nights and cooler days than the valley floor, with summer highs of around 85 degrees. It takes a lot of patience to grow vines here given the rugged, steep, volcanic terrain, but vintners are rewarded with a lot of direct sunlight and good drainage. Cabernet Sauvignon, Merlot, Zinfandel and Chardonnay are the main varietals grown here. The wines are intense and chewy, with strong flavors and aromas. Oak Knoll District Sea level-800 ft 8,300 acres This AVA is located at the south of the main valley at relatively low of Napa Valley (4,150 under vine) elevations. Cooling ocean breezes and fog that can last until the late morning ensure lower temperatures than other valley floor locations. Summer highs reach the low 90s. A wide variety of red and white varietals grow here, striking a perfect balance between sugar and acidity. The area is known for its delicately restrained wines. Yountville 20-200 ft 8,000 acres Many people rank Yountville among the best AVAs in Napa Valley. Located (2,600 under vine) at the south of the valley floor, the climate here is more moderate than higher up valley, with fog contributing to cool summer mornings, with summer highs around 90 degrees. Its long growing season produces thoroughly age-worthy Cabernet Sauvignon and Merlot. The wines are known for being supple and rich with firm tannins. Stags Leap District Sea level-500 ft 2,700 acres Located in the Vaca Mountains six miles north of the town of Napa, Stags (1,350 under vine) Leap earned its AVA status because of its unique soils, which vary from loam and clay sediments from the Napa River to volcanic mountain erosion. Summer temperatures can reach over 100 degrees. Cabernet Sauvignon and Merlot are the main varietals grown. The region is known for its lush, velvety, powerful wines. It was a wine from Stags Leap that claimed first place in the famous 1976 Paris Wine Tasting - the event that put Napa Valley on the map. Atlas Peak 760-2,600 ft 11,000 acres Located on the western slopes of the Vaca Mountains, the climate of Atlas (2,015 under vine) Peak is unique. Its high elevation means summer temperatures are 10-15 degrees lower than the valley floor and, because it sits above the fog line, the variation in temperature between day and night is low. Its west facing orientation ensures direct afternoon sun. The soils are volcanic and porous. Only a small portion is under vine, reflecting the difficult terrain. Cabernet Sauvignon and Chardonnay are the main varietals, but Zinfandel is increasingly in vogue. The wines are known for their bright, fruity flavors and good acidity.

The sub-appellations of Napa Valley in detail (continued)

AVA Elevation Size Description Oakville Sea level -500 ft 5,700 acres Widely regarded as one of Napa Valley's finest sub-appellations and home (2,865 under vine) to many of the region's star wineries, this region is virtually flat field, squeezed between the Mayacamas and Vaca ranges. The gravelly, well- drained soils are perfect for the world-class Cabernet Sauvignons that are made here. Temperatures often reach the mid-90s in summer, but the cooling wind and fog that rolls in late in the day play a key role in achieving the balance that Oakville is famous for. The wines are powerful, complex, multi-textured, with rich fruit and fine tannins. Rutherford Sea level-600 ft 6,650 acres This celebrated AVA sits just north of Oakville on the valley floor. (4,085 under vine) Rutherford soils are notoriously complex, comprising decomposed rock carried downhill from the mountains, intermingled with the silt, clay and gravel deposits of the Napa River flood plain. The soils provide excellent water drainage and allow deep rooting - ideal conditions for Cabernet Sauvignon. Temperatures peak in the mid-90s, with distinct day-to- nighttime variations. Rutherford is home to some of Napa Valley's most historic and world renowned wineries. The wines are known for their supple tannins and minerally, earthy feel. St. Helena 100-700 ft 9,000 acres St Helena is located up valley where the valley floor narrows, and is home (2,909 under vine) to the bustling town of St Helena. The soils and climate are quite different from the surrounding area. Temperatures are hotter than down-valley due to greater protection from the western hills, with less fog and wind. Charles Krug, one of the pioneers of Napa Valley winemaking, opened his winery here in 1861. The wines - principally Cabernet Sauvignon and Zinfandel - are known for being graceful, with concentrated fruit flavors. Spring Mountain 600-2,600 ft 8,600 acres Known for its mountain grown Cabernet Sauvignons, this region's first District (965 under vine) premium wines were actually whites. The vineyards here are small. Grapes are handpicked on the steep, east-facing terraces of the Mayacamas Mountains. Most vineyards sit above the fog line, although the region still sees cool afternoon breezes. Days are cooler and nights warmer than the valley floor and the growing season is long. The wines are powerful, tight and richly tannic and typically not as fruity as valley floor wines. Chiles Valley 600-1,200 ft 6,000 acres This narrow AVA in the Vaca Mountains along the northeast side of Napa District (1,000 under vine) Valley is really a "valley within a valley". The maritime influences that affect other parts of the valley do not reach this far inland. Summer temperatures peak in the mid-80s and nighttime temperatures drop to the 50s. Cabernet Sauvignon, Merlot and Cabernet Franc are the main varietals. The wines are lush, yet firm, with distinctive cherry and blackberry flavors. Howell Mountain 600-2,600 ft 14,000 acres Overlooking St Helena from the Vaca Mountains on the valley's northeast (1,005 under vine) side, Howell Mountain is known for its magnificently complex, earthy, robust wines. Because of the rugged terrain, only a fraction is under vine. The region sits above the fog line, but receives cool Pacific breezes and lots of sunshine. The soils are volcanic and porous, producing vines of low vigor and deep roots. is known for its Cabernet Sauvignon and Zinfandel. Diamond Mountain 400-2,200 ft 5,000 acres On the northeast side of Napa Valley in the Mayacamas Mountains, only (500 under vine) 500 rocky acres are under vine here, mainly of Cabernet Sauvignon and Cabernet Franc. Unique, porous, volcanic soils and extended sun exposure are the main reasons world-class wines are grown here. Known for being firm, rich and chewy, these wines have plenty of tannin for aging. Calistoga 300-1,200 ft 4,480 acres Calistoga is located in the north of Napa Valley. This AVA is known for its (3,320 under vine) volcanic soils, high daytime temperatures (up to 100 degrees in summer), and cool nights, causing the highest day-to-nighttime temperature variation, of up to 50 degrees. Despite sharing the name, Calistoga AVA does not include the entire town of Calistoga. Calistoga is noted for its topographical diversity and uniform volcanic soils. Cabernet Sauvignon, Zinfandel and Syrah are the principal varietals. Source: Napa Valley Vintners, Appellation America, California Winery Advisor, Wine Spectator and Wikipedia.