The Oakville AVA is home to some of the most famous names in Napa Valley – Robert Mondavi, Harlan, Rudd, Opus One and Screaming Eagle are well-known producers, there, and To Kalon and Martha’s Vineyard grow some of the most sought-after grapes in California.
The history of research and innovation in the region, which still thrives today, was instigated by Hamilton Crabb in 1868. The first “research station” in Oakville was Crabb’s To Kalon (Greek for “highest beauty”) vineyard, where he planted over 300 varieties. He purchased the 240-acre parcel in Oakville and, by 1877, he had over 130 acres of producing vineyard and sold cuttings to other Napa Valley growers. As the first commercial winery owner in Oakville, he was producing 50,000 gallons of To Kalon wine. Today, the University of California at Davis has a research vineyard in Oakville and Robert Mondavi Winery is renowned for its in-house research, part of it on the original To Kalon ranch. Crabb’s neighbor, Far Niente winery, began producing in 1885 and by 1887 over 1000 acres of vines were thriving in Oakville. In the long, arduous recovery from prohibition, the Napa Valley became the first AVA in America in 1981 and the Oakville District gained AVA status in 1993.
Oakville is just about in the center of Napa Valley, and is about two miles wide, it’s borders clearly marked by the western Mayacamas mountains and the Vaca range to the east. From its northern boundary, where it meets with the Rutherford District, to its southern boundary, the Yountville District, is just over a mile. At about 5,000 planted acres, it represents about 11% of the total vine-acres in Napa Valley.
At first glance, the soils appear to be relatively uniform and well defined – a mix of various loams, especially clay, sand and gravelly loam. They’re mainly the result of weathered, broken down rock that washed down the two mountain ranges over the millennia to mix with the with the river and stream deposits of clay, silt and gravel. They rest on a base of gravel that promotes, generally, very good drainage and deep root penetration. A closer look reveals that the two ranges have little in common. The western Mayacamas were pushed up from the bottom of the sea as the valley floor sank, millions of years ago, bringing up a chaotic mix of ancient marine rock formations, sandstone, limestone, serpentine (California’s state rock!), shale and metamorphic rocks. The two large, famous alluvial fans at the base of the Mayacamas are composed of rock and loamy sediment that washed down during storm after storm over the millennia. The eastern Vaca range, rather than pushing up, was formed, layer by layer, by the deposit of repeated volcanic eruptions caused by fissures in the tip of the San Andreas fault as it was dragged north by the Pacific and North America plates. It left compressed volcanic ash (tuff or tufa – often exposed tufa), lava flows, volcanic mudflows, a variety of other pyroclastic deposits (fragmental pieces of rock, such as minerals or glass, spewed by the eruption), and sedimentary rocks of volcanic origin. Virtually every knob and knoll you see in Napa Valley is of the same volcanic origin. Oxidized iron accounts for the noticeably-red soils in much of east Oakville. Heavy rainfall over the Mayacamas may explain the large size of the western alluvial fans. The eastern fans are small and the soil thin by comparison.
Oakville is noticeably warmer than the neighboring Yountville District, to the south, and just a tick cooler than the Rutherford District to the north. Moving from south to north, the valley heat increases as it moves away from the marine influence of the San Pablo Bay at the southern end. Oakville residents often experience afternoon temperatures in the mid-to-upper 80 and 90s, F., in the height of summer. The heat of the day forwards the maturation of the slow-ripening Cabernet Sauvignon that dominates the district. As the heat rises, it eventually pulls in cool bay fog and breezes, and it’s common to see temperatures drop into the mid 50s at night. The fog often lingers until mid-morning the next day, preventing over-rapid sugar accumulation and retaining color and refreshing acidity. This is about as good as it gets for Cabernet Sauvignon. The west side of Oakville is exposed to heavy winter rains and is in the shadow of the Mayacamas, late in the day, in mid summer. The east side experiences lighter rainfall and receives the full impact of the afternoon sun as the day wears on.
Cabernet Sauvignon is the clear favorite in Oakville but this king of grapes shares the acreage with other Bordeaux varieties, especially Merlot. The generously-warm climate promotes ripe, opulent black-fruit flavors of plum, black cherry and blackberry, often accented with a bit of mint. The well-drained soils lend the wines firm structure. Sauvignon Blanc is the only white variety of significance in the region and tends to be full, citrusy and fleshy.
Regional statistics (with thanks to the Napa Valley Vintner’s association):
Climate: Moderately warm, but 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 (87.5 cm) 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: Cabernet Sauvignon, Merlot, Sauvignon Blanc
Recognized as an AVA: 1993