The general pattern for the greater region is Mediterranean, and is great for grape growing. The nearby Pacific ocean dominates the climate, resulting in wet, cool winters, and 30-50 inches of precipitation which recharges the aquifer while grapes are dormant. Summers are warm to hot and very arid, allowing for a slow depletion of soil moisture which slows down vine growth at the perfect time, ensuring an ideally light-exposed crop, and the dryness greatly reduces pest and disease pressure. The Alexander Valley is cooled from south to north by marine air moving in from the Pacific Ocean via the Petaluma wind gap and the Russian River valley. The combination of enough heat to ripen the crop but a big enough cool down to preserve freshness and acidity are keys to wine quality.
GEOLOGY & SOILS
Rocky, Diverse Soils
Soils are rocky and less fertile than the valley floor, and tend to be well drained, leading to naturally balanced canopies and lower yields. Alexander Valley soils are diverse from a long history of plate movements that pasted ancient seafloor on to the continent, deposited younger volcanic and sedimentary rock, and then tilted, raised, sank, and sliced it all up.
Southwest Facing Vineyards
The vineyards in Alexander Valley are planted from the valley floor to the benchlands up to mountain vineyards with southwest facing slopes sitting on the Mayacamas mountain range. Ultra-premium quality Cabernet Sauvignon grapes thrive in the benchlands, rolling hillsides and mountain ridges due to the valley’s inland locale and its diverse array of soils rich in calcium, gravel, sand and clay typically above 400 feet in elevation. The dramatic west facing hillsides on the Mayacama Mountain range possess an exquisite profile of soil that drains extremely well and shares a favorable composition that optimizes mature flavors for Cabernet Sauvignon. In these areas, Bordeaux variety grapes achieve a higher quality of tannin and intense blackberry fruit.
Alexander Valley’s landscape gradually rises on the east into gradual benchland slopes, where soils change to gravelly, sandy loam, balanced in nutrients and organic matter—the result of mountain soils gradually eroding downhill over millennia to deposit layers of rich soils in the benchlands. Primarily Yolo and Cortina, are well-drained due to their sloping elevation and minimal amount of clay; they also possess the ideal calcium magnesium ratio required for high-quality Cabernet Sauvignon. Cortina’s added gravel texture helps create wines with rich tannins and purity of varietal character. The valley’s first bench snakes along the west side of Highway 128 with its gentle slopes barely noticeable as it rolls into the second bench. These two benchlands create long, lingering swaths of vineyard slopes with soils that elicit soft tannins and intense aroma in Cabernet Sauvignon and Merlot grapes.
ELEVATION & TOPOGRAPHY
Elevations range from 400 to 2500 feet. Stronger UV light causes thicker skins that add color, flavor, and structure. Late summer temperature inversion facilitates ripening despite lapse rate. Elevation adds another facet to the terroir of any site. Higher elevaton vineyards receive slightly more sunshine because the fog line burns off sooner—but their stressed soil conditions on the slopes extends the maturation a week to two weeks longer than the benchlands and valley floor. With these diverse terroirs, a mosaic of mature tannins that supply intense blackberry aroma and layers of tannin, giving broad flavors to the wine’s palate and contributing to a long elegant finish.
80% of the Alexander Valley vineyard parcels are grown in the valley’s benchlands and the majority of which are clustered in the middle of the valley at the base of the Mayacama Mountains planted to Cabernet Sauvignon. The quality comes not from the slope of the vineyard, but directly from the soil’s depth and composition.
Weathering, erosion, gravity, and water movement have further moved and settled things into a hodgepodge of soils that require testing and experience to match the right variety, rootstock, amendments and irrigation schemes to each site.