Exploring the Terroir of Sonoma County: A Guide to Its Unique Microclimates

You may be familiar with Roche Winery history. Our parents hadn't planned to open a winery; they were looking to purchase a country retreat where they could do a little farming and enjoy a peaceful escape from their hectic lives as San Francisco doctors.

They found a large estate in Sonoma Valley that was being offered for a song, because the area was assumed to be inhospitable for viticulture. That was a win, since they had no plans to grow grapes or make wine. They fell in love with the vistas and valleys, clean air and flowing streams, bought the property, and soon made it their permanent home.

Surprise! Five years on, they discovered it was an ideal location for grape growing. This happy ending illustrates how important it is to understand Sonoma County's climate diversity, which affects what will grow best in each location.

It Goes with the Terroir

When it comes to winemaking, Sonoma County doesn't have a single climate, despite the temperate weather that makes this a coveted place to dwell. Instead, the county comprises 19 microclimates, with diverse soils, topography, and weather, all of which affect the terroir, or wine-growing environment.

Sonoma's American Viticultural Areas (AVAs) include:

·      Alexander Valley

·      Carneros

·      Bennett Valley

·      Fort Ross-Seaview

·      Chalk Hill

·      Green Valley

·      Dry Creek Valley

·      Knights Valley

·      Fountaingrove District

·      Moon Mountain District

·      Northern Sonoma

·      Rockpile

·      Petaluma Gap

·      Russian River Valley

·      Pine Mountain-Cloverdale Peak

·      Sonoma Coast

·      Sonoma Valley

·      Sonoma Mountain

·      West Sonoma Coast

Why the Weather Matters in Microclimates

Sonoma County is a study in geography and topography, which determines what types of grapes can be successfully grown in each microclimate. A Pinot Noir and a Merlot need distinct microclimates in which to flourish, as do a Cabernet Sauvignon and a Zinfandel. We've read that Sonoma County boasts more soil varieties than the entire country of France, the world's viticulture capital. That's impressive!

Sonoma’s diverse soil ranges from a sandy loam and volcanic ash to rock. The soil can change the character of the grapes from one AVA to the next, and the soil itself changes over time, depending on weather conditions.

For instance, take our famous fog. The marine influence from the Pacific Ocean drives the climate in Sonoma County, and those who live here tend to appreciate how the temperature drops precipitously even on warm days once the fog rolls in, keeping the nights cool and comfortable. For grape growers, the fog keeps the crop from becoming overripe, with an excess alcohol content. 

But there's a downside: too much fog can "drown" the delicate grapes in moisture, so farmers need to stay vigilant to maintain healthy grapes that receive a balanced amount of sun, cool, and moisture for their specific varietal.

A Taste of Sonoma County Microclimates

Let's compare and contrast a few microclimates to illustrate the importance of knowing one's terroir.

Here in Carneros, Pinot Noir is popular because these grapes thrive in our cool, moist AVA, with no lingering fog and just the right amount of afternoon light to ripen the grapes to perfection. Its ideal climate is likely what led Carneros to become the first wine region in California to be classified by its climate characteristics rather than geographic boundaries. Carneros earned AVA status in 1983, and is one of the first seven AVAs in the region. And if you're seeking a sparkling wine, visit Gloria Ferrer, which created the first sparkling winery in Carneros, bringing the taste of Spain to Sonoma.

Contrast the Carneros AVA with Dry Creek Valley, one of the smallest AVAs in the region at just 16 miles long and two miles wide. Despite incredibly rocky soils, the terroir includes hillsides and dense floor vineyards, which combine to create the ideal growing environment for Zinfandel and Sauvignon Blanc, the region's signature wines.

Or consider the West Sonoma Coast AVA, which only earned its viticulture status in 2022. This diverse terroir, with elevations ranging from 400 to 1800 feet, has the cooler marine temperatures and coastal fog that favor its distinctive Pinot Noir and Chardonnay, which are layered with depth and elegance.

As you can see, how and where we choose to grow our grapes and make our wines is as personal a statement as where we choose to live, and there is infinite room for variety. Viticulture in Sonoma County's microclimates is a microcosm for life.