Suisun Valley prepares for harvest

Suisun Valley prepares for harvest

It’s the time of year our grape growers have been waiting for since the first green buds appeared on our dormant Suisun and Green Valley grapevines in March. The harvest season is finally here!

Over the next several weeks, we will start seeing an influx of workers in our vineyard fields, filling large containers on truck beds full of white and purple grapes to transport to our area wineries. Most will be out in the fields early in the morning, long before sunrise. If you drive in the valley in the morning hours, you may even see the bright lights of the trucks from the roads. Why harvest in the middle of the night? The temperatures are much cooler at night and cooler fruit means better control over the fermentation process. The night temperatures also keep the sugar composition of the grapes stable. By the time the sun rises in the sky and most wake to begin their day, the grapes are already at the wineries preparing for crush. That process will take all day, only for it all to start over again the next morning. 

Several of our growers have their production facilities next to their tasting rooms. Throughout the month of September, guests can travel the Suisun Valley ‘loop’ and visit multiple destinations like Wooden Valley Winery, Vezer Family Vineyard’s Blue Victorian, and G V Cellars to see the grapes coming in from the fields and wine makers working on the crush as you taste.

For our wine makers, the long days of the harvest season are a culmination of months of anticipation. From the small berries in April came the green grapes that began to change their colors in June and July.  This is known as veraison, when the fruit hanging on the vines transforms from small, green, hard berries into what we all know as grapes.  As the berries lost their green color, they began to take on the more mature hues we are seeing today in Suisun Vallley vineyards – greenish yellow for the white varieties and red, purple or almost black grapes for red varieties. 

Veraison doesn’t happen at the same time throughout a vineyard, or even for all grapes on a vine or within an individual bunch. In fact, depending on the variety, region, and wine style, this ripening process can last anywhere from 30 to 70 days after the start of veraison. 

During this period, growers closely monitor the development of the grapes. As the berries ripen, they become sweeter, and the sugars, which will be fermented into alcohol, increase. The more sugar in the grapes, the higher the potential alcohol level of the wine. Winemakers may test grape juice, from a sampling of grapes across different parcels of a vineyard, in a lab to check pH and Brix (a measurement of sugar) to help them determine how ripe the grapes are. But they’ll also head into the vineyards regularly—sometimes daily—to taste and examine the grapes in the weeks leading up to harvest. They’re checking for what’s referred to as phenolic maturity or physiological ripeness—gauging the intensity and character of flavors and the quality of the tannins. They’ll look at skin thickness, berry texture, seed color and texture and whether the stems have turned from green to brown. Ultimately, winegrowers are seeking a good balance between the sugars, acidity, tannins and flavor compounds.

Here is another fun harvest fact – the date of harvest is rarely ever the same from one year to the next. Our winegrowers must call it as best as they can. In the days and weeks leading up to harvest, they will be watching weather reports very carefully to stay ahead of sudden changes. A sudden heat wave could ruin a crop, as can excessive rain or a frost (but that’s not likely here in Northern California in September). Thankfully, our current weather reports show temperatures remaining in the 80s for at least the next week or two.

Did you know….

1. The time of day you pick is just as important as the time of year

You may know that August, September and October are the best months to harvest but did you know the time of day is also important? In the dead of night, tractor-mounted lights flick on and field hands load baskets full of grapes in a practice that is increasingly common in California and throughout the world. Harvesting at night saves money (no need to cool grapes before crushing), is easier on the workers and ensures a stable sugar level in the grapes, something that fluctuates when the temperature rises.

2. To manipulate sugars and acid, grapes are picked early or left on the vine

Collecting grapes takes several months because the optimum ripeness varies from varietal to varietal. In California, white grapes like Sauvignon Blanc are picked first because winemakers look for lower sugar to acid ratios to give those wines a crisp, almost tart taste. Red grapes are picked later and grapes for dessert wine, like “late harvest” Riesling, are left on the vine even longer so the fruit continues to ripen, i.e. produces more sugar, resulting in a sweeter wine.

3. Moldy grapes make some of the best wine

To produce sweet wine, vintners rely on a fungus called Botrytis cinerea or noble rot, which shrivels and decays the grapes creating two desirable traits: more sugar and a distinctive taste. Noble rot dries out the grapes making the sugar to water content higher which leads to a sweeter wine. The fungus also has an aromatic compound called phenylacetaldehyde that gives wine a “honey” or “beeswax” flavor. 

4. The sugar content in wine is evident before it’s barreled

Brix, a measurement of the amount of sugar in grape juice, is calculated after de-stemming using a refractometer. One brix equals one gram of sugar per 100 grams of liquid, which shows up in the refractometer as a shadow inside the instrument. Winemakers dip the device into the juice hoping for a reading between 24 to 27, which predicts an alcohol content between 12-15%.

5. It’s not the grapes that determine the color, it’s the skin

Red wine obviously comes from red grapes but can white wine also come from red grapes? The answer—sort of. To get the red color, winemakers leave the skins on red grapes during fermentation. To get white wine from red grapes, vintners remove the skins from red grapes before processing. The resulting wine is the increasingly popular rosé!

6. Fermentation happens in a fortnight

Once the juice is sealed in oak barrels or housed in stainless steel tanks, the yeast gets straight to work. Fermentation only takes two weeks but wine is left to age. During the aging process wine takes on distinct characteristics of the container and develops a unique flavor profile. Whether it’s aged for two years or ten, no bottle of wine is the same, which is what wine enthusiasts love about the surprise poured into each glass.


Want to learn more? Visit one of our Suisun Valley and Green Valley wineries! The friendly tasting room staff love to answer your questions, and you may even meet one of our winemakers pouring behind the counter!