The most exciting and demanding time of the year for vintners is the harvest season. The time we’ve been planning and preparing for all year.
Like birthdays and holidays, the harvest comes only once a year. The big difference is we never can predict for sure when it will arrive, nor do we know for sure what it will be like. There is a standard joke among vintners that we look forward to the harvest, but once it comes, can’t wait for it to be over. Working with an agricultural product vintners have only one shot a year at their creative field. When the grapes are ready, we have to be ready. How we envy authors who can rewrite their work or movie directors who can reshoot or edit their materials later on. Mother Nature does not allow second chances.
The grapes have been growing larger each week and are now close to full size. The red wine varieties are just beginning to show some color (veraison). By month’s end, they take on their typical blue-black hue. At the end of August, we begin monitoring maturing berries. The first matter is to obtain an estimate of the size of harvest by studying cluster count and berry count per vine. Should we discover during these field samples that the crop load per vine is high, we might want to reduce it. If so, we follow the cluster thinning approach where workers go through cutting off a percentage of the clusters from each vine.
Cluster thinning is the vintner’s last chance to maintain a balance between quality and quantity. When vines have too many clusters, they won’t perfectly ripen them. Cluster thinning allows the vine to direct all of its efforts toward fully ripening the fruit during the last few weeks of maturation.
By this time in the season, we make final adjustments in our vineyard practices. By September, we cut back or cease in irrigation because we want the vines to make a push to full maturity on their own so their flavors are concentrated.
All grape handling equipment is checked, cleaned and made ready for the harvest. Everything is put in working order, as we gear up for the first picking of the fruit. Throughout the month our thoughts are pre-occupied by the weather.
How do we know when it is best to begin the harvest? Some two or three weeks before the expected time of harvest we roam into the vineyards, taking field samples, and testing for sugar content. We will do this every few days as the grapes begin to reach full maturity.
To monitor the development of wine grapes, we use an instrument called a refractometer. It measures the sugar content (brix) of the 
grapes. This hand-held device requires only the juice of a few randomly selected grapes is squeezed onto a plate to give us a reading. It determines the sugar content by a “refractive index” or the measuring the amount of light bent as it passes through a sugar/water solution. The refractometer is held up to the light, and a shadow line in the scope of the instrument provides a sugar, or brix reading.
The ideal grape maturity, the optimum moment at which to signal the beginning of the harvest, consists of much more than sugar content. Grape maturity is a three-dimensional relationship between sugar, acidity, and ph. Historically, many vineyardists gave top priority to sugar content, measured in degrees Brix, to determine when to pick the grapes. But as grapes ripen and increase in sugar, they will decrease in total acidity. When that occurs, the pH increases.
Mature, ripe grapes with balance are our objectives. Total acidity, the combined measure of all major acids, especially tartaric acid, is crucial to wine quality. PH is a measure of the concentration of hydrogen ions in wine grapes (their charged or “active” acids.) All three are carefully considered by vintners before deciding to harvest.
Communications and decision making go hand in hand. The signal to our picking teams to harvest varieties when they have attained the ideal sugar/acid ratio must not be delayed. We monitor the progress of varieties still maturing in the vineyards, while greeting the first loads of early-ripening grapes such as Chardonnay, Pinot Noir and Sauvignon Blanc.
The vintner has the makings of dreams in hand. We practically are working around the clock, especially if warm weather has condensed the harvest into four weeks. Under mild or cool conditions, the harvest may stretch into seven weeks and take us dangerously close to the fall rainy season.
This month the vintage fills our every waking moment. The harvest is now upon us. We worry about the wines fermenting in the cellars, at the grapes still hanging on the vines, possible equipment breakdowns, and many other issues. We vintners wouldn’t have it any other way.
Ci vediamo!
P.S. If you happen to be driving thru Wine Country during the harvest, you may see alongside the road or on the back of flatbed trucks square, white plastic containers. These harvest bins are used to get the grapes from the vineyard to the winery. They are generally one ton in capacity (there are also half ton bins, but they are not as prominent.) Each one of these bins carrying 2,000 pounds of grapes will yield +/- 160 gallons of wine which translates into approximately 65 cases.