In early summer, we make estimates of how much potential crop exists in each of Navarro's fields. Our estimate is a product of three calculations: the number of vines, the average number of clusters per vine and the average cluster weight. The number of vines is easy to calculate since we store that information in a spreadsheet. The average number of clusters per vine is determined by counting the clusters on twenty-five randomly selected vines in each block. In some years, the amount of clusters varies widely from vine to vine, so it's possible that the specific vines selected can skew the results in one direction or the other. Cluster weight, the average number of berries per cluster times the average berry weight at harvest, is probably the most difficult to estimate since the calculations are made when the berries are green and haven't sized up. It is especially tricky in a year with millerandage, a condition in which the clusters contain full-sized two-seeded berries with smaller one-seeded berries. To make a long story short, we underestimated the amount of crop in one of our favorite Chardonnay blocks, and consequently didn't thin the fruit to the normal four tons per acre for our Reserve wine.

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