Five Factors to Determine When it is Time to Harvest Grapes

It’s harvest time in Oregon and a question we get asked frequently is, “How do winemakers know when to pick?” For us, it is a composite decision based on five main factors:

1)   Visual Inspection: Are most of the grape clusters in the vineyard dark purple or do green berries remain? What is the size of the grape clusters? Are the stems turning brown, indicating structural development? Are the skins intact, or has weather made them “mushy”? Is there any sign of mold? Are the leaves shutting down into senescence, suggesting that further development will be halted soon? Does the vineyard look vulnerable to predators (e.g., birds, deer)?

2)   Sugar: The Brix, or sugar level, will indicate alcohol level in the wine. For our Oregon Pinot Noir, we generally want to harvest between 21-24 Brix to keep ultimate alcohol levels between 12-14%.

3)   Acidity: We always want to have a balance between sugar and acidity, so pH is our acidity indicator. Ideally, we would harvest around 3.2-3.4 pH so that the end pH is around 3.5-3.6 and should be balanced with expected alcohol.

4)   Flavor Development: Are the juice flavors immature (guava, banana, green apple) or have they matured (cherry, raspberry, blackberry, spice)? Seeds will contribute to tannin development, so do the seeds taste mature (brown and crunchy) or rough (green and bitter)?

5)   Forecast: What does the weather forecast hold and will it allow further development? Do rains threaten the chance of developing mold?