Winemaker Blog – When to Harvest?


Marquette (red wine) Grapes

HARVEST PARAMETERS. We have lots of grapes schedule to arrive this weekend at Train Wreck Winery. We will be harvesting our own Marquette, and we will be getting Frontenac and Frontenac Gris grapes from several growers.

How do we know when the grapes are ready to harvest? Science and experience. In a perfect world, there would arrive a moment when the sugar and acids were in just the right amounts. That seldom happens. So we pull sample clusters from the vineyard, trying to get a representative mix of clusters. Clusters that are exposed to the sun will ripen faster than those that may be shaded.

We press the juice out of this sample, and test for pH, sugar %(called “brix”) and sometimes other things such as titratable acidity(TA) or yeast assimilable nitrogen (YAN). Because of variablilities of rain, sun and growing degree days, the numbers we measure in the lab are seldom exactly what we are aiming for. And even though our lab tests might dictate waiting, we may see degradation in the quality of the grapes in the vineyard, or maybe we have to pick this weekend because next week is the big game and nobody will want to help pick. So we pick when the science, our experience, and our gut tells us the time is right.