Countdown to Harvest

Ampelos Vineyards
It's an important time of year in the northern important time, that is, for grape growers and winemakers. If you have been to a vineyard in the last couple weeks, you probably saw a lot of little hard green berries on the grape vines. If you go back today, you may notice something has changed.

Véraison [vay-ray-ZON] is a wine term which refers to the onset of ripening. It is French word, but is used throughout the wine world. The official definition of véraison is "change of color of the grape berries." Véraison represents the transition from berry growth to berry ripening. In the northern hemisphere, véraison typically occurs anywhere from late June to mid August, depending on the climate.

Here is a short video from Adopt a Grape, discussing the importance of véraison in the vineyard.

Veraison '08 at Adopt A Grape from Adopt A Grape 2009 on Vimeo.

Following fruit set, grape berries are green and hard. They have very little sugar and are high in tartaric and malic acids. They begin to grow to about half their final size when they enter véraison. During this phase the colors of the grape change from green to red or yellow, depending on the variety. For those big on science, this color change is due to the chlorophyll in the berry skin being replaced by anthocyanins (red wine grapes) or carotenoids (white wine grapes). The berries start to soften as they build up sugars. Within six days of the start of veraison, the berries begin to grow dramatically as they accumulate glucose and fructose and acids begin to fall. If you were to look at a graph of acid versus sugar levels, you would see that véraison occurs when the decrease in acid crosses over the increase in sugar. The acids are actually being "burnt up" by the respiration of the grape berry. If you want to get into great detail on the actual science, check out "Wine Science Principles and Applications" by Ronald S. Jackson, or "Knowing and Making Wine" by Emile Peynaud. Both books are very technical.

Stoller Vineyards
Véraison, unfortunately for the wine grower, doesn't occur uniformly across the vineyard. Typically the berries and clusters that are exposed to warmth, undergo the change first, and those that are closer to the trunk and under the shade of the leaves (canopy), are last. There are things in the vineyard that can control the onset of véraison. Limited water stress and canopy management, that creates a high "fruit to leaf" ratio, can encourage véraison. So, skilled vineyard workers, who know how to thin the canopy properly, are worth their "weight in gold". On the other end, vigorous grape varieties, with lots of leaf shading for photosynthesis and water supply will delay the start of véraison, due to the vines energies being directed towards continued foliage growth and new buds. During this period the cane of the vine starts to ripen as well changing from green and springing to brown and hard. The vines begins to divert some of its energy production into its reserves in preparation for its next growth cycle. For the production of high quality wine, it is considered ideal to have an earlier véraison

Some wine growers will perform a green harvest, where less ripe bunches are removed. The idea is help concentrate all the energy into the remaining berries, which in turn, should produce more concentrated wines. There is a bit of a gamble however, namely if the remaining time between véraison and harvest experiences severe drought or excessive heat, the result could be dry berries, which produce unbalanced wine. So, when you visit the vineyard this time of year, you'll see growers checking their crop. They know that once véraison starts, they are only about 45 to 50 days from harvest. And that can be 45 to 50 days of holding their breath!

Let the countdown to harvest begin!

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