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The Seasons of the Grapevine – Harvest is Here in the Northern Hemisphere

The seasons of the vine.

Growing grapes is no easy task.  At any time throughout the year a variety of uncontrollable obstacles can arise including frost, hail, drought, fire, earthquakes, or landslides to name a few.  Equally dangerous are vine and grape diseases or problems caused by insects or animals.  Thus it’s no surprise that wine sometimes costs an arm and a leg, as the resources used to monitor the vines throughout the year can get up there quickly.  Winemakers have learned how best to use breakthroughs in science and technology to produce wine using what Mother Nature has provided.  None of their skills and training are necessary if the several months leading up to the harvest season are riddled with any of the aforementioned setbacks and the vineyards fail to produce any useable grapes.  As the harvest season begins in the northern hemisphere in these weeks, let’s revisit what’s happened so far this year.

In the northern hemisphere, the season of the vine begins in the winter months when vineyard managers walk up and down the rows of vines cutting back any remaining leaves or shoots from the previous year.  In February or March the vine begins weeping.  This is triggered when the temperature of the soil lingers around 50 degrees Fahrenheit.  The roots collect water and the sap in the vine is expelled through the cane ends.  Weeping is a sign for the winemaker to begin pruning the vine for spring.

About 30 days later, buds appear on the vine; the first sign of leaves.  Once the leaves are established, the vine produces

The author conducting harvest in southern Italy

embryo flowers, which will eventually become the grapes.  At this point in the cycle, soil temperature is more important than air temperature, so the heat-retention capacity of the soil is pivotal for the vine to grow properly.  From here on, any inclement or treacherous weather phenomena (wildfire, hail, floods, erosion), can damage the grapes beyond repair.  Should any of these occur, the grapes may still grow on the vine but will fail to ripen properly.  In other cases, the grapes will cease to grow any further.  Sadly, both scenarios result in lost production.

By June, the grapes increase in size as the acid levels increase.  The skins of the grape will remain green well into the summer. In many of the premier winemaking zones in the northern hemisphere, it’s commonplace that June, July, and August are extremely dry months with light and sporadic rainfall.  This is good for the vines as a lack of water forces the vine to focus all its nutrients on developing the grapes.  If there is an excess of water, the vine will continue growing leaves and shoots, while the grapes may go neglected.

Green harvesting is a subtle pruning and cutting process often conducted in the weeks before the grapes will be picked.  Vineyard workers walk up and down the rows cutting leaves and some of the grape bunches in hopes that the grapes remaining on the vine will get all the nutrients and resources the vine has to offer.  The less grapes remaining on the vine, the greater amount of nutrients each grape will receive.  Klaus Di Giovanna, a winemaker in Sicilia remarks, “when we see new growth of leaves after the green harvest, we know that the vine is still focusing on all around vine growth, and this means the vine is still maturing and is not quite ready to focus solely on the grapes.  If, however, there is no sign of new shoots, then it’s confirmation that the vine is putting all the nutrients into developing the grapes and that we can begin to harvest the fruit in the coming weeks.”  Viticulture professor and consultant, Cornelis van Leeuwen estimates that most of the winegrowing areas in the world operate at yields three to five times less than what is attainable from the vine.

Grapes changing from green to purple, almost time for harvest...

In August, about 150 days after the fruit buds first appear on the vine, the sugar levels rapidly increase, and if the grape is black-skinned grape like Cabernet Sauvignon or Merlot, the pigments in the skins finally give way from green to violet, a process called veraison.  Determining when to pick the ripened grapes is a crucial part of the harvesting process.  Winemakers can use instruments and science to help identify grapes with ideal levels of acids and sugars; however, winemaker intuition is still a coveted tool.  If the winemaker picks too early before the grapes are ripe, the finished wines may be overly acidic and taste “green”, “sharp”, and “tart”.  On the other hand, If the winemaker waits too long to pick the grapes, then catastrophic early frosts, freezing rain, or hailstorms can wipe out vineyards in a matter of minutes.  As a result, the decision of when to harvest the grapes is still a gut decision.

The grape harvest is a spiritual time in the winemaker’s life.  All the labor of toiling in the vineyards and working with nature’s offerings has created grapes that will now be processed into wine.  With a little more luck, all will go well in the winery.

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