Banner image for How Do Viticulturists Know When It's Time to Harvest?

How Do Viticulturists Know When It's Time to Harvest?

Erin O'Reilly - Certified Specialist of Wine

Does Tasting Wine Grapes Indicate When Harvest Should Be? Or Are There Other Methods for Knowing It’s Time?

Wine harvest season is afoot in the northern hemisphere. Long-awaited and greatly anticipated, wineries find themselves bursting with bins of grapes ready to be made into wine. But just how, exactly, do growers and producers know when the best time is to harvest grapes for wine? Setting the harvest date is an elaborate combination of art, science, and logistics – with the possibility of Mother Nature upending the best laid plans altogether.

woman in a vineyard tasting a wine grape

Wine Sensory Assessment

Swirl. Sniff. Taste. Savor. Wine lovers use their senses when drinking. But all great wines start in the vineyard, and that sensory analysis process so familiar to enthusiasts actually began back when the wine was nothing more than a humble bunch of grapes.

If you’ve ever wondered, are wine grapes edible?

The answer is: Yes!

Not only that, but how the wine grapes taste acts as an indicator for overall ripeness. Winemakers collect samples of grapes from throughout the vineyard and taste the individual berries for any green notes from under ripe seeds. As the berries mature, the seeds turn nutty, and the seeds’ tannins move from the front of the mouth towards the back of the palate.

How the flavors act on their tongue lets the grower know when the grapes are ready for harvest.

What do wine grapes taste like?

If you’ve ever wondered why you never see anyone snacking on wine grapes, there are a few reasons why table grapes are the optimal choice for eating.

Wine grapes are much smaller than table grapes, and they also have a thick and chewy skin on the outside and seeds in the middle. In addition, they are far more bitter than table grapes, leaving most people desiring to leave the wine grapes for drinking.

The ability to assess ripeness using only taste takes years of practice, and so winemakers also depend on science.

scientists testing wine grapes in a lab

Scientific Wine Assessment

Using those same grapes collected from around the vineyard, the winemaker will crush the berries together and take a few drops of the juice to measure its physical ripeness by testing sugar and acid levels.

The longer the grapes hang in the vineyard, the riper they become, but they also lose acid, which gives wine vibrancy.

The goal is to balance physical ripeness with physiological ripeness, or the grape’s flavors and tannins.

Winemakers can make minor adjustments in the winery if the numbers aren’t quite where they need to be, but the best approach is to time harvest when the sugar, acid, tannins, and flavors harmonize.

Wine Harvest Logistics

The final consideration, while unromantic, tops every winemaker’s checklist: logistics.

a group of people harvesting wine grapes with buckets of red wine grapesIf the grower uses a team for hand-harvesting, that team may travel between multiple vineyards throughout harvest season. Growers will often schedule labor in advance around their neighbor’s harvest dates.

The same consideration applies to mechanical harvesters that travel from vineyard to vineyard.

Other logistical considerations include the types of wine the winery plans on making. For example, various grape varieties ripen at different times.

Chardonnay ripens early, while Cabernet Sauvignon takes a little longer to mature. Wineries may make both.

When different varieties arrive at the winery on separate dates, the winemaker may need to calculate how long it takes to move one wine through fermentation so that there’s space available to process the next load.

What’s Mother Nature up to?

grape bundle covered in frost and snow

Let none forget that grape growing is an agricultural activity.

Harvest comes at the end of the season when the weather starts to cool down. In some regions this seasonal shift means frost, hail, rain showers, and even snow. Weather events can easily damage a precious grape crop sitting unprotected in the vineyard.

If the forecast calls for inclement weather, the winegrower may go ahead and schedule the pick even if the grapes aren’t perfectly ready. Making adjustments in the winery is a far better prospect than losing grapes due to weather damage.

So, when are wine grapes ready to harvest?

Winegrowers and winemakers work together to set the pick date based on the art of experience, a little assistance from science, and a lot of forward planning. A year’s worth of anticipation is wrapped up into a single day. And with a little luck, by sunset the new harvest’s bounty is soon on its way to becoming wine.

We here at Gold Medal Wine Club may not harvest our own grapes, but we pride ourselves on collaborating with the best winemakers in the industry. Trust us when we say these winemakers know the perfect moment to harvest.

Give some of their wine a try to see if you agree with us! Who knows, maybe you'll even find some inspiration to harvest grapes of your own!

Whether you're enjoying wine as a grower, a consumer, or anything in between, cheers!

Erin O'Reilly Author Bio Image Author Bio: Erin O’Reilly, Certified Specialist of Wine, is a wine writer and educator. She pens her work from Monterey wine country where she raises a glass to the growers and producers dedicated to crafting great wines.