dried grapes

The Art of Fruit Thinning and the Quest for Balance

Balanced vines make balanced wine

This week, many grape berries throughout our little corner of the world reached a very important milestone in their steady march towards becoming wine. Veraison (French for ripening), when grapes begin accumulating sugar, color and phenolics is a welcome sight for growers. For starters, powdery mildew is no longer a threat and  grapes start to taste like something besides tiny sour stinging orbs of acidity. It also triggers the second phase of berry growth, when cells which were multiplying like crazy after fruit set begin to expand, swelling the berries until it appears they may burst with flavor.

For grapegrowers, viticulturists and vineyard managers, it is also a time when they can, for a few moments at least, relax, take a deep breath and have a much-earned beer before gearing up for harvest. “There is no question that spring and early summer is the most intense and most stressful time in the vineyards,” says Steve Matthiasson. It is during this time when Matthiasson, who is both a legendary vineyard manager and an excellent winemaker, believes wine is truly made. “Springtime for a viticulturist is either like fighting a war or surfing a huge wave, depending on whether you are against nature or if you tend to marvel at the magnificence of it.”

Creating balanced vines prior to veraison is the goal of every grapegrower (just as creating balanced wine is the goal of every winemaker) — and creating that balance keeps them on their dust-covered toes from bloom to veraison. “It’s a relief when the vines settle into their mid-summer routine,” says Matthiasson. Every decision that is made in the vineyard will affect the quality of the wine: when you irrigate, leaf, hedge, mow, disc and fertilize can determine whether a wine sings with complexity, nuance or simply falls flat.  “Wine quality is dependent on keeping up with the drumbeat of the season,” says Matthiasson. “What you do is less important than when you do it. The old saying goes that ‘the difference between a good farmer and a bad farmer is two weeks.’”

The big decision that Matthiasson and others had to make in the last couple of weeks, and one that has a huge influence on the timing and rapidity of veraison, is that of fruit thinning. As heartbreaking as it is to see fully formed clusters lying in the dirt and shrivelling in the sun, it is a sacrifice that is often necessary. “Our goal is to have balanced vines,” says Ulysses Van der Kamp of the much-respected Van Der Kamp vineyard on Sonoma Mountain. As he walks through the vineyard, he examines each vine and takes his pruning shears to the peduncle of a pinot noir cluster from time to time. “But just what is ‘balance’ changes from year to year,” he says.

In a year like 2012, when fruit set was fairly consistent and plentiful, balance is more likely achieved by dropping some fruit than in years when many  flowers shattered or when fruit was lost to spring frost. “With the abundance of fruit this year, many growers are adjusting crop levels by dropping fruit to ensure quality and timely ripening,” says Isy Borjón, a maker of well-balanced red wines in Amador County. “Too much fruit on a vine can make grape flavors flabby and too thin — that is if the excess fruit will even ripen. This can ultimately make a wine thin, flabby and one dimensional.”

In Stagecoach Vineyard on Atlas Peak, viticulturalist and member of the Napa Valley Grapegrowers, Amy Warnock, is seeing the same thing: “Warm weather during bloom led to successful pollination and great fruit set. Cool temperatures during bloom in 2011 resulted in an average yield of less than 1 ton per acre in malbec and cabernet franc, so we are thrilled that this year a thinning pass is even warranted in these varietals.”

But, like everything else, how you thin and when, is critical. “Each of our 70 plus winery clients have a specific style of thinning that they request,” says Warnock. “ A common thread that runs through each is a quest for balanced vines with uniformly ripe fruit.”  During the “lag phase” of berry development, when the cells in berries stop multiplying but before they start expanding (a 35-day period between seed-hardening and veraison) is the appropriate  time to thin, according to Matthiasson: “Thinning before seed-hardening, while the berries are still growing, causes the vines to compensate for the crop loss and make the berries bigger. Thinning too late after seed-hardening can be a waste, since the effect of thinning fruit diminishes quickly as the season progresses.”

Another common practice, and one which winemakers like Matthiasson lament greatly, is that of over-thinning — thinking, wrongly, that less fruit equals better fruit (see Permission to Bitch Slap a Winemaker). What less crop often does equal is more sugar in the remaining fruit, which converts to higher alcohol in the wine. A healthy canopy is going to photosynthesize the same amount of sugar whether there are three clusters on a shoot or one, meaning that if there is too little fruit, it will simply get too sweet, making a fleshy, high-alcohol wine.

That being said, there are some standard practices that are widely accepted among most growers of quality wine grapes, according to Matthiasson: One is that each shoot should carry two clusters. “There is occasionally a third cluster on a vine, and that cluster typically doesn’t ripen properly.” Secondly: “It is critical that each cluster has room to hang separately from the adjacent clusters. If the clumps of fruit are left all balled up, the clusters on the interior of the clump will remain pink and watery and be susceptible to powdery mildew or bunch rot.” Thirdly: “Large wings (sometimes called shoulders) are occasionally removed. This can be very helpful in reducing rot in tight-clustered varieties that tend to throw large wings, like zinfandel and petit sirah, and it can also result in more uniform ripening in varieties like cabernet sauvignon and merlot.”

Finally, and most important, Matthiasson stresses that “the goal is not to have to thin at all.” After all, that is what all the hard work over the past few months was for.