It’s a Jungle Out There

Leafing is one of the foremost important decisions in winemaking

“The foremost important decisions about winemaking happen before a single berry even makes it into the winery,” says Greg La Follette of La Follette Wines. Right now, during the time of “berry cell division and berry cell expansion,” (or the first phase of berry development, which immediately follows bloom and lasts for about 4 weeks), decisions about leafing — choosing which and how many leaves to remove in the fruiting zone, keeps vineyard managers and workers busy between fruit set and veraison. It’s especially relevant this year, which Robin Lail of Lail Vineyards  in Napa Valley described recently as “a jungle year,” because of the explosive vegetative growth. The jungle-like heat and conditions don’t phase Bo Barrett of Chateau Montelena at all. When asked about the string of above-100-degree days in Calistoga he said, “Bring it on! It’s like the old days.”

“Balanced vines are an important key to producing premium grapes and wines,” says Richard Martella, president of the Amador County Wine Grapegrowers Association. “Leaf removal must fit into the overall canopy management and viticultural practice of the vineyard.” And because leaf or shoot removal runs from $250 to $350 per acre and can affect the ripening of the grapes in profound ways, to leaf or not to leaf and which and how many leaves to pull is a very important decision. “Canopy management is a critical component of high-quality grape growing,” agrees Steve Moulds of Moulds Family Vineyard in Oak Knoll and Vice President of the Napa Valley Grapegrowers. “Too few leaves may hinder ripening, while too many may create vegetal flavors.”

There are basically two reasons we leaf a vineyard. One is to open the canopy in order to increase airflow and “craft the perfect light environment,” as Jon Ruel of Trefethen Family Vineyards and President of the Napa Valley Grapegrowers puts it. This means removing leaves in the fruiting zone around the grapes. Dappled light, a “salt and pepper” mix of sun and shade, allows grape clusters to ripen evenly without getting sunburn. “The primary goal [of leafing] is to improve fruit quality, such as color and flavor development, and reduce the predisposition to diseases such as powdery mildew and bunch rot,” says  Martella.

Kevin Skene, PCA of Skene Viticulture in Sonoma County says “When we remove those leaves and lateral shoots out of the fruit zone, it can make the difference between preventing mildew and botrytis from occurring. After berry set, we start the leaf and lateral pulling process so we can prevent the occurrence of mildew.” Oh, and remember those tiny flowers from just a few weeks ago? “The flower caps and other flower parts left over from bloom can be the primary inoculum source for botrytis.” (And they looked so innocent!) “When we pull those leaves, we also remove a lot of those flower parts from the inside of clusters, thus lessening the occurrence of botrytis bunch rot,” says Skene.

La Follette is surprisingly aggressive with leaf removal for the purpose of sun exposure, especially for the thin-skinned pinot noir in the Hawk’s Roost Ranch Vineyard in Russian River Valley. “The answer to that lies in building its natural suntan. If I go out and work in the vineyard in the spring and I take my shirt off, by summer time I’m nice and tan. But If I go out in the vineyard in the middle of summer and take my shirt off, then in two hours I would be a lobster. And so what we’re doing is we’re pulling the leaves off exposing the clusters to the sun right at the point when they are going to produce their own natural suntan.” Martella agrees that “pinot noir in cool climate regions can handle some full sun,” but he cautions that “too much sun exposure can inhibit coloration and ripening of the clusters.” It will also thicken the skins of the grapes which may or may not be desirable. For pinot noir, La Follette explains that “thicker skins are desirable because then you get more skin to juice ratio. You are actually getting your tannins riper and at lower sugar.”

“When walking down the rows, what you’re looking for is about 35 to 50 percent of the fruit visible on the shady side of the canopy,” says Martella. This is where the fruit sees some intermittent or indirect sunlight during the day, but not direct sunlight for long periods.” Matt Hardin of Barbour Vineyards, as we reported last week, looks at the shadows cast between the row as one measure of proper light penetration.

Leaf or Lateral? A Question of Resources

But a leaf, and let’s give it credit where credit is due, does a lot more than provide shade for our precious grapes. It works hard all day converting the great sunlight we enjoy so much into energy for the plant. And this is where the second reason for leafing comes in: As leaves are growing, they are sucking energy out of the plant and when they are full grown, they are taking energy in. Laterals, or the secondary leaves just opposite of the grape cluster, compete with the grapes for some of that energy coming in. Which is why most vineyard managers would remove them.

But La Follette, who may be a good Catholic but is a heretic of a winemaker, removes the larger leaves that are pulling in energy for the vine and leaves the small, energy-sucking laterals. “We are trying to create a momentary carbohydrate deficiency [by both removing larger leaves and keeping competitive laterals] and provide enough strain and stress on the shoot tips so that the shoot tips stop growing earlier. Once those shoot tips stop growing, all that photosynthate can be repartitioned into producing all the flavor and color and yuminess of the fruit.” And during the time of berry cell division (right after fruit set), that lateral leaf competes with the grapes keeping them nice and small.

Essentially, we are “repartioning” the carbohydrate resources from going up the canopy to going down to the fruiting zone. Because we are makers of wine, not dolmas, “We want all the carbohydrate resources going into the ripening of the clusters.” It’s hard, detailed work and slow going. But if you’re going to say that wine is made in the vineyard, as winemakers love to say, well then, La Follette is right: One of the foremost important decisions about winemaking is happening right now. Does that make me a winemaker?