Through the Grapevine

In this multimedia series, we give you the insider's eye on Indiana wines. Tune in each Tuesday for a snobbery-free explor​ation of a host of viticulture and enology topics.

​​​​​Week 5: Weathering Climate Change—
Indiana Warms Up to Wine Grapes

By Natalie van Hoose

Frost-damaged wine grapes Frost-damaged wine grapes. Full-size image.
Photo by Bruce Bordelon.

Grapes have a hard-knock life in​ Indiana. Bitter winters, spring frosts and hot, humid summers require great hardiness from a vine that must flourish year after year.

This is why the majority of grapes grown in Indiana are hybrids, rather than the Vitis vinifera varieties that thrive in the mild climates of Mediterranean Europe and California. Hybrids such as Frontenac, Steuben and Traminette are better able to handle cold temperatures and the diseases that can result from heavy rainfall during the growing season.

But state climatologist Dev Niyogi says some aspects of Indiana's climate are becoming milder. Over the last 30 years, Indiana's mean annual temperature has risen slightly, night temperatures have increased, and the growing season—the number of frost-free days—has lengthened.

"The degree of change depends on which part of the state you are talking about, but change is happening," he says.

The shift has led some growers in the southern part of the state to take a gamble on Vitis vinifera, which can be damaged by sub-zero temperatures. Ted Huber of Huber Winery in Starlight, Ind., began planting varieties such as Cabernet Sauvignon, Cabernet Franc and Pinot gris in the mid-90s.

"In the '80s and '90s, we noticed that the weather patterns were changing," he says. "September, October and May were all getting warmer. We definitely have longer growing seasons than before."

Purdue University viticulture specialist Bruce Bordelon says warmer temperatures and a longer growing season could also be good news for late-ripening hybrid varieties such as Chambourcin, Norton and Vidal.

According to Niyogi, climate models forecast that temperatures will increase over the next few decades, the growing season will continue to lengthen, and there will be wider swings in rainfall patterns and a higher propensity for extreme weather. While the average amount of rainfall may stay fairly constant, storms are likely to be more intense.

For ripening grapes, heavy rainfall can be "disastrous," says Bordelon. Rain can cause berries to split and crack, leaving them vulnerable to disease and pests.

rainfall graph Graph showing the number of days in Indiana with more than one inch of rainfall. Full-size image.
Image courtesy of the Indiana State Climate Office, Purdue University.

The models also predict that days with temperatures in excess of 100 degrees will become more common. Severe heat can stall the development of flavor and aroma compounds in ripening grapes.

"Grapes don't really gain any benefits from temperatures above 90 degrees," Bordelon says.

The major concern for Indiana growers, however, is whether the unusual weather that characterized the past decade will continue.

Niyogi predicts it will. "More extremes is the new normal," he says.

Bordelon also expresses concern. "We've set major records for heat, drought and rainfall in recent years. If we have more fluctuations, then we'll likely experience more problems like frost damage, hail, drought and excess rain. A few years of crop failure would be devastating to growers."

Greg Jones, a climatologist at Southern Oregon University who researches the influence of climate on viticulture, says that the combination of warmer temperatures and increased humidity and rainfall will require growers to be flexible.

"Growing grapes is about​ adapting to what the climate gives you," he says. "That's what growers are good at."

plant hardiness zones U.S. Department of Agriculture plant hardiness zones.
Full-size image. Image courtesy of Bruce Bordelon.

He advises growers to plant varieties that are a good match for the local climate. "There's a reason hybrids do well in the Midwest. That's where they grew up."

But Jones suggests that growers experiment with a few varieties as well. "Look at varieties that will have future potential if the climate continues to warm."

For Ted Huber, the changes have been positive so far. The Vitis vinifera vines he planted nearly 20 years ago have done well.

"They've been in production ever since we planted them," says Huber. "The vine quality, grape quality and wine quality have all been outstanding. At one time, these were considered hard-to-grow varieties for southern Indiana, but they're not that much harder to grow anymore."

Credits: Web version by Andrew Banta. Through the Grapevine graphic by Russ Merzdorf.

Next Tuesday: From the vine to the destemmer, crusher and press—discover how wines are made as we track what happens to grapes harvested from Purdue's research vineyards.

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