Fresno, California. Every day, Dr. Sanliang Gu ponders for a moment a world too hot to grow fine grapes.
For a dozen years his obsession has been to manipulate the growing cycle of grapes around Fresno, California’s hottest and therefore earliest-ripening wine region. This week he succeeded: the 2011 vintage that normally would have been picked in July or August came off the vines in late November — about three weeks after Napa’s weather-delayed harvest ended.
In an industry where “hang time” is cherished for adding complexities to flavors, the implications are profound, especially for people anxious about the global impacts of climate change on historic wine-growing regions.
“If this can help incrementally improve the quality, it means big money for growers, especially in a global market,” said Joe Bezerra, executive director of the California State University Agricultural Research Institute, which is helping to fund the project at Fresno State University.
Gu’s immediate aim is twofold: to add complexities to the 150,000 acres (60,000 hectares) of wine grapes grown in California’s San Joaquin Valley, home to 44 percent of the state’s crop, and to open marginal areas to higher-end production.
“I hope it doesn’t get any hotter in Fresno,” he said, “but it doesn’t matter because we know now that we can manipulate the growing season.”
The San Joaquin Valley, stretching for 220 miles (350 kilometers) from Stockton to Bakersfield, is the U.S.’s most prolific grape-growing region. Along with heat-loving raisins and table grapes, vast tracts of wine grapes are mechanically harvested for popular labels such as Gallo’s economy brands and Bronco’s popular Charles Shaw, aka Two Buck Chuck, and blended into higher end wines.
Because grapes grown here ripen so quickly, growers are forced to harvest before the acids and tannins that contribute to a truly great wine can fully develop. Gu, a professor of viticulture, appears to have solved that problem by pruning off the first crop of clusters in June, which forces the vines to generate a new crop just as the weather really heats up in July.
In September, the 2011 grapes entered veraison, turning color as they began ripening, which is just about the time Fresno’s brutal summer temperatures begin to subside. The grapes then spent long weeks on the vine during the time the weather in Fresno more closely matches the summer temperatures in Napa or along the Central Coast.
“This is exciting,” Gu said last Tuesday, as he watched a crew of students bundled in winter jackets ferrying macro bins of cabernet sauvignon to the school winery. “We’re picking wine grapes in Fresno at Thanksgiving. That has never happened before.”
The grapes are better than the commercial crop the school harvested during the summer because the sugars, acids and pH are balanced within optimal levels, he said. The grapes harvested Tuesday have enough sugar to make a wine with slightly over 13 percent alcohol, on par with France but surprisingly light compared to most “big” California wines that hover near 15 percent.
But considering that some Central Valley grapes get so overly ripe that wineries have to add water to bring down the sugar levels, the harvest just two days before the Thanksgiving holiday (Nov. 24) is remarkable.
Gu’s efforts to force a later harvest have taken many forms. He first tried manipulating irrigation to slow the ripening, and when that failed he tried canopy management — using the vines to shield grapes from the blazing sun.
“Nothing made a difference because the overriding factor is temperature,” he said.
Then he remembered that some fruit growers in the tropics can get two crops a season, so he decided to try forcing a later harvest on a block of campus grapes.
“I thought that if we could shift the whole thing until later, it would be like growing in a cooler region,” he said.
He found that zinfandel grapes exposed to fall rains are too prone to the fungus botrytis, and chardonnay gets powdery mildew. Thick-skinned cabernet sauvingnon appears to be just right.
Gu said he doesn’t expect to replicate Napa quality in the Central Valley, but he does think that growers can improve the value of grapes grown here.
There are those who think the quality of grapes in the valley already is great, including Peterangelo Vallis, executive director of the San Joaquin Valley Grapegrowers Association.
“I really think the project is a great thing, but I have mixed feelings about it,” Vallis said. “It’s pushing the research away from taking advantage of what we do have here in the valley, and that’s a long growing season, great soil, good water and the lack of rain before maturity. How many times have those grapes he harvested yesterday been rained on?”
Everyone agrees the proof will be in the wine. The sauvingnon blanc Gu’s students made from last year compares favorably to wines from New Zealand, he said. Students again are making the 2011 cabernet sauvignon, but with increased research funding coming in for the 2012 vintage, he hopes to get a professional to coax the best-possible wine from them.
Gu must now find a way to make the process economical for farmers who grow on a scale too large to hand prune, and the yields must be high enough to be profitable. But he said that the process easily could be adapted now by boutique winemakers growing on a smaller scale in warmer regions such as Texas, New Mexico and California’s high deserts.
“Can you imagine Fresno with 300 wineries, each with about five-to-10 acres (two-to-four hectares)? That would be a good start,” he said, pausing to ponder the possibility. “I think so.”