Over at Kunde Family Winery in Kenwood, vintners are attempting a relatively new procedure in which a tractor drives through vines with a heat blower that shoots out a quick blast of heat — up to 350-degree air — to hasten the flowering process.
So far, the test project seems to be working. Winemaker Zach Long noted that a merlot block treated with the heat has reached about 90 percent of fruit set, while a similar untreated block is at 60 percent. The winery also is treating two blocks of chardonnay that have mostly reached fruit set. Overall, the winery uses about 2,000 tons of grapes in its wines annually.
“It’s already had a huge difference,” Long said. He noted that problem fruit set is his second biggest worry as a winemaker, right after frost.
The company that performs the service, Agrothermal Systems of Walnut Creek, contends a trial conducted in 2013 in Oregon, Washington and New Zealand showed the treatment increased the number of berries set per bunch by an average of 24 percent compared to those that were untreated.
Pilot tests also have shown that heat-treated grapes result in wine with better color and tannin structure, said Tim Matson, director of operations for Agrothermal Systems.
“We’re giving it a thermal shock instantaneously. Nothing in nature does that,” Matson said.
Last week, when the chardonnay went into bloom at Kunde, there were a few overcast days along with a high threat of mildew, Matson said. He said the extra heat sped up the process.
“Once it gets pollinated, then we bring it to a temperature that we’re not getting (in nature) to set the fruit,” he said.