High heat during much of the growing season prompted an early start to Idaho’s winegrape harvest, which is producing lower yields.
Harvest started around a week earlier than usual “just because it was so hot,” Idaho Wine Commission Executive Director Moya Shatz Dolsby said. Above-normal temperatures can stress the plant and result in undesirable impacts such as sunburned grapes.
Yields have been 25-30% lighter overall, she said. Results differ by location and variety.
“It was so hot that berries didn’t get as big and some just kind of shriveled up,” Dolsby said. “Flavors will be really good because it is concentrated” as resources are spread across less mass, she said.
The growing season had its advantages, she said. Spring was warm, and in the summer, “having it too hot is better than hail or a lot of other things that could have happened.”
Jay Hawkins, of Lanae Ridge Vineyard between Caldwell and Marsing, Idaho, produces only red varieties. He said Sept. 24 that his harvest was about 20% completed. As for quantity, “I would estimate we are easily 30% lower than the three-year average.”
Factors affecting tonnage include the number and size of clusters, and grape, or “berry,” size.
“The most noticeable thing is that in a fairly significant number of our varieties, the actual grape size itself is smaller than normal,” Hawkins said. To a lesser extent, clusters are smaller.
Grape size reduction is hard to quantify, but “you just look at them and you can see they are smaller,” he said. His Merlot grapes look slightly less than half their normal size. Among the vineyard’s eight other varieties, some grapes are about 80% of normal and others are closer to normal.
Hawkins said heat and wind also impacted pollination. In hot conditions in the middle of bloom, “we saw, in some cases, the grape clusters just kind of collapse.”
Total heat units to which area vineyards have been exposed are up 12.1% year-to-date, boosted by a June-July period with many 100-degree days, he said.
Hawkins said he irrigated substantially more this year, though grapes aren’t a high-water crop. Given the dry soil and unprecedented heat, “you just had to continue to apply some water to them just to keep them alive.
“At some point, you need to switch your mindset to producing fruit for the next 30-plus years,” he said.
Martin Fujishin, head winemaker for the nearby Fujishin Family Cellars and Free Dog Wines, said the summer heat may have led to some increased variability in ripening dates.
“Some varieties were impacted by the heat we saw during bloom, which led to somewhat lighter crop loads,” he said. “But that is not necessarily the case across the board.”
April-May heat “led to some of the varieties not setting as heavy a crop as they normally would,” Fujishin said.
The dry summer minimized powdery mildew impact, he said.
High summer heat prompted more irrigating, challenged crews and reduced some grapes’ size, Fujishin said. Early samples of the white Albarino variety showed a 10-15% reduction while the red Tempranillo was around normal or even slightly bigger.
He said smoke in the air was not enough in his area to taint grapes.