Mike Williamson had 6-8 inches of shoot growth in his vineyards in late May, far less than the typical 12 inches or more.
“Most varieties fared well through this, with some shoot loss,” said Williamson, who co-owns Williamson Orchards & Vineyards on south-facing slopes between Caldwell and Marsing, Idaho.
Cold, wet weather around the state in April and part of May caused some frost damage, but growers welcomed much-needed water.
“Because of the bit of frost damage we saw, it probably won’t be a bumper crop,” Williamson said. “I don’t know if it will be a deficit, but it won’t be maxed-out tonnage — probably down just a hair this year.”
Nearby, Ron Bitner of Bitner Vineyards said frost around April 10 caused some damage in the region but it is too early to tell how much. Early season cold can cause primary bud loss, though frost damage is variety-dependent.
“Even this week we lost some buds in low spots” from earlier cold, he said May 25.
Bitner said seasonal heat accumulation so far is below average. Wine grape development “might catch up some, depending on the summer.”
Williamson said each bud off the cordon — a horizontal, belt-high woody structure — can produce a primary, secondary and tertiary shoot. The secondary can take over if the primary is damaged, but its fruit cluster will weigh 30-50% less.
“We’ve made it through bud break and now we are up to the first big push, or shoot flush,” he said. Shoots will “push hard through to the middle of June, and by the end of June will be up to 3 feet” before crews limit growth.
Williamson said May 23 his vineyards could be about five days behind schedule, which could change.
In the Hammett area east of Mountain Home, Cold Springs Winery owner Arthur Reece said his vineyards had good fruit set, which bodes well for tonnage.
As for frost, “we had one night that was kind of scary, but I think we survived it,” he said. His grapes so far are on schedule.
Reece trimmed vineyards a bit differently. He expects to increase yield from last year, when harvest started about a month early following a prolonged period of high heat.
“Last year was so hot, all the grapes decided they needed to be picked at the same time,” he said. And the shorter season cut management time.
“If we get a normal summer, everything is going to work,” Reece said.
Art McIntosh, who co-owns Lindsay Creek Vineyards south of Lewiston, said buds on the property, which is at a higher elevation than some in the region, did not emerge before the freeze.
He said the vineyards look good but could use more heat. A return of wet weather would prompt the team to watch for powdery mildew.
Cold, wet weather set the vineyards back about a week but “we probably won’t put the sprinkler on for some time,” McIntosh said. “We have good moisture in the ground.”