With the nuts for California’s 2015 pistachio crop beginning to expand in mid-May, many growers are questioning just how many of those nuts will actually fill up with kernels by harvest time.

The concern involves the wide range in timing of the bloom from one tree to another, which a number of growers observed this spring.

“Each year, the industry experiences some level of lack of bloom uniformity across an orchard,” explains Andy Anzaldo, Vice President of Grower Relations for Paramount Farms. “But, this year, it was extremely variable. Only time will tell how that will impact nut fill in July and August.”

This year’s bloom was also the longest California’s pistachio growers have ever experienced, he adds. Trees sprayed with oil, in part to offset the low winter chilling hours, began blooming in mid-March. Non-oiled trees didn’t finish until around the end of April and early May.

However, the bloom also offered growers a bright side. “It appears that for about two-thirds to three-fourths of the trees, the male-female overlap was much better than last year,” he says.

For a fair number of growers that may not be enough to overcome the effects of poor winter chill, as evidenced by erratic leaf growth early in the season. That has led to a heavy drop of nut clusters, especially in younger trees, Anzaldo notes.

“It could mean that trees, which typically would have the potential to produce a 3,000-pound crop, may yield no more than about 1,000 pounds of nuts this year,” he says. “The high cluster drop didn’t affect the majority of growers, but it did affect a significant portion of them.”

Otherwise, most pistachio orchards look healthy, he says.

At this time, many growers are dealing with threats from both big and small bugs, including grasshoppers, plant bugs, and phytocoris, which thrived on the flush of vegetation in areas surrounding orchards resulting from rains in December. That vegetation has since dried out, so the bugs are moving into the pistachios to feed on the green tree foliage.

Going into bloom, observers were predicting this year’s crop could range in size from around 450 million pounds (inshell), assuming a significant impact on yields from low winter chilling, to as much as about 650 million pounds high, should any effects of winter chill be minimal.

“Paramount Farms is estimating production will come in at the lower end of that range, due to the extended and variable bloom and the uncertain water situation,” Anzaldo says. “But, keep in mind, we’re talking about pistachios. It’s foolish to have any confidence in projected overall production numbers until the harvert is over.”