A lack of chill accumulation can be challenging for growers later in the season, beginning with a straggled bloom. UC Cooperative Extension Orchard Systems Advisor for Yolo, Solano, and Sacramento counties, Kat Jarvis-Shean said trees waking up at different times can create a host of issues for growers. For pistachios, male and female trees can come out of dormancy at different times, affecting the potential for pollination. Similar issues can present themselves in walnut trees. Jarvis-Shean noted another common problem for walnut growers when low chill creates an uneven bloom.
“If they start the race at a different time, they’re going to end the race at a different time, which means they’re ready to harvest in different timings,” Jarvis-Shean explained. “So, either you have to come back for multiple shakes, or you end up leaving 10-15 percent just out in the orchard because it doesn’t pay to come back and collect that last laggard.”
The broader timeframe of a straggled bloom can also create much wider variability in the nuts. Jarvis-Shean said the nuts that start out earlier end up being a “bigger carbon sink.”
“They’re like the first piggy to the trough and they get really strong right away and they can be better at elbowing out the other piggies as they come along to the trough. So that ends up giving you a wider range of nut sizes,” Jarvis-Shean noted. “You have some big nuts from those guys that started first and then little peewee nuts from the ones that came along last.”
As of January 3, the UC Davis Chill Calculator indicates that the Durham CIMIS station has logged 42.8 portions under the dynamic model, with 808 hours below 45°F. The station in Manteca has registered 40.8 portions, with 754 hours. There have been 869 hours in Merced, with 42.8 cumulative portions. In Five Points, there have been 785 chill hours, equating to 40 portions. Finally, the CIMIS station in Shafter has registered 39.2 portions, with 768 hours.
Listen to the latest chill report below.