Cold snap hit just as walnut growers wrapped up harvest
By TIM HEARDEN
RED BLUFF, Calif. -- Cut into a young walnut tree in the northern Sacramento Valley, and chances are you'll see lots of green and white.
That's good news for growers, because that means the tree made it through the Thanksgiving freeze without significant damage.
Farmers and University of California Cooperative Extension researchers feared the cold temperatures Nov. 25-27 could devastate the more vulnerable young orchards, Red Bluff, Calif., farm advisor Rick Buchner said.
"We were very worried about it, but I've gone out cutting twice and I've not seen frozen wood yet on young trees," Buchner said, noting he was most concerned about trees up to 3 years old that were semi-dormant going into the cold snap.
"We were kind of scared of it getting down in the low 20s," he said, "but I think it stayed up in the high 20s."
Temperatures dipped as low as 29 degrees in Red Bluff and 27 degrees in Redding, as much of California dropped below freezing in the early morning hours.
The cold snap came as some walnut growers were just completing their harvest, which was expected to net 510,000 tons statewide, according to USDA estimates.
Janine Hasey, a UC Cooperative Extension farm advisor in Yuba City, Calif., said she'd received no reports of freeze damage from area growers. But she saw some trees while driving through the area that might have been damaged, she said.
To determine frost injury, growers take a sharp knife and cut into the outer bark. If it's green and white underneath, it's healthy and alive, Buchner said. If it's black, it's been killed by the freeze, he said.
Growers can prevent frost damage by first withholding irrigation water starting in early September to get the wood hardened by late autumn, Buchner said. Then, if there hasn't been significant rain, they irrigate trees and soil before a frost to give them moisture, he said.
"Where you see a lot of frost damage, we generally suggest painting the trees white, which seems to take some of the stresses away from them and helps them recover better," Buchner said. "If there's any life left in the wood at all, it gives the tree the possibility to self-heal."
UCCE Fruit and Nut Research and Information Center: http://fruitsandnuts.ucdavis.edu/Newsletters