Frigid temperatures in the low to mid 20s over the weekenddamaged the winter lettuce crop in Yuma County, Ariz., resulting in smaller harvestable heads, slower plant development and harvest, and higher prices for consumers.

“The ice formed on leaves is two-to-three leaves deep in some growing areas,” said Kurt Nolte, University of Arizona Cooperative Extension Director in Yuma County, following the freeze Saturday night into Sunday morning.

The hardest hit crops were whole head lettuces (iceberg and romaine) within three weeks of harvest.

“The freeze caused lettuce head blistering, puckering, epidermal peeling, and internal leaf burn,” Nolte explained.

Lettuce damage occurs when temperatures reach 28 degrees Fahrenheit after four hours.

As a result, winter lettuce prices have soared.

“Lettuce is in supply short with prices spiking to $25 per carton following the freeze and below-average temperatures over the last six weeks,” Nolte said.

He predicts lettuce prices will increase further with short crop supplies through mid-February.

Last fall, winter lettuce prices were in the $6 to $7 per carton range with an abundant supply caused by above normal temperatures which increased plant maturity.

Baby leaf types, including spinach, appear to have the least damage from the freeze. Little to no damage is expected in cole crops, including broccoli, cauliflower, kale, and cabbage.

The coldest areas this past weekend included the rural Dome and Gila Valleys in eastern Yuma County where temperatures did not rise above freezing until mid Sunday morning.

Vegetable growers in Yuma County and neighboring Imperial County, Calif. produce about 95 percent of the U.S. winter vegetable crop. The area is heralded as the Winter Vegetable Capital of the World.

“Harvest crews will need additional time to remove damaged leaves,” Nolte said Sunday. “Leaf removal means smaller,lighter lettuce heads, pluslower yields.”

The additional time required to harvest, trim, and pack lettuce means work crews will be hard pressed to meet order demand.

Sunday night-Monday morning temperatures were more moderate – about five degrees above the previous night.

Freeze warnings continue through Tuesday morning. Continued cold weather is predicted through this week which means little to no growth of young lettuce plants already in ground.