Posts Tagged: freeze
Homeowners should check for plants that are likely to be exposed to cold temperatures, said Judy McClure, UC Cooperative Extension master gardener coordinator.
“The lower spots in the garden tend to get colder than higher spots,” she said. “The bottom of the slope will be colder.”
McClure advises having a good supply of covers. She recommends against throwing a plastic tarp over trees, unless there is a frame to keep the plastic from direct contact with the tree. Contact with the plastic could cause damage by burning the foliage, she explained.
If the soil is dry, McClure said, it is best to water trees and succulents before covering them with blankets or frost cloths. When covering citrus trees, make sure the cover reaches the ground, she said.
The Fresno Bee reported that private meteorologist Steve Johnson has been tracking the approaching weather system since Nov. 25.
"The trajectory keeps it over land and it dries out," Johnson said. "This kind of thing doesn't happen very often. The pattern is very similar to what we saw in December 1998 and 1990."
For more on freeze protection from UC Cooperative Extension, review the following links:
- Citrus freeze protection (home)
- Methods of frost protection (orchards)
- Protecting avocados from frost
“We’ve had some very severe frosts in San Luis Obispo County and on the Central Coast over the years,” said Mark Battany, UC Cooperative Extension advisor in San Luis Obispo and Santa Barbara counties. “In 2011 we had the most severe frost in 30 years and many millions of dollars of crop and wine value were lost because of that freeze.”
Farmers take various measures to protect their crops when temperatures dip below freezing, such as mowing or tilling the vineyard row middles, or running sprinklers with water pumped from underground aquifers or diverted from streams.
“Sprinkler frost protection is very effective in many areas,” Battany said. “The concern we have in California is that water is becoming more limited. We don’t have the ability to easily import water from other areas to our coastal regions, and our local supplies are being stretched quite thin.”
Some farmers are considering wind machines, which mix warmer air high above the ground with air closer to the ground to raise the temperature. But wind machines are expensive, and the potential effectiveness depends on the strength of the temperature inversion. UC scientists are now gathering data to help inform farmers before making the costly investment.
Battany and his colleagues - Rhonda Smith, UCCE advisor in Sonoma County, Richard Snyder, UCCE specialist in the Department of Land, Air and Water Resources at UC Davis, and Gwen Tindula, UCCE staff research associate - are collecting temperature inversion data at different locations in 60 coastal vineyards throughout three counties to document inversions during frost events.
The scientists installed 35-foot-high meteorological towers with data loggers at the top and at the five-foot height to measure the difference in temperature. In the first year of the study, there were useful inversion conditions on nearly three-fourths of the nights when there was frost.
“That’s a fairly good success rate,” Battany said. “The wind machine will provide quite a bit of protection under those conditions.”
The study will continue this year and in 2014. Farmers who wish to install their own meteorological towers with data loggers can do so at a cost of about $250 each. Installation instructions and specifications are available on the UCCE website.
The UCCE research is funded with a grant from the American Vineyard Foundation and a CDFA Specialty Crops Block Grant.
For more details, see the video below:
It has been particularly cold at night in California for about a week, but it appears the state's citrus industry will emerge mostly unscathed, reported Oliver Renick on Bloomberg.com.
Thermometers dipped about 10 degrees below normal overnight during the cold snap, but growers efforts to keep the trees warm with wind machines and irrigation appear to have been successful.
"We are not anticipating any damage in the navels, maybe very limited damage on the outer row away from the wind protection,” said Shirley Batchman, the director of government affairs at California Citrus Mutual. “Certainly nothing that’s going to affect the orange production.”
From Dec. 3-10, temperatures dropped as low as 31 degrees in Fresno, 26 degrees in Madera, 27 degrees in Merced, 26 degrees in Napa, 25 in Redding and 27 in Redbluff. Growers in these areas were working to avoid damages like those suffered in 2007, when a freeze caused more than $1.4 billion in damage to citrus, avocados, strawberries, vegetables, nursery stock and other crops, the article said.
In northern areas, freezes blackened the tips of some young walnut tree branches, but those are generally pruned off anyway, said Rick Buchner, a University of California Cooperative Extension farm advisor in Red Bluff, Calif.
"There's been no serious damage in the big wood that I've been called to look at yet," Buchner said.
Newspapers up and down the state are covering the cold storm system approaching California. In addition to reporting the weather, Sacramento Bee reporter Loretta Kalb took the time yesterday to check on the impact of the storm on California citrus.
Even though it was Sunday afternoon, UC Cooperative Extension Butte County farm advisor Joe Connell contacted Kalb to tell her citrus crops should emerge with little or no damage from the week's storm.
"As far as citrus goes, for the naval orange, it takes about 3.5 hours at 26 degrees for the first orange to freeze," Connell was quoted in the story. "The orange juice itself has high sugar. It's like an antifreeze in the fruit. If it's colder, down to 25 degrees, after about an hour you'll get 5 percent of the fruit frozen."
At 27 degrees to 28 degrees, the low temperature forecast for most parts of the Valley, "I think most of the (citrus) fruit will be fine," Connell told Kalb.
The Redding Record Searchlight ran a story advising homeowners to protect their freeze-sensitive plants in the face of the winter storm. Citrus trees may be protected by a sheet or blanket, or as retired UC Cooperative Extension farm advisor in Fresno County Mark Freeman typically suggested this time of year: Wrap the tree in good, old-fashioned Christmas lights. They'll keep the tree warm and look festive at the same time.
More information from UC Cooperative Extension about citrus freeze protection and damage is available in a citrus freeze media kit.
A citrus tree damaged during a freeze.