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Cold Facts About The 2007 Freeze

UC Riverside Researchers Have the Cold Facts About the Freeze of 2007

Cooperative Extension specialists, faculty and other plant researchers can answer news media questions about the effects of this year’s freeze.

(January 17, 2007)

RIVERSIDE, Calif. — — University of California, Riverside experts can lend depth and perspective from the worlds of research and hands-on experience to ongoing news stories of this winter's freeze. As the impact of the potential loss of more than 70 percent of California’s oranges, lemons and tangerines — nearly $1 billion worth of fruit — becomes apparent, UCR researchers can help reporters focus on the key issues that the four-night freeze raised. Meanwhile, politicians have declared emergency; market watchers have predicted higher produce prices and scarcity; and farmers, farm workers, packers and produce haulers have braced for a bleak harvest.


  • Mary Lu Arpaia — Cooperative Extension Specialist, plant physiologist — “The real question at this point is whether trees have been damaged and to what extent,” Arpaia says. “This will influence the rate and extent of recovery for next year.” Arpaia evaluates pre-harvest and post-harvest factors on subtropical crop productivity and fruit quality, such as the effects of a prolonged freeze. As for the fruit itself, freezing and thawing can turn citrus bitter and dry. In avocados, the vascular bundles may turn black or brown discoloring the flesh, she added.
    Phone: (559) 646-6563


  • Don Merhaut — Extension specialist for ornamental and floriculture crops — “As far as ornamental plants at nurseries, the damage from this freeze was superficial,” said Merhaut. His research program focuses on whole plant growth and development with special emphasis on how spacing and timing affect nitrogen cycling in containerized ornamental crops. Vulnerable plants such as king palms, Bougainvillea, magnolias and tender annuals were hit hardest but in most cases, Merhaut says, the damage was limited to leaf burning. Most native plants and succulents such as agaves fared well and should rebound once temperatures have moderated.
    Phone: (951) 827-7003

  • Stephen Cockerham — Superintendent of Agricultural Operations, UCR. Agricultural Operations oversees two field stations to support UC scientist’s field research. His crew tends to the 420-acre Citrus Research Center and Agricultural Experiment Station adjacent to campus and the 540-acre Coachella Valley Agricultural Research Station, 80 miles southeast of campus at the south end of the Coachella Valley near the city of Thermal.
    Phone: (951) 827-5906


  • Stephen Morgan — Senior museum scientist with the UCR Botanic Gardens. The 40-acre UCR Botanic Gardens includes more than 3,500 species of plants from throughout the world.
    Phone: (951) 784-6962

  • Riverside County Master Gardeners — The telephone hotline is 951-683-6491, ext. 0, to ask questions regarding garden problems.


  • Tracy Kahn — Chief museum scientist and researcher at UCR’s Citrus Variety Collection, which contains two trees of approximately 1,000 types within the genus Citrus and within 27 of the 33 related genera in the subfamily Aurantioideae. Approximately 670 of the collection’s holdings are within the subgenus Citrus and encompass virtually all of the commercially important and historic citrus varieties of the world.
    Phone: (951) 827-7360

The University of California, Riverside ( is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion.

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