For many orchards, cold weather is a menace but in California’s Central Valley, mild winters are becoming a threat, says Valley Public Radio. Crops such as peaches, pistachios and almonds need a certain amount of frigid weather – chill hours in agricultural terminology – to set the buds that bloom into flowers that produce fruit and nuts.
“Predictions from multiple University of California studies say that within 30 to 50 years it may be too warm to grow many tree crops where they flourish today,” says Valley Public Radio. Pistachio trees, for instance, need more than 700 chill hours every winter. Grower Tom Coleman says his trees have slept less than 500 hours in recent years. “And as a result of that, they do not bloom uniformly and when they don’t have uniform bloom, it can dramatically reduce the yield of the field,” says Coleman.
Warmer winters will push crops further north, says one University of California scientist. The warmer weather would be good for annual crops such as tomatoes but hard on tree crops that have long lifespans and are expensive to replace. Another UC researcher is experimenting with short-term ways to cool off valuable trees, such as overhead sprinklers or painting them white to reflect sunlight. In Kern County, UC farm advisor Craig Kallsen is trying to breed a pistachio tree that needs fewer chill hours. “It’s pretty hypothetical,” he told Valley Public Radio, but he has some trees that he hopes to test this winter.