Texas fruit crops need rain, chill hours

Texas fruit crops are behind on chill hours necessary to trigger optimal blooms and good fruit sets, according to Texas A&M AgriLife Extension Service experts.

If Punxsutawney Phil was right, there are still enough winter days ahead, but experts said Texas’ fruit crops need cold, clouds and rain.

Fruit trees, such as peaches, apples and even blackberries depend on cool, cloudy weather in the winter to promote proper physiological growth in the spring, said Larry Stein, Ph.D., AgriLife Extension horticulturist, Uvalde. If plants do not receive the required number of chill hours, plants can be slow to leaf out, which typically leads to poorly developed fruit or no fruit at all.

“Growers in different regions of the state have plants with different chilling requirements,” he said. “Orchards in the Rio Grande Valley might have trees that require 200-300 chill hours, whereas the varieties that perform well in North Texas might require 900-1,000 hours.”

Clouds, cold equal chill hours

Chill hours begin to add up after the first freeze each fall, he said. Trees go dormant for the winter, but chill hours promote hormones that dilute growth inhibitors throughout the winter and prepare the plant to break dormancy and begin new growth, bloom and set fruit.

Growers want the timing of new growth and bloom to coincide with avoiding the average final spring frost, which would damage budding fruit.

Proper chill hours trigger good and well-timed leaf and bud development, Stein said. A lack of chill hours can lead to poorly developed buds and flowers that can have a cascading effect leading to stunted or misshaped fruit to no fruit at all.

Leaves help trees produce energy and protect limbs from sun scald, but multiple seasons of inadequate chill hours can kill plants, Stein said.

Damp, cloudy conditions and temperatures between 32-45 degrees are ideal for accruing chill hours, Stein said. Temperatures have been relatively cool, but drought and sunny days have inhibited the process.

Stein said there is still time to make up significant chill hours. Last year, chill hours were behind until Winter Storm Uri delivered cold temperatures across the state. The storm hurt some individual fruit growers and produced generally negative effects on agriculture, but the cold temperatures helped most tree varieties around the state, Stein said.

“Last year was marginal up to this point and then Uri arrived,” he said. “There were some low chill varieties that were becoming active, and they got hammered. But for the most part, that cold front put us over the top with the chill hours necessary to make a good crop.”

Blue bird days, go away

Jim Kamas, AgriLife Extension fruit specialist, Fredericksburg, said chill hours accumulation got off to a late start and remain behind. He does not expect chill hours to be as short as 2016-2017 when Central Texas received a little over 450 hours total. But more cloudy, cold weather is needed with chill hours just surpassing 600 at this point in the season.

Kamas said chemical growth regulators can mimic chill hours, but that availability could be an issue because the products are imported from Europe. And the product must be applied 30 days before full bloom, which on average is March 17.   

Unless producers have growth regulators to apply, or Mother Nature delivers cold, wet weather soon, Texas fruit crops from peaches to grapes could be at risk of lower yields, misshaped fruit with lower market appeal, delayed and inconsistent fruit harvests and stressed trees, Kamas said.  

“We have a saying that there are only two types of people who like 36-degree days that are gray, cloudy, misty, rainy and just plain icky to be out in – duck hunters and fruit growers,” he said. “Most people would disagree, but winter days like that bring a smile to their faces because they know good things are happening.”

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