Imagine a peachless cobbler. Or a peachless crumble. Horticulturalists are starting to ring a peach alarm bell as climate change takes a toll in such popular peach-growing states as South Carolina and Georgia.
Climate change is impacting high-value commodity crops such as peaches in Georgia and South Carolina, primarily through warmer winters, reduced chill accumulation, earlier blooming, and an increased risk of spring freeze damage.
"The first and most obvious effect is that the bloom or flowering time has advanced about one to two weeks earlier in South Carolina over the past 40 years," said Gregory Reighard, visiting professor and horticulture fellow in Clemson University's Department of Plant and Environmental Sciences.
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South Carolina's peach industry generates more than $100 million annually in crop value and has an estimated economic impact of up to $300 million statewide, according to the U.S. Department of Agriculture.
Georgia's peach industry generates more than $20 million annually in farm gate value, according to the University of Georgia's Farm Gate Value reporting system.
Reighard worked with peaches in South Carolina for four decades and said there have been noticeable impacts.
"The data show bloom has advanced an average of about seven to 10 days in my research orchard, so that's quite noticeable," Reighard said. "Despite warmer winters and warmer springs, there remains an increased risk of a late freezing event. Polar vortices bring damaging freezing temperatures that come during bloom and early fruit development."
Reighard said a polar vortex brought damaging freezing temperatures to parts of the United States this year.
"Meteorology has shown that a warming stratosphere weakens the jet stream, which contains the polar vortex, so that frigid cold air can be released across the North American continent," he said. "If the jet stream weakens in late winter or spring due to atypical atmospheric warming, a cold air mass rushes south, which increases the likelihood of late-spring freezes."
These extreme weather events during harvest time "can't be normalized by horticultural practices," Reighard said.
Annual average chill hours have lessened over time, he said, by an average of 130 hours over the past 50 years in parts of Georgia. "Therefore, the number of chill hours available for a peach variety to break dormancy has decreased over the past several decades throughout" the Southeast.
Shifting winter temperature trends are altering the accumulation of chill hours, defined as time spent between 32 and 45 degrees across middle and south Georgia, according to researchers at the University of Georgia.
Reighard said that about 50 years ago, most commercial peach varieties required between 600 and 1,100 chill hours to produce a normal crop, except in some coastal areas in the Southeast. In key peach-growing regions such as middle Georgia and South Carolina, varieties needing 600 to 850 chill hours bloomed reliably in roughly 90% of years.
Growers also planted some varieties requiring 900 to 1,100 chill hours because they bloomed later, and those generally flowered normally as well. In the Coastal Plain, varieties with lower chill requirements of 400 to 600 hours performed successfully.
Reighard said today most varieties being planted in middle Georgia and South Carolina require fewer than 850 chill hours, with 650- to 750-chill-hour varieties becoming more popular.
"However, these varieties also tend to bloom earlier on average than the older, higher-chill varieties, thus increasing the risk of cold damage," he said.
Srijana Thapa Magar, assistant professor and peach extension specialist in the Department of Horticulture at the University of Georgia, said extreme heat affects peach development, fruit quality and yields.
"Extreme heat triggers a cascade of stress responses that compound each other if not actively managed through irrigation," Magar said. "The visible symptoms, wilting and sunburned fruit and foliage, are only the surface of the problem."
Magar said the more serious damage occurs at the physiological and biochemical levels.
"Under heat stress, trees close their stomata to limit water loss through transpiration," she said. "This is a protective response, but it comes at a real cost. Closed stomata also restrict carbon uptake, which reduces photosynthetic assimilation. Less carbon fixation means fewer carbohydrates are available for new shoot growth, canopy development and fruit production."
Magar said that during this time, the tree is effectively forced to ration resources across competing demands at the exact moment fruit needs them most.
"Water stress compounds this further," she said. "Trees under moisture deficit tend to produce smaller fruit and are more prone to premature fruit drop. The tree will shed fruit rather than sustain it under limited resources. Stressed trees are also more vulnerable to pest and disease pressure. Heat and water stress weaken the tree's natural defenses at the same time pest and pathogen activity often increases in warm conditions."
Reighard said growers must plant lower-chill varieties as well as multiple varieties with different chill-hour requirements within each harvest window.
"This is because yearly variability in winter chill hours and increased periods of intense spring or summer heat result in some varieties not setting fruit or cause other varieties to ripen outside their normal harvest windows, leaving gaps in production and the supply chain for growers," Reighard said. "Another option, though expensive, is investing in frost protection such as wind machines to lessen the effects of increased risk from late-spring frosts and freezes."
Reighard said peach breeders are responding to changing climate conditions by developing varieties that require less winter cold to emerge from dormancy but more heat before flowers and leaves appear. This helps prevent trees from blooming too early and suffering frost damage. Researchers are also seeking varieties that can better withstand high temperatures and drought.
Reighard said peach growers have had to find ways to adapt.
"Peach growers have a few options currently to lessen the negative effects of climate change," he said. "Since peach varieties ripen during a specific period after bloom and all the fruit from each variety is picked within seven to 10 days, farm profitability relies on fruit being harvested, packed and shipped five to seven days each week during the harvest season. Gaps in production caused by little or no fruit significantly reduce farm efficiency and profitability."
This reporting content is supported by a partnership with Journalism Funding Partners.
Erica Van Buren is the climate change reporter for The Augusta Chronicle, part of the USA TODAY Network. Connect with her at [email protected] or on X: @EricaVanBuren32.
This article originally appeared on Augusta Chronicle: Climate change threatens peach crops in the Southeast | Exclusive