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The Treasure Valley’s weather is changing … So are onion growers

As the remnants of Tropical Storm Hilary washed over his Malheur County fields, longtime onion farmer Bruce Corn hunkered down in his office taking care of paperwork.

He was philosophical about the unpredictably changing conditions that have buffeted the Treasure Valley’s farmers over recent years.

“Every year is different. That’s just farming,” Corn said. “Each year you have different weather patterns and circumstances. You are working with nature and you are subject to those forces all the time.”

But weather extremes in the western Treasure Valley have become more common – including heat, drought, and precipitation. 

Shay Myers of Owyhee Produce in Nyssa said the drastic weather in the last few years has impacted yields. Some years have been good, others not.

Scientists say climate change has made seasonal weather more unpredictable. That could continue to complicate onion production – the biggest earner in Malheur County’s agriculture economy. 

Extreme conditions can damage plants, reduce yields, and disrupt farming practices. 

In 2021, an unprecedented heat dome blanketed much of the Pacific Northwest during the early growing season. And last summer, a very wet spring was followed by temperatures that rose quickly, shocking onion crops. 

Data from the state Department of Agriculture shows below-average onion yields in both years.

“All crops are sort of like Goldilocks, they do really well within a certain range of temperatures,” said Stuart Reitz, director Oregon State University’s Malheur Experiment Station. If temperatures get too hot or too cold at the wrong stage of their growth, plants can shut down.

“Maybe we are in a climate change period. I don’t know,” Corn said, in his farm office. “A lot of people tell us that is the case. But, nevertheless, we have to adapt and deal with the circumstances as they are.”

A key crop in a time of change

In the last decade, onion production brought in about $640 million dollars to growers in Malheur County, its highest-value crop. Spanish sweet and yellow onions were most common, and farmers also grew many red and white onions. Packaging sheds and processors in the county multiplied the economic value.

Generations have grown onions here. Myers said that’s because the Treasure Valley’s fertile soils give growers, “a great opportunity to produce great onions.” The growing season here has provided the optimum heat and dryness that the onions require. 

But recent years have brought more extreme heat to the onion-growing region. Nearby Boise is experiencing 22 more extremely hot days per year than in 1970, according to an analysis by Climate Central. 

When hotter temperatures don’t let up, onions can undergo heat stress, causing farmers to produce less. Heat stress can also cause the size of the onion bulb to be smaller. 

Hot temperatures can stop the onion plant from producing top leaves, which help protect the bulb from sunburn. And because onions have shallow roots, warmer topsoil can stress the plant from the bottom up.

Nighttime temperatures are warming faster than daytime temperatures, said Erica Fleishman, director of Oregon Climate Change Research Institute.

Since 1970, average summer nighttime temperatures have warmed by more than 7 degrees in Boise. 

Rising nighttime temperatures can be even more problematic for onions, Reitz said, because the plant can’t cool off at night. 

Hotter nights can encourage pests and mold. Thrips are one pest that thrives under hotter temperatures and can be a major threat to onions, damaging the crop and reducing production.

Wildfire smoke also can block sunlight onions need. 

Onions await harvest in a field on Railroad Avenue west of Ontario on Thursday, Aug. 31. (LES ZAITZ/The Enterprise)

Looking for water

Besides the new variations in temperature, recent decades have seen a shift in precipitation.

Long-term records show the Western U.S. experiencing less snowpack, earlier snowmelt, and less precipitation falling as snow. That change leads to greater water demand during the growing season, which can be problematic for the arid Treasure Valley where crops need to be irrigated.

In the last two decades, most years have been drier than the state’s 30-year average, Fleishman said. In 2022, most of Oregon spent more than 40 consecutive weeks in a drought. 

Bouts of intense winter storms don’t always bring recovery from droughts. Sustained precipitation is better for increasing soil moisture and replenishing groundwater needed for irrigation.

For farmers, long-term precipitation and the level of water in reservoirs play into calculations about how to raise the valley’s key crops.

“Last year we were in more of a drought situation, so cropping plans were totally different,” Corn said. “If you are not assured of an adequate supply of water you have to make adjustments about where you put your onion crop and a lot of that has to be determined about this time every year.”

That decision drives other actions to prepare for the next year’s crop, he said.

“For our high value crops, and onions are high value, by November, before this cropping year ends, we will have chemicals supplied and fumigation, all the land prep will be done,” Corn said. 

This year’s snowpack brought a good supply of water. Corn said full reservoirs can make decisions easier. 

“It’s like having money in the bank,” he said. “Any given year you can somewhat look forward, but any given year can be an outlier.”

Getting creative

To tackle drought and extreme heat, growers and researchers are getting creative. 

Researchers at the OSU Malheur Experiment Station – appropriately situated on Onion Avenue – are working on new varieties with all the attributes of Treasure Valley onions, but that are also resilient to heat, Reitz said. 

Growers are trying different methods to protect onion bulbs from the sunburn that occurs when leaves don’t fully develop due to heat stress, Reitz said. 

One solution is intercropping. Farmers plant other crops in between rows of onions to provide shade. But that solution can be challenging, depending on water demands and the irrigation set up needed for each crop. 

Growers are also using cover crops to increase the amount of nutrients in the soil as well as to keep the soil moist in between onion harvest and planting. 

Farmers have worked for years to improve irrigation, conserving water and making scarce supplies last longer.

“Twenty years ago, there were very few sprinkler systems or drip irrigation for onions,” Corn said. “Now you see drip irrigation everywhere. … Now you use half the water, and that makes the supplies you have to go much further.” 

“Adapt or leave” 

Reitz said that growers are “cautiously optimistic” that this will be a better year, even though a wet spring led to a slower start to the season. 

But until onions are harvested in late August through October, growers are on high alert. 

Myers said he is hopeful about the growth of onions in Malheur County.

He said farmers should come together and share their stories. And customers should, “Be willing to pay the extra dollar to support local.” 

Riding out the rains of Hilary, Corn was ready to take in stride whatever changes are coming.

“The climate has been something that has been an issue for a farmer since time immemorial,” he said. “So you either adapt or leave the farming life. 

This story was produced through a collaboration between the Enterprise and Climate Central, a nonadvocacy science and news nonprofit. Caitlin Looby of Minneapolis is a freelance reporter working with Climate Central. Pat Caldwell is reporter with the Enterprise and Shreya Agriwal was as a reporting fellow at the Enterprise in summer 2023.

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