Moises Mariona works on the Hines farm in Derwood, Md. It grows tomatoes and other produce. Harvesting at night improves the taste, farmer Mark Hines said. Amanda Andrade-Rhoades/ The Washington Post

Mark Hines’s workday starts while the sun sets, when the grass grows heavy with dew and the bugs are as loud as they are close. His friends call him the “Night Farmer.”

While others sleep, Hines roams his Derwood, Md., farm from 9 p.m. to 2 a.m., picking tomatoes, melons, pumpkins and lettuce by the light of a headlamp and well after the heat of the day. As he works, his puppy, Cooper, plays alongside him in the eggplant vines, a light-up tag buckled to his orange harness.

Rising temperatures in key agricultural regions across the United States are leading more farmers to harvest in the middle of the night to safeguard the quality of their crops. There isn’t much data on the pervasiveness of night harvesting, but agriculture experts and farmers said the practice is becoming an important part of the industry’s future.

“Inevitably, it’s going to be hotter during the day, and that’s going to mean even more night farming where it’s feasible,” said Daniel Sumner, a professor of agricultural economics at the University of California at Davis. “And when I say feasible, I mean where it’s profitable.”

Hines started farming in 2020 and gradually shifted to evening hours to contend with the hotter Maryland summers. This year was even more brutal; scientists say it was the world’s hottest summer “by a large margin.”

“I tell people the sun has felt brighter these past few years,” Hines said.

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Heat has become a major economic threat to the agriculture industry, and it’s only expected to get worse. By the end of the century, climate change could lead to worldwide crop damage five to 10 times greater than conventional climate models have predicted, according to a 2021 study published in the Journal of the European Economic Association. It’s also poised to cost the agriculture industry $4.65 billion annually in lost productivity by 2030, according to a study by the Atlantic Council think tank.

“Heat is the enemy of quality produce,” said Alan Schreiber, executive director of the Washington state commissions for blueberries and asparagus, and owner of a 200-acre organic fruit and vegetable farm in the Columbia River Basin.

Farmers are adapting as best they can. An entire industry has emerged to cool workers with ice vests and other technology. Some farmers are incorporating night harvests into their business for no more than the cost of headlamps, while others are investing hundreds of thousands of dollars in machines specifically designed to farm at night.

“The weather seems to be getting more intense, we’re having to adapt, and we’re working off hours,” Schreiber said. “But other things stay on the same schedule. The trucks that come pick up produce, they still come at the end of the day. . . . The days are getting longer.”

Moises Mariona, left, and Mark Hines look for stray vegetables at Hines’s farm in Derwood, Md., on Aug. 16. Amanda Andrade-Rhoades/ The Washington Post

While night harvests have become more common during recent heat spells, the practice “is as old as there is light,” Sumner said.

There are a number of advantages to picking fruits and vegetables at nighttime, but the most important is food quality. It’s easier to maintain the taste and texture of produce at cooler temperatures, and it takes less energy to store already cooled fruit and vegetables before transport, Hines and other farmers said.

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Night harvesting is most common during the summer but also can extend well into October, when farmers often pick fruits and vegetables for 24 hours a day before the winter frost kills their crops, said J.J. Dagorret, whose company makes farm equipment.

In California, fruit like peaches, which are firmer at night and usually picked by machines, have been harvested at night for decades, Sumner said. For smaller fruits like wine grapes, which require more precision while picking, some farms still prefer to harvest during the daytime when visibility is better – but that’s beginning to change as temperatures rise.

Picking crops at night also helps mitigate the risk of sun damage, which can cause tomatoes to burst open and blueberries to shrivel in the hands that pick them.

Hines farms on just a few acres with only one other person at a time, but larger operations are also following in the trend. Lauren LaPierre, the operations manager at LaPierre Farms in Zillah, Wash., says her 150-acre operation has been harvesting blueberries at night since a 2019 heat spell.

“It was during that heat wave that growers were all faced with this problem, how do we get our fruit orders out if it’s too hot?” LaPierre said. “I remember rushing to Lowe’s and Home Depot every evening trying to get the last of the headlamps because all the growers were out buying them.”

Harvesting overnight allows farms to sell a fresher product – blueberries picked at night can be delivered by truck the next morning, LaPierre said.

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Picking apples presents a particular challenge, Dagorret said. When temperatures reach 88 degrees Fahrenheit, usually in the middle of the day, trees are sprayed with water for hours to keep them cool. The fruit can’t be harvested while the trees are being sprayed down, so farmers will start at 2 a.m. to get in a full day’s worth of picking.

Dagorret said business is booming for his company, whose most popular products have night-work features such as special LED floodlights designed to reflect off the natural colors of apples and harnesses for workers so they don’t fall.

Machines such as Dagorret’s have become increasingly important for apple farmers in regions facing rising temperatures. He said his harvest-assist machines, which start at $70,000, have been sold not only to farmers in Washington, California, Michigan and New York, but also overseas to Australia, New Zealand and South Africa.

Mark Hines’s farm in Derwood, Md., gradually switched entirely to night harvesting to deal with hotter summers. Amanda Andrade-Rhoades/ The Washington Post

Heat-related ailments are serious threats in the summer to farmworkers, who have few legal protections from the deadly heat. Farmers such as LaPierre say that working during the night reduces the risk of fainting and heat exhaustion.

But there are trade-offs with the cooler temperatures.

Overnight work upends workers’ lives, said José, a 34-year-old farmworker in Washington state who has picked fruit for the past 16 years, regularly at night for the last four.

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“There’s days where you don’t see your kids because of the schedule,” José told The Washington Post through an interpreter. He spoke on the condition that his full name not be used, out of fear of workplace reprisals.

It’s also common for farmers to tell their pickers to come into work with only an hour’s notice, even as late as 12 a.m., said José and other farmworkers, who similarly spoke on the condition of anonymity. The workers comply in fear of being left off future schedules.

“Your body is used to sleeping during the day, you feel jet-lagged,” José said. “The majority of workers would prefer to work in the morning.”

Working in the dark comes with its own set of dangers. Without proper lighting, farmworkers are more prone to fall off ladders and hit their heads on branches, José said. Others have been injured while harvesting corn stocks in the dark with machetes and stepping on snakes impossible to see at night, said Anne Katten, a work safety director for the California Rural Legal Assistance Foundation.

Nearly 9,000 crop-producing farmworkers suffered injuries during overnight hours between 2011 and 2020, the most recent year for which data is available, according to the Bureau of Labor Statistics.

In 2021, the California Division of Occupational Safety and Health released safety guidelines for night harvesting in response to the practice’s growth and sharp uptick in overnight injuries nationally between 2019 and 2020.

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José isn’t convinced that large farms that switched to night harvesting have done it for safety reasons. “They prefer it because the fruit is firm at night,” he said.

He and Maryland farmer Hines agree on the superior quality of night-picked produce.

Mark Hines owns a small farm in Derwood, Md., where he harvests produce at night. He’s usually accompanied by his dog Cooper, whose job includes chasing off foxes, Hines said. Amanda Andrade-Rhoades/ The Washington Post

For Hines, the proof was in a watermelon that he harvested on a recent night and stored for a week. Red juice splashed onto the bed of his red pickup truck as he cleaved the fruit into wedges for a snack. The melon was crisp and sweet down to the rind. Hines said he can “taste the difference” in crops picked at night versus during the day.

The evidence goes beyond the anecdotal.

Produce picked at night probably has more water content than produce picked during the day, which is especially important for fruits such as grapes and blueberries. “You don’t want to harvest raisins,” said Colleen Doherty, a professor of molecular and structural biochemistry at North Carolina State University.

Perhaps even more important, plants, like humans, have a circadian clock that can tell the difference between night and day. That can cause them to taste different based on the hour they’re picked, she said.

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In a part of the school’s lab she calls “the secret life of plants at night,” Doherty has studied how plants produce certain compounds to defend against stress or insects. “The things that make the taste we like, a lot of those compounds are defense compounds,” she said.

Those substances require energy that plants can’t bear to expend during the heat of the day. But at night they convert sugars into antioxidants, vitamins and other metabolites – things that can affect a crop’s taste, texture and nutritional value.

“If the plant is timing those compounds at night when the pests are out, those will be good to harvest at night,” she said.

Picking a plant interrupts that process, causing some crops to pause their development at the time they were harvested, Doherty said. That means the watermelon Hines picked late at night was likely collected at its flavorful peak, its citrusy notes and smooth finish uniquely encoded to the very moment it was severed from the vine.

At the Maryland State Fair in August, Hines put his technique to the test. Three varieties of his watermelon won first prize in the farm and garden growing competition. So did his winter, Hubbard and butternut squash, picked from rows planted side-by-side with melons. His tomatoes, harvested hastily overnight this summer to keep them from bursting during pummeling heat and rainstorms, won in four categories.

Hines was crowned the fair’s grand champion, an honor reserved for the farmer with the most first place ribbons; 18 of his 47 entries won their categories. Nearly every winning crop, he said, was harvested at night.

Even his dahlias, plump like pincushions in plumes of white, purple and pink, took home first prize. The flowers are the last plants he tends to each evening, when their stalks stand straight up and their petals jut happily into the cool breeze.

“They show more vigor and health at night,” Hines said.

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