An indoor agricultural evolution is in the making. That’s how some people see the surge of interest in growing leafy greens in greenhouses. No doubt about it, this approach to farming has increased dramatically in every corner of the country, even the South.

Not surprisingly, food safety has been one of the driving forces pushing indoor farming forward. Repeated recalls over the past several years  of romaine lettuce contaminated by the potentially deadly E. coli O157:H7 pathogen grown in the Yuma, AZ, and Salinas, Calif., regions have been enough to have consumers shying away from the popular lettuce and often other leafy greens. 

The most recent romaine outbreak just before Thanksgiving 2019, originating in the  the Salinas, CA, growing  area triggered yet more apprehensions about the lettuce. 

Advice to consumers from the CDC just after Thanksgiving solidified those fears. The Centers for Disease Control and Prevention advised consumers not to eat any romaine at all from the Salinas growing area until the outbreak was over — unless it was grown indoors. That outbreak has since been declared over.

In effect, the CDC was giving greenhouse-grown romaine a food safety thumbs up. 

“Hydroponically and greenhouse-grown romaine from any region does not appear to be related to the current outbreak,” said the agency on its December 2019 update about the outbreak in the Salinas growing area. It also noted that the lettuce might be labeled as “indoor grown.”

That came as welcome news to greenhouse growers — and also to buyers such as restaurants and other foodservice establishments that wanted to keep offering romaine to their customers. In many cases, demand outstripped supply.

“The more outbreaks we have, the more this trend will probably grow,” said Kirk Smith, director of the Minnesota Integrated Food Safety Center of Excellence, one of six centers around the U.S. designated by the CDC to strengthen the safety of the nation’s food system.

“There’s an upswing in interest in a big, big way,” said John Bonner, co-owner of Great Lake Growers. “I’ve seen consumers’ knowledge base about this increase. They like that it’s safer, fresher and lasts longer. It’s almost like ‘why wouldn’t you buy greenhouse salad greens.’ It’s a catalyst for change.”

Looking ahead, he believes indoor growing will happen on a bigger scale yet, although, as he quickly concedes:  “It might take 20 years. “But it’s coming,” he said.

Ryan Oates, founder and owner of Tyger River Smart Farm in South Carolina, sees hydroponics as “the future of farming” because there are so many advantages to it, among them conserving water and nutrients. Also, you can do it year round.

“We’ll see more and more of it,” he says in a video on Tyger River’s website. “You’ll see a lot of crops moving in that direction.”

As for food safety, Oates said the biggest advantage is that you’re growing inside greenhouses, which allows me to keep things really clean. “It’s a lot easier to do that than growing outdoors.”

Because indoor growing is a controlled environment, the farmers don’t have to deal with wildlife, domestic animals, and birds flying overhead — all of which can contaminate the crops.

Bendon Kreieg, a partner and sales manager at Revol Greens said that the government’s advice on this is definitely helping.

“We are seeing an uptick in demand from retailers and restaurants because it has such a major impact on their business when they suddenly can’t serve salads,” Kreieg said.

A spokesperson for Gotham Greens, a New York-based operation with three locations in New York City, two in Chicago, one under construction in Baltimore, and more underway in other states, told a reporter that the farm has been selling out of its greenhouse grown leafy greens every day.

Janeen Wright, editor for Greenhouse Grower magazine, said that although the publication has always covered greenhouse cultivation of vegetables — as well as ornamental and nursery plants — it has been covering the vegetable side of the industry a lot more recently. 

Referring to the romaine recalls in 2018 and 2019, Wright said growers have told her that the recalls have really helped them “get a name for themselves.” 

“Unfortunately, all of these recalls will be a concern for consumers,” said Scott Horsfall, CEO of the California Leafy Greens Marketing Agreement. “The plantings (for romaine lettuce) are down but there’s still demand for it.”

As for whether greenhouse lettuces and greens will overtake field grown lettuces and greens, Horsfall doesn’t think that will ever happen especially considering the vast quantity of the crops that are field grown.

“I certainly haven’t seen concerns about this on the production side of the industry,” he said.

Even so, greenhouse farming is making important strides. During the 52 weeks ending Sept. 29, 2019, sales of produce marked as greenhouse grown increased 7.6 percent and sales of produce described as locally grown increased 23.2 percent, according to the latest Fresh Facts on Retail report from United Fresh Produce Association, a trade organization.

The “local” aspect is important because greenhouses are located in many regions of the country and therefore lettuces grown in them don’t have to be shipped across the country from Yuma and Salinas during the winter months. Because the lettuces and greens can be grown year-round they have an extra “local” advantage.

In the winter, more than 90 percent of the lettuces and greens in the United States are grown in the Yuma, AZ, and Salinas, CA, growing regions. Salinas is often referred to as America’s “Salad Bowl,” and Yuma, the “Lettuce Capital of the World.” 

Yuma is home to nine factories that produce bagged lettuce and salad mixes. Each of these plants processes more than 2 million pounds of lettuce per day during Yuma’s peak production months, November thru March.

“It’s a long way from Yuma to Cleveland,” said John Bonner, co-owner of Great Lake Growers based in Ohio. He pointed out that the difference in distance between the two is part of why the lettuces and greens don’t arrive in stores and restaurants as fresh as they do when they arrive in establishments that are near his greenhouses.

In addition, consumers’ interest in locally grown food has risen dramatically. Some are even referring to the lettuces from the Yuma and Salinas growing regions as “corporate lettuce.”

Controlled-environment agriculture, another way to describe greenhouse cultivation when done according to certain standards, is helping grow the local food market. The USDA estimated they would reach $20 billion in sales by 2019, up from $12 billion in 2014.

Peace of mind about food safety is another important part of the puzzle when it comes to increased demand for greenhouse produce. A spokesperson for Gotham Greens agrees that the food safety scares originating from large-scale farms have buyers looking for lettuces and greens grown on a smaller scale and closer to home.

For the most part, greenhouse growers don’t use pesticides or other harmful-to-humans chemicals on their crops, and many follow strict organic standards.

Greenhouses: The indoor option
When you think of farming, you think of soil.

In contrast, most indoor farming — or greenhouse growing — does away with soil. Instead, crops are grown hydroponically in controlled sterile environments.

In most hydroponic systems, plants are grown in nutrient-rich water, instead of in soil. The water is rich in phosphorus, nitrogen and calcium.  

At the top of the list when it comes to the advantages of hydroponics is that it requires only 10 percent to 16 percent of the same amount of water to produce vegetables as conventional irrigation systems in outdoor farming. That’s because water in a hydroponic system is captured and reused, rather than allowed to run off and drain into the environment, according to indoor growers.

That’s especially important in areas where water is scarce. In California, for example, conventional outdoor agriculture accounts for 80 percent of total water use. 

The Food and Agriculture Organization of the United Nations has been implementing hydroponic farming in areas of the world beset with food shortages. There are currently ongoing projects to establish large hydroponic farms in  Latin American and African countries. 

NASA has even gotten into the act. In the late 20th century, physicists and biologists put their heads together to come up with a way to grow food in space. They began by growing plants on the International Space Station, opting for hydroponices because it needs less space and fewer resources — and produces vastly higher yields — than growing in soil.

In 2015, astronauts actually dined on the first space-grown vegetables.

Although there hasn’t been much government funding for research on greenhouse agriculture, the U.S. Department of Agriculture (USDA) recently gave Michigan State University $2.7 million for research into indoor growing techniques. In addition to that, the researchers have won industry grants bringing the project total to $5.4 million.

A focus of the research will be gathering information on the economically viability of greenhouse growing. 

Food safety and hydroponics
Food-safety scientist Kirk Smith, who has been leading investigations into food safety outbreaks for many years, said one thing that has emerged in outbreak investigations is that E. coli contamination in produce almost always comes from irrigation water used on fields. 

Making things more complicated, the Food Safety Modernization Act, signed into law by President Obama in 2011, has yet to establish definitive standards for agriculture water quality.

Leafy greens, including romaine lettuce, are chopped and washed in huge volumes as part of the bagged salad production process. This allows bacteria on one head of lettuce to be spread to hundreds or thousands of bags. Photo illustration

Another challenge beyond irrigation is washing the field-grown produce after it’s been harvested. That step is when using clean water is especially critical, otherwise contamination from one head of lettuce can spread to the rest of the produce in the factory. 

Food safety scientists warn that even though a package of bagged salad greens that have been field grown says the greens have been triple washed, that doesn’t mean there’s no chance of some of the greens being contaminated. In the case of E. coli, for example, the pathogen can hold on tight and resist being washed away.

In contrast, most greenhouses use municipal water and many wash their greens with running water instead of dunking them into a tank. Some don’t even need to wash them since they never come into contact with any water simply because it’s the roots that are being watered, not the leaves.

Bonner said that his farm makes sure the water it uses is clean and tested.

“We have extensive testing for E. coli,” he said. “We’re monitoring it every second.”

As for farmworkers, Bonner said one part of the audit his company goes through is dedicated strictly to food safety and farmworkers.

“We’re in a building, and the bathrooms are right there,” he said. “And we have handwashing sinks all over the place.”

Because most greenhouse farms grow food year round, there’s no need to rely on a seasonal workforce. In Bonner’s case, the company works with a local Amish community whose young people are eager to work for his company.

In other cases where greenhouses are located in cities, farmworkers live in city apartments. This stability in housing and location gives greenhouse farms a stable workforce.

Nothing’s perfect
Of course, there’s no guarantee that a foodborne pathogens will never occur in greenhouse settings. 

And because most lettuces and greens are eaten raw, they don’t go through a “kill step” to kill pathogens that might be on them.

Many of the foods popular with indoor growers — lettuces, sprouts, fresh herbs, microgreens and wheat grass  — carry the highest risk of outdoor produce, some of that because it grows so close to the ground.

That’s why prevention is so important, the greenhouse growers say. This would include paying attention to how water, tools, animal intrusions, pests and human handling plays a role in preventing food from being contaminated. 

What is it about romaine?
Romaine lettuce is “particularly susceptible” to E. coli, said Keith Warriner a University of Guelph (Canada) professor, in an interview with City News.

During research, Warriner said, scientists discovered that out of all the lettuces, E. coli likes romaine the best.

A study the food safety scientist conducted showed that extracts of romaine lettuce actually brought E. coli out of a dormant state when it’s in the soil. Once out of its dormant state, which can last up to a year, it can flourish.

The FDA included this Google Earth view in its memorandum on the environmental assessment related to the E. coli outbreak. It shows a section of the Wellton canal that is adjacent to a 100,000-head feedlot. Portions of this image (in gray) were redacted by the government. However, the FDA report says the image shows the locations of the feedlot, sites where E. coli-positive water samples were collected, unlined sections of the irrigation canal, and a retention pond at the feedlot. The water in the canal flows from west to east.

Warriner describes several reasons why romaine is particularly susceptible. To begin with, the crop is mostly grown in Arizona and California. That’s cattle country, and irrigation water used on the romaine fields can become contaminated with bacteria from animal feces via water runoff and dust in the air.

Added to that, because both states have hot weather, the lettuce needs an abundance of water.

Warriner pointed out that even though other leafy greens like spinach and kale are also grown in the same areas, and under similar conditions, their leaves are, as he described them, “as tough as nails.”

Romaine is considered the most nutritious lettuce when compared to red leaf, green leaf, butterhead and iceberg.

Although it’s low in fiber, it’s high in minerals, such as calcium, phosphorous, magnesium, and potassium. It’s also naturally low in sodium. Another plus is that romaine lettuce is packed with Vitamin C, Vitamin K, and folate. And it’s a good source of beta carotene, which converts into Vitamin A in the body.

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