Having a “hands-off” policy – where no human hand touches the greens – is one way hydroponic growers keep crops safe.
Photo courtesy of Little Leaf Farms

by Tamara Scully

Chances are that the lettuce or other leafy greens eaten by the majority of consumers aren’t grown anywhere near their homes, unless they live in Arizona or California. According to recent data from the USDA’s Agricultural Marketing Service, Arizona and California dominate the market for shipped romaine. In 2019, over two billion pounds of romaine lettuce were shipped from these two states.

Growing salad greens year-round in the controlled atmosphere of a hydroponic greenhouse, and marketing that crop regionally to area supermarkets, is an emerging trend, particularly in the Northeast and the northern tier of states along the Great Lakes, where cold weather limits the growing season and fresh produce travels long distances to store shelves.

No Soil Growing

In hydroponic systems, the nutrition needed for plant growth isn’t substrate-based, but is fed to the plant through a nutrient solution and can be precisely maintained. Hydroponic growing media and nutrient solutions can readily be renewed, making problems such as pests, diseases and fertility imbalances less likely and easier to correct than when growing in soil.

Little Leaf Farms in Devens, MA, opened in 2016 and became one of the largest growers of hydroponic baby greens, now with 10 acres of lettuce cultivated under glass. Transparency, food safety, freshness, renewable resource use and growing practices which don’t include chemicals are all important parts of their mission. Their product is billed as “the local lettuce locals love.” They aim to provide fresh greens to consumers across New England, within a day’s drive of their greenhouse.

Little Leaf’s head grower, Pieter Slaman, is a fourth-generation farmer with years of experience growing under glass in his native Netherlands, where he managed the largest organically certified greenhouse in the world, growing crops in 25 acres of soil under glass.

BrightFarms is another rapidly growing greenhouse-based leafy greens grower, utilizing hydroponic systems in several locations throughout Pennsylvania, Ohio, Illinois and Virginia, plus a recently added location – their largest yet at 280,000 square feet – in North Carolina. They distribute to area supermarkets, with product from each individual greenhouse shipped directly to stores in their coverage region.

Like Slaman, Denise DeRue, the former head grower at BrightFarms’ inaugural and smallest location in Yardley, PA, is a firm believer in the niche the hydroponic greenhouse-grown salad greens play in the local food system.

“Our baby leaf greens are grown year-round and are offered in local supermarkets, so we’re able to reach a larger group of consumers. Unfortunately, a lot of local farmers can’t compete with the high consumer demand, so we’re filling that gap to bring local produce to more people year-round. We consider ourselves competitors of long-distance growers, not local farmers,” DeRue explained.

Trending Now

By building their salad greens model on local distribution to supermarkets, along with an emphasis on reducing their brand’s environmental footprint, these and other hydroponic growers are capitalizing on the desire for convenience and locally grown food. The economies of scale inherent in the greenhouse production of salad greens, where large volumes of greens are grown quickly and continually in a controlled environment (about 25 days for baby lettuce or 45 for head lettuce at Little Leaf Farms), helps to keep the price competitive with shipped-in field-grown alternatives. Their model meets many of today’s mainstream consumer needs.

“One of the main benefits of our system is the quick growth cycles. As a result, it is difficult for pests and diseases to get established in our crops, which gives us the ability to be pesticide-free,” DeRue said. “Our production varies season to season due to many factors such as what varieties we are growing and how much natural light we are getting. We are, however, able to maintain fairly consistent yields as a result of the controlled environment.”

DeRue oversees the production of 500,000 pounds of greens annually from the 56,000 square foot (about 1.25 acre) greenhouse. Other BrightFarms greenhouses are at least twice as large.

At Little Leaf Farms, an automated system moves the mobile gutters, in which plants grow, to keep the plant density maximized while minimizing any shading as the plants grow. The density of production inside their hydroponic greenhouses means that Slaman is constantly monitoring the growing environment to minimize stress and maximize plant growth.

“We never use any chemical pesticides, herbicides or fungicides on our crops. Biological control is something that you need to constantly monitor and scout for daily,” Slaman said. “We have never experienced any disease or pest issues that have negatively impacted our crops, and we strive to keep it that way.”

Sustainable, Too

These hydroponic production systems come with other environmental bragging rights. At Little Leaf Farms, the water is 100% recaptured rainwater, which is recycled through the system. At BrightFarms, they estimate that they use 80% less water than it would take to grow the same amount of greens in the field, and much of the water comes from reclaimed rain and snow melt. Little Leaf Farms heats with natural gas and recaptures the carbon dioxide generated by the heating system so the plants can use it, enhancing photosynthesis.

Both BrightFarms and Little Leaf Farms utilize natural sunlight, making them unlike other types of controlled environmental growing operations, where artificial lighting keeps plants alive in warehouses, containers and other locations.

“It’s important to note that we’re big believers in the sun, and that our system is based on maximizing natural sunlight,” Slaman said, although at Little Leaf Farms they do supplement with some LED lighting during the low light winter months in New England.

But what about that soil? Both growers promote the fact that they aren’t eroding any topsoil in the production of their crops. Heavy metals can be an issue in field-grown greens, Slaman said, and Little Leaf Farms monitors them via monthly tissue sample analyses. They can readily modify this, or any other concern encountered, in the controlled greenhouse-growing environment. In field-grown systems, modifications of soil properties are much more difficult.

“This is an area where we have a significant benefit, as a traditional land farmer can’t change the environment that his or her crop is living in to make it better for them,” Slaman said.

The sunlight, humidity and temperature outdoors have some impact on the indoor growing climate. Growers monitor and adjust the greenhouse’s controlled environment to maintain heat, humidity, air pressure and carbon dioxide levels needed to optimize plant growth. They also monitor nutrient levels, scout for pests, check on germination and plant growth and perform the seeding, transplanting and harvesting of crops.

“These are all things a traditional [soil-based] farmer might do as well,” DeRue said. “We rely on sun, water, air and nutrients just like a traditional farmers does.”

BrightFarms also promotes the safety and cleanliness of their greens by focusing on the lack of soil – and therefore soil contaminants such as E. coli that plagues the field-grown leafy greens shipped from across the country – which keeps their leafy greens safe and ready to eat right from the package, with no washing required.

Having a “hands-off” policy – where no human hand touches the greens – is a selling point used by both operations.

Whether consumers will fully embrace hydroponic greenhouse growing as a legitimate system of food production that solves some local food system dilemmas remains to be seen. Greenhouses, whether soil-based or hydroponic, may solve a portion of that on-demand dilemma for local food systems.