Growing Hydroponic Strawberries

Strawberries are one of the best fruits for growing hydroponically. Not only do they taste better than most traditionally grown strawberries, they respond well to nutrient solution and can be grown at an elevated height. This has been a huge benefit for commercial growers as the picking rate is much faster and less tiring, while the cultivation of plants is easier.

At the University of Arizona’s Controlled Environment Agriculture Center (CEAC) and at Ohio State University (OSU), Dr. Chieri Kubota (who worked at CEAC and is now at OSU) decided to add sustainable strawberries to her greenhouse repertoire to research growing them hydroponically.

Growing up in Tokyo, she savored fresh strawberries in the winter, a possibility she once referred to as “an unusual cycle against nature.” She thought, “If fresh berries can be winter grown in Japanese greenhouses, why not in CEAC gardens?” Her ahead-of-its-time thinking paved the way to successful production in Arizona’s blazing triple-digit summertime temperatures and, conversely, she refers to Canadian greenhouses (like Mucci Farms in Ontario with a humble beginning in a wooden frame poly greenhouse in the early 1960s) as a leader in the challenge of year-round production in cooler climates.

Read also: The Art of Growing Hydroponic Grapes

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Kubota and fellow CEAC researcher Mark Kroggel designed an under-the-bench fogging system that helped by intermittently (three times an hour, for five minutes over three hours) spraying the crop in a greenhouse bathed in diffused light.

Because nighttime temperatures are key for large and flavorful berries, they kept an optimum evening temperature at 50°F (anything higher increased acid content and made the fruit tarter). “The size and flavor of strawberries are more driven by the type of cultivar and the temperature than they are by nutrition and irrigation,” Kubota says.

Nestled in Styrofoam troughs suspended waist-high in her greenhouse are long rows of lush green leaves protecting bright red berries. “Hydration is important because if the water doesn’t reach the leaf tips at night, they get tip burn, an unsightly calyx at the base of the berries,” says Kubota.

Kubota ended up at Ohio State University where she is now a professor of horticulture working in a 1,200-square-foot greenhouse studying the effectiveness of LED lighting on various food crops, particularly strawberries and tomatoes.

Because there is a paucity of information about growing greenhouse strawberries, both the CEAC discoveries and the OSU findings are important to the emerging hydroponic berry industry as a whole.

Kubota is a strong proponent of indoor strawberry growing. Prior to her departure from CEAC, she emphasized: “In a greenhouse, both aerial and root zone environments can be maintained in an optimum range that maximizes plant productivity — less water and nutrients required, no fumigation or pesticides needed, humidity and temperature controlled, and there’s less stoop labor required to grow and harvest.”

Read also: A Beginner’s Guide to Growing Berries in Containers

Although it’s a subjective interpretation, her greenhouse berries taste better than off-the-shelf grocery store varieties. “Supermarket strawberries look good cosmetically but flunk the flavor test as growers trade off taste for extended shelf life,” she said. “The goal is to establish off-season hydroponic production of a value-add, year-round crop that will actually taste good.”

In an interview with the University of Arizona News Bureau, Kubota explained her experiments with optimal growing conditions were aimed at producing sustainable, off-season, hydroponic berries, slow-growing them because they accumulate more Brix content (sugar) in the fruit. “Most traditional greenhouse crops are predictable, but not strawberries — although they are adaptable,” she said.

Research has shown strawberries prefer a daytime temperature range of between 65-75°F, then get cooled down at night to maintain fruit quality. A previous Maximum Yield article (“How to Grow Four Types of Berries Hydroponically,” August 2017) noted hydroponic strawberries were “relatively easy to grow” — if flowering, pollination, and fruiting all went according to plan — but their counterparts, like blueberries and raspberries, grown in soilless greenhouse environments “require more in the way of time and effort.”

Healthy strawberries stay healthy with at least six to seven hours of daily sunlight and a pH between 5.8-6.2.

The CEAC scientists are currently planting California cultivars bred for yield and disease resistance — what their growers called high-maintenance/low-yield, but very flavorful varieties. Coordinator Dr. Gene Giacomelli says: “We’re growing new cultivars now and when they reach maturity this fall, we’ll start monitoring them through the winter production cycle, looking at number and quality of fruit and its sugar content. We’ll be looking at two things, how different cultivars respond and their root zone growth.”