Water world

The many advantages of hydroponics

October 15, 2007

“In the winter, you want a good tomato so much that you start to think about buying a hothouse tomato,” wrote a commenter on the blog The Inadvertent Gardener this past January. “Thankfully, you were strong and resisted!”

Someday soon, hothouse tomatoes (tomatoes grown in greenhouses) may become not only harder to resist but unavoidable — and perhaps even delicious. The four largest U.S. greenhouse growers (located in Arizona, Texas, Colorado, and California) together make up 67 percent of domestic tomato production. All of them use hydroponic growing systems, in which tomato plants are grown with only water and nutrients. That’s right: no dirt required.

The hydroponic tomato first hit the U.S. market in the 1960s. By the 1980s, production was still limited; the tomatoes, often wan in color and dull in flavor, tended to be mealy or just plain hard. But beginning in the early 1990s, production of hydroponically grown tomatoes began to increase nationwide. Today, nearly 40 percent of the fresh tomatoes sold at retail around the country are hydroponic. In that time, overall U.S. tomato consumption has exploded; in the past 20 years, our chomping of fresh tomatoes has grown more than 30 percent, to approximately 20 pounds per capita per year. And as demand has increased, growers are trying to find ways to improve the flavor and texture of the hydroponic tomato.

Hydroponic lettuce grown in a greenhouse.

Tomatoes are merely the first in what growers hope will be a long line of commercially successful greenhouse-grown products. The sheer volume of tomato production worldwide overshadows all other hothouse vegetables, but greenhouse cultivation of herbs, cucumbers, and salad greens is continuing to expand. Much experimentation is also being done with strawberries, which are highly susceptible to soil-borne diseases that are no longer treatable with the toxic and ozone-depleting methyl bromide.

Customers focus mostly on greenhouse-grown vegetables in January, but availability isn’t the only motivator behind water-grown produce. Hydroponic growing appears to be the next big revolution in worldwide agriculture. Many believe it has the potential to feed large populations while using fewer chemicals, making better use of resources, worrying less about contamination, and harvesting much higher yields per acre.

Ditching the dirt

Flavor in a vegetable comes from a number of variables, including the plant variety, the conditions it’s grown under, the water and nutrients available to it, how mature it is at harvest, and how much time elapses between harvest and dinner. Much as the French tout terroir, the concept of tasting the place where something was grown or produced, soil in fact contributes very little to a vegetable’s flavor. All dirt does is give a plant a place to put down roots.

The two primary influences on the taste of hydroponic vegetables are plant variety and mineral content. Decades ago, the tomato varieties that growers first planted in greenhouses were selected not for flavor but for yield and uniformity. But as consumer values have shifted from appearance to taste, greenhouse growers are making a parallel shift. Many smaller hydroponic operations are already meeting the demand for better taste; Todd McWethy, for example, who owns McWethy Farms in Three Oaks, Michigan, is growing hydroponic tomatoes sought out by local chefs and shoppers.

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Last year, McWethy experimented with heirloom tomatoes, which are not particularly suited to hydroponic growing. “The heirloom tomatoes have been a big hit, although I was told they would not work,” he says. “The selling point was the beauty, especially as heirlooms are generally gnarly-looking things. Last year I couldn’t keep up with the demand. The quality really shines.”

Once they’ve chosen which varieties of plants to grow, hydroponic cultivators then manipulate nutrient mixes and growing conditions in order to obtain the healthiest plants and highest yields possible. Many growers also focus on producing tastier veggies. Nevertheless, “no one can produce a better tomato than in your back yard, or like grandma did,” says Gene Giacomelli, the director of the Controlled Environment Agriculture Center at the University of Arizona, Tucson. But that doesn’t mean, he adds, that hothouse tomatoes are necessarily a flavor disaster.

“They taste different, not bad,” Giacomelli says. “I won’t tell [consumers] what flavor is good or bad. That’s constantly being worked on.” Shoppers looking for product reliability, he says, can look to large commercial hydroponic growers to produce tomatoes with a consistent flavor. Maybe the flavor’s not quite what you were hoping for, he says, but at least it’s not a surprise.

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