In Minnesota, we’re weeks away from the spring thaw that signals crops are ready to be planted outside, yet John Skarie’s tomato plants—a warm-weather crop that can’t survive frost—have already been germinating for two months. Skarie began watering his seeds in January and moved the plants into his quarter-acre Detroit Lakes greenhouse in February. 

“You control exactly what those plants get and how much they get, which is important because, in the greenhouse environment, you want to have maximum ability for production,” says Skarie, a third-generation farmer.  

Members of the Skarie family and Lakeview Greenhouses standing inside a delivery truckAfter a germination period of 90 to 100 days, Skarie will be able to harvest clusters of tomatoes weekly from his 3,000 plants, totaling more than 100,000 pounds of tomatoes throughout the duration of his growing season, which ends at the beginning of December.  

This extended growing season is made possible by controlled environment agriculture and a process known as hydroponics. According to the U.S. Department of Agriculture, this technique for growing plants, using a water-based nutrient solution rather than soil, can include an aggregate substrate, or growing media such as vermiculite, coconut coir or perlite.  

“With outdoor garden farming, which we do as well, you’re more limited to what nature is giving you,” Skarie says. “Is it a cold day or a warm day? Is it humid or is it windy? Those things affect you, and you have to just roll with it. But the greenhouse allows us to keep that perfect environment.”

The Hype Around Hydroponics

While hydroponic growing is becoming more popular, it’s not a new concept. One of the earliest examples of “water gardening” dates to 600 BCE, when the ancient city of Babylon’s lush hanging gardens thrived because of what is believed to be a water pulley system.  

“‘Hydroponics’ is a Greek word,” says Dr. Nathan Eylands, an assistant professor in the University of Minnesota’s Department of Horticultural Science. “When you break it down, it’s ‘hydro,’ meaning water, and ‘ponic,’ meaning working. So it’s just ‘water working.’”

There are many different types of hydroponic growing methods (see the sidebar on page 18) but one of the simplest—especially for small-scale growers—is deep water culture. With this method, “plants are suspended above a tank of water and the roots hang into the container where they absorb water and nutrients,” explains an informational guide put out by the U of M Extension.

Another common system is nutrient film technique: Plants sit in a shallow trough sloped at a subtle gradient, and a thin film of water constantly rolls across the root surface. The water is collected at one end and is recirculated to the top of the reservoir. 

Hydroponic systems like these are beneficial for plants because oxygen, pH levels, temperature and lighting can all be controlled by the grower.  

“It creates the perfect environment for that plant,” Dr. Eylands says. “When we look at a greenhouse using hydroponics, compared to the same square meter outdoors in a field, you can grow probably 10 times the amount of food in one year.” 

This yield increase is crucial as world leaders consider how to feed the nearly 10 billion people the United Nations predicts will inhabit our planet by 2050, necessitating a 56% increase in food production—a goal unlikely to be reached by traditional agriculture output alone.  

High on the list of potential solutions is hydroponic growing, which also has a myriad of environmental benefits. Case in point: Soilless growing means an elimination of the soil-borne pathogens you might find in a field. 

“A part of the benefit of hydroponic growing is trying to be more sustainable. Hydroponics only uses about 10% of the water you would use in a traditional field,” Dr. Eylands says. Plus, “salts for fertilizer are mined out of the ground, so the less mining we do, the better off we’re going to be.”  

From Greenhouse to Grocery Store

Anything can be grown hydroponically, but it’s most economically feasible to focus on crops that are high-value and fast-maturing—causing Skarie and his father, Don, to start with tomatoes in 2000. 

After half a century of turkey breeding on the farm Skarie’s grandfather established in 1953, Skarie and Don were intrigued by this unique operation model that would allow them more control over their profits and the greenhouse-to-grocery store distribution of their crops. 

“Tomatoes were the thing that we could use to get into a market,” Skarie says. “Living in Minnesota, you don’t really get quality tomatoes in your grocery store. They’re coming from Mexico or California, and they pick them before they’re ripe. So tomatoes were considered one of the better things to grow and develop a market with because people really want good tomatoes.” 

While tomatoes make up 90% of Lakeview Greenhouses’ business, Skarie also hydroponically grows lettuce, peppers, cucumbers and herbs like basil and cilantro. In addition to selling their tomatoes to grocery stores and restaurants, some of their crops are used by Skarie’s mother, Pam, at her catering company, Lakeview Catering. They also vend at a local farmers market, offering produce, salsas and infused salts to customers willing to pay a premium for higher-quality, freshly picked products.

  Skarie hopes more farmers will begin growing hydroponically, whether on a small or commercial scale. “We started big with the idea that this was going to be a family business,” says Skarie, whose wife Lisa and their five kids also assist in the greenhouse. “But I know a lot of smaller growers who just like to sell at markets on the weekends or who are selling out of their homes, which is great. The more people who do this, the better. The more local foods that are available to everyone, the better we all are.”

How Hydroponic Growing Works

There are many ways to execute hydroponic growing, but these are the most common methods, according to University of Minnesota Extension.

Deep water culture: This is the simplest method for hydroponic growing—especially for small-scale growers. Plants are suspended above a tank of water and the roots hang into the container where they absorb water and nutrients.

Ebb and flow: Plants are grown in a substrate-filled tray with either a porous bottom and a nutrient reservoir is placed directly below or a drain connected to the reservoir via tubing. Using a pump, water is pulled from the reservoir and deposited into the growing tray, where it drains through the substrate before returning to the reservoir.

Nutrient film: Plants sit in a shallow trough sloped at a subtle gradient, and a thin film of water constantly rolls across the root surface. The water is collected at one end and is recirculated to the top of the reservoir.

Drip system: Similar to the nutrient film technique—but instead of water flowing through a trough, it goes through a hose with holes spaced in accordance with your plants.

What You Need to Get Started

Hydroponic growing isn’t just for experienced growers. Anyone can participate in water gardening with the right materials. “There are very easy and cheap ways to get started if you’re willing to do some construction yourself,” says Dr. Nathan Eylands, an assistant professor in the University of Minnesota’s Department of Horticultural Science. “And YouTube is fantastic. There are some great videos from people who want to put instructional materials out there.” Here’s what you’ll need for the deep water culture setup, the simplest small-scale hydroponic growing method.

Any clean, food-safe container with a lid will work. How large it is should be determined by the mature size of the plant you’d like to grow.

Net pots and substrate
Perlite, hydroton, pumice, gravel, coconut coir and Rockwool are some common substrates that can replace soil in the net pots. 

In the summer, you can grow hydroponically outside on your sun-exposed balcony or patio. Inside, use supplemental lighting in the form of LED or fluorescent bulbs. 

pH test strips
Plants do best when growing in water with a pH of 5.4 to 7. Every few weeks, test your water as it comes out of the tap and after you add fertilizer. 

Liquid or dry fertilizer can be used to supply hydroponic plants with the nutrients they need to grow and develop properly. 

Provide your plant oxygen through passive aeration by only partially submerging your net pots, or get a porous airstone connected to an external pump, which pushes oxygen through the stone to release air bubbles.