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Sep 15, 2023

Lorenzen Family Produce gleans from garden year

The geo-air greenhouse as Lorenzen Family Produce near Wakefield, Neb., is 132

The geo-air greenhouse as Lorenzen Family Produce near Wakefield, Neb., is 132 feet long total, with the grow room measuring 120 feet.

Tantalizing red tomatoes. Crispy, fresh lettuce leaves. Artichoke globes larger than your fist. Bright, yellow lemons plump with juice.

No, this is not the produce section of your local grocery store. You have just stepped into the geo-air greenhouse at Lorenzen Family Produce near Wakefield, Nebraska.

The greenhouse is teeming with vegetation of all kinds. A passion fruit hangs low as you enter, just setting flower buds on its expansive branches. Grapes trellis the walls, and pineapple tops rise up from pots along the walkway. From houseplants such as Christmas cactus to exotic finds like the South American Yacón, every plant entices the eyes or taste buds.

"I am constantly playing in here," said Ryan Lorenzen, who built the greenhouse in 2019. Since then, he and his family have been propagating plants and eating fresh produce year-round. They also give tours to others interested in the concept.

You could easily miss the 132-foot long structure, even though it is right next to Highway 9 just two miles south of Wakefield. The majority of the greenhouse is buried underground and covered by translucent polycarbonate paneling to allow sunlight to filter in to the plants growing below.

Ryan Lorenzen, right, learned about Russ Finch, left, and his geo-air greenhouse in 2018. Finch designed and built the original geo-air greenhouse in 1992. Allen Bright, center, has taken over the business and continues to sell geo-air greenhouse kits.

Lorenzen has been a gardener his entire life. In 2018, he saw a segment on Nebraska Public Media about Russ Finch and his geo-air greenhouse. The geo-air system provides warmth by capturing geothermal heat radiation, then circulates the warm air through underground tubes. Burying the structure partially underground augments the geothermal benefits.

Finch built the original geo-air greenhouse in Alliance in 1992. Unfortunately, the famous "Citrus in the Snow" greenhouse did not survive under the weight of the 10-12 feet of snow that fell in the Alliance area this past winter.

After seeing Finch's greenhouse in person, Lorenzen said he was hooked. He had to convince his wife Rhonda about the idea, but his daughters Hannah and Sarah were completely on board.

He planned to build the greenhouse after retiring, but his daughters persuaded him to pursue the project sooner. So in 2019, Lorenzen rented the equipment to move dirt and dig trenches.

Finch's company, Greenhouse in the Snow, sells geo-air greenhouse kits. They fabricate the materials and bend the metal frames so all the Lorenzens had to do was assemble the pieces. He and Sarah put together 80% of the greenhouse.

"It goes together like a big erector set," Lorenzen said, showing how the twin-walled panels overhead are sandwiched together. Only four screws are needed to attach the 6-foot wide panels to the metal frame underneath.

"We started construction in June of 2019. We finished by the fall equinox and started planting, then growing through that first winter," said Lorenzen.

The inside of Lorenzen's geo-air greenhouse is dug at different levels to accommodate all sizes of trees, fruits, houseplants and vegetables.

The greenhouse is divided with an entrance room and a grow room. The grow room measures 120 feet long.

"At the time we built ours, we had the longest growing room," Lorenzen said.

Grow rooms of 150 feet are now being constructed for commercial operations. The smallest size offered that is efficient and cost effective is 54 feet long.

The entrance room acts as a buffer in extreme cold. Even when the outside temperature is -20 F, this room is still 20 F, said Lorenzen. Pointing to the tubs of robust rosemary, parsley and sage in his entrance room, he added, "These have been in the entrance room all winter. Plants are hardier than we think."

Geo-air systems circulate air through tubes using a 10-inch squirrel cage fan, similar to those in a household furnace. Traditional geothermal greenhouses use water as a conductor of heat, requiring compressors and other equipment. Geo-air systems have a lower initial cost and long-term maintenance than geothermal greenhouses, said Lorenzen.

The geo-air design is simple. For the heat circuit, loops of field tile are buried no less than 8 feet in the ground. These act as geotubes to provide heat in the winter. In Lorenzen's greenhouse, 22 tubes are buried underground in a 250-foot loop. There is one tube for every 6 feet of overhead panel.

A separate series of exhaust tubes require two tubes for every six-foot panel. These measure only 40 feet long.

The intake tubes, considered the "air conditioning" element, are one-third the length of the geotubes.

"Believe it or not, in the winter time you are more concerned about cooling than heating," Lorenzen said. Newer designs are incorporating more intake tubes to increase air circulation, he noted.

To heat the geo-air greenhouse when the temperature inside reaches 50 F, air circulates through a series of field tile buried underground.

Because fresh air is so important to maintaining proper humidity levels and temperature within the greenhouse, the doors and windows are open as much as possible.

"When you close the greenhouse up in the fall, it turns into a terrarium. All the moisture stays in here," said Lorenzen.

Condensation on the panels rains on the plants below, recirculating the moisture and creating a humid climate. Not realizing this his first winter, Lorenzen "overwatered way too much." As a result, white mold overtook the greenhouse and plants. He is still dealing with the effect but learned a valuable lesson about how air-tight his geo-air greenhouse truly is.

He is also finding a balance in adequately watering the plants. Last winter, he went two months without watering during winter. In summer, he typically waters on Sundays.

The unique climate within the geo-air greenhouse lets Lorenzen grow plants that would not normally survive in Nebraska. The heat inside would prevent native crops from producing. He has found that plants suitable for zones 7-9 thrive in the geo-air greenhouse year-round.

Ryan Lorenzen likes to experiment growing different plants in his greenhouse.

Because of this, his orchard inside the greenhouse does not contain fruit trees typical to Nebraska. Thirteen trees span the 120-foot length, planted in the trench running the middle of the greenhouse. These include pomegranate, banana, sweet cherry (Bing, Rainier and Black Tartarian grafted together), mango, avocado, peach, lemon, mandarin, lime and grapefruit.

Within this underground space are also trellised plants. Tomatoes grow up, down and back up 8-foot tall cages. Some are nearing four years old.

"I have plants that have been growing since 2019. They just keep growing," Lorenzen said. He prunes them annually around February or March.

The greenhouse climate has two growing seasons in line with the two equinoxes. Lorenzen finds that the seasons within his greenhouse coincide perfectly with when Nebraskans are harvesting their own gardens. For example, the greenhouse is too warm to put on tomatoes during summer, but that is when outside gardens are abundant. When his crop is ready in early spring and late fall, people are eager for a fresh tomato.

The Meyer lemon tree is the "quintessential tree" at Lorenzen Family Produce. It produces large, juicy lemons.

Grow beds run along the two outer walls of the greenhouse at ground level. By standing on the walkway that is dug down into the ground, the Lorenzens do not have to bend over to weed or pick produce in the grow beds.

Lorenzen showed a patch of carrots planted in the grow bed two years ago. Healthy green tops were nestled in the black soil. He said the geo-air greenhouse becomes a walk-in cooler during winter, so there is no need to dig up the carrots sooner.

"If you need three carrots, you come out and harvest them," Lorenzen said.

A thermostat will turn on when temperatures inside the grow room reach 50 F. Two propane heaters add supplemental heat to the geo-air system. Lorenzen uses the heaters an average of three weeks out of the year when temperatures dip dramatically.

"As long as it's not sub-zero, we can maintain temperature just by circulating ground heat," he explained.

Surprisingly, Lorenzen wants a cool period for his plants inside the greenhouse.

"We let it go through the seasons and get cold," Lorenzen said. "The plants actually need that."

He said a traditional greenhouse shuts down in the winter because it is too costly to maintain a climate in which plants can survive. By utilizing the earth's natural heat, the geo-air greenhouse can run all year at minimal cost.

Lorenzen monitors electrical use through a meter dedicated to the greenhouse. Power usage peaks in January at an average of $1.72 per day. The lowest period is May at $0.48 per day. In summer, power usage is "next to nothing" since the windows and doors are open for natural ventilation.

His next project is to install solar panels to make the greenhouse a self-sufficient unit.

Passion fruit blossoms greet you when you first enter the grow room of the Lorenzen geo-air greenhouse.

Lorenzen considers the geo-air greenhouse his retirement plan. A land surveyor by trade, he recently retired from the U.S. Bureau of Land Management, where he worked as a cadastral land surveyor.

Feeding his family is Lorenzen's main goal with his greenhouse, but excess produce is sold "farmers market style." He would like to start a cooperative to provide a fresh food source for local people year-round.

"We live in some of the best growing country in the world, but all our food comes from overseas," Lorenzen said. Plus, it "tastes so much better when you grow it yourself."

Lorenzen encourages anyone interested in learning more about the geo-air greenhouse to come for a tour. Contact Rhonda at 402-369-0410 or visit their Facebook page, Lorenzen Family Produce.

Lorenzen has visited other gardeners with geo-air greenhouses around the U.S. Each grow room is set up differently. Some have shelves of microgreens, while others are dedicated to growing fruit trees. Still others focus on vegetable production.

The grow room function is limitless, but the structure's main design must be adhered for efficiency in heating and cooling.

"There's a method to the madness in how it's shaped, all due to air volume," Lorenzen said.

Find more information about geo-air greenhouses at https://greenhouseinthesnow.com/.

Garden-fresh produce at your fingertips in the dead of winter may seem like a dream, but garden enthusiasts in all climates can have this luxury.

"Nothing is better than coming out here when it's -20 F and smelling the dirt and seeing the green plants," said Lorenzen. "It's good for the soul."

Reporter Kristen Sindelar has loved agriculture her entire life, coming from a diversified farm with three generations working side-by-side in northeastern Nebraska. Reach her at [email protected].

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Agriculture Reporter

Reporter Kristen Sindelar has loved agriculture her entire life, coming from a diversified farm with three generations working side-by-side in northeastern Nebraska. Reach her at [email protected].

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