Frost coats the frozen ground outside as Ryan and Rhonda Lorenzen mill about in their greenhouse two miles south of Wakefield. Fresh dirt stains the knees of their jeans. Saccharine citrus trees permeate the air with their fragrant blossoms.

The 132-foot-long structure overflows with thriving plants in balmy, 50-degree warmth. In the midst of winter, this geothermal greenhouse has been the Lorenzen family’s oasis of year-round fresh produce since 2019.

Thirteen tree varieties grow from the center aisle. Plump red pomegranates weigh down a branch. Mangos turn from ash-green to their rainbow hue. Citrus trees bear fruit – mandarin oranges, Meyer lemons, limes and grapefruits.

At ground level, pineapples sprout spiky stalks and line the walkway at the greenhouses’ entrance. Plants frame the walls of the grow room, from typical heartland crops such as tomatoes, onions and garlic, which will eventually grow outdoors, to exotic, tropical plants like avocados or passion fruit.

 

The Lorenzens’ journey into year-round growing began over six years ago. As Ryan approached retirement as a land surveyor for the U.S. Bureau of Land Management, he sought a meaningful way to fill his time. In 2018, he came across a 3-minute television program on Russ Finch, the original creator of the geo-air greenhouse in 1992 (featured in “Citrus in the Snow,” November/December 2021). Intrigued, Ryan traveled to Alliance to learn more about Finch and his partner Allen Bright’s state-of-the-art system.

Finch’s dedication to producing his own fruits and vegetables resonated strongly with Ryan and Rhonda, who wanted to feed their family and become more self-sufficient off the land. “Finch believed it was ridiculous to buy from the grocery store. We sit on some of the best, fertile land in the world and still buy things from overseas,” Ryan recalled, echoing Finch’s philosophy.

Ryan purchased a frame kit from Finch and Bright’s company, Greenhouse in the Snow, and got to work in June 2019. The family of four – Ryan, Rhonda and their daughters Sarah and Hannah – tackled all the construction themselves, except for electricity and water.

“We wanted to prove your standard family with minor construction experience can put one of these things up,” Ryan said. The Lorenzens finished the greenhouse by the fall equinox with enough time to start growing for their first winter season.

At its simplest, the greenhouse is a model of low-maintenance, sustainable gardening. It draws heat from the earth and uses a geo-air system to circulate warm air through underground tubes.

A 10-inch squirrel fan, no more complex than a household furnace, powers the system. It moves air through 250 feet of drain tiles buried eight feet underground. These tubes gather and store the earth’s natural warmth, enabling the greenhouse to stay at a moderate temperature, even during Nebraska’s harshest winters.

The structure’s translucent polycarbonate panels allow sunlight to filter in, creating the perfect balance of additional heat and natural light for the plants inside. The system practically runs itself – and does so without an extravagant investment in outside energy.

In fact, the challenge isn’t keeping the greenhouse warm; it’s keeping it cool. On sunny days below zero, the greenhouse’s average temperatures remains between 90 to 100 degrees when sealed shut. To combat this, Ryan cracks open windows and doors to regulate the temperature with air flow.

The family learned this the hard way, cautioning prospective gardeners to water plants in moderation. “Once you close up for the winter, it turns from greenhouse to terrarium. Every drop of water stays in there,” Rhonda said.

The result was an unexpected battle against white mold in their first year of growing. They’ve since learned to reduce their watering and regulate temperatures through better ventilation.

The greenhouse has also allowed the Lorenzens, who have been avid gardeners their whole life, to extend their growing season. Ryan and Rhonda still enjoy planting outside when the weather is conducive. They continue to grow cold-hardy crops such as garlic, onions and potatoes through the winter, then transfer them outdoors in the summer when the greenhouse becomes too warm.

Other resilient plants, such as rosemary and saffron, thrive in the 12-foot entryway of the greenhouse, which acts as a buffer between the cold winter air and grow room.

Though the family offers tours to prospective greenhouse growers, the greenhouse itself is not a one-size-fits-all solution. Each structure is highly customizable, allowing for different layouts, growing beds and plant arrangements to suit each grower’s needs.

For Ryan, the grow room is “where the magic happens.” The greenhouse has become a laboratory where his curiosity roams free. Over the last six years, he has tried his hand at growing everything from saffron to yacón, a South American root vegetable.

The greenhouse requires a delicate touch to balance temperatures for so many varieties of plants. One year, the Lorenzens attempted to grow vanilla orchids for their oldest niece who made homemade vanilla extract. However, the plant needs a consistent temperature of 60 degrees to thrive, which was difficult to maintain without backup heat – and not justifiable enough for one plant.

Alternatively, the couple found that rosemary grew better in the 20-degree entryway of the greenhouse, unbothered by the cold.

Even as their knowledge of plants deepens, the Lorenzen’s approach remains rooted in the enjoyment of gardening and providing fresh produce for themselves, their family and neighbors.

“We’ve always been the homesteader, prepper types. It’s always been the way we’ve lived. The greenhouse allows us to do that year-round,” Ryan said.

Rhonda, a former paraeducator at Wakefield Community Schools for 21 years, has also enjoyed sharing their abundant bounty with their community. In October 2019, 5th grade students made compost bags as part of their science class lesson. Rhonda brought each bag home and added the students’ contributions to her greenhouse compost so that each student could share in feeding her garden – and just in time for their first growing season.

From 2021 to 2023, she brought fresh tomatoes, celery and cucumbers to feed students through Nebraska Thursdays, a program that allows schools to buy and serve harvests from local farmers.

Both Ryan and Rhonda are now retired. Every morning, as the sun weakens its grip on winter, Ryan steps inside the warm world of his greenhouse sanctuary. Rhonda, usually in tow, brushes the snow from her boots to join him.

“There’s nothing better than that smell of fresh dirt and green stuff growing. Being able to do that in the dead of winter is really enjoyable,” Ryan said.

Their greenhouse does not have a sign out front or a storefront, and that’s the way they like it. For the Lorenzen family, it’s a reminder of the food sovereignty that drives their every day.