Four Season Farming in the Polar Vortex

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Four season farming? Winter harvest? Season extension? Those ag-speak terms equal big changes on central Kentucky dinner plates: locally grown fresh greens in January and February, and slices of dead- ripe local tomatoes a month early. We owe all that to a Kentuckian who died more than half a century ago and to what he called “field greenhouses.”

New England writer/grower Eliot Coleman typically gets credit for discovering in the 1980s that cold-tolerant plants will grow in winter in unheated plastic greenhouses. Instead, we owe these ingenious structures to the work of Dr. Emery M. Emmert, born in Iowa in 1900 and hired to teach horticulture at the University of Kentucky in 1928. When he died in 1962 after 34 years on UK’s faculty, Dr. Emmert had developed ways to use plastic and the earth's own heat to grow vegetables and fruits earlier and later than usual, offer fresh produce in winter months, and increase yield. Today, growers call the plastic-covered, unheated, lightweight structures he introduced “hoop houses” or “high tunnels.”

Krista Jacobsen, assistant professor in UK’s Department of Horticulture, shared Emmert’s story as a way of explaining the decades-long reach of UK hoop house research. Practical application by central Kentucky growers is still in its infancy, though.

“In Kentucky we have outstanding growers using high tunnels,” Jacobsen said. “There’s Au Naturel Farm near Bowling Green and growers in northern Kentucky and Louisville, but we don’t have that many locally yet.”

Perhaps any grower wearing her thinking cap would look at the winter we just survived and be shocked to see that any midwinter crop production survived the extreme conditions. Yet UK and other experienced hoop house growers produced at least some fresh winter vegetables in spite of 2014’s boomeranging polar vortex. UK’s January and February harvests from three fixed and three movable hoop houses included kale, arugula and carrots.

Erik Walles began growing cold-loving vegetables in an unheated green house in 2006 at his Berries on Bryan Station. He said that season extension has benefitted the Community Supported Agriculture (CSA) baskets produced at his farm by allowing the CSA season to start earlier and providing stronger and fuller baskets.

“It allows the farmer to have a unique advantage,” he said. “You can sell good food early, and that secures loyalty.”

Walles calls the hoop houses “beautiful tools, great technology.” He added a hoop house in 2012 and just completed a new hoop house this winter.

“They are in constant production,” he said of his three structures. The earth itself provides their only heat.

This year so far, Walles managed to save his early chard, but the cold in December overwhelmed his lettuces. In past years, in addition to offering CSA shares and other sales, Berries on Bryan’s lettuces and greens have filled plates at nearby Windy Corner Restaurant every month of the year.

Even this cold year, Walles delivered his first 10 pounds of greens to a restaurant client on the first day of spring, well ahead of outdoor crops –– credit Emmert for the assist.

Count Henkle’s Herbs & Heirlooms in Nicholasville among the latest growers to put Emmert’s findings into practice. Though relatively new to season extension, husband-and-wife team Mark and Velvet Henkle pour out enthusiasm for growing their business, and back that up with sheer hard work. Mark Henkle said, “I planted 34 varieties of pink tomatoes this year –– I have no self control.” And yes, he planted the rest of the rainbow, too.

“In January, we sleep,” Velvet Henkle said.

“Or we used to,” Mark added with a laugh. This January, after years of preparation, saving, grant writing, construction wrangles and sheer effort, the couple completed an eco-friendly wood boiler-heated greenhouse.

Like many organic and sustainable vegetable growers who need healthy, organic transplants in months when none can be bought, the Henkle's plan to rely on the separate strengths of their heated greenhouse and the unheated hoop house they built in 2012. The heated greenhouse will provide the warmth that seeds need to germinate. Once the plants reach transplant size, the hoop house will provide moisture control, protection from wind and other benefits, without requiring heat.

While the Henkle's built most of their two plastic-covered season extension “tools” themselves, funds came from multiple sources, including the Kentucky Agricultural Development Fund, the Jessamine County Community Agricultural Investment Fund, and the Natural Resources Conservation Service of the United States Department of Agriculture.

Special help comes from Mark Henkle’s father, Hubert, who often takes the deep night shifts when the temperature drops and the greenhouse boiler needs fresh wood every four hours.

“He’s living my dream,” Hubert Henkle said of his son.

Emery M. Emmert helped realize that dream. Emmert Farm Road, which leads to UK’s research farm off Nicholasville Road, reflects UK’s esteem for this 20th century horticulturist. When you eat that perfect local strawberry three weeks early this spring, tip your fork to his legacy.

Erik Walles of Berries on Bryan

Facts about four season farming and season extension

• Before plastic, the construction of greenhouses, orangeries, and conservatories depended on glass. Plastic shields many greenhouses today.

• Typically, but not always, greenhouses include a heat source and can be closed on all sides, with plants growing in containers that hold planting media. Hoop houses (high tunnels) often feature open ends, with plants often growing directly in soil.

• Growers use both hoop houses and greenhouses to stretch the growing months (i.e., lettuce in January) and to produce tender crops early (i.e., strawberries and tomatoes a month early.) These practices give growers market advantages.

• Hoop house kit vendors offer options suited to both typical northern winters and typical southern winters. “Northern” kits feature sturdier construction, in anticipation of greater snow and lower temperatures.

To learn more about hoop houses, greenhouses and season extension in general, check out these great local resources:

• “Greenhouses and Similar Structures: An Overview,” University of Kentucky Cooperative Extension Service

• “Season Extension Tools & Techniques,” University of Kentucky Cooperative Extension Service

• EQIP is a good resource for hoop house cost share and technical assistance: http://tinyurl.com/eqipfayette

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