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Spinach grown in high tunnels during cold weather is tastier for growers, even for chefs seeking fresh-cut fixings, suggests UNH research.

John Vogel, Editor, American Agriculturist

November 30, 2016

2 Min Read
COOL SPINACH IS ‘HOTTER’: Spinach varieties, such as Emperor, are tastier when grown in cold weather, opening premium winter market opportunities for high-tunnel growers.

Spinach is a “hot” health food crop, but you can’t grow it in cold weather, right? Wrong, especially if you grow it in high tunnels.

Old Man Winter’s coldest months can be a boon to Northeast growers interested in adding spinach to their winter crop production system, suggest researchers at the New Hampshire Agricultural Experiment Station. They’ve found that spinach grown in unheated high tunnels during the coldest months of winter has the highest sugar content.

That makes it tastier and translates into higher demand. That’s especially true for growers already producing lettuce for winter markets.

Spinach is a suitable crop for winter production, even in New Hampshire, due to its ability to continue producing salable leaves at very low temperatures, says Kaitlyn Orde, a University of New Hampshire graduate student doing research at the Woodman Horticultural Research Farm.

Fall transplants into high tunnels can result in winter-long harvests and significant spring yields. “That opens an avenue for growers to meet strong consumer demand for local greens during the off-season,” adds Orde.

Two years of trials focused primarily on three spinach varieties: Regiment, Space and Tyee. They were planted at six different dates throughout the fall. They also investigated Carmel, Corvair, Gazelle, Emperor and Renegade.

3 take-home discoveries

Temps down; sugars up. With colder temperatures in the days leading up to harvest, sugar content in the leaves increased. Lowest sugar measurements were recorded during the warmest periods of the experiment (October, November, March and April). The highest measurements were recorded during the coldest months, February in particular.

Transplant timing is important. Earlier transplant dates resulted in higher fall yields of spinach. However, for spring harvest transplanting as late as mid-October didn’t negatively impact spring yields. Even the latest planting dates produced good spring yields. That means optimum planting dates will depend on the timing of growers’ markets.

Variety affected sugar content. Gazelle and Emperor had higher average sugar content than other varieties during both years. But differences in sugar content between varieties weren’t enormous. All were of a high eating quality.

A 48- by-30-foot rolling Rimol high tunnel was used. It was covered by an inflated double layer of 6-mm, four-year plastic plus polycarbonate end walls.

“New Hampshire’s traditional growing season is very short, limiting the period for local food production. Growing systems like this can extend production and supply more locally produced food on a more consistent basis,” Orde adds.

For more details on this research, visit

About the Author(s)

John Vogel

Editor, American Agriculturist

For more than 38 years, John Vogel has been a Farm Progress editor writing for farmers from the Dakota prairies to the Eastern shores. Since 1985, he's been the editor of American Agriculturist – successor of three other Northeast magazines.

Raised on a grain and beef farm, he double-majored in Animal Science and Ag Journalism at Iowa State. His passion for helping farmers and farm management skills led to his family farm's first 209-bushel corn yield average in 1989.

John's personal and professional missions are an integral part of American Agriculturist's mission: To anticipate and explore tomorrow's farming needs and encourage positive change to keep family, profit and pride in farming.

John co-founded Pennsylvania Farm Link, a non-profit dedicated to helping young farmers start farming. It was responsible for creating three innovative state-supported low-interest loan programs and two "Farms for the Future" conferences.

His publications have received countless awards, including the 2000 Folio "Gold Award" for editorial excellence, the 2001 and 2008 National Association of Ag Journalists' Mackiewicz Award, several American Agricultural Editors' "Oscars" plus many ag media awards from the New York State Agricultural Society.

Vogel is a three-time winner of the Northeast Farm Communicators' Farm Communicator of the Year award. He's a National 4-H Foundation Distinguished Alumni and an honorary member of Alpha Zeta, and board member of Christian Farmers Outreach.

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