Winter lettuce could be North Country cash crop
Monday, March 11, 2013 - 11:42 am

Trials funded by the Northern New York Agricultural Development Program are evaluating winter lettuce production methods for the North Country.

A team of Cornell University researchers and extension specialists is investigating the use of prototype low-wattage heating strips to warm the soil to enhance lettuce production during the winter months in St. Lawrence and neighboring counties.

With consumers willing to pay up to $12 per pound for lettuce-based salad mixes year ’round, this research holds out the promise a high payoff value if it proves to be successful and cost-effective under North Country conditions.

Cornell University Cooperative Extension Vegetable Specialist Judson Reid says, “This research in northern New York is the first attempt at developing a system for heating the greens-growing environment inside high tunnels using heating strips primarily designed for in-floor radiant heat.”

Amy Ivy, Cornell Cooperative Extension Horticulture Educator for Clinton and Essex counties, says, “While spinach can be grown and harvested year ’round in northern New York with a minimal addition of heat largely in January and early February, lettuce crops are more cold-sensitive. Our question is can growers cost-effectively add heat to grow the salad greens year ’round without sacrificing profitability.”

“There is great demand by consumers and by regional restaurants clamoring for local greens,” Ivy said.

Cornell University Research Associate Michael H. Davis explains that “on clear, sunny days during the winter, temperatures inside a high tunnel can be 20 to 40 or more degrees warmer than the outside air, and, as a result, lettuce plants can be grown and harvested. The key to high tunnel winter lettuce production is helping the cold-sensitive lettuce plants survive frigid nighttime temperatures.”

To warm the lettuce production beds during the night, 8- or 15-watt electrical heat strips – prototypes not yet commercially available -- were buried eight inches below the soil surface in the 30-by-96-foot Ledgewood pipe-frame high tunnels at the Willsboro research farm.

To retain the heat around the lettuce plants, the production beds were blanketed with a double layer of rowcovers supported by wire hoops that straddled the growing beds and kept the insulating layers from touching the plants.

Black seeded Simpson head lettuce plants were seeded indoors on January 1, 2012, and the seedlings were transplanted to the tunnels on Feb. 6. Five Star baby lettuce mix seed was planted directly into the high tunnel growing beds on Feb. 8.

Reid says, “It is notable that on nights when the outdoor temperature dropped into the teens and single digits, the soil temperature at 1.5-inch depth in the heated lettuce beds with rowcovers never dropped below 40 degrees Fahrenheit, and the air temperature never dropped below 32 degrees Fahrenheit. In contrast, the air temperature 8 inches above the uncovered and unheated beds dropped into the low teens during the night of 2/12/2012.”

The initial trial results provided insight on issues with the placement and width of the heat strips, the benefit of combining the heat strips with the use of low rowcovers, and the proximity of the lettuce plants to the high tunnel exterior.

The complete report is on the NNYADP website at www.nnyagdev.org under Horticulture: Vegetables.

The Northern New York Agricultural Development Program is a farmer-driven research, outreach, and technical assistance program serving New York’s six northernmost counties. Learn more about horticultural crop production in Northern New York at www.nnyagdev.org or contact your local Cornell Cooperative Extension office for more information.