Chris Wien, a professor in the Department of Horticulture at Cornell University, offers a few pointers to growers to help them protect their high tunnel crops from frost this spring. Specifically, he points out two procedures that can be implemented immediately and a third technique that is more for long-term production.
1. Construct a low tunnel over the crop in the high tunnel. Spun-bonded fabric works best, with the heavier materials (1 to 2 ounces per square yard) providing better frost protection, he says.
“The fabric should not touch the plants, but be held up by wire hoops or pipes,” explains Wien. “The fabric itself will freeze, so if the plants are touching the fabric, they also will freeze.”
2. A gas-fired heater can be used in the high tunnel for those cold nights when crops are inside. This also will help to slide snow off the high tunnel plastic on days when wet, heavy snow threatens to collapse the tunnel, he adds.
Make sure that the tunnel plastic covering the high tunnel is an IR (infrared)-blocking kind, says Wien. “On those clear, cold nights in spring when the temperature dips below freezing, reducing the heat loss from the tunnel with IR-blocking plastic will keep temperatures inside 2 to 4 F warmer.”