The recent sub-zero temperatures across much of the Midwest and Northeast are of concern for alfalfa, especially since upwards of half the crop died last year due to winterkill.
"Alfalfa can survive temperatures of 10° to 15°F," says Dan Undersander, a forage agronomist with the University of Wisconsin.
"As little as 4 inches of loose snow will insulate against 16°F of air temperature," he says. "The crown [of the alfalfa plant] is insulated by soil as well. Therefore, the crucial temperature is the temperature at 2 to 4 inches below the soil surface.
As a result, soil temperatures at depths of 2 to 4 inches covered by 4 inches or more of snow will generally still be at 28° to 32°F, Undersander says. "This situation should indicate little or no injury or kill of alfalfa from the recent cold snap," he says.