EVALUATION OF COLD-HARDINESS BY CONTROLLED FREEZING OF FIELD-HARDENED FORAGE CROPS

Abstract

Field-hardened grasses and legumes were evaluated for hardiness by subjecting the crowns to sub-zero temperatures while the roots were maintained at 20°F, which is near normal winter temperature 6 in. below soil surface. The plants were removed from the field in cores, and were trimmed to fit into food cartons 3 in. in diameter and 8 in. deep. A thermal box was designed to maintain the desired temperature of the root zone while the crowns were subjected to sub-zero temperatures.Highly significant correlations were obtained between survival after controlled freezing and survival after natural winter exposure in studies with 10 orchardgrass varieties, 15 alfalfa varieties, 16 grass species, and 43 lines of white clover.