522 THE EVALUATION OF COLD HARDINESS IN HAZELNUT

Abstract

Laboratory freezing tests were conducted for two consecutive winters to determine the cold hardiness (CH) of hazelnut trees (Corylus).Thirty-six different genotypes were evaluated. LT50s were calculated for female inflorescences, catkins and vegetative buds. Most (> 70%) female flowers achieved their maximum hardiness in January. Nearly half (45 %) of all female flowers had LT50s between -38.0 C and -21.4 C. Catkins were most hardy in December after which they began to elongate and lose their CH. In December, catkin CH ranged from -33.0 to -13.4 C. Vegetative buds were more hardy than both female flowers and catkins. LT50s ranged from, -40.0 to -26.8 C with 95% achieving maximum CH in January. More than half (54%) had LT50s between -30.0 and -20.0 C. In summary, vegetative buds are more CH than female buds which in turn are more hardy than catkins.