Freezing behaviors of cells in dormant buds of katsura (Cercidiphyllum japonicum) tree were examined. Intact dormant buds showed high survival rates after freezing to -30℃ at a rate of 5℃/day (slow freezing). However, flower primordia isolated from dormant buds showed a remarkable decrease in survival rate after slow freezing to -10℃ in the presence of ice crystals adjacent to tissues, while isolated scales showed a high survival rate after slow freezing to -30℃. Katsura buds exhibited a typical pattern of extraorgan freezing, accumulation of large extracellular ice crystals within scale layers, by freezing to -30℃. Cryo-scanning electron microscopic analysis revealed that both extracellular freezing cells without freezable water in the cytoplasm and supercooling cells with freezable water in the cytoplasm of partially dehydrated cells are contained in primordial tissue and extracellular freezing cells existed in scales in dormant buds exhibiting extraorgan freezing. In isolated tissues, intracellular freezing occurred in about 50% of the cells of the flower primordia by freezing to -10℃, but extracellular freezing occurred in all scale cells by freezing to -30℃. These results suggested that katsura dormant buds adapt to subfreezing temperatures by segregation of supercooling primordial cells which are susceptible to extracellular ice crystals, from ice crystals.