What cultivars fare best where the winter is severe?

The following varieties can survive in very cold temperature:
Wulong Pengsheng (Black Dragon Holding Blossom), Luoyang Hong (Luoyang Red), Ying Ri Hong (Sunrise Red), Shanhu Tai (Coral Tower), Cai Hui (Colorful Painting), Fen Zong Guan (Champion Pink), Kunshan Yeguang (Night Glow on the Sacred Mountain), Yin Hong Qiao Dui (Silver Red), etc.