Stem cold hardiness of 38 crabapple taxa (Malus L.) was evaluated on 6 dates throughout the dormant period of 1992–93. Differences in cold hardiness among taxa were detected on all sampling dates, with no single cultivar being consistently most hardy. Midwinter hardiness levels ranged from −32C (−26F) for ‘Jewelberry’ to −44C (−47F) for M. baccata ‘Jackii’. ‘Dolgo’, ‘Red Jade’, ‘Red Splendor’, ‘Selkirk’, and M. baccata ‘Jackii’ were all hardy to at least −40C (−40F) in midwinter and also exhibited excellent early-and late-season hardiness. Large differences in hardiness among crabapple taxa were observed on November 9 and April 26 sampling dates [14C (25F) and 17C (31F), respectively], indicating that taxa vary substantially in timing and/or rates of acclimation and deacclimation. Although most cultivars demonstrated adequate hardiness for use in USDA hardiness zone 4a, the acclimation and deacclimation characteristics of some taxa may predispose them to injury from extreme low temperatures in the fall and early spring.
Journal Series Paper number 22,219 of the Minnesota Agricultural Experiment Station.
2Scientist and Professor, respectively.