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FARGO — As frost season approaches, gardeners must make decisions about whether or not to protect sensitive plants. Non-native annual plants such as tomatoes die when subjected to freezing temperatures. Some plants, such as petunias, can manage a little frost but will die in extreme cold. Some plants, such as cone flowers and hydrangeas, will die back gradually in the fall and then re-emerge in spring from the roots. Native hardwood trees such as oaks and maples go dormant but do not die in winter.
The differences in the way various plants deal with frost are rooted in their internal chemistry. If the cells of a plant freeze, the cell walls will burst, killing the plant. If the cells are not frozen, but are surrounded by ice, they can be severely dried. Plants which are evolved to survive winter, do so by changing their chemistry to avoid freezing; a sort of natural antifreeze. They adjust their internal liquid content so that some or all of the plant does not freeze.
