That depends on what deciduous species you are over wintering. The root sensitivity is most important according to Michael Hagedorn. A table that gives average temperature for killing plant roots is below. Table 1. Average killing temperatures for roots of selected species of woody ornamental plants. Greenhouse & Floriculture: Overwintering Container-Grown Ornamentals | Center for Agriculture, Food, and the Environment at UMass Amherst. Euonymus is more cold hardy than maple. Learn lots. Share with others. Have fun.
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