Remember that the map is based on average annual minimum temperatures. Although there is a global warming trend, we continue to have cold temperatures each winter in Maine. Environmental Factors that Impact Plant Growth Low winter temperature is just one factor that affects plant growth. A plant may be adapted to the temperature of a location, but may die because of a problem related to another environmental factor. Or a plant may be stressed due to other problems, and may then die from the extra stress caused by a very cold winter.
Plants survive within a more or less broad range of temperatures.
They thrive within a more narrow range of temperatures. In Maine and other cold climates, minimum temperatures generally determine whether plants will survive. Plants survive very low temperatures only when they are fully hardened off. If a very low temperature occurs in late fall, before a plant has fully hardened off, it may not be able to withstand the stress. High temperatures during the summer and temperature fluctuations throughout the year also impact a plant's success.