Low temperature is one of the most critical environmental limitations for plants.
Some plants, like annual flowers and vegetables, simply avoid the cold of winter by dying at the end of summer. Such plants have a threshold temperature below which they will die. These threshold temperatures determine how far north plants will survive. It is a guide to help you to assess plant hardiness. The map above shows the plant hardiness zones of Maine based on average yearly minimum temperatures, from data for each year from 1974 to 1986.