As the nights have been getting progressively colder, our plants have been moving gradually into dormancy. A drop in temperatures followed by a rise will often slow this move and increase the chance of frost damage. Watch for unusually warm periods followed by sharp drops in temperature. During the early winter and early spring when temperatures fluctuate is when most frost damage occurs. Warning signs of potential frost in Cochise County are the same as in other parts of the country: still air, no cloud cover, very bright stars, low humidity, and low temperatures in the early evening (45? or lower by 10:00 PM)
The best frost protection strategy is to plant only those varieties that are hardy to frost. If you have already planted frost-tender ornamentals outside, you should probably move them to containers for the winter or replant them in warmer microclimates in your yard. Other frost protection strategies are cardboard boxes inverted over plants at night (removed during the day), vertical water tunnels made of plastic, and old quilts, blankets, or sheets laid over planting beds at night and removed each morning. An unusually cold spell or long, hard frost can kill or seriously injure mature trees that are only marginally cold hardy.