Summer annuals, mostly indigenous to areas outside of Arizona, are colorful and easy to grow, but generally die back (freeze) at the end of the season, and rarely return the next year. Examples include Periwinkle (Vinca), Moss Rose (Portulaca), Zinnias, Marigolds, Verbena and Salvias. Along the same principle, summer vegetables such as tomatoes, peppers, corn, summer squash and melons, love the heat and consequently have a very difficult time withstanding any freezing weather and recovering the following spring. And leading in to the next question, many of your woody shrubs, trees or vines, even though some are not native to the desert southwest, will freeze. However, if they’ve had the time to establish an adequate root system, which would be unaffected by the cold weather (our ground generally does not freeze here like it does back east), that would enable them to recover and resume their growth the next growing season.