A good rule of thumb for any gardener: Grow outdoor plants that are hardy in your climate unless you plan to bring them indoors for the winter or let them die off. It would be fantastic if the weather cooperated with this practice, but some seasons are colder than normal. Consider the microclimates in your own landscape, as well. The area near your garage, for instance, might always be two or three degrees warmer than the open spot on top of a hill. Learning temperature trends in your landscape and how your yard compares to the weather report helps you determine when protective measures are in order. Select one or more methods of frost or freeze protection so your plants come through the cold with flying colors, literally in many cases.
Grow outdoor plants that are marginally hardy in your climate and susceptible to freezing temperatures in a protected area that is warmer than other areas of your landscape. Protected areas include under an awning; on the south or west side of a home; near a wall, shrub or another structure. Open and low-lying areas are the places where these plants are most likely to freeze.
Irrigate outdoor plants well with 1 inch of water so the water penetrates deep into the soil. Do this the morning before an expected freeze, because moist soil absorbs and retains more heat than dry soil. It also radiates more heat at night when the plants need the extra heat the most. If your plants are succulents, do not use this method to prevent freeze damage. Cold-sensitive succulents may burst if they are too hydrated during a freeze.
Apply a 2- to 3-inch layer of mulch, such as chopped leaves, around your plants if the roots are sensitive to freezing temperatures and the tops have already died back from frost. Otherwise, remove mulch before a freeze so the soil radiates more heat at night to increase the temperature around the plants. If plants are short and can be easily covered with straw, cover them in the evening before temperatures begin to drop. Remove the straw the next day when temperatures begin to rise above the damaging point. Repeat each day, as necessary.
Cover outdoor plants the evening before a freeze; keep the covering from touching the foliage and flowers as well as possible. Sheets, blankets or drop cloths strung on tall wooden stakes, draping to the ground -- not tied to trunks or stems -- work well. Place a chair or box over the plants as a simple way to protect them from freezing. A 100-watt outdoor-safe light under the covering to increase temperatures at night. Outdoor holiday lights strung in trees and shrubs, or along the ground around smaller plants, can also protect plants from freezing. Remove coverings in the morning and re-cover in the evening, if necessary.
Spray foliage with an antitranspirant or antidesiccant in winter before a freeze is expected. Make another application three months later if freezing temperatures are a consistent issue in your climate.