Many people are surprised when they learn it gets cold enough in Phoenix to cause frost! Quite often between December and early into March nighttime temperatures can drop below freezing which can damage plants and trees if you do not take the proper precautions. Below are some general rules and guidelines to follow to help protect your landscape.
1. Understand which plants and trees are sensitive to frost. Some of the most common choice plants for our clients are frost sensitive are Pigmy Date Palms, Hibiscus (all types), Sissoo Trees, Ficus Trees (all types), Cacti (some types) and Bougainvillea (all types). Citrus trees are a popular choice in Arizona and also frost sensitive. If your plants are new or your yard was recently landscaped, you will need to protect your plants.
2. If you choose to have plants that are sensitive to frost as part of your landscape, you should try to plant them in places that would help minimize frost damage. Placing plants on the South or west sides of your property or next to rock or concrete structures that will retain heat from the sun are the best choice for plant placement.
3. Plants need to be covered to be protected from frost. Sheets, burlap or light blankets are all great choices for plant covering. You should be able to find sheets of a plastic covering, that is porous and light, specifically made for this purpose at your local hardware store. Be sure to plan ahead and have protective covering on hand in case Arizona experiences early frost or cold weather.
4. In order to retain warmth under your plant coverings, ensure that your cover touches the ground.
5. Do not use non-porous plastic (ie tarps) to cover your plants. Moisture may become trapped under the plastic and cause frost damage to your plants. When covering your plants, you are not supposed to allow the covering to rest on your plants but most people do not usually accommodate this detail. As long as you don’t use heavy blankets or cloths that can absorb moisture and in turn become heavy enough to damage plants, your plants should be okay.
6. Young citrus trees need frost protection. You may find it challenging to cover larger trees but if you choose not to cover them, you are risking that your tree(s) may suffer irreversible frost damage. Most mature citrus trees will come back from frost exposure the following Spring unless it is a severe frost.
7. Continue to water your plants throughout the winter months. You should water trees and plants in the morning hours so that leaves will be dry as the colder temperatures move in after dark.
8. Leave your tree and plant covers on until late in the morning the next day. Temperatures tend to be coldest right before sunrise.
9. Do not remove damaged parts of your plants or trees if they suffer frost damage. Dead leaves and branches serve as protection for the reset of the plant that is still alive. Proceed to prune any frost damaged plants in the spring.
If you are faced with cold and freezing temperature evenings, it is best practice to do something for your trees and plants rather than nothing at all. You can use boxes or paper bags on vulnerable flowers and ground covers. Drape coverings over as much of a plant or tree as possible. If you follow these practices, when winter is over, you may still have a plant that is viable.