Cold Weather Plant Protection

Cold Weather Plant Protection

By ALICIA LAMBORN 
Horticulture Agent
Baker County Extension Service

Now that the cold weather is here to stay, most of northeast Florida will be experiencing freezing night temperatures for the next few months. As we all know, low temperatures can damage our tropical and subtropical plants if some sort of protection is not provided.

The ability of plants to withstand freezing temperatures is affected by day lengths and the fluctuations in temperature prior to a freeze. A gradual decrease in temperature over a longer period of time allows plants to acclimate and withstand cold temperatures, whereas an abrupt drop in temperature in a short period of time usually results in more plant injury. Also, in Florida we tend to get short periods of warmer weather in between freezes which actually deacclimate plants. In some cases, this causes them to break bud and flower, subjecting them to further injury when the next freeze hits.

So what can you do to minimize cold damage to plants in winter? Start by selecting a good planting site and adopting proper cultural practices. Plants will have weak, shallow roots which are more susceptible to cold injury if planted in poorly drained soils. Planting under a canopy of trees or near windbreaks, such as fences, buildings, and other plants, will also help reduce cold damage. Proper plant nutrition is also important, since plants grown with optimal levels and balance of nutrients will tolerate cold temperatures better and recover from injury faster. Avoid late fall fertilization of nutrient deficient plants and fall pruning which may cause latent buds (buds that are present but not visible) of the plant to break. Both of these practices will cause a late flush of new growth that is very sensitive to cold temperatures.

If a freeze is predicted, water plants 24-48 hours before the freeze (unless it rains). Moist soil absorbs more heat during the day which will be released during the night. Watering will also help prevent desiccation or drying out. The sun's rays combined with dry winds during the day can quickly result in excess water loss from the leaves of the plant. A plant that has been deprived of water will show damage along the leaf margins and leaf tips, or in severe cases, the entire leaf will turn brown. However, when watering repeatedly for cold protection, be mindful of prolonged saturated soils which cause roots to rot.

Covering cold sensitive plants with cloth sheets or black plastic is also helpful if the covers extend all the way to the ground (reducing heat loss), are not in contact with plant foliage (avoiding injury by transferred heat from foliage to the colder cover), and are removed (especially plastic covers) after temperatures rise above freezing. For perennial plants, renewing the mulch or adding pine straw or leaves will help protect dormant crowns during hard freezes. Young citrus trees also need some protection. Bank clean sand around the graft union or wrap it with foam pipe insulation to protect it from freeze injury. Containerized plants can be pushed together and covered or moved under a sheltering tree or eave where radiant heat will be trapped after dark. Be aware that covering plants protects them more from frost than from extremely cold temperatures, therefore some tropical plants may need to be moved inside or to a more sheltered location.

Irrigation can also be used for freeze protection, by keeping the leaves of plants wet. However, this method is tricky since you have to start irrigating as soon as the temperature reaches 32 degrees and keep it on until thaw is complete. The water must be distributed evenly and the right amount must be applied to maintain a film of liquid water on the leaf surfaces. There is also the danger of breakage due to ice buildup on limbs and root rot problems from the excess water. This method of cold protection is used commercially where it can be carefully controlled, and is best left to the professionals.

If you have questions regarding cold protection and would like more information, please contact Alicia Lamborn, Horticulture Agent, at the Baker County Extension Office by calling 259-3520 or email alamborn@ufl.edu.  

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating.