Protecting Plants From Freeze Damage

Protecting Plants From Freeze Damage
by Jane Morse, University of Florida/IFAS Pinellas County Extension Agent

The cold weather season is here and freezes are possible. Here are some things you can do to help your plants survive cold temperatures:

Proper plant selection and placement are the most important steps toward having a healthy landscape. Cold-sensitive plants should be placed in the warmest sites on your property. Usually a south-facing area protected by walls, fences or evergreen plantings will provide some plant protection. Plant in higher areas since cold air will settle in low areas. Also, poorly-drained sites result in weak, shallow-rooted plants which are more likely to suffer from cold damage. Best choice -- choose plants that will easily tolerate the temperatures you are likely to receive. We are in hardiness zone 9b, so choose plants suited to zone 9b.

Fertilize (if needed) at the right time. Plants in south central Florida can be fertilized up to 4 times per year. Apply 1.6 pounds of 6-0-6, or 1.2 pounds of 8-0-8, or 0.8 pounds of 12-0-8, or 0.6 pounds of 16-0-8 per 100 square feet (an example would be a 10’ x 10’ area for 100 sq. ft.). In the fall decrease the amount of fertilizer to half the standard rate because plants are not actively growing and use less water and plant nutrients. Always use slow-release fertilizers because they provide nutrients over a longer period of time and decrease the likelihood of nitrogen getting into our water supply. Fertilizers should only be applied when you are looking for a particular plant response such as growth, more blooms, or to correct a nutritional deficiency. If plants are looking healthy you can hold off on fertilizing.

Provide tree shade or cover. Plants in shady areas go dormant earlier and remain dormant later in the spring. Tree canopies also provide protection from “radiation” freezes. This type of freeze occurs on cold, clear, still nights because heat “radiates” from objects into the air. Providing a tree canopy over tender plants will help hold the heat they radiate and keep it from escaping into the night sky. Mulches help to protect the roots (always keep mulch at least an inch away from the trunk or stem of plants). Coverings such as cloth or plastic protect more from frost than from extreme cold. Covers need to be raised above the plant and go all the way to the ground. Plastic covers need to be removed on sunny days so the plants don’t burn. Cardboard boxes large enough to cover the entire plant work great. Use windbreaks. Fences, buildings, a row of hardy evergreen plants and temporary covers can protect plants from cold winds. The height, thickness and location of windbreaks will determine how much the wind speed is reduced.

Watering. Watering landscape plants before a freeze can help protect plants, but avoid having the soil saturated for a prolonged time.

Maintenance practices. Avoid pruning in the late summer or early fall. Healthy plants withstand cold better than sick plants. Choose plants wisely and put them in the right place for their needs. Some plants such as gardenia, azalea and ixora develop nutrient deficiencies when placed in an alkaline (high pH) soil, and soil fertilizers will not correct the problem no matter how much is applied. Our coastal soils tend to be alkaline. Remember that tropical plants and summer annuals cannot take temperatures below freezing and many are injured by temperatures below 50 degrees Fahrenheit.

For more information on caring for your Florida plants, call your local University of Florida/IFAS Extension Service in Pinellas County at (727-582-2100). The Lawn and Garden Help Desk phone line is available Monday, Tuesday and Thursday from 9 AM to Noon, and 1 PM to 4 PM. Walk-in service is available M-F, from 8 AM to 5 PM. We are located at 12520 Ulmerton Road, Largo, FL (just south of Animal Services and EMS).