What to do when the temperature drops in the garden
We have had some pretty cold weather recently and your garden may be looking the worse for it. Cold temperatures have different effects on different plants. Many subtropical plants used in our landscapes may be borderline cold hardy here and other plants are summer annuals up north. Cold may affect the entire plant or only certain parts like the fruit/flower buds or the roots. Roots of potted plants may be especially susceptible because they are much more exposed in pots above the ground than roots in the ground. Roots function more slowly when cold and some damage may look like drought because the cold roots cannot supply enough water on windy, cold, sunny days. Leaf damage from cold may appear as totally brown leaves or brown edges if the roots are not functioning properly, or the whole top, leaves and stems, may collapse and turn brown from ice forming inside the tissues.
Protect From the Cold
The first thing to consider is protecting plants from cold. The Florida Automated Weather Network (FAWN) can help you to know when to expect cold with a forecast tracker and links to the National Weather Service as well as tools to help you find out critical temperatures for various plants. When you are expecting frosts or freezing temperatures you can use frost blankets or quilts over tender plants to protect them. If applied properly so that the ends are secure to the ground, blankets can protect from frosts and some cold. A source of heat like a light bulb or Christmas lights under the blanket is needed for freezing temperatures. Using plastic, or not securing the ends to the ground will not protect the plants. Plastic is too thin to provide insulation, and open ends allow the cold air to get in.
Grafted or budded plants like gardenia and many fruit trees need to have the graft union protected so that if the top dies back from severe cold, the scion wood will remain alive and regrow. Protect the graft union with 1-2 feet of mounded soil or commercial tree wraps, but be sure to remove them in the spring.
Turn off any in-ground irrigation system. Commercial fruit growers use irrigation to keep water constantly freezing on the leaves to keep their crops at 32 degrees F, but home irrigation systems are not designed to provide enough water to protect plants from cold. Running the irrigation system usually does more harm than good, causing worse damage, broken limbs, saturated soils, and root rots as well as wasting water.
After The Cold
After a cold spell there are several things you can do to help your plants recover. If it was a dry, windy cold, irrigate the plants to rehydrate and thaw the roots. Dead leaves may be removed to look better, but pruning is usually best left to spring when plants start to grow again. You can scrape the wood with your fingernail to check to see if the tissue is dead or alive. If it is green just underneath the bark, the tissue is still alive although the leaves may be dead. If the tissue is brown or black underneath, the tissue is dead. You can prune back to where the green is found under the bark to remove the dead wood. If you are not sure if it is dead or alive, wait until spring to see where regrowth occurs and prune back to that point.
Severe cold damage is not usually a problem in this area of Florida, but history tells us that we can still have some freezing temperatures and plant damage. Be ready to protect your plants and know what do to when you do have damage.