South Florida gardeners have been fortunate so far this winter. The temperatures have been mild and what cold weather we had didn’t last long. The commonly cultivated palm trees, for the most part, are tolerant of our Florida winters. But if the change in temperature is too severe, or if the palm is not well prepared for it, wintry weather can devastate palm trees.
Damage can come in a multitude of ways. The mildest damage occurs in the leaves. The cells break apart and the leaf can’t photosynthesize. If this is the extent of the damage, then the palm will produce new leaves and the old leaves will die, discarding all damage from the chilly temperatures.
Frigid weather may damage tissue in the trunk of the palm, stopping the flow of nutrients and water throughout your plant. Depending on the extent of the wound, some individuals can continue to grow while others may not. The most severe cold damage is trauma to the bud, the growing point. If the bud is damaged, it will rot, and the palm will slowly but surely die.
Weather severe enough to cause this type of damage does not come often to southern Florida. But, when it does, we should be ready to protect our plants. Here are some tips to care for your palms in the event of a winter chill.
Before cold weather: Plant cold-tolerant palms such as dwarf palmetto ( Sabal minor), needle palm ( Rhapidophyllum hystrix), Mexican fan palm ( Washingtonia robusta), European fan palm ( Chamaerops humilis) and windmill palm ( Trachycarpus fortunei). But, if you are expanding your palm garden collection, planting only cold-hardy palms may not be the best option.
In this case, design your palm garden for frosty weather. Plant palms so they are protected from winds — behind walls or sheltered by shrubs. Also, plant palms in warmer microclimates like next to a pond or canal.
Proper fertilization is the final step in preventive care. A healthy palm is less likely to be injured by wintry weather, and a healthy palm is a properly fed palm. No need to go overboard on the fertilization; just spread twice a year (in the spring and fall) to maximize health.
During cold weather: Cover the bud and crown with a blanket. This technique is best for nighttime. The blanket should be removed in the morning; strong sun may overheat the plant and exacerbate damage. If temperatures drop below freezing, put a floodlight or another heat source under the covering. A heat source can be used without the blanket, but it won’t work as well.
There are some obvious issues with covering your palms. Some palms are simply too big or too tall to be covered. In this case, try other options to protect your palms. Do not prune your palm during the winter months. While brown leaves may look unsightly, they provide essential insulation and protect the bud and newly developing leaves from damage.
After cold weather: The first thing to do is assess the damage. It is possible that with good preventive care, your palms are hunky-dory. But most likely there is some damage. At the very least, some leaves are beat up.
It is important not to prune leaves that have any green at all, regardless of tears or brown tips. These leaves provide nutrients to the tree, and a palm that has just experienced a winter chill can use all the help it can get. It is best not to prune any leaves until the palm shows signs of growth.
While leaf damage should be assessed slowly, bud damage needs to be addressed immediately. If you suspect the bud has been damaged, simply pour a tablespoon of hydrogen peroxide into the bud of your palm. This will stop bud rot from plaguing and eventually killing your palm. While many horticulturalists suggest copper fungicide, hydrogen peroxide provides the same function, in a safer and more cost-effective way.
The most important part of saving a cold-damaged tree is patience. You probably won’t know until spring or early summer if it will pull through. Just give your palm some time to rebound.
While our sub-tropical winters generally aren’t too chilly, sometimes they do get cold enough to cause some damage. It is important to know how to care for your palm trees properly before, during and after the wintry weather in order to maintain a healthy, happy palm garden.
Sara Edelman is the palm and cycad manager at Fairchild Tropical Botanic Garden