While palms may survive, or even thrive, for years in climates cooler than those to which they are native, eventually they may experience temperatures cold enough to cause injury. The January 21st snow and wind chill is likely to take a toll on many of the palms in Northwest Florida. We have experience with this since it also happened in January 2014 and December of 2022. Unfortunately, much of the damage in 2014 was not evident for 18-24 months and we are not out of the window for 2022. Healthy palms can hold on with stored food reserves, but repeated events can continue to weaken them. When cold damage is severe, plant tissues are destroyed and water uptake into the plant may be reduced for years. Many times, it is only the protected bud that will remain alive. These palms can still be saved if the bud remains alive. Winter is not over, even though the temperatures are now creeping higher and higher. So, evaluate what damage you may already have and prepare for any additional, yet to come. Here’s a reminder of what to do.
One of the most common problems associated with freezes is that the freeze-killed lower portion of the spear leaf is degraded by secondary fungi and bacteria that are always present in our natural environment. Palm owners are often anxious to trim off the damaged leaves following a cold weather event. Avoid the temptation to remove these fronds until danger of additional freezes has passed. Even dead leaves provide insulation to the critical bud. As the weather warms, the dead fronds need to be removed from around the bud so that the spear can begin to dry out. Drenching the bud area with a copper fungicide will reduce the secondary microbes. Repeat applications will need to continue as the palm leaves develop. Copper fungicides, unlike other fungicides, are active against bacteria and fungi. Be cautious to not use a copper nutrient spray rather than a fungicide. Delay fertilizer application until new fronds have developed. The best analysis for palms is 8-2-12 + 4Mg. Utilization of proper palm fertilization can improve cold hardiness of palms.
Palm trunk decay appeared 2 years after 2014 freeze.
Palms damaged by cold can still show symptoms six months to three years following a freeze. New leaves in the spring may appear misshapen. Usually, the palm will outgrow the damage. However, sometimes the palm loses its ability to take up water. If there is a sudden collapse of the fronds in the crown during the first hot days, the palm may die. There is nothing that can be done to save the palm.
Gardening in the Panhandle LIVE! is launching Season 6 with new topics starting on March 6, 2025! Each episode is delivered live on Zoom Webinar then posted to our YouTube Playlist. If you would like to join us live and help drive the panel discussion, be sure to click on the title below to register and submit your questions a few days prior to air date.
Learn how to incorporate edible plants into your landscape. Whether your goal is a large vegetable garden or one tree with edible fruit, we can help you find ways to make your landscape a source of fresh food!
Are you trying to create a tropical look in your North Florida yard but frustrated with freeze damage? Let us teach you what plants can offer lush foliage and withstand cold weather!
Not only people love Florida’s climate, but many plant pests thrive here, too. Learn how to identify and manage landscape pests using Florida-Friendly Landscaping practices.
We all know the importance of pollinators, but how can you help to support them? Join us to learn how to attract, identify, and count for the 2025 Great Southeast Pollinator Count!
Growing houseplants can be tricky since our indoor climate is very different from outdoors. Learn how to help your houseplants thrive while keeping your home comfortable!
Flowering bulbs can create dramatic impact in the landscape, but some have specific requirements that might not fit our climate and soil conditions. Learn how to select the right ones for your North Florida landscape!
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Frost on Dune Sunflower Picture by: Pam Brown UF/IFAS Extension
December is finally here and that means consistent nights of watching for dropping temperatures. Tropical plants and newly installed shrubs are susceptible to cold injury. Those colorful, blooming plants that have added a tropical look to the landscape all summer may begin to suffer when the temperatures drop below 500 F. Leaves may turn yellow and flowering stops. These plants will need to be moved inside or have temporary greenhouse built around them. But, hardy plants that haven’t established a sufficient root system will also need additional attention when the temperatures drop dramatically.
The ability of plants to endure a freeze depends on the species and the weather leading up to the extra cold night. Gradual decreases in temperatures helps plants acclimate to winter. But, a sudden one day drop of 40-50 degrees results in a rapid freeze that causes ice to form inside the plant cells. Leaf and stem tissue expands so quickly that it splits, resulting in parts of the plant incapable of transporting water and nutrients, as well as, performing photosynthesis. However, it may be late the following spring before the damage is noticed, when that section of the plant has slowly staved to death.
Cracked bark from frost
Additionally, plants can experience desiccation or drying out. This happens when dry winds and solar radiation result in the loss of more water from the leaves than can be transported by a cold root system. The resulting symptom is marginal and/or tip burning of leaves that leads to totally brown leaves.
Freezes (when the temperature drops to 320 F) are characterized as radiational or advective. Radiational freezes occur on calm, clear nights when heat radiates from the surfaces of plants, making them colder than the air due to the rapid loss of heat. If there is moisture in the air, ice will also form on the surfaces. Under these conditions, ice forms between plant cells, rather than within the individual cells. Most hardy plants can tolerate these type of freezes if they are properly hydrated.
Advective freezes occur when cold northern winds move in rapidly, dropping temperatures quickly, and causing widespread foliage desiccation. Cultivation and maintenance practices can impact a plant’s ability to endure extended periods of low temperatures. Shade-tolerant species installed under the canopy of a tree typically display less injury from radiational freezes because the trapped heat from the ground and the overhead foliage creates a microclimate. Well-watered soil around a plant will absorb solar radiation during the day and re-radiate heat over night, raising the temperature around the plants. Shrubs that are not pruned in the late summer or fall have leaves that can withstand frost and wind. But, the removal of foliage late in the growing season triggers a flush of new growth, that is very sensitive to lower temperatures. The same response can result from fertilizer applications after plant’s have slowed down in growth.
Irrigation Frost Protection on Citrus
Row Cover Picture by: Univ of Maryland Extension
So, what can you do to prepare for upcoming freezing temperatures? Begin by avoiding pruning and fertilizing at the end of the season and making sure that the plants have been watered within 24 hours of a cold night. Next, insulate against water loss and increase heat radiation by adding a three-inch of mulch, as well as, covering the trunks of sensitive trees with a commercial tree wrap. Then, consider what needs to be covered. Frost cloth or other breathable fabrics can trap heat for the night and provide a protective layer from frost settling on the leaves. It needs to be placed by mid-afternoon and removed the next day when temperatures are above 320 F. Plastic is not recommended unless the timing regime can be followed reliably and a structure is used under the material to keep the plastic off the foliage. Anchoring of the cover is critically important in the event of an advective freeze.
Finally, turn off the sprinkler system. Commercial agriculture often uses a running irrigation system to keep the leaf surface temperatures near, but not below, 320 F because sprinkling utilizes latent heat released when water changes from a liquid to a solid state. The thin layer of ice melts and re-freezes on the surface throughout the night, without ice forming within the plant tissues. For the technique to work, sprinkling must begin as freezing temperatures are reached and continue until thawing is complete. Landscape systems are not designed to deliver the amount of water over the length of time required to accomplish this type of frost protection.
When the cold nights have passed, don’t forget to check your plants for water. But, wait until winter has passed before pruning out the frost damaged stems.
In Northwest Florida gardeners are fortunate since it is possible to grow ample supplies of vegetables throughout the winter months. While the Florida Panhandle does receive the occasional hard freeze, many winter vegetables such as radish, onion, lettuce, carrot and the various cole crops, can easily withstand mild freezes.
When a hard freeze occurs, defined by temperatures that dip below 28°F for over five hours, it is important to be prepared with frost cloth, cotton sheets or other suitable material. Frost cloth is a good option since it protects plants from morning frosts while still allowing for a little air transfer. It is a synthetic fabric which offers 4-8 degrees of protection and is available through many online greenhouse and agricultural suppliers. Old cotton sheets, often found at thrift stores for very low cost, offer good protection from frost damage. With both of these products, ensure that the coverage extends completely to ground level with no gaps, to not allow cold air to infiltrate from the bottom.
While these methods will not provide enough protection to allow summer vegetables to be grown during winter months, it can be beneficial in reducing frost and freeze damage to winter vegetable crop.
Additional Tips:
Do not use plastic covers, since they radiate cold and heat more readily. Even if they protect the plants from the cold, they can quickly trap heat in when the sun rises and “cook” the plants.
Additionally, it is important to keep vegetables well-watered at all times, but this is especially true during frost events since moist soil holds more heat. Healthy, appropriately watered plants withstand cold stress at greater rates.
North Florida’s gardeners are facing a new set of challenges dealing with the effects of cold weather. However, a little planning and creativity can make plant protection in the landscape a relatively simple process.
Covering plants to protect from frost. UF/IFAS Photo: Sally Lanigan.
Many homeowners and landscape managers want to know when plants will need protection. The point of freezing is a good rule of thumb for most temperate zone plants.
It is worth noting there is a difference in the terms used for cold weather conditions. Frost, freeze and hard freeze all describe different circumstances.
Frost is when water vapour freezes on surfaces. It usually happens on clear nights with still air and can happen when reported air temperatures are above freezing.
Freezing is when cold air moves in and causes temperatures to drop below 32 degrees Fahrenheit. This condition commonly involves low humidity and wind, making drying out a big problem for plants.
A hard freeze is when temperatures dip below 28 degrees Fahrenheit. Some tropical plants will survive a few degrees below freezing for very short periods, but extended periods of freezing or heavy frost may require lights or other heat used safely in combination with covering the plant.
Some plants can be moved indoors for the holidays and incorporated into the interior décor, rather than cramming them last-minute into a chaotic bundle when a freeze looms.
Get prepared by identifying old sheets, blankets and drop cloths which can be used as covers for tender or tropical zone plants which must remain outside. Test potential covers beforehand to assure all plants will be thoroughly covered.
It is best if the covers enclose the plant entirely without crushing it. Heavy blankets are great insulation, but only a good idea on the sturdiest of plants.
A tomato cage or other support structure can be used to keep the weight off the plant. Covers also need to be secured at the ground with pins or weights to assure cold air does not enter from below and collect under the cover.
Finally, keep storage bins handy and remove the covers in the daytime if temperatures are above 55 degrees Fahrenheit.
Monitor weather reports and react accordingly so tender and tropical plants see spring 2016.
