While cold hardy palms can tolerate freezing temperatures, tropical palms may suffer from the cold damage. Usually, palm tree owners, that live in the warm climates, don’t need to worry about cold weather.
But, with unpredictable winters in the last couple of years, freezing temperatures don’t come as a surprise. Here is what you can do to protect your palm trees from freezing cold by applying:
- Palm fertilization
- Palm heavy mulching
- Palm heavy watering
- Antitranspirant spraying
- Copper fungicide spraying
- Palm warm cover
- Palm trunk and foliage wrapping
- Heater and light-bulbs
- Heat cables
- Temporary greenhouse
How Does Cold Affect Palm Trees
Cold weather can affect palm trees in different ways. Cold temperatures will slow down the root activity and growth rate of the palm.
Freeze or frost can damage the palm tissue in the trunk, which may limit the ability of the palm to provide leaves with enough water. Unfortunately, palm trees can’t regenerate conducting tissue and will likely die after a while. If the bud, also called “palm heart”, gets damaged, the palm will not survive.
How Cold Is Too Cold For Palm Trees
Palm species very greatly in their sensitivity to cold. Some types of palms can tolerate cold temperatures down to 10 – 15F for a short period of time, while others gets damaged when the temperatures drop below 45F.
Cold tolerance of the palm also depends on summer care, plant age, and time of establishment. If you are trying to figure out what is the lowest temperature your palm can survive at, start by checking cold tolerant for this particular species.
You can find it in my palm tree catalog under ‘Cold Hardiness’ section in the palm profile. Keep in mind, that by providing winter protection, you can push a palm’s tolerance by one-half or full USDA zones which means a range of 20 – 30F (12-18C) for subtropical and temperate plants.
10 Ways To Protect Palm Trees From Winter Freeze, Cold, or Frost
Before we talk about different cold protection options, it’s important to understand that a little bit of cold weather is actually good for the palms, because it promotes dormancy and also makes palms more cold tolerant (cold hardy). So, don’t start winterizing your palms too soon.
If there is no sudden temperature drop, let the palms acclimatize a little to the colder conditions. The goal is to protect the most important part of the palm which is the bud and to minimize the damage to the leaves and stems in case of an unexpected freeze.
Thankfully, there are number of things you can do to prepare and protect your palm tree during winter. Some of them are very simple while others are more complex. It’s good to know that even the simplest measures can add one-half to a full USDA zone to your garden.
1. Palm Fertilization
Palm tissue deficient in nutrients is less cold tolerant. Thus, it is important for the palm tree to receive right amount of fertilizer in the months leading up to the period of cold weather.
According to recent studies from University of Florida, fertilization improves cold hardiness of palms. Of course, the fertilization schedule will depend on where you live and the length of your growing season.
If you live in a climate with cold winters, the key is not to apply fertilizer late in the growing season, since the palms will continue to grow into the early winter. That will delay the dormancy and open them to more cold damage.
I recommend using a slow-release good quality fertilizer that has the same amount or close of Nitrogen (N) and Potassium (K). You will know the ratio by looking at the three numbers on the label (NPK): 15-5-15 or 20-15-15. Avoid using lawn fertilizer with ratio of 27-2-2 because it will promote foliar growth instead of root and flower development.
You can see what top 10 fertilizers I recommend in my palm tree fertilization post.
2. Palm Heavy Mulching
Heavy mulching is the most effective way to minimize leaf damage and maximizing tree survival.
You are probably already applying mulch all year round, but during winter mulch your palm more heavily. Adding 4-6 inches of mulch will protect ground from freezing deeply, thus protecting roots and lower trunk of the tree.
Since a lot of cold tolerant palms have their buds underground, mulch will keep the temperatures relatively constant protecting it from cold damage caused by rapid temperature fluctuations.
Also, unfrozen roots will be able to replenish the moister lost during winter transpiration. I recommend using organic mulch like course wood chips, maple or oak leaves, wheat straw or pine straw because they don’t compact too much over winter and moderate soil temperatures, suppress weeds, conserves moisture, and add nutrients to the soil as they decompose.
Another benefit of using whole deciduous tree leaves with the mulch, is that they release considerable amount of heat while decomposing. To keep the mulch from blowing away you can use a wire netting enclosure. Put the mulch 1-2 ft away from the trunk of a small palm and about 3-4 ft away from a large tree.
You should leave the mulch until your area is done with the frost and then gradually remove it over a period of a 3-4 days. Removing it slowly will provide your palm with more time to get used to increasingly stronger sunlight and also provide some protection against a late frost.
3. Palm Heavy Watering
While mulching will prevent roots from freezing, it won’t help with the water uptake that gets dramatically reduced once the temperatures falls below 40°F (5°C). Adding to the stress, cold winter winds in combination with the afternoon sun cause winterburn and defoliation of the palm.
To maximize water availability to the leaves, make sure the palm is well-watered entering winter season and the soil is saturated throughout the winter.
Since moist soil loses heat less rapidly than dry soil, water heavily the soil around the palm prior to a cold snap. I recommend using lukewarm water instead of a cold one because it will somewhat warm up the ground increasing the water uptake of the palm.
4. Antitranspirant Spray
Another way to reduce water loss from the leaves is to use antitranspirant spray. It forms a soft, clear, flexible film on the plant’s foliage which holds moisture reducing water loss during plant stress. I like spray called ‘Wilt Stop’ by Bonide.
I use it for winter protection or to minimize a transplant shock if I am transplanting a palm during growing season. It protects plants from drought, wind burn, sunscald, winter kill, transplant shock, and salt damage while at the same time allowing them to grow naturally.
You will only need to spray it once per season. BTW, it will also extend the life of Christmas tree by preventing it from drying out too quickly.
5. Copper Fungicide Spray
Stressed by cold temperatures, palm trees can become vulnerable to bacterial and fungal infections. The low levels of bacteria present on healthy palm tissue are harmless but becomes a problem once the palm has been damaged by cold.
That is why it is a good idea to spray the tree with fungicidal copper before the freezing temperatures in order to reduced the amount of bacteria to the lowest levels possible.
Spray the stem and foliage with a broad-spectrum fungicide/bactericide like Liquid Copper Fungicide by Southern Ag a few days in advance when you are expecting cold weather. It has a unique formula that helps fight both bacteria and fungi.
You should also spray open-crowned palms, because water collected in those crowns might freeze and thaw causing the damage to the tissues and providing perfect conditions for bacteria and fungi.
6. Warm Cover
During cold days, it is a good idea to cover your palm. If your palm tree is small, you can cover it with a weighted down box or a blanket. On sunny days, partially open a box to avoid air heating up to damaging temperatures inside.
This can happen even with the outside temperatures being below freezing. Don’t let the tree sit under the cover for more than 3 days in a row. After 3 days, uncover your palm during the day to provide it with some light.
When placing the blanket over the tree, allow for the cover to drape loosely so that warm air rising from the soil will be trapped under the cover. This will keep your palm 4-5 degrees warmer than the outside air.
You should remove all the covers once the weather is warm again. Avoid using a plastic for covering, as it may traps moisture underneath that will freeze and cause more damage.
7. Palm Trunk and Foliage Wrapping
Trunk and foliage wrapping is another great palm winterizing technique if you have a palm with a central trunk. Again, it’s best to use a material that does NOT absorb moister like synthetic blanket, burlap or a landscape fabric.
Before wrapping the tree, spray the area being wrapped with fungicide/bactericide spray like Liquid Copper Fungicide by Southern Ag.
Next, wrap the material around the trunk and secure it with a duck tape. Continue to wrap up around the lower leaves while gathering the leaves closer and closer into a bunch. Wrap as high as the stiffness of the leaves will allow it. Don’t worry, the foliage is not going to be damaged.
You can usually wrap the whole foliage mass of a smaller palm tree covering it completely. At this point, your palm might look like a mummy. During extreme weather, you can easily drape a cover over the open foliage on the larger palms removing it once the cold has passed.
While you can apply multiple layers, even one layer adds 2°-3°F (1-2C). Multiple layers of synthetic blanket can even add a full USDA zone of protection keeping the temperatures under the wrap 6°-8°F (4°-5°C) degrees warmer than the outside.
Some gardeners use bubble wrap, but I don’t like it because it might cause condensation that will lead to some problems.
Expert Advice: To minimize the fungal and bacterial problems, place sticks around the trunk before wrapping it so that the wrap does not touch the trunk.
It is safe to leave the wrap on until early spring.
8. Heater and Light Bulbs
Another way to warm up your palm, is to place a small propane heater near the palm and use a fan to blow the warm air towards it. Keep the heater far enough from the tree to prevent overheating or burning.
Perhaps even more effective way, is to winterize your palm tree with Christmas lights. Simply wrap them around trunk a little denser than normal. As long as there is no wind, the lights will add 2°-3°F (1-2C) during cold winter night. In windy conditions the heat disappears too quickly to provide any warmth.
Using holiday lights underneath a loose landscape fabric, can add another 2°-3°F (1°-2°C) of heat. Some palm enthusiasts use the holiday lights underneath the wrap easily adding 10°-15°F (6°-9°C). While this sound like the best solution, it might dry up the tender leaves.
Expert Advice: Be careful with the light bulbs if you are relying on snow as your cover. The lights can melt the snow around the palm leaving it fully exposed to freezing air and cold winds.
9. Heat Cables
Another popular palm winterizing technique is the usage of the low-wattage heat cables. Typically used to wrap water pipes to prevent freeze damage, heat cables can be found in any of the hardware stores. Just like the holiday lights, they can be used around the trunk and the foliage of the palm.
The cool thing about heat cables is that they are extremely safe and reliable and most of them come with a built-in thermostat that automatically turns the heating cable on below 40°F and off above 55°F.
Some gardeners also use heating cables to wrap around the root ball when planting a palm. Then, they can active it during a cold winter to heat the root zone and prevent the roots from freezing.
Additionally, this warms up the water and as a result provides supplementary heating to the above ground plant tissues when the water moves up the roots system.
10. Temporary Greenhouse
If you have a lot of time and energy, you can build a temporary greenhouse around your palm. Adding a supplementary heat to the greenhouse will add two or even more full USDA zones to your garden.
This is the most involved method that will allow you to grow palm trees almost anywhere. Of course, the greenhouse structure has to be strong enough to withstand strong winds, freezing rain and heavy snow.
Built a wooden frame above the tree and cover it with double plastic sheet nailing it to the frame. Wet snow is very heavy, so make sure to built a slanted roof.
If I see a cold weather coming my way, I usually use heavy mulching, saturate root area with water, spray tree with broad-spectrum fungicide/bactericide and apply Christmas lights.
If the cold weather is going to last for a few days, I use antitranspirant spray and a wrap under Christmas lights. That’s usually enough. Since I live in a warm climate, I really don’t need more advanced winterization techniques.
I hope my tips will help you prepare your palm trees for cold weather. Let me know if you have any questions.
- 5 Ways To Save Cold Damaged Palm Tree
- Top 10 Cold Hardy Palm Trees
- Importance of Microclimate When Choosing Cold Hardy Palms
- Top 5 Factors Affecting Cold Hardy Palm Tree Growth
- How to Save a Dying Palm Tree