5 Ways to Protect Tropical Outdoor Plants From Frost Damage

Frosty weather can take a serious toll on your tropical plants, especially when it's unexpected and outside of the norm. Florida Gardener Melissa Strauss has some tips for what to do when you need to give them some extra TLC.

A snow-covered garden with tropical plants that need protection from frost.

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It’s shaping up to be a chilly year in the South. Frosty weather has me worrying about some of the tropical plants that typically live quite comfortably in my garden. If you, too, have concerns about the life of your tropicals, there are steps you can take to protect them, or at least their roots, through the winter weather. 

Tropical plants are typically not frost-resistant. Meaning that their foliage, at least, won’t survive temperatures below 32°F (0°C). As a Zone 9 gardener, I have a unique set of circumstances that make these plants both possible to grow and difficult to keep alive during some years. While we rarely experience a hard freeze, yearly frosts are common here. 

This year, we are experiencing a polar vortex, which is bringing extra cold weather to the Southeastern United States. That, combined with more potentially unpredictable weather ahead, means that frost-tender plants need some extra care. We may not be able to save every bit of foliage. But, there are steps you can take to keep roots alive and hopefully salvage some of your favorite tropicals. Let’s dig in. 

Bring Them Indoors

Close-up of tropical potted plants, including Calathea, Dracaena, and Inch Plant, in a greenhouse.
Consider indoor storage for your most cherished plants this winter.

The obvious solution, whenever possible, is to bring frost-tender plants indoors during freezing weather. Obviously, this is not possible for most of those that are on the ground. However, if you are especially attached to one and want to make sure it survives, you can dig it up and store it indoors for the winter. 

Understand that when you dig up a mature plant, there is a strong chance of damaging the roots. This will result in some dieback of the foliage or wilting until recovery is possible. Make sure that the benefits outweigh the risks. Also, consider keeping this plant in a container for the duration, as severe weather will likely reoccur. 

Something to keep in mind is that many tropicals can withstand a light freeze with only minimal damage to their foliage. As long as the ground doesn’t freeze, they will bounce back in short order. Still, I bring anything that’s in a container into the house from the first frost until the last anticipated frost date. 

YouTube video

Cover Them Up

A man wraps an exotic Pandanus Veitchii plant in a burlap fleece winter protection cover to shield it from the cold in the garden.
Frost cloth can protect leaves from freezing overnight temperatures.

In Zones 10-12, you’re unlikely to experience a hard freeze, where the roots of your plants are in jeopardy. That doesn’t mean that a frost won’t do damage, but it does afford you the reassurance that the plant in question will recover. Still, there are ways to mitigate the superficial damage. 

Covering your plants with frost cloth will go a long way toward protecting them. The main issue in a light frost is that dew settles on the leaves. Then, when the temperature drops below 32°F (0°C), it freezes, and that’s the end of those leaves. This happens right before dawn, the coldest time of the night. 

Frost cloth or other covering prevents the dew from settling on the leaves. If they stay dry, there is less chance of damage. These coverings can also bolster the temperature around the plant. Not by much, but sometimes, all you need is a degree or two. This is because you are locking the heat from the ground inside of the covering. 

With that knowledge, it makes sense that the covering should extend to the ground when you’re covering things up. If you want to be thorough about it, weigh down the covering to trap the warmer air inside. 

Mulch

Tropical garden featuring cannas, lilies, and cordyline plants on a bed covered with a layer of mulch made from dry leaves.
Applying a layer before cold weather keeps roots insulated.

Mulch is one of the best defenses that you can give the roots of your plants during the winter months. There is an art to applying that mulch, though, to make it as effective as possible.

Mulch serves two purposes. It helps the soil to retain moisture, and moist soil is warmer than dry soil. It also acts as an insulator, holding the existing heat in the soil beneath. In both of these ways, it provides significant protection for the roots of your tropical plants. 

When it comes to the application, timing is the most important element. Since we want to lock in heat, applying your mulch while the soil is still warm makes sense. Try to get this done in the fall, when you do your autumn cleanup, for optimal results. Otherwise, it’s best to get it done as soon as possible. If you have a few warm days ahead, wait until just before you expect a drop and lock in whatever you can. 

Water Regularly

A woman wearing gloves waters a flowering Bird of Paradise plant in the garden using a hose with a spray nozzle.
A well-watered plant handles winter stress much better.

Even more vital than mulch, keeping your tropicals adequately watered is of great importance. For the sake of the roots and foliage, a hydrated plant is a healthier one. A healthier plant tolerates stress more efficiently and recovers faster

Unlike deciduous plants, tropicals don’t go fully dormant in the winter. While some may slow growth and enter a semi-dormant state, they still need water and light to make it through the winter. Fertilizer is a different story, and you should drastically reduce fertilizing in winter, but water is a must. 

If your area gets consistent precipitation through the cooler months, it’s probably nothing to worry about. But, if you go through a period of dry weather, make sure to water everything. Once every two weeks should be sufficient, as the water evaporates more slowly in the absence of heat.

YouTube video

Water the Morning Before a Freeze

Close-up of a female hand holding a hose, watering exotic plants in the garden, including ferns, palms, and others.
Deep watering before cold weather boosts root temperature.

As I mentioned, moist soil is warmer than dry soil. The reason for this is air. Dry soil has more space for air, and any pockets that exist will freeze along with the rest of the surrounding air. 

It takes a prolonged period of below-freezing temperatures for the ground to freeze. Most places where tropicals can survive in the ground don’t ever experience this duration of freezing weather. Thus, keeping the soil moist will maintain a slightly higher temperature around your plant’s roots. 

If you know that freezing weather is coming, watering the morning before is a good idea. Make sure that you don’t water if the temperature is below 40°F (4°C). Ideally, water early in the day, during the warmest part of the morning. Water deeply, allowing it to soak the ground all the way to the base of the roots and at least as far out as the drip line of the plant you want to preserve. 

If you do this and take care to mulch and cover your tropical plants before freezing weather, it will go a long way. Even if the cold damages the foliage, the roots should survive, and it will recover along with the warmer weather. 

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