How To Protect Potted Plants From Frost


When cold weather looms on the horizon, gardeners everywhere begin to think about how they can protect plants from frost.  You may be wondering if there is anything you can do to protect potted plants, which are often too heavy to move.

So, how do you protect potted plants from frost?  One of the best ways to protect potted plants from frost is to provide insulation with cloches, row covers, water bottles, and straw bales.  Choosing the right container and the right location will also protect potted plants from frost.  Finally, choosing cold-hardy plants will make it much more likely that they will survive cold weather.

Of course, there are lots of ways to insulate plants, and lots of choices for containers and locations.  However, there are also some mistakes you can make if you are not careful.

Let’s get into more detail on how to protect potted plants from frost, and what you should avoid doing to prevent damage to your plants.

How to Protect Potted Plants from Frost

A hard freeze will kill many plants.  However, a light frost may only damage or kill the ones that are left unprotected.

frosted leaf
A little frost protection can go a long way in keeping your plants alive.

If you want to extend your growing season, you can take some steps to protect young plants from late spring frosts (or to protect mature plants from early fall frosts).

You can also use some of these ideas to ensure survival for plants that otherwise would not make it through the winter.

Cover Your Potted Plants

Covering your potted plants is an obvious but effective method of protecting them from frost.  Any covering that can provide even few degrees of protection can be the difference between life and death for your plants!

There are many ways to cover your potted plants and their containers, including cloches, row covers, blankets, and other coverings.

Let’s start with cloches, which are often used for smaller plants.

Cover Potted Plants with Cloches

A cloche is a plastic or glass container that is used to cover a plant.  A cloche provides protection against cold by trapping heat from sunlight inside (due to the greenhouse effect).

water bottles
You can make a cloche by cutting the bottom out of any plastic bottle and putting the top over a small seedling or plant. Take the cap off to make a vent for the plant on a hot day!

Some of this heat also gets trapped in the soil underneath the cloche, and is released later on when needed.  At night, when the worst cold threatens plants, the heat trapped inside a cloche keeps plants warm.

A cloche can also protect plants from wind, hail, and pests.  A cloche may even prevent the spread of diseases, which often spread by water, wind, or soil.

You can make your own cloche by cutting out the bottom of any ordinary plastic container.  A clear plastic container is best, since it will allow sunlight through.

If you want, you can even take off the bottle cap on hot days to act as a vent.  If the weather forecast calls for cold, just put the bottle cap back on before nightfall to trap heat inside the cloche.

A cloche is usually used for young seedlings or small plants, since an ordinary plastic bottle will not cover larger plants.  To cover large plants, you will want to use row covers, blankets, or tarps as coverings.

Cover Potted Plants with Row Covers

A row cover is a piece of cloth that is used to cover an entire row of plants, or to wrap around a large plant.  A row cover serves a similar function to a cloche: it protects plants from cold, and may also help protect against wind, hail, and pests.

You can choose row covers that allow sunlight through, so that your plants can continue growing even during a cold spell.  You might also choose to use row covers in addition to cloches in order to offer extra protection to plants.

Just remember to remove any coverings if the weather turns around, since heat can also kill your plants if you’re not careful.

Cover Potted Plants with Blankets and Coverings

Row covers tend to be a bit thin, so if you want something thicker to protect plants from colder temperatures, then blankets or tarps may be just the thing you need.

blanket
Use a blanket to cover potted plants (or the container itself!) to protect them from cold.

Heavy coverings can break stems or branches on your plants, and the cold can get right through if the coverings are in contact with the plants.

To avoid this, drive some stakes into the ground around the perimeter of the plants you want to protect.  Make sure that the part of each stake that stays above ground is taller than the tallest plant.

After you have your stakes in place, wrap the blanket around the stakes and use another piece to go over the top of the structure.  You may need to secure the whole thing with rope or twine.

For more information, check out my article on types of twine and their uses.

You can also use chairs or cardboard boxes as part of the structure to hold up blankets.  Another clever idea is to use chicken wire to reinforce the structure and put coverings right over the wire.

As with any other cold protection method, be sure to remove these coverings before hot weather, or else you could kill you plants with suffocating heat instead of frost or freezing cold.

For more information, check out my article on protecting tomato plants from cold and frost, and my article on protecting pepper plants from cold and frost.

In addition to blankets, you can also consider using burlap as a covering to protect potted plants from frost.

For more information, check out this article from Clemson University on protecting plants from cold.

If you are looking to protect shrubs and trees specifically, check out this article from the University of Nebraska Extension on cold protection for potted trees and shrubs.

Surround Your Potted Plants with Insulation

There are other ways to insulate your potted plants from frost and cold besides the coverings mentioned above.  With a little creativity and resourcefulness, you can take some household items or yard waste that you have lying around and turn them into cold protection for your plants.

First, if it is feasible, move your potted plants close together.  That way, they can keep each other warm.  Also, it makes things easier when you use coverings or other insulation methods.

Once your plants are close together, fill some plastic water jugs or five-gallon buckets with warm water, and put them around the plants.  This will help to keep the plants warm for a bit longer on a cold night.

water jugs
Put jugs of warm water near plants to keep them a little warmer when it gets cold.

You can switch out for new water jugs and buckets the next night to protect plants during an extended cold spell.  Watering the soil itself can also keep the soil warm, but this is not a good idea if a freeze is imminent.

Another way to protect plants from frost is to put mulch on top of the soil in a container.  However, be careful in the type of mulch you use, and when you apply it.

For the purpose of protecting potted plants from frost, straw is a great choice of mulch.  Straw does a good job of insulating the soil against temperature changes, so it will retain heat in the soil.

You can also remove straw easily once the cold has passed.  Removing the straw allows the sun and air to heat up the soil in the container during the day.

If you have an entire group of potted plants together in one location, you can also consider using a ring of straw bales as a thermal barrier to protect all of the plants at once.

There is one important thing to keep in mind when using any type of mulch.  Once the soil is cold, mulch will actually keep the soil cold, instead of making it warmer.

Insulation works both ways: it keeps warm things warm and cold things cold.  Thus, mulch will prevent the sun from warming up cold soil.  This can prolong dormancy of plants in the spring.

For more information, check out my article on mulching around tomato plants, and my article on how too much mulch can kill plants.

Finally, don’t insulate your plants with mulch too early in the season, or else they can get too hot, which can kill them just as easily as frost.

Choose the Right Container

Your choice of container may not seem like a big deal.  However, choosing the right container can play a big part in helping to protect your potted plants from frost.

First, choose a bigger container for your plants – as large as is practical.  If you need to move the plants indoors for the winter, a smaller container might be ok.

If your plants are staying outside for the winter, then use a bigger, thicker container and fill it with extra soil.  The larger mass of the soil and container will stay warmer for longer.

You can choose either clay or plastic pots, depending on the type of plant you are growing.  Clay pots are better for plants that prefer drier soil, such as succulents.  They also provide better insulation than plastic pots.

clay pots
Clay pots insulate better than plastic pots, but they are heavier and the plants will need more frequent watering.

On the other hand, plastic pots allow you to water less often, so they are better for plants that need moist soil, such as seedlings.  They are also much lighter than clay pots, making it easier to move them indoors for the winter.

For more information, check out my article on plastic and clay pots.

You can also opt to use grow bags as a container for your plants.  Grow bags are made of burlap or other cloth material, and they allow better air circulation than clay or plastic pots.

Grow bags also drain faster than clay or plastic pots, which helps to avoid root rot.  Grow bags are also easier to store than clay or plastic pots.

For more information, check out my article on the pros and cons of grow bags.

Choose the Best Location for Potted Plants

Choosing a good location is important for protecting potted plants from frost, especially if they are heavy and difficult to move.

To give your potted plants protection from wind, plant them near a wall, hedge, or other natural barrier (such as a berm).  Without the wind chill, plants won’t get so cold, and they won’t dry out as much.

hedge
Put plants near a hedge to give them a little protection from the wind.

Remember that elevation also matters when it comes to frost protection for potted plants.  The roots are more sensitive to cold than the top part of the plant, so it is more important to insulate the roots.

To do this, you can partially or fully bury your containers in the soil during the winter.  You can also pile up soil or mulch against the container and remove it when spring comes around.

Finally, remember that large temperature changes are also harmful to plants.  Do not put a potted plant in a location where the temperature changes rapidly.

Bring Potted Plants Indoors

You can also choose to bring potted plants indoors if the size is practical.  The plant must be short enough to fit inside your house.  Also, the plant, along with its soil and container, must be light enough to move it indoors before winter and back outdoors in the spring.

If you want to protect your plants without bringing them in your house, consider using your garage or a greenhouse to provide partial protection from the cold and wind.

No matter where you put your plants, just make sure that they get enough sunlight.  Put them near windows or under a skylight to give them enough sun.

Avoid putting them in areas where they might get exposed to a cold draft (near windows) or hot air (near heating vents).

Choose Cold-Hardy Plants

Choosing cold-hardy plants is one of the most important things you can do to keep your potted plants alive during winter.  When looking at plants to buy, check the cold hardiness zones that the plants can survive in.

Then, look up your USDA Plant Hardiness Zone to see if the plant will survive where you live.

If you live on the borderline between two hardiness zones and you are not sure if a plant will survive there, keep it in a greenhouse, or bring it indoors during the coldest part of the winter.

Can I Cover Plants With Garbage Bags?

No, you should not use plastic garbage bags to cover potted plants as protection against frost.  Instead, you should use cloches (for young seedlings or small plants) or row covers and blankets (for larger plants or entire rows of plants).  A support structure such as stakes and chicken wire can help to hold up these coverings.

If you want to use plastic over cloth coverings, then you can do that for extra insulation.  Just make sure to remove them when the temperatures go back up, to avoid suffocating the plants in the heat.

Conclusion

By now, you have a much better idea of how to protect potted plants from frost.  You also know what you should avoid doing when cold weather threatens your garden.

I hope you found this article helpful – if so, please share it with someone who can use the information.

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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