How to Best Warm Up a Plant Exposed to Cold Temperatures

There will be a time when you’re faced with a cold-damaged houseplant. This could be from accidentally leaving the potted plant outside or by an open window when the temperature drops. The question is, can you save them?

The short answer is it depends! The extent of the damage and the plant’s hardiness determines whether your plant can bounce back from the cold exposure. 

Either way, giving them immediate care is vital. Here’s how you can get started: 

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1. Bring the Plant Indoors/Move It Away from the Cold Area

Removing the plant from the cold is the first thing you need to do. However, DO NOT place them next to a heater or on a heating mat to warm it up quickly. Remember, plants are slow. Causing a sudden temperature change could stress the plant further. Weather doesn’t go from frost-bite cold to warm in a few seconds, the plant is already dealing with a faster than normal temperature change because it came indoors. If you use things to speed up the process any faster, you’ll only be decreasing your plant’s chances of recovery. 

Instead, let the plant acclimatize to the room’s temperature slowly. Like people, experiencing hot and cold temperatures multiple times in a day can make anyone miserable. Take pity on your plant baby and let it warm up gently.

If you can’t bring your potted plants indoors, you can simply move them closer to your house, preferably by the wall and under a roof. If you have a greenhouse, even better! The idea is to minimize the plant’s exposure to cold as best as possible. 

2. Water the Plant Deeply with Room Temperature Filtered Water

You need to thoroughly water the plant until excess water flows out from the pot’s drain holes. This step may sound ridiculous, but it actually will help your plant a lot. The water will not only warm up the soil but also rehydrate your plant. If you’re watering your plants outside, wait until it’s not below 50 degrees F. Otherwise, the water will immediately crystalize in the plant’s soil. Not only is the plant not getting any moisture, but it’s also likely to suffer freeze damage to its roots.

It may be tempting to use hot water to quicken the process but let’s try not to cook your plant. Again, extreme temperature differences serve to only worsen your plant’s condition. It’s best to provide it with room temperature water instead. In terms of water type, use filtered water or rainwater where possible. You can use tap water only if it isn’t hard water and/or doesn’t have high mineral content.

For watering frequency, you can expect to water your plant every 2 weeks or so, depending on its size and type. However, be careful. You’re in more danger of overwatering than underwatering your plant, cold/dormant plants need less water. When in doubt, always use the knuckle test before watering, regardless of whether it’s the warm or cold season.

3. Cover the Plant’s Pot Entirely with Burlap to Retain Heat

Plants in pots and containers are more susceptible to freezes and cold damage because the roots are above ground. It doesn’t have the same protection as in-ground plants where the earth can keep the roots snug and warm. You can easily accommodate your indoor plants by wrapping the pots in double layers of burlap and securing them with twine or a thin rope (Amazon links). You can also use blankets or sheets as an alternative. 

For outdoor plants, you need to additionally cover the rest of it with horticultural fleece (Amazon link), especially if the plant doesn’t have any form of shade. Not only does this help the plant retain heat, but you also inadvertently increase its surrounding humidity. Ensure the covers are tightly secured to prevent cold winds from blowing them off the plant.

Keep in mind to remove these wrappings every morning when it’s no longer cold. Yes, it’s kind of like putting pajamas on your plants. But if you want to warm them up each time and make sure they survive the cold, swaddle the plant baby in its burlap blanket every night.

4. Leave Cold-Damaged Parts of the Plant to Protect the Rest of the Foliage & Branches

For plants outside, this is very helpful in insulating other plant parts from the cold. However, it is best to remove any visibly rotting parts for indoor plants, mainly if it’s soft-stemmed. Where possible, if the damage doesn’t look to be an immediate problem apart from it looking not its best, leave it as is. 

Remember, your plant is still taking time to warm up and recover. Any pruning you do forces it to grow new parts, further stressing the plant. At the end of the day, it’s a judgment call on your part. But let’s keep the cutting tools away for now and see how it fares for at least a month. After that, you can lightly snip off all the unsightly parts.

5. Provide the Plant with LED Grow Lights or Indirect Sunlight

Only do this after a month has passed and your plant looks considerably better. Before this, you can use a grow light (Amazon link) to ensure it still receives light. Ensure to introduce the plant to more sun gradually, inching it little by little into the bright spot one day at a time.

However, skip this step if your plant is undergoing its annual winter dormancy period. This is when a plant entirely sheds its foliage and looks like it’s dead. You can easily look up whether your plant goes dormant in winter with a quick search online. If your plant has gone dormant then, you need to ensure it stays that way until the weather warms up in spring. Here’s a general brief on taking care of them: 

• Place the plant somewhere cool, like a basement or unheated garage.
• Keep the plant lightly watered for the next 3 months. 
• If you see new growth sprouting in spring, slowly introduce the plant into sunlight until it revitalizes once again. 

You can read more about how to overwinter these types of plants here in our Japanese Maple article and Oxalis Triangularis article.

6. Avoid Giving the Plant Any Fertilizers

This is an obvious one, but it still needs to be said. Fertilizers will only harm the already weakened plant – it’s like drinking seawater if you’re stranded, it may seem like it will help but, when that many salts (and/or fertilizers for plants) end up in your digestive system ( or on your roots) it ends up sucking out more water than you ingested and you get dehydrated. Don’t take the risk of killing your plant’s roots, you’ll have plenty of time to fertilize later.  

If you have a fertilizer routine, you can only start again once the weather warms up in late spring. Until then, hands off those pellets. 

References:

https://gardeningsolutions.ifas.ufl.edu/care/weather/treating-cold-damage.html

https://pender.ces.ncsu.edu/2014/01/protecting-garden-and-landscape-plants-during-cold-weather/

https://chatham.ces.ncsu.edu/2016/02/protecting-landscape-and-garden-plants-during-cold-snaps/

https://chatham.ces.ncsu.edu/2016/04/protecting-fruit-plants-during-frost-or-freeze/

https://extension.msstate.edu/blog/how-protect-plants-during-winter

https://www.canr.msu.edu/news/winter_dormancy_and_chilling_in_woody_plants