Cold snaps can be quite the unpleasant surprise, with icy roads, rooms becoming too cool for comfort, and all the rest. But we usually can, at least temporarily, escape the cold—now imagine what it’s like for the poor plants that have to sit there and endure the freeze! Thankfully, with some good effort on your part, you can help your green pet make it to that first day of spring even after a severe frost.
How to rescue a potted, frost-damaged plant
First things first—if you suspect your plant has been damaged by a cold snap and you can move it, bring it inside. Do note, however, that being plunged into room temperature immediately out of the freezing cold will be quite stressful for it. So, move the plant some place where it’s just slightly warmer than the outdoors. A garage, windowed balcony, closed-off porch, or an unheated room are all good initial choices. Then, once the plant warms up, you can move it into heated conditions. Refrain from placing the plant too close to a heater, as it can dry out the foliage and cause additional stress via excessive heat.
Frost damage usually manifests as wilting, yellowing, darkening, and watery-looking foliage. It might not be apparent immediately, instead showing up one to a few days later. You can prune the most affected shoots once you bring the plant inside, though it’s best not to overdo it. Instead, wait 5 to 10 days for it to adapt to the indoors before cutting the less damaged areas. Use either sharp scissors or pruning shears to do this, sanitizing the tool with rubbing alcohol beforehand.
Once the plant has adapted to warmth, give it a lukewarm (68–77°F / 20–25°C) drink. Take care to provide it with optimal watering and humidity from this point on. For tropical species, water and mist regularly, but allow the shoots and topsoil to dry off to avoid rot. Since the plant’s roots may also have been damaged, it might not take up water as quickly as it otherwise would, making it easier to overwater by accident. This is even more important when it comes to succulents, as they’re easily prone to rotting. Refrain from using fertilizers until the plant fully recovers and starts growing again.
What about plants in the open ground?
Here, warming the plant up immediately is just as important as it is for a potted one. Cover the shoots with either thick burlap or non-woven garden fabric, securing the material with strong ties or ropes. You can also use fir branches, sticks, or straw if necessary. This way, you’ll protect the plant from frost, rain, hail, cold fog, and strong wind, up to a point—that is, the minimal temperature at which the material will be effective.
Your second goal is to protect the root system—if it becomes too damaged, the plant won’t be able to draw in nutrients to replace its damaged shoots. To do this, place a 2–4 in (5–10 cm) thick layer of mulch around the dripline (the surface directly under the crown). If snow is present, remove it beforehand; you can then put it on top of the mulch to further insulate the roots.
Once the nightly temperatures stably rise above 32°F (0°C), you can remove the shoot covers and mulch. Inspect the plant closely afterward. Prune the damaged shoots with sanitized pruning shears, and remove any cracked or peeling bark, cleaning out the areas around it. Give the crack some time to dry off, then close it up with pruning sealer. Once the temperatures rise above 41°F (5°C), you may water the plant thoroughly.
Full recovery from frost damage can take a lot of time and will require patience on your part. An ounce of prevention is worth far more than a pound of cure when it comes to plant health, so it’s best to be prepared for cold snaps in the future. Keep your eye on the weather forecast and cover your plants in advance of cool conditions and frosts. Beyond winter, make sure to stop fertilizing in mid-to-late fall so that they won’t produce vulnerable new growth. Last but not least, check if your USDA zone is suitable for a plant before purchasing and growing it outside. For potted plants, the lower limit will be 2–3 zones higher than usual due to their roots having little insulation around the pot’s sides.