It’s disappointing to watch your plants struggle after a cold snap. But how do you know for sure whether it was the frost that damaged them?
Frost damage tends to have a few distinct characteristics, including limp, droopy leaves, long cracks on tree trunks, and leaves that gradually turn black and die in as little as a few hours.
But even if a plant loses all of its foliage after freezing weather, it doesn’t necessarily mean that it’s dead. And even if a plant looks perfectly fine after a frost, the damage could take months to appear.
This article will detail the telltale signs of cold damage, what to do about it, and how to prevent it from happening again.
What Are The Signs Of Frost Damage On Plants?
Like with many plant health concerns, the symptoms of one condition often overlap with others. But when you combine all of the evidence you can see with environmental clues, you get a clearer picture of what may have happened.
Here are some of the signs to look for when you think one of your plants might have frost damage:
- The foliage on the plant might look very droopy, and the stems might be soft and limp. Sometimes the leaves appear to be soaked.
- On woody plants and trees, severe frost damage can cause the bark or stems to split, leaving long, narrow cracks. This is due to the sudden shift in temperature and is more common in young and old trees with smooth bark.
- Frost-damaged plants may have white or yellow marks around the veins in the leaves, where the dead cells are located.
- According to Clemson’s Cooperative Extension, desiccation is another term for a plant drying out. It can dry out when moisture rapidly leaves a plant before it is replenished. Desiccation is common in winters that follow dry autumn months when the ground is frozen to a greater depth than the root system. When plants are affected by desiccation due to the cold, you will often notice discolored, burned leaves or needles on evergreens.
What Do Plants Look Like After Frost Damage?
Depending on the species and the degree of temperature change they are subjected to, frost can affect some plants differently. For example, some plants might look sick immediately after sustaining frost damage.
Other plants might seem fine at first, but could show signs of damage anywhere from a few hours to months later. One surefire way to tell that the cold hurt a plant is when it seems fine the morning after a frost, and then starts to turn black and wither within the next several hours.
Sometimes, frost damage can go unnoticed until you’re well into the growing season. For instance, a flowering plant or tree might not produce as many blooms in the spring after it was affected but appears healthy otherwise. In these cases, you may never figure out the cause of the lack of blooms.
How Long Does It Take For Plants To Get Frost Damage?
Frost damage can occur anytime a plant is exposed to freezing temperatures, but the likelihood and extent of the injury depends on the following:
- A plant exposed to temperatures as low as 29-32 degrees Fahrenheit for an hour might only sustain minimal, short-term damage. Such weather is known as a “light frost.” A “hard freeze” is when temperatures drop below 29 degrees for an extended period, often killing non-hardy plants.
- Some tender plants might be able to survive a light frost, especially if protective measures were in place. Others, like young or already struggling plants, might not fare as well.
- Some plants might lose all of their foliage after a frost but still survive because the roots stayed above freezing temperatures. Plants whose root systems are partially above ground are more vulnerable to cold damage.
Can Frost Damaged Plants Be Saved?
In general, once frost damage to a plant has been done, there are no actions you can take to reverse it. Since you can’t undo the cold temperatures that occurred, only time will tell how significantly your plants were impacted and whether they will bounce back from their injuries.
Whether a plant damaged by frost can survive depends on several different factors:
Extent Of Damage
If your plant has minor foliar damage after exposure to freezing temperatures, chances are good that it will be okay. If a few days pass and the damage hasn’t spread or gotten worse, the chance of recovery is still not guaranteed, but increased.
However, if immediate damage is apparent to the base or the plant’s crown, it may not survive. Branches or stems that are split with deep cracks can also be a formidable sign. Again – only time will tell, so it’s best to wait and see what happens.
The Overall Health Of The Plant
The most vulnerable plants to frost damage are ones that are young, old, or were already in poor health before the frost.
Seedlings and plants that were recently propagated or transplanted need time to harden off, or adjust to their new living conditions before the weather gets colder. Sudden temperature changes can shock tender seedlings and roots that have not established themselves in a new area.
Plants native to your area have the best chance of surviving a frost since they are used to the climate. But non-native plants, even if advertised as hardy within your agricultural zone, may sustain damage if they haven’t been acclimated to your environment.
It’s also important to note that plants considered “tender perennials” often die back to the ground after the first freeze, but this does not mean they are dead. Although their foliage cannot withstand freezing temperatures, their root systems survive underground and usually come back each spring.
Length Of Cold Temperatures
The chance of survival for a plant exposed to freezing temperatures is different based on the length of the frost. A plant subjected to a freeze for a few minutes has a much better chance of recovering than one in freezing weather for a few hours.
The fluctuation in temperature also determines the plant’s level of success. Continuous freezing followed by thawing in quick succession is detrimental to a plant’s health.
Does Watering Plants Help Prevent Frost Damage?
Watering your plants before a frost is one of the ways you can protect them from damage. Since plants that are underwatered or drought-stressed are more susceptible to cold injuries, it’s best to keep them watered and in good health before they are subjected to harsh weather.
Here are some other good ways to prevent frost damage:
Pay Attention To Your Zone: Make sure you’re planting according to the USDA’s Plant Hardiness Zone Map. This is the best way to determine which plants will triumph over freezing temperatures in your area.
Protect Container Plants: If you plan on keeping potted plants outdoors for the winter, group them together and cover them with plastic. Ensure the plastic does not directly touch the plants – this could damage the leaves. You can also place mulch or soil in a mound around the pots for insulation to the roots. Some gardeners also cover their perennials with plastic nursery pots in the spring if they emerge before the threat of frost has passed.
Don’t Encourage New Growth: Although it might seem counterintuitive, giving your plants fertilizer and pruning them in early fall can risk their health. These two actions can stimulate new growth, which will be the first thing damaged in a frost. Fertilize earlier, during the active growing season, to ensure that your plants have adequate nutrition for optimal health before winter.
Harden Off Seedlings: Even cold-hardy plants in your area should not be placed outside in the spring as seedlings without hardening them off. To do this, place the plants outside, out of the direct sun on a warm day for an hour at a time, and then bring them back in. Gradually increase the amount of time they spend outside over the course of a couple of weeks before leaving them outdoors full-time.
Should I Water My Plants After A Freeze?
Wet soil is warmer than dry soil and can help to insulate plants if further cold weather is expected. Unfortunately, watering frost-damaged plants will not help them recover or improve their appearance. It likely won’t hurt them, though, and could provide some needed moisture to the root system.
One thing you should not do, however, is rush to prune the damaged areas of your plants after a frost. Since some damage can take months to appear after it was sustained, it’s best to wait until the full scope of the injuries can be assessed before you trim. Also, if more freezing weather is expected, the plant’s damaged, or dying parts can help protect the healthy tissue from the elements.
Once your plants start to show new growth in the spring, you should be able to determine where it will be safe to prune them. You can also check for dead wood on trees by scraping the bark gently with a fingernail. If the wood is black or brown underneath, it will not recover and should be cut back.
Although many practical ways exist to prevent cold damage to your plants, a frost can sneak up on even the most experienced gardeners. So even if you lose a plant (or 2 or 3), at least you learned how much your plants could handle, and you can plan for next year.
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About the author:
Kathryn is a plant enthusiast and freelance content writer who specializes in home and garden topics. Based in New York, you can get in touch with Kathryn at https://kathrynflegal.journoportfolio.com/.