You know that saying, “If a tree falls in a forest and no one is around to hear it, does it make a sound?”
Well, it turns out that a falling tree is not the only way that trees make noise. In fact, something called frost cracks in trees have made such a loud, striking sound that they have been compared to a rifle shot!
A frost crack is a long, vertical gash down your tree, and is the result of a tree bursting open. Frost cracks occur during the winter (and sometimes spring), and can affect any kind of tree where the trunk is exposed to the sun, but most especially young trees or trees with thinner bark, such as honeylocust, linden, and maple trees (though we’ve seen plenty on aspens as well).
So how and why do trees split open like that?
Frost cracks have to do with a rapid change of temperature during winter. During the day, the sun shines on the tree’s trunk. Unlike the summer months, when the trunk and branches are shaded by leaves, the sun has full access to the bark in winter. The sun’s rays warm up the inner wood and raises the temperature of the water flowing through it.
But then the sun goes behind a cloud or sets that night, and the tree is faced with an extreme change in temperature. The temperature outside the tree drops, but the inner wood that has been warmed by the sun takes longer to adjust to the cooler temperatures.
This extreme difference in heat starts to affect the tree. Even during the winter months, there is water flowing through trees (similar to the blood in our veins). As temperatures drop, water in the bark freezes, causing the bark to contract. At the same time, the much warmer water in the inner wood is still flowing, and this difference causes the bark and the wood to split – suddenly and LOUDLY.
When are frost cracks most likely?
Frost cracks often happen after cold, sunny days, when nighttime temperatures drop precipitously. Because the sun hits the south and west sides of a tree, those are the areas most susceptible to damage.
Young trees and those with thin bark are the most likely to suffer from frost cracks, as the sun can more easily warm the inner wood. On evergreen trees, if a large branch has recently been removed, the newly exposed part of the trunk that the branch once shaded could be affected.
If you have wrapped your trees in the fall to prevent sunscald or frost cracks, your trees should be okay – just remember to remove the wrap right away in the spring, or you might inhibit the tree from growing.
One (or more) of my trees has a frost crack. What should I do?
If you notice a long vertical crack in your tree, especially one that wasn’t there before the winter, it is probably a frost crack.
The good news is that the tree already has all hands on deck to try to heal this wound. You’ll notice in the summer that the crack will seem visibly smaller. The tree will also start producing “reaction wood” as a sort of scab to try to heal itself.
Be prepared, however, as each winter the crack will again get wider. It’s a constantly fluctuating hole in your tree that reacts to the weather and the temperature around it.
The bad news is that the tree is putting a lot of energy into healing that wound which means that it needs all the help it can get. Make sure it’s getting enough water, watch for any pests or diseases (they will try to enter the tree through this new gaping crack), and look for any other signs that your tree is in distress.
If you’re not sure how to spot this or if you want us to take a look and assess the health of your tree, give us a call at 303-674-8733 or schedule a consultation online so we can check if any treatment options are necessary.
Most trees survive long after frost cracks, and some have survived more than one. But knowing that your tree has a frost crack is vital to help it survive, so be sure to look over your trees the next night you hear any loud noises coming from your yard!