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Why Do Trees Make Loud Cracking Noises in Winter?

frost crack on apple tree

Healing frost crack in an apple tree branch

 

Imagine this:

It’s a freezing cold winter night, typical here in Dayton. You’re bundled up indoors, protected from the cold night air. Everything is quiet, settled down for the evening. Suddenly, you hear a large CRACK! It sounded like a rifle shot! Startled, you peek out your window and turn on the outdoor lights, but everything seems calm in your tree-filled backyard.

The next morning, you go outside to look for footprints, but none can be found. As you’re walking past one of your trees, however, you notice a large vertical gash in the trunk. That wasn’t there before.

Based on the information above, do you know what happened?

What are frost cracks?

frost crack in Norway maple

Long spiral frost crack in a Norway maple. Image courtesy of Joseph OBrien, USDA Forest Service, Bugwood.org.

Though the events mentioned might sound straight from the pages of a mystery novel, it’s actually a common natural occurrence here in the Midwest. The noise that was heard was the tree breaking from the cold. It caused the large split in the trunk, known as a frost crack.

So how does cold cause a tree to split apart like that?

Accomplice #1 – the sun. During the day, the sun shines on the exposed tree’s trunk, which is no longer shaded by its summertime foliage. Most common on trees with thinner bark, the sun warms the inner wood on the south or west side of the tree. It especially affects young trees, as their bark has not thickened much yet.

Accomplice #2 – clouds or nighttime. When the sun moves behind a cloud or sets for the evening, the outdoor temperature drops, causing the bark to shrink. The inner wood, however, takes longer to adjust to the temperature change and stays warm for longer. Remember, there is water flowing through the tree, just like blood flows through our veins. The water in the bark freezes and makes the bark contract, while the water in the inner wood is still flowing. The difference in the water temperatures causes a contraction, causing the bark AND the wood to split. The split is sudden and loud, which is why the noise has often been compared to a rifle shot.

Frost cracks most often happen after cold, sunny days.

Which trees are likely to suffer from frost crack damage?

As most people don’t check on their trees during the cold winter months, you may not notice the gash in your tree until spring. If, however, you’re concerned that your trees may be susceptible to frost cracks, here are some trees in the Dayton area that are commonly afflicted (along with any type of young tree):

  • Willow
  • Walnut
  • Oak
  • Maple
  • London plane
  • Linden
  • Horse chestnut
  • Goldenrain tree
  • Elm
  • Crabapple
  • Beech
  • Apple

For young and susceptible trees, you may want to wrap the tree trunks in the fall to prevent this kind of injury – just be sure to remove it right away in spring, or you’ll hamper the tree’s growth.

What should I do if I find a frost crack?

Frost cracks form reaction wood as they try to heal the damage. Image courtesy of Joseph OBrien, USDA Forest Service, Bugwood.org

Whether in the winter or spring, if you notice a large vertical crack in your trees, it is probably a frost crack. During the spring and summer months, the crack won’t be as wide as the tree tries to heal itself. The tree will also produce “reaction wood” to try to seal up the wound.

Keeping your trees healthy so that they can deal with these wounds is important, so focus on keeping them well-watered and pruned for health. Because of the crack, insects, fungi, and diseases can easily make their way inside the tree, so keep an eye out for any signs of distress.

Frost cracks tend to widen each winter and then close up in the spring, so if you notice it getting wider during the colder months, this is to be expected.

If you’re concerned about the health of your tree due to a frost crack, schedule a consultation with us so we can check if any treatment options are necessary.

And the next time you hear a loud noise, be sure to check your tree for frost crack injuries!