Did you know trees here in Colorado can make loud cracking sounds on winter nights? It happens more often than you might think. Many residents think they hear a gunshot, when in reality, it might be a frost crack on your tree.
A frost crack is a long, vertical split in a tree’s trunk caused by sudden temperature changes. It usually happens in winter (and sometimes spring) when the trunk expands and contracts quickly. While any tree with sun-exposed bark can develop frost cracks, younger trees and those with thinner bark – like honey locust, linden, and maple – are most at risk. Aspens can get them too! Here’s what you need to know about frost cracks in Colorado.
Key Takeaways:
- Frost cracks occur when rapid temperature changes cause tree trunks to split, often making a loud noise similar to a gunshot.
- South and west-facing sides of trees are most vulnerable to frost cracks, especially in young trees and species with thin bark.
- While frost cracks will reopen each winter, most trees can survive and heal with proper care and monitoring.
- Prevention through proper tree wrapping, mulching, and winter care is the best defense against frost cracks in Colorado’s extreme climate.
How to Spot a Frost Crack
Before we dive into why these dramatic splits happen, let’s talk about how to identify a frost crack. Think of it as a vertical zipper running up and down your tree’s trunk – usually starting near the base and extending several feet upward. Unlike the jagged, splintered damage you’d see from a lightning strike or the rough edges from mechanical damage, frost cracks are relatively clean splits that follow the tree’s grain.
Here in the foothills, we typically see these cracks on the south or southwest side of trees. Why? That’s where the sun hits hardest during our bright winter days. The cracks can be subtle at first – maybe just a slight seam in the bark. But over time, they often become more pronounced, sometimes creating a raised ridge of callus tissue as the tree tries to heal itself.

Photo by Joseph OBrien, USDA Forest Service, Bugwood.org
How and Why Do Frost Cracks in Trees Occur?
Frost cracks happen when temperatures change rapidly in winter. During the day, the sun warms the tree’s trunk, especially since there are no leaves to provide shade. This warms the inner wood and the water flowing inside it.
But when the sun sets or disappears behind clouds, the temperature outside drops quickly, while the inner wood stays warm longer. This sudden difference causes stress on the tree. Water still moves through the tree in winter, much like blood in our veins. As the outer bark cools and contracts, the warmer inner wood remains expanded. This tension eventually causes the bark to split – suddenly and loudly – often sounding like a gunshot.
When Are Frost Cracks Most Likely to Occur?
Frost cracks often happen after cold, sunny days, when nighttime temperatures drop suddenly. Because the sun hits the south and west sides of a tree, those are the areas that are 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 also be affected.
Here in Jefferson County, we’ve noticed that certain trees are particularly vulnerable. Beyond the honey locust, linden, maple, and aspen we mentioned earlier, we also frequently see frost cracks in:
- Young oak trees, especially those recently transplanted
- Fruit trees, particularly apple and cherry
- Norwegian maples
- Newly planted Kentucky yellowwood
The higher elevation of our foothill communities can make the problem worse, as temperature swings tend to be more extreme than in lower-lying areas closer to Denver.
Preventing Frost Cracks: An Ounce of Prevention
While we can’t control Mother Nature’s temperature swings, there are several ways to protect your trees during winter:
- Wrap those trunks! 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. We recommend using light-colored tree wrap, starting at the base and working your way up to the first main branches.
- Add a 2–4-inch layer of mulch around your tree (but not touching the trunk) to help maintain more consistent soil temperatures, which can reduce stress on the tree.
- Prioritize regular tree maintenance to keep it healthy year-round. Regular watering (yes, even in winter during dry spells), proper fertilization, and professional pruning all help build stronger trees.
What to Do if One (Or More) of Your Trees Has a Frost Crack
If you notice a long vertical crack in your tree that wasn’t there before winter, it’s likely a frost crack.
The good news is that trees naturally work to heal themselves. In summer, the crack may shrink as the tree produces “reaction wood,” a natural defense similar to a scab. However, frost cracks don’t heal permanently. Each winter, the crack will expand again as temperatures drop. This cycle of opening and closing puts stress on the tree.
To help your tree stay healthy, make sure it gets enough water, especially during dry periods. Keep an eye out for pests and diseases, as they can enter through the crack. Also, watch for signs of distress, like dead branches or slowed growth. With proper care, your tree can continue to thrive despite the damage.

Photo by Joseph OBrien, USDA Forest Service, Bugwood.org
Long-Term Care for Trees with Frost Cracks
Here’s what we recommend for ongoing care:
- Water deeply but infrequently during dry spells, including winter months when temperatures are above freezing
- Monitor the crack for signs of decay, insect activity, or fungal growth
- Watch for any discoloration in the leaves or canopy dieback, which could indicate the crack is affecting the tree’s overall health
- Consider having one of our Certified Arborists assess the tree annually to catch any problems early
Common Myths About Frost Cracks
Let’s clear up some misconceptions we often hear:
- Don’t fill the crack with cement or other materials – this can actually harm the tree by preventing natural movement and healing.
- Don’t paint or seal the crack – trees have their own natural healing processes.
- Don’t assume a frost crack means automatic death for your tree – many trees live long, healthy lives with properly managed frost cracks.
Get Expert Help Protecting Your Trees from Winter Damage from LAM Tree Service
Most trees can survive frost cracks, and some even endure multiple cracks over their lifetime. But catching them early and providing proper care can mean the difference between a strong, thriving tree and one that struggles with ongoing issues. So, if you hear a loud crack in your yard on a cold night, check your trees the next day – you might just catch a frost crack before it becomes a bigger problem.
If you’ve noticed vertical cracks in your trees or want to prevent frost cracks from developing, the Certified Arborists at LAM Tree Service can help. Call us at 303-674-8733 or fill out our online form to schedule a professional inspection. We’ll assess your trees’ health and recommend the best ways to help them thrive through every season.