Frost Cracks in Trees

Frost cracks are vertical cracks in a tree that are caused by temperature changes. They occur during winter when the daytime sun warms the bark causing tissue expansion. Later, when the sun goes down and the temperature drops quickly, the outer layer cools and contracts faster than other portions. This expansion and contraction results in vertical cracking. Cracks can be several feet long and a few inches wide.

Imagine being outside and exposed to cold temperatures all winter. Sure, trees are adapted to outdoor living. However, they are not always well suited to being alone in the open. Exposure to winter weather and changing temperatures can be particularly problematic for trees that are planted outside their hardiness zone. Young trees are also more susceptible to winter injuries.

In fact, when it comes to frost cracks, they usually occur on trees with a thin bark, especially young trees. Further, when a tree’s stem is fully exposed to the southern or south western winter sun, it is more vulnerable. Usually this side of the bark warms the fastest so damage is commonly seen on the south or southwestern side.

Preventing Frost Cracks

Tree selection is the first step. To avoid frost cracks, and many other problems, select trees that are hardy to your zone. Be sure to consider the species if you plant in unprotected areas. Trees including sycamore, ash, beech, maple, tulip tree, apple, crabapple and cherry are more susceptible. Additionally, plant young trees in spots that are protected by other trees or structures.

If you have a thin bark tree in an exposed area, wrap the stem during the winter months with a tree wrap or tree guard product. The goal is not to keep the tree warm. Rather, you are protecting the stem from intense sun exposure, followed by freezing nighttime temperatures. Be sure to remove wraps in late winter or early spring as temperatures begin to warm. Keep in mind that you should only have to wrap a tree while it is young. As it matures and develops a thicker bark, it will be less susceptible to frost cracks.

What if my Tree has a Crack

Unfortunately, frost cracks are permanent. They cannot be repaired. However, a tree can live with a frost crack.  That doesn’t mean, however, that you should ignore them.

Frost cracks can expose wood tissue to infection by decay organisms. They also serve as an entry point for destructive insects called tree borers. As such, it’s a good idea to have them routinely inspected. Identifying any concerns early can help prevent development of serious diseases or insect infestation.

Though they may never fully seal up, the tree may attempt to form a callus along the crack over time. Subsequent temperature changes can cause the wound to reopen.

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