Tree Bark Cracking or Splitting? Here's What It Means for Your Tree Tree & Shrub Care Submitted by Elisa Edelstein Reviewed by Expert Patrick Parker, Director of Plant Health Care Is a crack in tree bark always an issue? While tree bark cracks may seem alarming, they aren’t always indicative of something problematic. As trees grow, their bark naturally cracks and sloughs off. The outer bark is made of dead tissue, and as the trunk expands, that tissue separates and sheds. On older trees, this creates the rough, furrowed appearance we commonly associate with mature bark. Small, surface-level cracks that follow the bark's natural grain are typically nothing to worry about. Take a closer look if a crack is deep, runs vertically along the trunk, or exposes the wood beneath the bark. Knowing the difference between normal bark changes and signs of structural damage can help you decide when to monitor the tree and when to call an expert. Types of bark cracks and what they signal Not all bark cracks have the same cause or require the same response. Some are part of a tree's normal growth, while others develop due to extreme weather, environmental stress, or disease. Understanding what type of crack you're seeing can help you determine whether your tree is growing or just needs monitoring or a professional evaluation. Vertical frost cracks running up the trunk Frost cracks are long, straight splits that develop vertically along the trunk. Some extend several feet, while others are much shorter. These cracks most often occur on the south or southwest side of the tree after a sharp temperature drop. During the day, sunlight warms the bark. When temperatures fall rapidly overnight, the outer bark contracts faster than the wood beneath it, creating enough stress to split the bark. Although frost cracks often look dramatic, they're rarely the reason an otherwise healthy tree declines. In many cases, the crack gradually closes during warm weather and reopens during the following winter as temperatures fluctuate. Thin-barked species such as maple and cherry are especially susceptible, as are young trees that haven't yet developed thick, protective bark. Sunscald damage on the south-facing bark Sunscald develops similarly but produces a different type of injury. On sunny winter days, bark warms considerably, then cools rapidly after sunset. This repeated cycle can damage living tissue beneath the bark, eventually causing the bark to crack, loosen, or separate from the trunk. The damage isn't always obvious immediately. In many cases, symptoms don't appear until the following growing season, when sections of bark begin to flake away, revealing discolored wood beneath. Wrapping the trunks of young or thin-barked trees with a light-colored tree wrap in late fall can help reduce the risk of sunscald. Unwrap it once spring hits and temperatures are consistently above freezing, as leaving it on during the growing season can invite other conditions to take hold. Deep cracks that expose heartwood Cracks that develop beneath the bark deserve more immediate engagement. When damage reaches the structural wood inside the trunk, the tree may become more vulnerable to decay, fungi, and wood-boring insects. Depending on the crack's size and location, structural stability may also be affected during storms or high winds. If you notice a deep crack, particularly near the base of the trunk or on a large tree close to your home, schedule an evaluation with your local ISA Certified Arborist. A professional assessment can determine whether the tree is managing the injury or whether it needs additional treatment or structural support. Common causes of tree bark cracking and splitting Bark cracks don't happen for a singular reason. Weather, environmental conditions, growth patterns, and disease can all contribute. Identifying the underlying cause is often the first step toward determining whether the damage is cosmetic or a sign of a larger issue. Winter temperature extremes and frost Repeated freeze-thaw cycles place significant stress on tree bark. A frost crack that develops one winter often reopens in the same location the following year, creating repeated opportunities for fungi and other pathogens to enter the tree. While many trees successfully compartmentalize these injuries, it's a good idea to monitor the affected area each spring for signs of decay or disease. Drought stress followed by heavy moisture Extended dry periods can make bark less flexible. When heavy rainfall follows, the wood beneath the bark may expand faster than the bark can stretch, resulting in splitting. Maintaining consistent soil moisture during dry weather helps reduce this type of stress. Deep, regular watering is generally healthier for trees than alternating between prolonged drought and infrequent heavy watering. Rapid growth in young or overfertilized trees Fast growth can also contribute to bark splitting. Late-season nitrogen fertilizer applications may encourage a flush of new growth just before winter, when trees are less able to withstand sudden temperature changes. Young maples and many fruit trees are especially susceptible. To reduce the risk, avoid applying nitrogen fertilizer after midsummer unless it's part of a treatment plan your arborist recommends. Canker disease and fungal activity Not all bark cracks begin with environmental stress. Some develop after fungal or bacterial infections create patches of dead, sunken bark known as cankers. If the tissue surrounding a crack appears sunken, discolored, or dead, disease may be the underlying cause. Once the bark opens, additional fungi and insects can enter the wound, making early diagnosis especially important. How to respond to a cracked tree trunk A crack in the bark doesn't automatically mean your tree is in trouble. The key is determining whether the damage is stable or changing over time. In many cases, careful observation is all that's needed, while other situations call for a professional evaluation. What to monitor on your own If the crack is narrow and the tree has a full canopy with healthy leaves, monitoring the tree is often the appropriate first step. The crack's size matters less than whether it's changing. Some frost cracks remain stable for decades, while even small cracks that keep widening may indicate an underlying structural issue. Avoid sealing or painting the crack. Wound sealants and tree paints can trap moisture against the wood, creating conditions that favor decay rather than helping the tree recover naturally. When to contact a certified arborist Professional evaluation is recommended if the crack: Extends deeper than the bark. Exposes visible decay. Is accompanied by canopy dieback. Has oozing sap, fungal growth, or other signs of disease. Is located near your home or another high-traffic area. Depending on the tree's condition, cabling and bracing may provide additional structural support and help preserve the tree. An ISA Certified Arborist can determine whether the tree can be safely maintained or whether removal is the better long-term option. The bottom line Most bark cracks are simply part of a tree's natural growth and aging process. The important part is recognizing when a crack is natural and when it's a sign of a deeper structural or health concern. If you're unsure what you're seeing, schedule a complimentary consultation with your local SavATree ISA Certified Arborist. We'll evaluate the tree, explain what's happening, and recommend the best course of action to help protect the health and longevity of your landscape. Contact us today to schedule a consultation with an expert arborist.