How to Detect Tree Rot: Signs, Prevention, & Treatment Tips Insects & Diseases A rotting tree may not always look sick on the outside—but internal decay can make it unstable, hazardous, and vulnerable to failure. Whether you're managing a residential landscape or overseeing a commercial property, detecting tree rot early is essential to protecting your investment and ensuring the safety of your surroundings. In this guide, we’ll walk you through the most common signs of tree decay, how to prevent it, and when to call in professional tree service for help. What Causes Tree Rot? Tree rot, also known as wood decay, is caused by fungal pathogens that enter a tree through vulnerable openings. These may include pruning wounds, cracks in the bark, storm damage, or areas where lawn equipment has scraped the trunk. Once inside, fungi break down the wood tissue, weakening structural integrity from within. Some of the most common contributors to tree rot include: Poor drainage or excess soil moisture Mechanical injury from construction or lawncare Improper pruning or neglected maintenance Tree species with naturally soft wood Over time, decay can spread throughout the roots, trunk, and major branches, leading to canopy decline and structural instability. In some species, like poplar and silver maple, this process can happen quickly, making regular tree assessments all the more important. Signs of Tree Rot: How to Identify Decay Early Rot often hides deep within the tree, but if you know what to look for, you can catch early warning signs before serious damage occurs. Soft, Spongy, or Cracked Wood The most obvious sign of internal rot is soft wood—especially near the base of the trunk or around large wounds. If the wood feels spongy or sounds hollow when tapped, tree rot may be progressing beneath the surface. Visible cracks in the trunk or major branches can also indicate structural weakness and advanced internal decay. Fungal Growth on the Trunk or Roots The presence of mushrooms, conks, or bracket fungi growing along the trunk or around the roots often signals a serious problem. These are the reproductive bodies of decay fungi, and they only appear once the infection is well established inside the tree. Some tree fungi, like Ganoderma or Armillaria, are aggressive and pose a significant risk to living trees. Peeling or Missing Bark When you see bark coming off tree trunks, it could indicate underlying rot. If you’ve been wondering how to spot tree rot, this is often one of the first visible clues. As decay advances, the dead tissue can no longer support bark adhesion, leading to sections that peel away or fall off entirely. Since bark acts as a natural barrier, its loss exposes the inner wood to even more pathogens and pests. Hollow or Cavities in the Trunk It’s possible for a tree rotting from inside to remain standing for years, but that doesn’t mean it’s safe. Trees with large cavities or hollows are often structurally compromised. This is where a professional assessment becomes essential. A TRAQ (Tree Risk Assessment Qualified) certified arborist can evaluate whether the remaining wood is strong enough to support the tree or if removal is necessary. Sudden Leaning or Weak Branches If a previously upright tree suddenly starts to lean, especially after a rainstorm or high winds, internal root or lower trunk rot may be the culprit. Leaning trees are unstable and often require immediate attention. Likewise, branches that snap off without warning—especially large scaffold branches—can be a red flag that rot is weakening the internal structure. Unhealthy Leaves & Canopy Dieback Foliage health often mirrors what's happening inside the tree. Signs like wilting, yellowing, or thinning leaves, especially at the top of the canopy, are classic symptoms of internal decay. This canopy dieback typically starts at the outermost tips of branches and works inward, as the tree loses its ability to transport nutrients and water. How to Prevent Tree Rot & Decay While you can’t control every environmental factor, proactive care goes a long way toward reducing the risk of tree rot. Regular Tree Inspections & Health Assessments Annual evaluations by a SavATree ISA Certified Arborist can help detect rot early—before it becomes dangerous or irreversible. Spotting small cracks, fungal growth, or insects early means more treatment options and less chance of structural failure. These assessments are particularly important for mature or high-value trees. Proper Pruning Techniques Pruning is essential for shaping and maintaining healthy growth, but poor cuts or over-pruning can expose your tree to infection. Improper techniques leave open wounds that invite decay-causing organisms and pests. That’s why it’s best to leave pruning to the professionals. If you’re unsure how to prune properly, consult your local ISA Certified SavATree arborist or refer to our seasonal tree care guidelines. Managing Soil & Moisture Around Trees Excess moisture is one of the leading causes of root and trunk rot. Overwatering, poor drainage, or compacted soil can create ideal conditions for fungi to thrive. To reduce the risk: Keep mulch 2–3 inches away from the trunk Ensure proper grading to direct water away from the root zone Use deep, infrequent watering to encourage strong root systems Avoiding Mechanical Damage to Trees Mechanical injuries, like gouges from lawnmowers and weedwhippers or excavation near the base of the tree, create easy access points for pathogens. Even a small wound can become the starting point for a serious fungal infection. Use mulch rings, fencing, or signage to protect trees in high-traffic areas. Treatment Options for Rotting Trees Treating a rotting tree depends heavily on how far the decay has progressed. Here’s how to approach recovery or safe removal. Identifying If a Tree Can Be Saved It’s not always easy to detect tree decay from the outside. An ISA Certified Arborist can perform a comprehensive risk assessment using specialized techniques and tools like resistance drilling or sonic tomography to check on the structural integrity of the tree. Because decay fungi often spread slowly, some trees can live for years in a compromised state. But if the structural integrity is questionable, even a living tree may still pose a risk. In some cases, understanding how to tell if a tree is dead can help clarify your next steps. Pruning Out Affected Areas If the rot is confined to a single branch or small section, pruning it out may stop the spread. A professional arborist can recommend the best course of action, which may include pruning 6–12 inches below the visibly infected wood, into healthy tissue. Applying Fungicides & Tree Sealants Fungicides can sometimes help in early-stage infections, but they’re typically used as preventive treatments—not cures. They’re most effective when applied proactively in high-risk conditions. Tree sealants, once widely used to close wounds, are now considered outdated. Most arborists agree they can trap moisture and promote further rot, so they’re best avoided unless specifically recommended by a professional. When to Call a Professional Arborist A SavATree ISA Certified Arborist can perform a comprehensive tree risk assessment using advanced tools and diagnostic techniques. This includes evaluating visible signs of decay as well as detecting internal structural weaknesses through methods like resistance drilling and sonic tomography. Our experts follow the International Society of Arboriculture’s (ISA) Tree Risk Assessment Qualification (TRAQ) methodology, ensuring a science-based, consistent evaluation of tree condition, likelihood of failure, and potential damage if failure does occur. Based on this assessment, we’ll recommend an appropriate course of action—whether it’s strategic pruning, long-term monitoring, or safe removal to reduce risk. In cases where extensive decay compromises structural stability, tree stump removal may also be advised to prevent spread to nearby plants or turf. SavATree’s tree risk assessment and mitigation services are designed to help property owners make informed decisions about their trees—prioritizing both safety and sustainability. Don’t Wait on Tree Rot If you suspect your tree is rotting from the inside, don’t ignore it. Internal decay may not be immediately visible, but it can compromise the safety of your landscape, your home, and your family. Spotting the signs of tree rot—from mushrooms at the base to soft wood or sudden leaning—gives you the power to act early. Whether your tree can be saved through tree disease treatment, or whether it’s time to consider removal, timely action is key. With the right care, prevention methods, and expert support, you can preserve your trees and protect your property from hidden hazards. Sources: Penn State Extension. Understanding the Spread of Decay in Trees. https://extension.psu.edu/understanding-the-spread-of-decay-in-trees Texas A&M Forest Service. What’s Wrong With My Tree? My Tree’s Bark Is Peeling. https://tfsweb.tamu.edu/uploadedFiles/TFS_Main/Urban_and_Community_Forestry/About_Urban_and_Community_Forestry/Urban_Forest_Information_Sheets/What's%20wrong%20with%20my%20Tree%20-%20My%20Tree's%20Bark%20is%20Peeling.pdf University of California Agriculture and Natural Resources. Wood Decay Fungi in Landscape Trees. https://ipm.ucanr.edu/home-and-landscape/wood-decay-fungi-in-landscape-trees/pest-notes/#gsc.tab=0 Contact us today to schedule a consultation with an expert arborist.