How Do You Identify Fungal Growth on Tree Trunks?
Quick Summary
Fungal growth on a tree trunk usually appears as hard woody shelves called conks or brackets, soft mushrooms at the base or roots, or thin white or tan sheets under the bark. Each form signals internal decay, so any new growth deserves a closer look at the tree's condition.
Fungal growth takes three main forms: conks and brackets, mushrooms, and mycelial fans.
Soft, spongy wood or bark that crumbles when pressed is a warning sign.
Cracks, cavities, or oozing sap near fungal growth point to a problem.
Even a single small conk can indicate decay that has spread deep into the trunk.
Treat any new growth as a reason to inspect the tree more closely.
Table of Contents
What Fungal Growth on a Tree Trunk Looks Like
Last Updated: November 2, 2026
Fungal growth on a tree trunk is often the first visible sign that something is wrong inside the tree. Most of the damage happens out of sight, so spotting a fungus early gives you a head start. The good news is that many of these growths are easier to recognize than you might think.
Fungal growth on trees generally takes one of three forms. Each one tells you something different about the tree's condition.
Conks and brackets: Hard, woody shelves that stick out from the trunk or main limbs.
Mushrooms: Soft, fleshy caps that grow from the bark, roots, or soil at the base of the tree.
Mycelial fans: Thin, white, cream, or tan sheets that spread under the bark or on the wood surface.
Fungus on trees is a sign of a fungal infection, not a cause in itself. A fungus that signals internal decay can weaken a tree, so you can learn how to prevent storm damage to trees with pruning, cabling, and hazard checks. The growth is the fruiting body, the part of the fungus that releases spores. The real work happens inside the wood, where the fungus breaks down the tree's structure over time.
Watch for these signs on the trunk:
Shelves or brackets that are hard, woody, or leathery
Mushrooms growing from the base of the trunk or from roots
Soft, spongy wood or bark that crumbles when pressed
Cracks, cavities, or oozing sap near the fungal growth
Thin white or tan sheets under loose bark
A common mistake is assuming a small, pale growth is harmless. You can learn to identify hazardous trees before they fail by checking warning signs from roots to crown. Even a single small conk can point to decay that has spread well into the trunk. Treat any new growth as a reason to take a closer look.
Not every spot on the bark is fungus, though. Our guide to common tree diseases in Des Moines covers symptoms, prevention, and care for local problems like oak wilt and Emerald Ash Borer. Lichens, moss, and certain bark textures can look similar at first glance, and we cover those lookalikes later in this guide.
Frequently Asked Questions
What fungus grows on tree trunks?
Several kinds of fungi grow on tree trunks, and most of them are wood-decay fungi. Common examples include conks (hard, woody, shelf-like fruiting bodies), brackets and bracket fungi that attach to the bark, and honey-colored mushrooms that appear at the base of trees in clusters. Some fungi form thin white or gray mycelial fans under loose bark. Because many species look alike, the fruiting body alone rarely identifies the species. A close look at where it grows, its texture and its color helps narrow things down, but a certified arborist can confirm what you have and whether it signals active decay.
Is fungus on trees harmful?
Fungus on a tree is often a sign of harm rather than the cause of it. Wood-decay fungi break down the heartwood and roots over time, which weakens the trunk and can make the tree unstable, especially in storms. Not every fungus is dangerous, though. Some species live on dead wood or only on the surface and cause little structural harm. The risk depends on the species, the location of the growth, and how much of the trunk or root system is affected, so a professional inspection is the reliable way to judge it.
How can I get rid of fungus on my tree trunk?
Removing the visible fruiting body does not remove the fungus, because the living mycelium stays inside the wood and roots. Most tree fungus treatment focuses on managing the tree rather than eliminating the fungus. Pruning out dead or hazardous limbs, reducing soil compaction, watering during dry periods and avoiding trunk wounds can help a tree tolerate the infection. Chemical fungicides are rarely effective against established wood decay. If the decay is extensive, removal may be the safest option, and a certified arborist can explain the options for your specific tree.
Should I remove a tree with fungal growth on its trunk?
Not automatically. A tree with fungal growth may still be stable if the decay is limited and the structure is sound. Removal becomes a serious consideration when the decay covers a large share of the trunk, when cavities or cracks compromise the load-bearing wood, when the tree leans or has lifted roots, or when it sits close to a home, driveway or power line. For current pricing on removal, contact Anderson Tree Care directly for a quote.
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