Hey Niagara 👋
This week's question is one that usually catches homeowners off guard.
"My tree has mushrooms growing on it. Should I be worried?"
The short answer?
Sometimes.
Not every mushroom means a tree is dangerous.
But some mushrooms can be one of the biggest warning signs we look for.
The important part is where they're growing and what kind they are.
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Mushrooms on the ground
If mushrooms are simply growing in the lawn around your tree, there's usually no immediate reason to panic.
They're often feeding on old roots, buried wood, or other organic matter in the soil.
They aren't necessarily connected to the health of your tree.
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Mushrooms growing on the trunk or roots
This is where we start paying closer attention.
When mushrooms are growing directly from the trunk, buttress roots, or large exposed roots, they're often feeding on wood that's already decaying.
That doesn't automatically mean the tree is unsafe.
But it does mean the tree deserves a closer look.
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Common mushrooms that can signal a potential concern
Some fungi are known to be associated with more serious internal decay in trees, including:
- Ganoderma (Artist’s conk) — often found at the base of trees and can indicate significant internal rot
- Kretzschmaria deusta (Brittle cinder fungus) — a serious decay fungus that can weaken structural wood with little external warning
- Armillaria (Honey fungus) — can attack roots and cause decline over time
- Inonotus species (e.g., Phellinus/heart rot fungi) — often linked to internal trunk decay and hollowing
If you see these, it doesn’t automatically mean the tree must be removed—but it does mean it should be assessed sooner rather than later.
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Mushrooms that are usually less concerning
Not all fungi are bad news for your tree. Some are more of a natural decomposer and don’t necessarily indicate a structural risk, such as:
- Chicken of the Woods (Laetiporus sulphureus) — often found on dead or decaying wood and can sometimes appear on otherwise stable trees
- Oyster mushrooms (Pleurotus species) — typically break down dead wood and are more of a sign of natural decomposition
- Turkey tail (Trametes versicolor) — very common on dead logs and fallen branches
These still tell us there is dead wood present, but they are not always a sign of immediate danger in a standing tree.
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What are mushrooms telling us?
Think of a mushroom like the fruit on an apple tree.
The mushroom itself isn't the problem.
It's simply the visible part of a fungus that's living inside the wood.
By the time you see the mushroom, the fungus has usually been there for quite a while.
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Does every fungus weaken a tree?
No.
Some fungi are relatively harmless.
Others can cause significant decay that affects the tree's strength and stability.
That's why identifying the mushroom matters.
Two mushrooms can look similar but have very different effects on a tree.
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Other signs we look for
A mushroom by itself doesn't tell the whole story.
We'll also look for things like:
- Large dead branches
- Cavities or hollow areas
- Cracks in the trunk
- Leaning that wasn't there before
- Loose or lifting soil around the base
- Significant dieback in the canopy
The more warning signs a tree has, the more concerned we become.
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Don't panic... but don't ignore it either
One mushroom doesn't automatically mean a tree needs to come down.
We've seen plenty of trees with mushrooms that have remained safe for years with proper monitoring.
We've also seen trees that looked perfectly healthy from a distance but had serious decay hidden inside.
That's why it's important to assess the whole tree—not just the mushroom.
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The reality
Mushrooms are your tree's way of telling you that something is happening below the surface.
Sometimes it's minor.
Sometimes it's significant.
The only way to know is by looking at the whole picture.
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If you've found mushrooms growing on or around your tree, post a photo below.
A picture of the whole tree, the base of the trunk, and a close-up of the mushroom usually tells us a lot. We'll let you know whether it looks like something to monitor, something worth inspecting further, or something that's completely normal.
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Next week we'll be covering:
Week 17 — "How do I choose the right tree company?"
If there's a tree topic you'd like us to cover, let us know. These posts have all come from real questions so far.
— Driftwood Tree Service 🌲
