Mushrooms on Your Tree? What It Means and What To Do

As summer gives way to cool, moist fall weather in Otisville, Michigan you may notice more mushrooms popping up around your yard. A lot of times there are typical mushroom fungi, but sometimes you will see round mushrooms, called puff balls, or fungal growths on trees called shelf or bracket fungi.

Why Fungi Grow on Trees or Around Trees?

Most Otisville homeowners notice fungi only when mushrooms pop up on a tree trunk or around the roots. While mushrooms can be surprising, or even concerning, they’re just the visible part of a much larger organism living inside the tree or soil. Understanding why fungi feed on trees and what it means for your landscape can help you make smart decisions about tree care.

Why Do Fungi Feed on Trees?

In simple terms: fungi feed on trees because trees are full of sugar. All living things, including fungi, need carbon, hydrogen, and oxygen to grow. Trees store these elements in their wood, especially in two key materials:

• Cellulose: A long chain of sugars that forms the tree’s structure
• Lignin: A natural “glue” that holds cellulose together and gives wood strength

To fungi, cellulose and lignin are a buffet. They use special enzymes to break these materials apart and turn them into food and building blocks for their own growth.

How Do Fungi Actually Feed on Trees?

Fungi grow as a network of tiny threads called mycelium. This network spreads through wood or soil, breaking down complex tree tissues into nutrients the fungus can use.

When conditions are right fungus produces a mushroom, which is just the reproductive part of the organism. Think of the mushroom as the “apple,” and the mycelium as the “tree.” The real fungus is hidden inside the wood or soil.

Can Trees Protect Themselves From Fungi?

Yes - healthy trees can defend themselves. Their bark acts like armor, keeping fungi out. But when bark or roots are damaged, fungi can slip inside.

Common entry points for fungi include:

• Storm damage
• Lawn equipment hitting the trunk
• Improper pruning
• Construction damage
• Tree workers climbing with spikes

If a tree is strong, it can “wall off” the infected area through a natural process called compartmentalization, limiting how far the fungus can spread.

What Kind of Fungi Might Be Growing on My Tree?

Most mushrooms you see on trees belong to a group called Basidiomycetes, often known as “club fungi.” Within this group, fungi fall into four categories:

1. Saprophytes (The Recyclers)

These fungi feed only on dead wood, not living tissue. They help break down fallen branches, old stumps, and decaying heartwood inside older trees.
A tree with saprophytic fungi may be hollow inside but still structurally sound. Only a trained arborist can determine whether the tree is safe.

2. Parasitic Fungi (The Harmful Ones)

Parasitic fungi attack living wood, especially the cambium layer - the part of the tree that moves water and nutrients. Because this tissue is rich in sugars, it’s a prime target.

Parasitic fungi can cause:

• Structural weakness
• Decline in tree health
• Sudden tree failure

Often, there are no visible mushrooms until the tree is already compromised.

3. Saprophytic Parasites (Both Harmful and Opportunistic)

Some fungi normally feed on dead wood but can switch to living tissue under certain conditions. A common example is Ganoderma, which produces large shelf like mushrooms at the base of trees.

These fungi can break down both living and dead wood, making them especially dangerous.

4. Beneficial Fungi (The Good Guys)

Not all fungi are harmful. Mycorrhizal fungi form a partnership with tree roots, helping trees absorb water and nutrients in exchange for sugars.

Signs of healthy mycorrhizal activity include:

• Mushrooms near the base of the tree
• Rich, organic soil
• Strong, consistent tree growth

Arborists often add mycorrhizal fungi during deep root fertilization applications to improve tree health - especially in urban soils.

What Should You Do If You See Fungi on Your Tree?

If mushrooms appear on your tree, don’t panic, but don’t ignore them either.

An ISA Certified Arborist can:

• Identify the type of fungus
• Determine whether it’s harmful or harmless
• Evaluate the tree’s structural stability
• Recommend treatment options

Tools like the Resistograph Decay Detection Tool help arborists measure internal decay without damaging the tree.

It’s important to keep in mind that a tree with fungus does not automatically need removal. Many trees can be treated, strengthened, or safely monitored, often saving homeowners money while preserving valuable landscape trees.

If you live in, or around, Otisville and notice fungal growths on or around your trees contact us for an inspection of the affected plants. You can send us message or give us a call at 800-724-6680 to set up an appointment.