🌋 Why Volcano Mulch is Slowly Killing Your Trees

Why Volcano Mulch is Slowly Killing Your Trees

Published by Urban Garden Solutions

If you've ever driven through a neighborhood and noticed mulch piled high like a cone around the base of a tree, congrats, you've spotted a “volcano mulch.” While it may seem like a neat, tidy way to protect your landscape investment, this common practice can do more harm than good.

At Urban Garden Solutions, we believe in proper tree care rooted in science. Volcano mulching is one of the most frequent mistakes we correct during property visits.

What Is Volcano Mulching?

“Volcano mulching” refers to piling mulch high and tight against a tree trunk—often in a cone or mound shape. It’s usually done with good intentions: to retain moisture, keep weeds down, and make things look tidy.

But this approach creates a hostile environment for the tree.

Why It’s So Harmful

1. Encourages Bark Rot

Mulch piled directly against the trunk traps moisture, leading to constant wetness on bark tissue. This creates an ideal environment for fungal decay, bacterial infection, and pest intrusion—all of which can weaken or kill the tree from the base up.

2. Promotes Girdling Roots

Excess mulch can cause surface roots to grow inward toward the trunk, eventually circling it. These girdling roots strangle the tree over time, cutting off water and nutrient flow and often leading to sudden decline years later.

3. Attracts Pests & Rodents

The warm, moist conditions beneath a mulch volcano create a perfect hiding spot for insects, rodents, and disease pathogens, especially during mild North Texas winters.

4. Leads to Poor Root Development

Mulch mounds make roots grow into shallow, unstable areas. This weakens anchoring, reduces drought tolerance, and makes trees more vulnerable to windthrow and summer stress.

The Right Way to Mulch

✔ 2–3 inches deep, never more
✔ Keep mulch off of the root flare
✔ Extend the ring out to the dripline if possible
✔ Use organic mulch like shredded bark or hardwood chips for best results

Pro Tip:

Proper mulch application improves soil moisture retention, reduces weed pressure, and encourages healthy microbial activity.

Need Help? We’ve Got You.

If you’re unsure whether your trees are mulched correctly or if you're seeing signs of bark rot or decline, Urban Garden Solutions can help. Our certified arborist team can assess your trees, correct mulch issues, and help restore tree health.