How much mulch should I put around my tree, and is a mulch volcano bad?

Mulch is one of the best things you can do for a tree — but the "mulch volcano" (a tall cone of mulch piled against the trunk) is one of the worst. Done right, mulch should look like a flat donut, never a volcano.

Why mulch volcanoes kill trees (slowly):

• Mulch against the trunk traps moisture against the bark, inviting decay, cankers, and rodent/insect damage
• It encourages girdling roots to grow up into the mulch and circle the trunk, eventually strangling it
• It can bury the root flare, suffocating roots and mimicking the damage of deep planting
• Symptoms appear years later as unexplained decline — by then the damage is done

How to mulch correctly:

1. Apply a 2-4 inch layer of organic mulch (wood chips, shredded bark).
2. Spread it in a wide ring — ideally out to the dripline, or at least 3-4 feet in diameter. Wider is better than deeper.
3. Keep mulch 3-4 inches away from the trunk so the root flare stays visible — "donut, not volcano."
4. Refresh, don't pile on. Fluff old mulch and top up only to maintain depth; don't keep adding layers.

Benefits of proper mulch: conserves soil moisture, moderates soil temperature, suppresses weeds, reduces mower/string-trimmer damage to the trunk, and slowly enriches the soil.

If a previous volcano has buried the flare, pull the mulch back now and expose the root flare. See our Planting Guide for more.