Mulch can help a tree, but piling it against the trunk can slowly kill it. The biggest mistake here is the classic “mulch volcano” that traps moisture where it does not belong.
The real danger is under the surface. Too much mulch against the bark can lead to rot, fungal growth, and bad root formation, even if the tree still looks fine for a while.
The right way is simple: spread about 2–3 inches of mulch in a wide ring and keep a few inches of open space around the trunk so the root flare stays exposed.
If a tree has been over-mulched for years, the damage may already be underway. The safest move is to pull the mulch back, expose the flare, and remove any roots growing up into the mulch instead of down into the soil.
Do you like dead trees? Wish you had several of them in your backyard?
But, did you knowif you mulch your trees the wrong way…
You could injure or kill them!
Here is EVERYTHING you need to know about mulch volcanos and how to fix them... “Quick answer: mulch trees in a wide ring 2–3 inches deep and keep the trunk clear, because piling mulch against bark can lead to rot and root problems.”
In my experience, this phenomenon is something I see all too often, and it's a costly mistake. At the same time, problems may not be immediately apparent. However, the situation beneath the mulch is quite different.
There are several problems with "volcano" mulching, including:
Retaining moisture against hardened bark which leads to rot,
Promoting fungal growth,
And causing improper root formation.
While you may not see the issues forming above the mulch, problems are developing that will eventually kill your trees under the surface.
Why do so many use the tree volcano method?
A mulch volcano can undoubtedly enhance the aesthetic appeal, which is likely a significant reason for its popularity.
Further, whether you prefer to buy bags of mulch or buy it in bulk. It's a natural part of mulching if you are unaware of the issue. Think about it when you bring a wheelbarrow full of mulch. If you’d rather have someone handle mulching and planting, compare landscaping in Phoenix, AZ. Your instinct is to put it right up against the tree trunk.
As a result, when you spread it, if you don't know any better, you leave a pile of mulch against the tree.
Simply spread 2-3 inches of mulch evenly around the tree, and leave a few inches around the tree's trunk so the root flare can remain exposed. Ensuring that no mulch is touching the trunk itself. Ideally, you want to mulch out to the drip line of a tree.
A thinner layer of mulch over a broader area is much better than a mulch volcano for the health and longevity of the tree.
This allows the tree to "breathe"; rather, it allows the moisture to escape, preventing the growth of fungus and minimizing rot and decay.
Better yet, the tree will still benefit from the mulch application.
Pro Tip! If there is too much mulch to add more, but you still want the look of fresh mulch, simply rake away the excess mulch before reapplying a new layer.
Can I fix an over-mulched tree?
Unfortunately, if your trees are already damaged by mulch volcanoes, there may not be much you can do.
This depends on how long the mulch has been piled up against the tree's bark. If it's only been a season or two, you will likely be ok.
On the other hand, if it's been more than three years that mulch has been piled against the trunk. There may already be too much damage to repair.
Either way, here is how you can address an over-mulched tree:
Steps to repair an over-mulched tree
Step One: Remove the mulch until you expose the flare of the tree. Be careful not to damage the bark of the tree.
Step Two: Once you have exposed the flare, you will likely find roots growing in the mulch. Use a set of pruning shears and remove those roots carefully.
Suppose it's gotten to a point where an above-ground root ball has formed. It's advisable to leave the root ball undisturbed.
Creating the Raised "Volcano-Like" Appearance the Right Way
You can use two methods to create a raised appearance without damaging your trees. These methods are most effective when you plan your landscape in advance, prior to planting the tree. If you want a pro to handle mulching, planting, or tree-bed work, start here: How to Request Landscaping Services using Your Free GreenPal Account.
And if you are looking for some great ideas on what trees to add to your garden, refer to the best trees for small gardens.
Method One: Create a small mound of dirt when you plant the tree. So that when you put the tree in, it will naturally sit a few inches higher.
Method Two: Edge the border of your mulch ring with a small trench. While it won't make a huge difference as far as height goes, a clean edge will still give off the appearance that the tree is raised more than it is.
Mulching At the End of the Day
Whatever type of mulch you decide to use, mulching the proper way can help your trees thrive!
While volcano mulching looks aesthetically pleasing, it is terrible for the health and longevity of your trees. So avoid "volcano mulching" around trees. Proper mulching involves spreading 2-3 inches of mulch evenly around the tree, leaving space around the trunk.
And when that tree dies, it may become a risk to your home if it's big enough. Either way, losing a tree can lower your home's value. It can harm the ecosystem and trees. Which most of us can agree is undesirable.
About The Author
Gene Caballero
Hi, I'm Gene Caballero and I'm the co-founder of GreenPal. At GreenPal, we're helping hundreds of thousands of Americans solve one of the trickiest problems: a reliable, fast, and affordable way to get lawncare taken care of. On behalf of GreenPal, I've been featured in the Indianapolis Star, the Sacramento Bee, Entrepreneur, Inc.com, and dozens more. Please feel free to say hi on or connect with me on LinkedIn.
Hi, I'm Gene Caballero and I'm the co-founder of GreenPal. At GreenPal, we're helping hundreds of thousands of Americans solve one of the trickiest problems: a reliable, fast, and affordable way to get lawncare taken care of. On behalf of GreenPal, I've been featured in the Indianapolis Star, the Sacramento Bee, Entrepreneur, Inc.com, and dozens more. Please feel free to say hi on or connect with me on LinkedIn.