Volcano Mulch will not harm trees

Interesting comment from the Garden Professors.  I always thought volcano mulching would be harmful.

On volcano mulching:  Myth "In addition to promoting bark decay, it causes the tree’s roots to grow up into the mulch layer, rather than down into the soil…the tree may eventually die, and even topple."
Response:  There is NO published evidence, anywhere, that proper mulches (i.e., coarse arborist chips) are going to injure bark. They do not cause bark decay. Furthermore, tree roots grow where they have water, nutrients, and oxygen. This might be in the mulch layer. Growing deep into the soil is unlikely (not enough oxygen) unless the soil is excessively sandy or otherwise well drained. Any toppling of trees can be directly correlated with poor planting techniques that prevent roots from contacting and establishing in the site soil.

While I have never seen volcano mulch, I feel it might be something akin to biochar.  Rock dust and remanents of burned vegetation.

Might be really good if someone had access to it to do some experiments to see what happens.

Volcano mulching is where you pile the mulch up against the trunk of the tree.

I see a lot of “volcano” trees along our neighborhood streets. I do notice that this will cause some trees to grow roots higher up along the trunk, rooting out into the mulch “volcano.”  It may not be harmful to the tree, but on a grafted tree you could get the scion wood growing roots which may have unintended consequences. E.g a dwarf tree growing to standard size.

I am seriously in love with the term "Volcano Mulch."

I'm cautious about the process it refers to specifically; I don't like to bury tree trunks.

But great gawd almighty, if you put that name on any sort of nutritious mulch, you will make a fortune. Volcano Mulch 2.0 anyone? "Your plants will erupt!" This is just too sexy to miss. My 2c.

Dennis Bangham wrote:Volcano mulching is where you pile the mulch up against the trunk of the tree.

Dennis, thank you for explaining.

Our daughter uses decomposed rock mulch that I have never seen either so I thought this was something similar.  Maybe I need to google more.

I think it just refers to when someone piles deep mulch around the trunk of a tree to the point it looks like a little volcano, often neglecting to put any mulch at all over the root zone. Lack of published evidence and opinions of "Gardening Professors" aside it is very bad for a tree, not to mention it looks really stupid.

Just can't help myself :)

It came up in an image search and wanted to share.

Volcano mulching is NOT done for the good of the tree.

The tree will NOT benefit from this.

Some trees may accept garbage around its trunk.
Some varieties will suffer or possibly die if this is done.

It is done to make life easier for humans who do not want to weed wack around trees.

The squirrels like to sit in the center of the pecan tree when they eat all my nuts.  I realized late last year that the empty shells were piled 4 to six inches deep against the trunk.  When I raked it back, sections of the bark on the trunk were already rotting away. I don't think it was going to develop new roots.

Paul from Back to Eden movie says he pulled wood chips 18" deep in his entire orchard right up the tree trunks with no I'll effects. He is in a very dry climate, so that may be the difference.

I can't know for certain if volcano mulch is harmful or not. I know the trees I have seen treated that way aren't doing well and often appear to have fungal issues or be dying. Mostly, mulch volcanoes seem like a pattern I don't see much in nature. So even if it isn't always harmful, I don't feel inclined to do it. I also find it ugly, personally. I would much prefer to see the beautiful trunk and root flare of the tree with some plants growing around it.

I see the mulch volcanoes most often in super manicured yards and around street or parking lot trees. The first I suspect is mostly aesthetic and/or motivated by not wanting to mow around roots. The second context makes less sense to me. Often, those trees are transplanted in as quite large trees already with a small root system. Usually in a limited space surrounded by pavement. I don't know how or if they are watered to establish properly. It seems like spreading the mulch out further from the trunk would be more beneficial for improving water retention and root development further out from the trunk. Or depending on rainfall and location, maybe the tree planted in a mulched basin. I guess I just don't understand the mulch volcano as helpful strategy to grow healthy trees. I've seen a variation, with an elevated mulch ring about a foot or more out from the tree, but not against the trunk. This seems to make more sense to my brain. Interesting too that it's usually landscapers doing the mulch volcanoes and organizations planting trees for environmental reasons that use the mulch ring strategy.

I actually love the mulch ring when I am planting new trees... actually I usually do a mulch u on the down slope side to maximize rainwater retention in the root zone.  If I hose watered more I would do the full ring.  A u seems better foe water catchment

I'm usually pretty leery of blanket statements that something is either good or bad. I'd be willing to bet that for at least one type of tree volcano mulching is perfectly fine, and for another type of tree it's tantamount to a death sentence.

Dennis Bangham, the research data is in and no longer a myth.  Volcano mulch structures are definitely detrimental to the root system and is more likely to promote disease in the tree.  Furthermore, my father was a horticulturalist and he discouraged watering trees, to entice the roots to go deeper to find water underground.

Welcome to the forum.

This older thread from 2022 seems to imply it is beneficial though it appears that there is a lot of speculation on this subject.

Properly applied organic mulches are very beneficial for trees. Preferably two-to-three inches deep, not physically touching the trunk, and extending out to the drip line.

However, trouble starts when the mulch is applied more heavily and in constant contact with a larger section of the tree's trunk. When wet, the mulch holds too much moisture against the bark, which can cause it to start to break down. As the mulch starts to compost, it heats up, which can further damage the bark and the underlying vascular tissues, compromising the tree's ability to transport water and nutrients.

https://extension.psu.edu/mulch-volcanoes-are-erupting-everywhere