Just say no… to volcano mulching.

October 15, 2021
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You’ve seen it. I’ve seen it. We’ve all seen the twelve- to eighteen-inch deep piles of mulch wrapped neatly around the base of the tree — for who knows what reason. That practice is called volcano mulching, and no one knows why, or where it started.

What we do know is this:

Volcano mulching is bad for trees.

Bad. Bad. BAD. Don’t do it. Step away from the mulch volcano.

Why? Northern Virginia’s go-to mulch supplier will tell you why.

Smothered roots, that’s why

JK Enterprise Landscape Supply is in the business of plants and trees and — of course — mulch. And as such, we’ve spent a lot of time talking to our customers about proper tree planting depth, and why it’s critical for the long-term success of any tree. A tree that’s planted too deeply doesn’t allow for sufficient gas exchange through the soil horizon, and the roots become smothered.

Volcano mulching does the same thing; your tree’s living, breathing roots are buried beneath mounds and mounds of mulch, which will seriously limit the tree’s ability to flourish.

Fungus and rodents, that’s why

Deep piles of mulch around the trunk of a tree are the perfect breeding ground for decaying fungus. Crown rot, root rot, you name it: Volcano mulching will cause it. Not to mention the rodents. Mice and moles who love to snack on tree bark also love a moist, damp burrow made of volcano mulch.

Money wasted, that’s why

Yes, absolutely, we want to sell you mulch. (We’ll even sell it to you online: Buy mulch online.) But what we don’t want to do is sell you mulch you don’t need, for a practice that might ultimately kill your tree. No way. Instead, come to JK Enterprise Landscape Supply for the mulch you need, to fertilize your garden; to conserve water; and to protect your trees’ and plants’ roots from the winter chill to come.

So what’s the right way to mulch?

So far, we have given you plenty of reasons why volcano mulching is always a mistake. But this may be leaving you bewildered, wondering how you are supposed to go on landscaping now that you know you’ve been mulching all wrong. Luckily, as the northern Virginia mulch experts, JK Enterprise has the instructions you need to become an expert mulcher. 

Give the tree space to breathe

The main drawback of volcano mulching has to do with the depth of the mulch which surrounds the tree, for all of the reasons discussed above. But before determining how much mulch to pile on top of the tree roots, it’s important to make sure that the mulch is not too close to the tree. Experts nearly universally recommend allowing a roughly three inch space between the trunk of the tree itself and the mulch you pack around it. It can be OK to give the roots even a bit more space than this, but it generally should not be more than a six inch gap. 

Another helpful rule of thumb is to allow the “root flare” to stay visible — this means that you should not put mulch over the area where the roots first enter the soil. Failing to do this can do just as much damage to the roots and the tree itself as would piling up too much mulch on top of the roots.

Get the depth right

So you know that you should not pile huge mountains on top of your tree roots with “volcano mulching,” but what depth is the right depth? Luckily, the answer is fairly simple. For most types of mulch and trees, just a two-inch layer of mulch should do the trick. This amount of mulch is generally just right for allowing the mulch to provide its nutrient and protection benefits to the soil and the tree’s roots, without being so much that the roots become suffocated. If you are using a more porous type of mulch, or if you think your tree needs an especially deep layer for whatever reason, it should be OK to pile the mulch up to a four-inch depth. Conversely, if you are using special textured mulch or any type of mulch that is known for retaining moisture just one inch of mulch should be enough. Even with such a shallow layer of mulch, tapering the small mulch pile as it extends away from the tree can have great aesthetic and functional benefits.

Extend the mulch far enough

Finally, you want to make sure that your shallow mulch pile extends far enough away from the trunk of the tree. Unlike the question of how deep the mulch layer should be, there is a lot of freedom for creativity in terms of width. There is no real drawback to spreading the mulch too far, except for the factor of using more mulch than is actually necessary. One way to determine how far from the root you should spread the mulch from the root is determining the “drip line,” which is the length that the tree canopy extends from the trunk. Because this line will extend outward as the tree grows, you can add more mulch horizontally as the tree matures.

Use the right mulch

These instructions should give you all you need to lay your mulch layer correctly. Now all you need to do is get the best mulch in the Northern Virginia area, available to you from JK Enterprise!