Volcano Mulching Kills Trees
This latest mulching technique that is detrimental to trees has been nicknamed “Volcano Mulching” for good reason. I’m not sure where or how this started but it is destroying trees in landscapes across America. Probably beyond our borders as well, but I don’t know for sure about that.
Take a look at these two photos.
Volcano Mulching
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Volcano Mulching
Notice how high the mulch is around the trunk of this tree. That is not good. All plants, trees and shrubs, have a root crown. That’s the point where the roots stop and the upper part of the plant begins. Roots need to be covered with soil at all times and not exposed to air. Roots know how to deal with moisture and are designed to absorb moisture to provide nutrition to the plant. The stem of trees and shrubs should not be subjected to the same kind of moisture. It will damage the stem of the plant.
The two photos that I am showing you here have way too much mulch around the stem of the trees. In other words, the mulch is too deep. Actually these two trees are mildly over mulched compared to many that I’ve seen. When you pile the mulch up around the stem of the tree the excessive moisture that the mulch traps will begin to decay the bark of the tree. Pretty soon the bark will begin to pull away from the tree, exposing the cambium layer to the air, and allowing insects, disease and fungi to go to work between the bark of the tree and the tree itself. Eventually the tree can die.
It’s important to understand that right below the outer layer of bark is a layer of tissue known as the cambium layer. The cambium layer is the circulatory system of the tree. All of the moisture and nutrition that feed the tree travel through that cambium layer. That’s why it is so important to protect the cambium layer.
When you plant a tree or shrub you should never plant it so anything except the root crown is covered with soil. In most cases I suggest people install plants so the root crown is at least one inch above grade, then covered with soil and a light layer of mulch. No more than two to three inches of mulch and even that should be pulled away from the trunk of the tree so there is air flow between the mulch and the trunk of the tree.
Where and how this volcano mulching thing started I have no idea. I first started working in the landscape trade when I was 18 years old, that was almost 40 years ago, and we never did this volcano mulching thing, nor did anybody else. But then a few years ago I started seeing these huge piles of mulch around the base of trees in parking lots etc. Then unknowing homeowners see this practice and start repeating it at home.
You’d think that people in the industry, meaning the landscape contractors that take care of these commercial properties, would know better. I’m sure most of them do, but it’s the few that seemed to have started a trend that truly needs to be reversed. Believe me, I’m not the only one on this band wagon.
Be kind to your trees.
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I recently ran into this issue on a property I work at. A number of different landscapers and gardeners had worked the property over the course of about seven years. I started noticing that lots of trees and bushes health was declining rapidly. So I started checking for water issues and pests to determine the problem. The problem was the mulch, not the plants. Over the years all the past gardeners topped the gardens once or twice a year with fresh humus or mulch to keep the gardens looking good, but rather than getting under the trees and bushes and removing old mulch from the top of the root ball to control depth, it was now piled up to close to a foot in places witch was suffocating the trees and shrubs and also starting to create trunk rot. Very important to rake back mulch to top of root ball to maintain 2-3 inches of cover when retopping gardens to maintain health and beauty of your plants. This really applies to all plants, not just trees and shrubs. So if you are a mulch user and your gardens are starting to decline, without signs of water stress(too much or too little)or pests, check your mulch to maintain proper depth so the plants do not become suffocated from lack of oxygen intake and to cut down problems with inadvertant layering and trunk rot.
Hey Mike:
I love your articles….I am passing this on to my family and friends, keep up the good work.
God Bless
Hi Mike,
I love the info you send out. I am a plant maniac, artist, landscaper and appreciated those who are passionate about these things. Maybe you should post a photo of proper mulching around trees so people can see a comparison.
Just a thought. Keep it coming.
Thanks,
Dixie
Dixie, you’re right. I’ll try and snap a photo and add it to the page first chance I get.
Hi Can I put mulch around my roses? Thank You Joan
I haven’t been mulching– period, I am new to Indiana and mulching wasn’t common where I lived in the past. Maybe I should start?
Maybe you could do a pimmer on mulching?
Thanks, Shirley
You really don’t NEED to mulch. However, proper mulching helps conserve moisture for the roots of the tree, especially if it’s newly planted. It also means less frequent watering, which conserves water. ALWAYS keep mulch 6″ away from the trunk of the tree…and it shouldn’t be more that 3″ deep.
This is very useful info! Thanks so much!
Dear Mike – I’m a big fan! Really love your articles – they are so informative and down-to-earth (no pun intended!) And I love the way you manage to provide all the pertinent details on a given topic – while seemingly talking “off the top of your your head”. That is a characteristic of a great teacher -and you are a natural…
I am not even afraid to ask what I think is probably a really stupid question! In the effort to conserve water loss from my very sandy soil I recently mulched around my entire garden areas, trees and shrubs with shredded bark mulch. I did read about it beforehand and did know to keep the depth below 2-3″ and away from trunks – but I do have a question… Prior to mulching everything (our water bill last summer almost put me in the Coronary Care Unit) I used to add sphagnum peat moss to the gardens every year. Now I wonder (a little late, I know…) how does one go about adding soil amendments to gardens that have a mulch over them? Are there different techniques depending on what is being added? For example, if I sprinkle fertilizer over the top of the mulch and water it in – will it actually make it down into the soil? Do I need to alter the amount of fertilizer I add if I don’t pull the mulch back and rake it in? How do I go about adding compost/humus/peat to gardens that are mulched with shredded bark mulch? Will compost make it down into the soil if I spread a layer over the mulch and lightly rake it in? Or do I need to pull all the mulch back, spread the compost, rake it in, and then rake the mulch back in place? Do I even need to add compost now that I have an organic mulch in place? Thanks again for all the great info!
Michele,
Good choice with the shredded hardwood bark mulch. It is the best for the plants and the soil. Hardwood bark mulch breaks down into really good organic matter that will enrich the soil. So now that you have mulch, I really would do anything for now. Bark mulch will harden and get crusty and you should loosen that up once a year. When you do that it will break down quickly. Then you can add compost if you like. But if you just continue to apply a light layer of mulch every other year you will enrich the soil. Just make sure that you loosen the mulch before you apply more.
Dear Mike,
First let me say, I loved your Father’s Day tribute to your Dad. How wonderful to have left you with such pride for him ! Happy Father’s Day to You ! I have worked in landscaping for the past 15 years and I fully agree with you on the mulching techniques that have changed in the past few years. I have been complaining about the depth ’til I feel like “no-one” is listening or caring. Their responce to me is almost always the same, ” It helps keep the weeds and sucker branches from growing.” Or The owner says, “It looks so much neater. ” I have watched many trees, shrubs and flower beds die slowly because of this crazy practice that somebody came up with because they didn’t like weeding or whatever their reasoning , but I’m with you, I wish they would stop because I, for one, am really getting fed up with correcting their mistakes and having to start the gardens over.
Thanks for the tips to help educate the unknowing to help them realize what they are “really” doing to the plants and trees. Kathy
I think I had the same problem with a dwarf apple tree. I planted periwinkle around it and water it often. The tree died.
So show a picture of how you do it right.
Gordon, I need to remember to get that photo, but the easy short answer is about 3″ of mulch with about 1″ of air space around the base of the tree.
Here in my town they like to put retaining walls filled with dirt around trees. You can drive around and see what’s left of the tree!! A trunk, and the funky landscape timbers filled with dirt that smothered the tree. JEEZ!!
Dear mike I like your blog and find it very handy. I have a question What about thoes old shreded tires made into a ring to keep grass from growing around the tree trunks. They cost about $20.00 and do keep the grass from growing. Are they dangerous for a tree. Such as your valcano mulching? Thanks
Al, I don’t honestly know, hard to picture. But I wouldn’t use anything around a tree to keep grass from growing. Especially anything that is not bio-degradable. Removing the grass, putting down newspaper or paper bags then mulching works pretty good. Nothing is really all that permanent.
How do I kill mimosas? I had one that I cut down that is close to my vegetable garden and I cannot kill the roots. Someone suggested black plastic. Maybe cover black plastic with very deep mulch?
Think organic. Tire contain chemicals and about 5-10 gallons of petroleum.
Oh Mike.. I can’t tell you how many ” so-called ” Pro Landscapers ” I’ve seen doing this around here.” You know People who have large trucks or even Trailers with so & so Lanscaping go buy after leaving a site.
Then you see what they actualy did & somebody paid them too. I just walk by and think to myself ..there’s another landscaper that kills his own work.
Then he’s off to his next job. I want to scream NOOOO!! Please you are killing rare trees , specimen trees. NOOOO! Sincerely Charles W.
The cynic in me thinks that maybe some of the tree suppliers/planters know the trees/shrubs will eventually die from this and need to be replaced. As a note, some plants, like tomatoes, can actually benefit from being planted deeper since they develop new roots where the stem is in contact with the soil. This applies particularly to older seedlings.
Hi Mike! Thank you for all of your wonderful information. I really look forward to your emails. As for the volcano mulching, I have seen a lot of this. One problem in trying to correct this is that once it has been done under a maple tree, the roots rise up to get water and make a fibrous mat. It’s about impossible to rake away the extra mulch to start over and give it a nice little coat. The landscape guys just pile it on over the mat, making things worse for the next year. Also, on trees in the park strip, they seldom increase the size of the circle, so you have this little circle with a huge pile of mulch within it. I hate to think of what is happening to the root system as they are cutting the new circle!
Correction – I didn’t actually mean that the existing roots rise up. The tree forms a whole network of new little fibrous roots near the top of the mulch to get to the water that usually can’t get down through the crust! They never break up the old mulch, so the water just runs right off.
They do it everywhere here in Virginia. Monkey see, monkey do. Landscapers profit from the difference between what they purchase mulch wholesale and charge the client.