Stop Overmulching Your Plants! No More Mulch Volcanoes


Bark Mulch is good for trees & shrubs for a number of reasons.

It looks good in the landscape and can help tie the whole landscape together among different planting beds.

It keeps weeds down from underneath.

It helps to keep roots cool in summer months and holds moisture in the soil.

It can also keep soil from eroding on slopes.

It can also help to insulate roots from extreme winter cold.

When mulching I suggest that you use a weed fabric that is allowed to breathe under the mulch in an attempt to keeps weeds down. Just make sure you don’t use standard rolled plastic sheets. It does not allow rain or irrigation water to penetrate to the root zone, and it also may also restrict oxygen to the roots.

But mulch can cause problems if it is applied improperly. I often see mulch applied incorrectly daily in the summer months. The # 1 culprit is applying so deep that air cannot penetrate into the soil and roots will suffocate. It can also be so deep that water cannot penetrate and the roots may dry out. Sometimes the feeder roots grow upwards into the mulch. Neither of these conditions is healthy for the trees or shrubs.

One of my biggest pet peeves is the Bark Mulch Volcano. (see picture below)

mulch-volcano.JPGmulch volcano

The biggest problem with too much bark mulch can be seen in many places. A mulch volcano is just one.

Mulch volcanoes are the mounds or cones of bark mulch that are two or three feet deep, and piled up along the trunks of trees and shrubs.

I am not sure why this habit has developed, but these deep mulch piles can cause much damage to trees & shrubs. I suspect professional landscapers are the originators and sometimes the worst culprits. Not all of them, but many of them.

You see, professional Landscapers get paid to do work. When customers ask for fresh mulch every spring to freshen up the landscape, the landscaper can’t and doesn’t usually turn down the work. After all, this is how they make a living.

Tree & shrub trunks are covered with bark that is designed to protect the trunk. They need air and light. If you pile too mulch onto the bark, it will be exposed to dark and moisture. As the bark continues to be in the moisture, it will begin to rot. Rotted bark cannot protect the tree from diseases, and in fact, diseases grow better in the dark moisture of the mulch. The offending trunks are more likely to get diseases and allow harmful insects to damage trees.


Some trees have shallow roots, especially maples. If bark mulch volcanoes are piled around the trunk, the roots will start to grow into it. These roots tend to stay in the mulch volcano and will then grow around the trunk in the mulch. As the root grows in diameter, it pushes against the trunk, which is also trying to grow bigger. These roots will eventually strangle the trunk. This type of root is called a “girdling root”. The trunk will keep growing wider above and below the girdling root, and may actually encase the root.

It also doesn’t encourage the tree and shrub roots to expand out in a healthy fashion. Healthy root growth has many agronomic advantages, but it also aids in stability.

Bark mulch is best when pit down to a depth of about 3-4 inches if you are starting from scratch.

Try this if you need a handy bark mulch calculator. Punch in desired depth, bed measurements and PRESTO, the correct amount pops out.

Even though bark mulch does break down some, after 2-3 years of annual mulching on top of mulch, it often accumulates to unhealthy levels for you plants.

So what do you do instead of annually piling more mulch on top of mulch?

I’ve got a better way that is less expensive, healthier, and with much less work.

MULCH MAGIC (or similar product)

Mulch Magic

Mulch Magic® is an easy-to-apply, long lasting spray colorant which restores the bright, original-looking color to faded fibrous mulch products like cedar, cypress, redwood bark, pine straw and more. With one quick application, it helps keep landscapes looking freshly groomed for three months or longer.

Looks Great and easy to apply!

With Mulch Magic®, one person with a sprayer can quickly restore the color to keep existing mulch looking its best. As the existing mulch breaks down naturally and renews the soil, replace with new mulch to keep your landscaping investment looking sharp throughout the growing season. Mulch Magic® will also help blend the color of the older mulch with the newer mulch. Enjoy all the benefits of colored mulch because of the endless design possibilities using color, contrast, and texture in your landscape.


At only 3-4 oz per gallon of water, will also allow you to freshen up your mulch for a few years, saving money and labor.

BEFORE before

AFTER new-new-mulch.JPG

So instead of spreading unhealthy levels of bark mulch yearly, try a product like Mulch Magic or similar every other year or for 2 years in a row before adding new mulch.
Your trees & shrubs will love you for it!!

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2 responses to “Stop Overmulching Your Plants! No More Mulch Volcanoes

  1. As the mulch decomposes, doesn’t the Mulch Magic colorant break down into your soil – can’t this be harmful? Is it organic? What type of “chemical” is in the Mulch Magic colorant?

  2. I believe the product is just a mulch dye. It doesn’t contain any pesticides and many of the mulches that are bought have similar dyes on them to begin with. As mulch decomposes, the dye will simply fade and not affect the soil at all.

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