The Danger of Mulching Too Much

mulch around treeMulching is a great practice that can contribute to the health of trees and plants as well as the overall beauty of your landscaping.  But too much mulch will not help – in fact, it can be detrimental to trees and plants.  Here is an overview of the damage that can be done when you get too aggressive in your mulch application.

  1. Trapping too much moisture around trees.

    One of the key benefits of mulch is that it helps keep moisture in the soil around plants and trees.  However, too much water held in the surrounding soil can be devastating.   When mulch is piled too high or mounded up the base of the tree trunk, it can retain too much moisture, causing the roots, bark, and cambium to rot.  The cambium is the layer of tissue just under the bark which transports water and nutrients to the leaves of a tree.  Without it, your tree will die.

  2. Choking out the oxygen in the soil that plants need.

    We don’t often think of plants needing oxygen, but they do.  And they receive this oxygen through their root system.  Too much water in the soil prevents the roots from getting the oxygen they need, literally choking them.  When roots are deprived of oxygen, they cannot live and neither can the plant or tree.

  3. Exposing plants to excessive heat.

    You may have noticed as you have applied mulch that it can sometimes give off heat.  This heat is created as the mulch decomposes.  When mulch is applied too thickly, this heat can become trapped without a way to escape into the air.  Plant tissue that is exposed to this heat may suffer irreversible damage.

  4. Creating a haven for bacteria, fungus, and other pests.

    While to all appearances, a thick layer of mulch may seem like a protection for plants and trees, it actually can harbor harmful organisms.  A wetter soil environment, which is maintained by an abundance of mulch, makes a perfect place for bacteria and fungus to grow and thrive.  Obviously, these are a threat to trees and plants.  Furthermore, insects and small animals can find shelter in mulch, and these pests can inflict chewing damage to the tender bark or cambium of a tree.

The important thing to remember is that mulch is good, but too much of a good thing is definitely harmful in this case.  Even if you see neighbors or professional landscapers applying thick “volcanoes” of mulch around trees, you will save yourself a lot of trouble with a more conservative application.  In general, you should keep mulch less than 3 inches deep, and it should not be applied directly against tree trunks.  If you have a question about tree care, call the professional arborists at Ping’s Tree Service (317-298-8482).  We have the expertise to answer your questions and accurately evaluate any problems with your trees.