A mulch volcano is a type of garden design made by piling mulch up around the base of a tree or shrub in the form of a cone or volcano-like structure, either with or without an opening at the top. The purpose of creating a mulch volcano around a tree is twofold: to improve water retention in the soil and to improve the aesthetics of a landscape. Mulch can also be used to help protect young trees from debris and temperature fluctuations. While the mulch will not provide the trees with any extra nutrition, it will help to trap moisture in the soil and provide the tree with a buffer from changing temperatures. It is a bad practice and must stop.

Mulch Volcanoes are Bad

| Jan 10, 2023 | DIY Landscaping Ideas, Garden Advice Gulf Coast, Garden Advice Sugar Land, Garden Tips, Horticultural Advice, Houston Garden Consultant, Mulch Volcano | 0 comments | 3 min read

Mulch Volcanoes are Bad

Garden Guy’s warning about mounding up mulch around trees 

  • 🔑 Key Takeaways with Garden Guy
  •  Mounded, Volcano mulch covers bark, and weakens trees.
  • The bottom section of a tree needs air and light.
  • Tree bark that stays moist will rot.
  • The volcano-mulched tree may be more susceptible to disease and insect damage.
  • Properly applied mulch is about 2 inches deep and does not touch the base of the trunk bark.
  • It looks awful. Stop it.

Stop mulching trees like a volcano. It's harmful to the trees. Aggie Horticulturist, Todd Farber from Garden Guy warns.

Article begins…

A mulch volcano is made by piling mulch up around the base of a tree or shrub in the form of a cone or volcano-like structure, either with or without an opening at the top.

Mounded mulch covers bark, stops allowing for tree root flare or trunk flare. The bottom section of the tree needs air and light. Mulch volcanoes stop the air and light period. Bark that stays moist will rot. The tree may rot in those covered areas and may also be more susceptible to disease. Definition of tree root flare : The root flare, also called the trunk flare, is where the first main roots attach to the trunk. Remove excess soil to expose the root flare, as well as across the top of the entire root ball. Definition of mulch volcano: 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 sometimes large shrubs.

Image Courtesy of Joe Boggs, OSU Extension

The original purpose of creating a mulch volcano around a tree was probably for water retention and to also help protect young trees from debris and temperature fluctuations.

As far as the Gulf Coast is concerned though, this volcano mulching practice is out of control; destroying and weakening trees and large shrubs instead of protecting them.

While mulch does not provide trees with any extra nutrition, it does help to trap moisture in the soil and provide the tree with a buffer from changing temperatures. If applied correctly, mulch around a tree acts as just that, a moisture trap.

HOT TIP : Trapping moisture against bark is a recipe for a weak, diseased tree. 

When mulch is piled around a large tree or shrub touching the bark, it DOES TRAP MOISTURE.  In this case, that is not good.

Trapped moisture on tree bark will cause a weakening of the base of the tree and make it more susceptible to insects and diseases.

Also, I love this point made by the University of Nebraska at Lincoln: ROOTS NEED TO BREATHE!  Tree roots respire.

” First, roots respire, meaning they take in oxygen and release carbon dioxide.  This exchange of gases, as it is known, takes place in the upper 18 inches of soil.  It’s no accident that roots proliferate in the top 18 inches because this is where oxygen is most readily available.  Bring in a boatload of mulch and suddenly the lower roots no longer have access to oxygen.  This leads to stressed and dying roots which in turn stresses the tree.  A stressed tree has fewer defenses than its properly-mulched counterpart, leading to susceptibility to otherwise-minor insect and disease problems.”  Nebraska Extension in Dodge County 

“Mulch should be applied on the ground no more than 2-3 inches deep surrounding the tree at ground level and should not touch the bark,”

advises Todd Farber, Aggie Horticulturist of Garden Guy

proper mulching for trees

Image Courtesy of Sustainable Saratoga

 

Lastly, this mulching volcano foolishness looks awful.  Stop it.

Go out and remove the mulch from around your trees.  Compost the mulch or do something with it that is positive.  Take the mulch down to a 2-inch level and give your tree a chance to thrive and your neighbors a break from seeing this ugliness in the landscape.

A mulch volcano is a type of garden design made by piling mulch up around the base of a tree or shrub in the form of a cone or volcano-like structure, either with or without an opening at the top. The purpose of creating a mulch volcano around a tree is twofold: to improve water retention in the soil and to improve the aesthetics of a landscape. Mulch can also be used to help protect young trees from debris and temperature fluctuations. While the mulch will not provide the trees with any extra nutrition, it will help to trap moisture in the soil and provide the tree with a buffer from changing temperatures. It is a bad practice and must stop.

 

 

 

Sabrina Farber

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