How to Mulch Around Trees: Benefits and Steps

Using mulch around trees comes with several benefits, but there are a few dos and don’ts to keep in mind when using mulch around trees. Mulching is especially advantageous to young trees, but old trees can also benefit from a layer of mulch around their base. In this post, we’ll discuss the benefits of mulching, how to mulch around trees, types of mulch, and how to avoid mulching volcanoes. 

If you need expert tree care and property services, don’t hesitate to contact us. We’re Santa Monica’s expert tree service providers.

Benefits of Mulching Around Trees

Mulch is one of the most powerful tools that a gardener has at their disposal. While some people view mulch as an aesthetic element, improved curb appeal is just a bonus. Other benefits of mulching include:

Improves soil structure: Organic mulch improves the soil as it breaks down, adding byproducts back to the soil in the form of organic matter.

Conserves water: Mulch slows evaporation, helping to retain moisture available to plant roots.

Helps prevent weeds: a two- to four-inch layer of mulch prevents weeds from thriving by blocking their growth and access to sunlight.

Prevents soil erosion and mechanical damage: Mulch protects your plants from erosion in some cases and mechanical injury from lawnmowers and other equipment.

Root insulation: A layer of mulch helps regulate soil temperature to keep plant roots warm in the winter and cool in the summer.

Air exchange: Mulch allows more gasses to reach the roots and improve respiration.

Types of Mulch

You can mulch around trees with wood chips, bark mulch, or shredded leaves. Medium- to coarse-textured wood chips often work best as fine material such as shredded bark mulch can prevent water from reaching the roots. If you opt for leaf mulch, consider shredded leaves because they break down and release nutrients more quickly than whole leaves. Alternatively, you can make your own mulch using shredded pine needles.

Avoid Mulch Volcanoes and Collar Rot

A mulch volcano usually results from building a circular raised bed around a tree, then filling it with mulch. The mulch gets steeper as it gets closer to the tree. Although mulch volcanoes are pretty common, they present several problems:

  • Water runs off the sides of the mulch volcano and away from the tree’s base, thus depriving it of water.
  • Excessive mulching can suffocate a tree’s roots.
  • Much of the water that would otherwise reach the tree’s roots gets trapped in the mulch volcano.
  • Deep mulch can invite pests and diseases.

Improper mulching retains moisture at the tree’s base, introducing collar rot, which occurs at the soil line where the plant emerges. The best way to avoid collar rot is not letting any mulch touch the tree trunk.

How to Mulch Around Trees

Once you have your mulch ready, here are a few tips to keep in mind for applying mulch around a tree.


Excess mulch can limit oxygen exchange between roots and the atmosphere. Covering roots with mulch greater than four inches deep prevents the roots from breathing.


Spreading the mulch ring further out from the tree creates less competition with grass for water and nutrients. You also want to leave the tree’s base slightly exposed to avoid volcano mulching.


When roots hit a plastic edge, they start to grow in a circle. You can prevent this by going for a natural edge. Consider digging a two- to four-inch-deep trench around the outside of the ring that will allow the mulch to fall into it naturally.

Hire a Professional Tree Service Company Today

Are you looking for a licensed and experienced tree service in Santa Monica, CA, or the surrounding area? Contact the experts at International Environmental Corporation. Dial (818) 892-9341 to learn more about tree health care services and schedule service.

International Environmental Corporation

Our team of certified arborists boast a vast knowledge of tree services, making us the top choice in full-spectrum tree care and property services. Our work helps to improve the safety of residential and commercial properties that play home to trees of all sizes.


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