March 15


Roots, Soil, and Mulch: DIY Root Inspection For Struggling Trees

By Gabe S.

March 15, 2024

There are many potential reasons a tree may struggle, and some reasons are more obvious than others. One of the less obvious potential causes is the way and location in which the tree has been planted. Soil, specifics of tree placement, and root tending at the time of planting all have huge impacts on tree health. The evidence may be invisible, buried underneath the earth. Concerned about your own trees? Read on for some helpful Do-It-Yourself information for assessing the planting area of your own trees, as well an advisement of when assistance with professional equipment may be needed.

The Importance Of Soil

Many tree health issues in Colorado urban forests begin with poor root zone conditions including high soil compaction, low nutrient availability, and improper planting depth. Canopy dieback can often be associated with these soil conditions – not necessarily foliar disease or pest issues. Getting close to the tree and handling the dirt near the base can help homeowners assess their soil issues.

Start by checking soil compaction and organic matter composition visually. Handle the soil and break it apart to closely inspect its composition. Darker brown or black soil that crumbles easily has more organic matter than dense red clay soil. Clay soil is typically highly compacted and low in nutrients, meaning our trees need extra help to maintain optimal health. If you find mostly clay soil at the base of your tree, we may recommend a root zone excavation service that removes the top layer of compacted soil and replaces it with compost, soil amendments (fertilizer and mycorrhiza), and fresh mulch within 2 feet of the trunk.

Why Would I Need A Root Excavation?

Typical reasons for performing a root excavation include poor overall soil, planting a tree too deep, or mulching a tree too high after planting. Many housing developments in Colorado had the topsoil stripped before construction, and most landscape trees are planted directly into the poor quality rock and clay soil left after construction. Amending these soils with fertilizer and microorganisms will make the root zone a healthier place for your tree and provide much better growing conditions than compacted clay soil.

We routinely remove up to 1 ft depth of clay soil from mature tree root zones and replace it with compost and mulch. Many trees exhibit a flush of new growth after the process, as they are instantly able to move more water and nutrients through the root system to the upper canopy.

Proper Planting For Flourishing Trees

Proper planting depth is critical to new tree planting, as the root ball needs access to oxygen from the atmosphere to properly grow and support the canopy above. If a tree is planted too deeply in clay soil, the roots will likely suffocate or new adventitious roots will grow out higher on the trunk and girdle the main stem, with either situation leading to a dead tree. If your tree looks  like a telephone pole with a straight round trunk going into the soil, it’s likely the root flare is buried beneath dirt or mulch and needs to be excavated.

Check Your Mulch

“Volcano mulching,” or mounding mulch against the base of the trunk, is also detrimental to tree health and may invite decay into the trunk. At least two inches of space should be left between the trunk and mulch pile to avoid decay, and the depth of mulch should be 2-3 inches once settled. Rock mulch should always be avoided over a tree’s root zone, as the sun will heat up the rocks faster than wood mulch and can dry out or burn the fine root hairs near the surface, Turf grass should also be kept far from the trunk of the tree, as it will absorb water and nutrients before the tree will, and can also allow moisture to sit against the trunk and lead to decay.

Additional Resources

Unsure of what you’re looking at? Our ISA Certified Arborists can provide a proper assessment and recommend the necessary steps to keep your trees healthy. Call 303-466-3175 or contact us via “Request A Quote” to schedule a visit.

Looking for more information? Use CSU and other online resources to learn more:

CSU Yard and Garden resources:

CSU Tree planting guide PDF:

Urban Tree foundation planting guide:

Tree watering guidelines:

Trees are Good “Tree Owner’s Manual” PDF:

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