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Mulch and Fill Soil Over the Root Flare

The stem girdling roots grow upward to the top of the mulch volcano and then wrapped around the trunk.
1. The upper canopy of this live oak shows, thin, sparse foliage, reduced canopy opacity, and branch tip dieback. All attributed to years of improper mulching against the root flare.

Often, we are asked to excavate recently installed, young live oaks (Quercus virginiana) with mulch volcanoes and to fix the problems we find. The clients wonder why the trees have never looked very healthy, even after applications of fertilizer and pesticides. We know from experience that we will likely find some nursery ropes, straps and wire baskets left behind that are beginning to girdle the growing trunk. We also expect to find an occasional stem girdling root. This is a persist and pervasive problem in the landscaping industry.

The problems weren’t found in just a few isolated instances but rather every tree that had a mulch volcano had some degree of stem girdling roots.Typically, we encounter tree bases that have been covered with layer after layer of mulch onto the trunk creating what we affectionally call “mulch volcanoes.”

To do the root crown excavations, we use an Air Spade excavation tool which uses a 200 CFM air compressor and directs a stream of high velocity air at the mulch and soil safely removing the soil and mulch from around the roots without damaging the roots.

Once the soil and mulch have been cleared away, the remaining exposed wires from the wire basket need to be cut and removed and nylon ropes used by the nursery for transport and to lower the tree and root ball into the planting hole are also cut and removed. In most cases the wire baskets and the ropes have either become completely enveloped by the roots or are beginning to cause girdling and strangulation of the expanding roots and trunk. 

We also find that the excessive layer of mulch placed around each tree encourages root growth upward from the soil into the mulch. These vertically growing roots eventually begin growing horizontally once they reach the top of the mulch pile and then started growing downward across the trunk or root flare. The result of this unnatural root growth pattern is many of these newly formed roots above the natural soil grade become stem girdling roots that strangle the root flares and trunk. Time and time again, excavated trees are found to have some level of damage from wire baskets, girdling from nylon ropes and root flare or trunk strangulation caused by stem girdling roots. Does this kill a tree? It can, but more often if keeps the tree in a stunted and unhealthy state, making it susceptible to nutritional deficiency, and infestation by pests and or fungal pathogens. 

2. After removing the top layer of mulch and soil, we discovered a dense layer of woody adventitious roots that had been slowly strangling the old tree.