Walk up to a healthy tree and the trunk widens at the bottom, spreading into a buttress where it meets the ground. That widening is the root flare, and when it is missing, the trunk goes into the soil straight, like a post sunk in a hole.
On a mature tree in Lehi, a missing flare is the most useful warning sign we have, because it usually means girdling roots are wrapped around the base. Girdling roots kill slowly and quietly, over a decade or more, and most homeowners never connect the thinning crown overhead with what is happening at the soil line.
How Girdling Roots Form
A root that meets a hard edge does not stop. It turns and follows the obstruction. In a nursery container, the obstruction is the wall of the pot, so roots circle the inside of the container and keep circling. When that root ball goes into the ground without the circling roots being cut and redirected, they keep the shape they learned.
The same thing happens in a planting hole dug in heavy clay. Glazed, compacted sidewalls act exactly like a pot wall, and roots track around the inside of the hole rather than pushing out into native soil. Add deep planting or a mound of mulch against the trunk, and the tree grows new roots up into that material, where they cross the stem and tighten over time.
What Girdling Roots Do to the Trunk
Here is the part that surprises people: the root does not squeeze the tree. Both the root and the trunk add wood every year, expanding in diameter, and where they touch they simply run out of room. The pressure comes from growth, not from strangling.
What gets crushed is the phloem, the layer of living tissue just under the bark that carries sugar made in the leaves down to the roots. Phloem cells are soft and thin-walled, and they fail first. Once that pathway is pinched, the root system below the constriction receives less and less food, so it grows fewer absorbing roots each year. The tree then cannot take up the water its canopy needs, even in a well-watered yard.
Why the Symptoms Look Like Something Else
Girdling roots produce a decline pattern, not a distinctive symptom, and that is why they get missed.
- Early leaf color in fall, weeks before neighboring trees of the same species.
- Smaller leaves and shorter annual twig growth.
- Scorched leaf margins in July even when irrigation is adequate.
- Thinning or dieback concentrated on one side of the crown, the side the offending root is on.
- A trunk that enters the ground with no visible flare, or with a flat spot or inward dip on one side.
Every one of those also shows up with drought, compaction or root rot. The trunk base is what separates them, so that is the first thing we check.
A Lehi Maple With a Buried Flare
A common version in newer Lehi subdivisions looks like this. Picture a Norway maple that went in as a container tree when the landscape was installed, in soil that was graded and compacted by equipment. Rock mulch and fabric went over the root zone, and the grade got raised a few inches against the trunk during the final cleanup.
Twelve years on, the tree colors two weeks early, the crown is thin on the south side, and the trunk meets the rock with no flare at all. Pull the rock back and excavate carefully by hand and you are likely to find a root as thick as a wrist crossing the stem just below the surface, with bark pinched flat where the two meet. Nothing about the top of that tree would tell the owner where the problem is.
What Can Be Done About Girdling Roots
The options depend on how far the constriction has gone.
- Excavate and inspect. Soil or an air tool is used to expose the root collar so the roots crossing the stem can be seen and mapped. Nothing gets cut before that.
- Sever the offending root. A root that is crossing but has not yet flattened the bark can often be cut out cleanly, and the tree recovers. The cut is made away from the stem so the wound is not against the trunk.
- Partial removal over two seasons. When several roots are involved, taking them all at once removes too much of the absorbing system at one time, so the work gets staged.
- Leave it and monitor. When a root is already deeply embedded and the trunk has grown around it, cutting can do more harm than the root is doing.
Timing matters. We prefer to do this work outside the heat of midsummer, when a tree has reserves to spend on recovery.
Preventing Girdling Roots at Planting
Every case starts at installation, which makes this one of the few tree problems that is genuinely preventable.
- Slice or shave circling roots off the outside of the root ball before the tree goes in the hole.
- Find the top-most structural root and plant so it sits at or just above finished grade.
- Dig the hole wide and shallow, and rough up glazed sidewalls in clay.
- Keep mulch off the trunk. A ring, not a volcano.
- Remove all twine, burlap and wire from the top of the ball once the tree is set.
Utah State University Forestry Extension and University of Minnesota Extension both publish planting-depth guidance that matches what we see in the field. Our tree planting crews handle root-ball correction as part of the install.
Safety and When to Call
Root collar excavation sounds like a shovel job, and that is how trunks get injured. A shovel blade cuts bark, and a bark wound at the base is a direct entry for decay fungi, which is exactly what you are trying to prevent. Hand work and air excavation exist for that reason.
There is a structural side to this as well. A tree with a heavily girdled base has compromised wood where the whole load is carried, and those trees fail at the ground line in wind. Never take a chainsaw to a root or a trunk base on a leaning tree, and stay away from any tree within reach of a power line.
Call us when a mature tree has no visible flare, when one side of the crown is thinning, or when a tree that was planted in the last fifteen years has stopped putting on growth. Tree preservation work begins with exposing the root collar and finding out what is down there. The USDA Forest Service has documented the same failure pattern in urban plantings nationwide.
Girdling Roots FAQs
Can a tree grow out of girdling roots?
No. Both the root and the trunk keep expanding, so the contact point only gets tighter with every growing season. Time makes this one worse, never better.
Is it safe to cut a large root off a tree?
It depends on the size of the root, its distance from the trunk, and how many other roots are supporting that side. Cutting a major structural root close to the base can reduce anchorage, which is why the decision gets made after the collar is exposed, not before.
Do girdling roots affect young trees too?
Yes, and that is when they are easiest to correct. A tree in its first few years can have circling roots cut out with almost no consequence, and the root system reorganizes outward.
Will mulch cause girdling roots?
Mulch piled against the trunk can. Roots grow into moist organic material held against the stem, and those adventitious roots cross the trunk as they thicken. Mulch spread flat over the root zone, with the trunk left open, does the opposite and helps.
Your Next Step
If you cannot see where a trunk widens into the ground, that is the tree to look at first. Call Rivendell Tree Experts to schedule a root collar inspection in Lehi, or send a photo of the trunk base through our contact page and we will tell you whether it needs excavating.