Girdling Roots: The Slow Strangulation Nobody Notices

A tree that has been in decline for years with no obvious cause — thinning canopy, early fall color, dieback at the top, no pests, no disease, adequate water — is worth checking at the base. Frequently what you find is a root wrapped around the trunk, slowly cutting off the tree's circulation.

Girdling roots are one of the most common causes of urban and suburban tree decline, and they are almost entirely a product of how the tree was grown and planted.

What Happens

A root that circles the trunk instead of growing outward eventually contacts the trunk as both expand. Neither can move, so pressure builds. The root compresses the tissue just under the bark — the phloem and cambium — which is how the tree moves sugars from the leaves down to the roots.

Choke that off and the roots below the constriction begin to starve. The tree declines slowly, over years, and the decline is usually blamed on drought, disease, soil or age.

The tree also becomes structurally weaker at that point, and girdled trees can fail at the base in storms, which matters a great deal in a hurricane zone.

The Symptoms Are Frustratingly Generic

• Gradual canopy thinning, often starting on one side
• Dieback in the upper canopy
• Smaller leaves, off-color foliage
• Early autumn color on deciduous species, or early leaf drop
• Reduced growth compared to similar trees nearby
• Decline that does not respond to water or fertilizer

The one specific clue: the trunk does not flare properly at the base. A healthy tree widens where it meets the ground, like a bell. A girdled tree often goes straight into the ground like a telephone pole, or shows a flat side or an indentation where the root is compressing it.

If you look at the base and there is no flare, dig.

Finding It

Carefully excavate the soil and mulch away from the base of the trunk, down a few inches, and look. You are looking for roots running across or around the trunk rather than radiating outward from it.

Be careful — you can damage bark with a shovel. Hand work or gentle water excavation is safer. An arborist can do this with an air excavation tool that removes soil without harming roots.

Also look for mulch piled against the trunk, which both hides the flare and encourages roots to grow up into the mulch and around the trunk.

Where They Come From

Container growing. A root reaching the side of a pot turns and follows the wall around. By the time the tree is sold, it may have a substantial circling root system. Planting that root ball without correcting it plants the problem.

Planting too deep. A tree set too low, or with soil piled over the root ball, encourages roots to grow upward and around near the surface.

Mulch volcanoes. Mulch mounded against the trunk causes roots to grow up into it and circle. This is one of the most common landscape practices in Florida and one of the most damaging.

Small planting holes in compacted soil. Roots hitting hard soil at the edge of a small hole turn and follow the perimeter, the same way they do in a container.

Confined planting spaces. Tree pits and narrow strips force circling.

Prevention: The Planting Is the Whole Game

Inspect and correct the root ball before planting. Wash or tease soil away from the outside, find circling roots, and cut them. Yes, cut them — a severed root regrows; a circling root strangles. Slice the outside of the root ball vertically in several places if it is heavily bound.

Plant at the right depth. The root flare visible at or slightly above final grade. Nursery stock is often potted too deep, so dig into the ball to find the flare rather than trusting the soil line in the container.

Dig wide. Two to three times the width of the root ball, no deeper. Loosen surrounding soil so roots have somewhere easy to go.

Mulch correctly. Two to three inches, in a wide ring, pulled back several inches from the trunk. Never against the bark, never mounded.

Treating an Existing Girdling Root

Sometimes a girdling root can be cut and removed, relieving the constriction. Whether that is advisable depends on how large the root is, how much of the tree's root system it represents, how far the compression has progressed, and the tree's overall condition.

It is genuinely a judgment call. Removing a large girdling root removes a significant portion of the tree's anchorage and absorption, and on a tree already in decline that can be the final stress. This is a case where having a qualified arborist assess it is worth more than a general rule.

Catch it early on a young tree and it is a straightforward fix. Catch it on a mature tree in advanced decline and the honest answer may be to plan a replacement.

Check Your Recently Planted Trees

If you have planted trees in the last several years, go look at the bases now. Pull back the mulch, find the flare, and see what is there. Correcting a circling root on a young tree takes minutes. Discovering it on a twenty-year-old tree usually means you are watching it die.

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ArboristRX assesses tree health and root problems across Edgewater, New Smyrna Beach, Port Orange, Oak Hill and Volusia County. If you have a tree declining for no apparent reason, call (386) 444-5959 and we will look at the base first.