Here’s the thing about girdling roots: they are one of the few tree problems that can show almost nothing visible for a decade, and then take the tree down in a year. A root that was the size of a pencil at planting time grows slowly, quietly, wrapped around the trunk under the soil — and twenty years later, that root is the size of a fire hose and it is cutting off the tree’s own water and sugar supply. The tree is strangling itself. Most homeowners in Central PA have at least one tree on the property doing this right now and do not know it.
What a girdling root actually is
A girdling root — sometimes called a stem-girdling root, or SGR — is a tree root that grows around the trunk instead of outward away from it. As both the root and the trunk expand over the years, they compress against each other. The root gradually cuts into the trunk’s vascular tissue, the outer sapwood where water moves up and sugars move down. Strangulation is the honest word for what happens.
University of Minnesota Extension publishes one of the most widely cited homeowner references on stem-girdling roots and has documented the link between SGRs and the decline of urban and suburban trees — particularly maples, lindens, and pines. The USDA Forest Service has supported research making the same point: SGRs are a leading driver of “unexplained” mature tree decline in landscape settings.
Where girdling roots come from
Most people think girdling roots are a random accident. They aren’t. They come from three very specific, very preventable practices, and they start at planting time.
- Container-grown nursery stock that circled in the pot. When a young tree grows too long in a container, its roots hit the pot wall and turn sideways, then continue circling. When that tree gets planted without any root correction, the circling roots keep circling underground. A few of them inevitably end up wrapped around the trunk.
- Burlap and wire baskets left on during planting. Some B&B (balled-and-burlapped) trees arrive with synthetic burlap and wire baskets that do not decompose. Roots bend when they hit the basket and find their way into circling patterns. ISA planting guidance has shifted over the last decade toward removing the top third of the basket and all synthetic burlap before backfilling.
- Planting too deep. Here’s the kicker: a tree planted with its root flare buried beneath soil will often grow adventitious roots from the buried trunk — and those adventitious roots have no reason to grow outward. They circle. Penn State Extension’s planting guidance specifically calls out visible root flare as a non-negotiable after planting.
The short version: a tree that was mishandled for five minutes at planting can have a problem that shows up thirty years later.
How to tell if a tree has girdling roots
The signs on a mature tree are subtle until the tree is already failing. What to look for:
- No visible root flare. A healthy tree’s trunk widens at the base and the structural roots are visible or near the surface. A tree that looks like a telephone pole stuck in the ground — straight trunk disappearing into the soil with no flare — almost always has either fill soil over the flare, a girdling root, or both.
- One-sided canopy decline. If a mature maple has thinning foliage on one side of the crown and full foliage on the other, the root problem is usually on the thin side. The root on that side is choking the vascular tissue that feeds the corresponding part of the canopy.
- A flat spot on the trunk at the soil line. Sometimes a girdling root compresses the trunk hard enough that the trunk develops a flat or concave area instead of a rounded profile.
- Slight lean with no obvious cause. A girdling root that has compromised the structural roots on one side can leave the tree with a quiet lean that worsens over years.
- Slow, unexplained decline over five-plus years. No pest, no disease, no construction event — just progressive thinning and smaller leaves. A girdling root is worth ruling in or out.
Can the tree be saved?
Sometimes. It depends on how far the root has gone.
Early identification — ideally when the tree is still young enough that the girdling root is small — can be corrected surgically. A certified professional can carefully excavate the root zone (typically with an air spade), identify the circling or girdling roots, and sever them cleanly. The tree often recovers fully.
Late identification is harder. If a girdling root has already grown into the trunk tissue — visible compression, flattening, or vascular damage — cutting it out can destabilize the tree and rarely restores full canopy health. At that stage, the conversation shifts from “can this tree be saved” to “when does this tree become a hazard.” A tree health assessment is how to tell the difference.
Prevention is a 10-minute step at planting
For anyone planting a new tree this season in Central PA: shake off the container soil, spread the roots outward, cut any circling roots before they get bigger, and set the tree with the root flare clearly visible at the final soil grade. Ten minutes of work at planting time prevents thirty years of quiet decline.
For mature trees showing the warning signs — buried flares, one-sided canopies, unexplained decline — an assessment in Centre County and the surrounding region is a call to (814) 553-0303. Arbor Pro’s Tree Service operates under PA Contractor License PA079160.