A girdling root is a root that grows around the trunk of a tree rather than outward from it. Over years and decades, as both the root and the trunk expand in diameter, the root compresses the bark and underlying cambium — eventually cutting off the flow of water and nutrients between the crown and the lower trunk. Trees with severe girdling roots develop slowly, show recurring dieback, and eventually die from what looks like a mystery decline.
The problem is often invisible above ground. The diagnostic clue is the trunk profile — and the fix requires getting below the mulch and soil to see what's happening at the root flare.
