Girdling Roots

Before placing a bare-root tree or containerized plant in the ground, check for girdling roots.

Girdling roots work very much as your great-grandmother’s elastic undergarment did. They cut off circulation and restrict movement. Girdling roots can kill your tree.

Girdling roots (cultivar413) CC BY 2.0

What is girdling?

To ‘girdle’ means to surround something. When girdling happens aboveground, it refers to the removal of a ring of bark. This bark contains the cambium layer, which houses the vascular bundles  that transport water, oxygen, and nutrients. Tree supports can result in girdling if left in place too long or installed improperly. Girdling roots create the same problem by encircling the trunk and neighboring roots, effectively cutting off the supply of water, oxygen, and nutrients. Wherever girdling occurs, whatever lies beyond the girdle will, in most cases, die.

Healthy trees

Perennial roots of healthy trees reach out horizontally, anchoring the tree in place and providing a pathway for resources to enter the tree. Those elements move through the xylem of transport roots after being collected by feeder roots. Unless they can’t, that is.

Sometimes, containerized plants become root-bound. If you take the plant out of its pot, you will see that the roots are circling, looking for a way out.

​As these roots grow more robust, they slow or halt the transport of life-giving water, oxygen, and nutrients, effectively choking themselves to death.

​This problem often starts with improper planting depth.

​Planting depth

Root-bound containerized plants rarely thrive

Roots emerge just below the root collar, where the trunk flares out. Trees planted too deep look more like pencils sticking out of the ground.If the root collar is buried below the soil level, as often occurs with modern, mass-produced trees, girdling, pest infestations, and fungal diseases are more likely. Planting trees too deep makes it harder for roots to access the water, nutrients, and oxygen they need.

Symptoms of girdling roots

In some cases, girdling roots can be seen simply by looking at the base of the trunk. If the problem is occurring underground, these symptoms may provide a clue about what is happening underground:

• Trees leaf out late.
• Leaves drop occurs early in the season.
• Leaves are small and chlorotic.
• New twigs die back.
• Indentations or flattening at the base of the trunk or bole may occur.

In severe cases, the bole indentation can create structurally weak areas prone to twisting or breaking. Of course, a tree will struggle on, growing but not thriving. Within 2 to 10 years, the tree dies for no apparent reason.

How to prevent girdling roots

Inspect the root system before planting a tree or shrub. Loosen and straighten any circling roots. Remove any that are too woody to straighten.

Next, ensure the planting hole is of the proper depth and diameter. Do not “spin” roots into a too-small hole. Dig the hole wide enough to allow the roots to spread out horizontally. Wider holes are better. Deeper holes are not. Dig the planting hole as deep as needed to keep the roots slightly below the soil surface. Planting it any deeper than that is setting the stage for failure.

Loosen compacted soil, or the new roots will circle in this new ‘container’. Building foundations and big rocks can cause girdling roots. Mulching the area with arborist wood chips is an excellent way to (slowly) reduce compaction while keeping down weeds, stabilizing soil temperatures, and retaining moisture.

Responding to girdling roots

Giving a tree with girdling roots more water and fertilizer will not fix the problem. The offending roots must be exposed and removed. If that sounds like a lot of work, it is. 

First, remove enough soil to expose the choking roots. Make the first cut six to twelve inches from the trunk, usually with a chisel or a saw. This first cut prevents damage to the tree trunk. Very often, there is a lot of tension held in big roots. Suddenly releasing this tension in the wrong way can be catastrophic. For example, an apple tree with a 20” diameter trunk can weigh nearly 2-1/2 tons, so tension is probably occurring somewhere. 

The final cut is where the root meets the trunk. You can leave the severed roots where they are. Eventually, they will decompose. And this allows helpful microorganisms to migrate and continue their good works.

Substantial roots must be removed in stages by a professional arborist. Cutting them off all at once eliminates their supply of water and nutrients, putting the tree at risk.

Tree roots provide the lifeblood of the tree. If those roots start circling, you need to take corrective measures for the tree to survive.