We are taught at a small age that the roots of a tree are very important. They provide nutrition, water, and stability. One can imagine that a large tree would have a quite substantial root network. And while the rate and expanse of root growth is different for all species, industry experts say that the root system can be as large as 4-7 times the size of the canopy! It is also subject to geography and soil composition. In ideal soil conditions, roots will spread far, deep and wide. However, in urban developments, roots may not have the ample space, or preferred soil texture to reach their full potential. This creates a problem known as Root Girdling. This occurs when roots wind around the base of a tree, restricting the flow of nutrients. As trees grow the diameter of both the trunk and the roots will increase. Tangled knots and circling snares will become tighter and eventually strangle the tree itself. Often, trees and saplings grown in burlap or containers will respond to the constricted space by winding their roots in a circular fashion. The condition can be exacerbated by incorrectly planting the tree to deep. As you venture out into the nicer weather and watch your buds bloom, keep watch for these tell-tale symptoms that something might be brewing under the surface.
One of the most visible signs of root girdling is the lack of natural trunk flare at its base. A tree with girdling roots will resemble a telephone pole, shooting straight down into the ground. This is due to the restriction that the offending root places on the natural expansion at the base of the trunk. The roots will naturally reach and expand during the growth season. Healthy trees will have a gradually expanding base that will “flare” at the soil surface. Roots that are winding around the trunk will compress and restrict this natural expansion, resulting in a straight trunk entering the ground.
Affected trees will show signs of distress in certain areas. A section of the tree may present with lighter or sparse foliage. The leaves may also be small, wither and turn color early in the growing season. Certain branches may seem to die off and in more serious cases, the girdling roots can compress the vascular system enough that it can be fatal to the entire tree.
If you suspect that your tree my be strangling itself, you should immediately consult your arborist! Root Excavation, when done with the proper equipment by a trained professional can SAVE YOUR TREE! Using an Air Spade, your arborist will carefully remove the soil from the suspected area and visually inspect the root system. Any knots or tight tangles can then be carefully removed, alleviating the restriction and allowing the system to heal and recover.
 Iowa State University Forestry Extension- https://www.extension.iastate.edu/forestry/tree_biology/roots.html