I can’t say it never happens in the wild, but encircling or “girdling” roots are rarely encountered. A tree left in a container for too long is almost sure to have potbound attitude.
If you take a tree out of a container, especially a plastic pot, dig a hole and stuff it in without a thought about the condition of the root mass, you are ensuring that a problem down the road awaits…
If the young tree sits in a pot for too long, you may have to cut off enough roots to correct the problem that you actually kill the tree in the process!
Correcting girdling roots on a large tree in the landscape can be just as daunting.
Imagine putting a collar around a puppy’s neck and NEVER adjusting the collar as the puppy grew. Pretty gruesome thought, yet people do the same thing to trees all the time. The result would be pretty much the same, the tree will slowly suffer until it died from the choking effect.
Even if you see a moderate flare of the trunk at ground level, do not assume that all is hunky dory at the actual root collar itself. More often than not, a tree that has been planted too deep (very common) even by a few inches, will have some adventitious roots that have sprouted and found their way around the mainstem.
Watering the base of a tree planted too deep almost guarantees this condition.
If the root mass that throttles the stem is large enough, it may have to be removed in stages over time to prevent shock and /or stress to the tree.
Removal of soil around roots without causing injury to the roots is tricky!
The cool tool for this is an air spade. This setup uses a concentrated jet of air humming along at around one thousand four hundred miles per hour, or twice the speed of sound! It melts porous soil particles away like magic WITHOUT harming root tissue, plumbing, underground utilities etc. This tool is so far superior to excavating by hand, it will be the only way I will ever do a root collar excavation on a tree bigger that a few inches in diameter.
I recently air spaded a few large mature ash trees at the SOU campus that I suspected might have a girdling root or two. I was shocked to find the worst encircling root condition I will probably ever see. Roots up to 9” in diameter were literally buried into the trunk so far, it took a chainsaw and plastic falling wedges to dissect and remove the offending roots! This tree had a flare at ground level, but the condition of the canopy indicated a closer look at the all important root collar was in order. Had this condition not been remedied, the tree would surly have succumb to the “choking”. When in doubt, plant high, take time to inspect the root crown, and water away from, not up to, your new tree.