Last year I worked on a large mall planting project. A number of trees had to be pulled out to make way for a new parking layout; the islands they had been growing in were removed and paved over, with new islands located in a different configuration. Most of the trees were hauled away by the landscape contractor, but one ended up in a discard pile next to the mountain of loam that had been excavated for reuse.
I was interested in the root configuration on this six-inch caliper red maple. A mass of fibrous roots wrapped closely around the tree’s trunk, much like cotton-candy filaments spun around a paper cone. Looking at it more closely, I found that the fibrous roots grew out of thicker woody roots, some of which had been cut during the tree’s original ball-and-burlapping, and some of which, growing since that operation, were circling the trunk. Take a look:

Pulled away from the trunk, the roots clearly are circling it. Over time, as the tree grew in girth, these roots likely would have constricted the flow of nutrients between root mass and crown
- This sort of circling root is usually seen when the soil mass in a B&B root ball is of different porosity from the soil surrounding it; moisture will not move from one soil mass to the other until one mass is completely saturated. Because roots tend to grow where moisture and oxygen are available, they will often stay within the root ball, and circle around the trunk as they grow. The problem is made worse when burlap is not pulled away from the ball, as the burlap constitutes yet another interface for the moisture to move through.

Here's the tree's underside. Note the girdling root snaking on top of the big torn root facing the camera, and the curiously self-contained look of this root mass. The tree's problems likely began early in its life.
Not every B&B tree has these problems, and in those that do, not every rooting problem can be remedied at planting time. Judicious treatment — looking for circling roots that can become girdling roots, cutting back girdling roots and cutting or redirecting circling roots, roughing up the sides of the root ball, removing or cutting down wire baskets, pulling down or removing burlap — can go a long way in helping B&B trees establish better in the landscape, and in remedying problems that threaten a tree’s long-term health and viability. For more discussion on root issues affecting B&B trees, check out this post on Matt Foti’s station at the MAA’s Elm Bank bare-root workshop in September 2009.