One of the most important steps of planting a container tree is cutting the outer layer of circling roots. This is easy to miss, and unfortunately, trees suffer the consequences.
Recently, a neighbor brought a tree stump cut in half over to us to look at. For years, the tree had been stressed and did not grow as expected. Finally, the neighbor had pulled the tree out. It was clear from the stump that the tree was stunted due to root circling. When planted or transplanted, the circling roots had not been cut, and had resulted in the trees stunted growth and final removal.
Here are a couple photos of the stump.
As you may notice, the tree was plagued with circling roots, literally cutting off vital nutrients from traveling up the outer phloem. The tree may have been planted too deep as well, resulting in the roots circling the trunk.
A study was conducted by the University of Minnesota, Department of Forest Resources on the effects of cutting root bound plants and shows that the best way to cut them is by taking the outside circling roots completely off. This will help the trees establish well, and prevent future death by root circling.
At the nursery, we do our best to make sure roots are cut well in transplanting, but we cannot control how roots are cut when being planted in a landscape. It is so important to make sure that all roots on the outer 1-2 inches of the root ball are cut off in planting for plants that have started to develop circling. If no root circling is present, simply cutting some roots on the outside to loosen them can be sufficient.
Another important aspect of planting to be noted, is to ensure that soil is not above the root flare, where roots begin to grow into the soil. If soil is, as the stump brought to us was, the roots will grow up and around the trunk resulting in tree death.
Hopefully this advice can help you as you are planting trees, or training your customers on how to plant theirs.