The lone voice of horticultural reason

“Always plant a tree at the same level as the soil in the pot or top of the root ball.”

 Listen up please! I so rarely get to write something important!

Big news just rolled out of the University of Minnesota. After checking over 500 potted trees randomly selected from wholesale and retail nursery yards, University researchers discovered a great many that were potted too deep, with, on average, six to eight inches of soil packed above the first set of lateral roots (or “shoulder” roots). The same situation has been found in trees dug and sold with the root ball wrapped in burlap.

If homeowners plant a tree at the same level as the soil in the pot, but don’t check to see if excess dirt became packed over the top of the shoulder roots when the tree was dug and prepared for sale, they could be planting the tree too deep. Planting a tree even six inches too deep can cause root girdling, as the roots, sensing they’re too far below the surface, tend to grow up, then in, circling the trunk. The tree either will die in five years, go down in a storm in twenty, or live but disappoint.

At the nursery, scrape away the soil around the trunks of trees sold in containers, and be certain you find the start of the shoulder roots immediately. Bring along a straight piece of coat hanger wire when choosing ball-and-burlap trees. Plunge the wire through the burlap next to and parallel with the trunk of the plant. If you don’t hit shoulder roots immediately, the plant was not dug and wrapped properly. If you wind up purchasing a tree with excess soil packed over the shoulder roots, remove all of it, then plant the tree so that the shoulder roots are just barely beneath the surface.

It all came back to me. Last year we were shooting an HGTV deal on planting a tree, and the potted tree the production crew brought for me to plant, a ten-foot Maple, had exactly six inches of excess dirt on top of the roots that I had to remove before taping the episode.

How widespread is this problem? Assume that it’s nationwide, and assume it’s been going on for years. The State of Minnesota runs a pretty tight ship when it comes to nursery industry knowledge and professionalism, Department of Agriculture supervision, University of Minnesota testing, research, and the like. So if it happened here it could well be a problem in your state or country. Some of the trees found at fault in the study were Minnesota-raised and some were from out of state. If you find one, don’t read the riot act to your local retail nursery; most often it was dug improperly at the wholesale level. Be on your toes.

Don Engebretson
The Renegade Gardener