Over the last few weeks I’ve said a lot of complimentary things about the Minnesota Nursery Industry and how they’re careful to avoid situations where trees are planted too deeply. What I haven’t mentioned is that there is a reason for this. During the 1980s and early ’90s trees were usually planted deeply with lots of soil over the uppermost roots. It was just common practice. Unfortunately this practice led to roots growing across the trees stems and, when those roots cross the stem, the roots always win (as you saw in Linda’s quiz last week)! Many, many trees planted in that era have trunks which enter the ground looking like the picture below. You can clearly see the roots strangling the tree. This photo was actually taken last year on this campus!
This tree is one of the lucky ones. These girdling roots were removed, the layer of soil over the crown was removed, the crown of the tree was inspected, and it was determined that this tree could survive. Many others planted during the 80s and 90s are not so lucky — in fact, many are suffering or dead.
An outcry over the last dozen years or so, mostly from cities (St. Paul and Minneapolis), led to changes in harvest by the nursery industry, and by the landscapers who install the trees. Yesterday I received a plan for planting trees up and down a major highway here in St. Paul to review. The specs were very specific — and similar to the specs that we see now across the Twin Cities and most of Minnesota. Root flare must be at, or even above, the surface of the soil.
I don’t want anyone to get the wrong idea. There are still those who sell nursery stock with the root flare buried deep under soil in the ball, and there are landscapers who dig a hole twice as deep as the depth of the ball before planting, but it’s becoming less and less of an issue as, in general, we seemed to have learned from past mistakes.