When you plant your tree, the trunk should flare out all the way around as it enters the soil. If you plant your trees, too deeply, new roots will be put out by the tree above the root flare, and those new roots can often circle, girdle and choke the main root system underneath and eventually kill your tree. You won’t see effects of root girdling for many years often. I can’t always respond to comments so for those of you that are experienced gardeners, please jump in and help as much as you can