Roots systems vary from one tree to the next and from one soil type to the next. These oak trees were grown from acorns. The one on the left was more dense than the one on the right. Cutting propagated trees of oaks and perhaps other trees have more uniform root systems. Click here for research report showing less variation on cutting propagated trees. (Note the circling root close to the trunk on the tree in the center resulting from growth in a #1 container when the tree was a small liner.)