A Lesson on Tree Biology – Eric Hoyer
Excerpt:
In the early part of my career, we thought it was OK to top trees to reduce their size. You were supposed to apply a black tar-like substance after pruning limbs to “seal” the wounds. And, you were supposed to cut the branch flush with the trunk. In the late 1970s, a Dr. Alex Shigo (then with the US Forest Service Research Lab) unveiled a whole new way to look at trees which resulted in a change in the way we prune.