Pruning the Big Parts
I once heard the great J.C. Raultson speak at a Memphis Horticulture Society meeting about the horticultural education that South Korean children receive in elementary school. In addition to learning to identify trees and shrubs, they learn, we were told, they are taught things like proper pruning techniques.
As a result, whether a kid goes into any field related to landscaping or gardening or not, they have the basic understanding of WHERE TO MAKE A PRUNING CUT AND WHY as a way of life…something even 98% of USA based landscaping and tree trimming crews have NO CLUE. Just take a look at your local commercial plantings and also how your utility companies brutalize trees.
It is just as easy (most of the time) to make the cut so that the tree or shrub has the very best chance to heal quickly and go on to have a pleasant or even beautiful shape as it does to just randomly chop.
Where a branch is joined to the larger branch or trunk there is a row of special cells. These special cells are capable of growing much faster than the regular bark cells. They are designed to quickly cover the raw and exposed wood and they do a great job. You can usually see these collar cells clearly if you look right where the branch begins to grow out from the trunk. They are usually a slightly different color, often darker, and sometimes they look like a little wrinkle band.
These collar cells trigger the growth of “wound wood” which is that swollen looking donut shaped smooth bark which rapidly surrounds and grows over the cut.
Sometimes the special collar band is called the “branch defense zone”. Should a branch on a tree become badly damaged, these defense zone cells have the ability to seal the branch off from the rest of the plant and allow the affected branch to cease growth and naturally decay away and fall off.
Another pruning consideration is the age and diameter of the branch. Branches smaller than two inches are usually what is called sapwood. Once the branch approaches four inches, it is more likly to contain heartwood. Sapwood is more resistant to decay than heartwood. So it is always best practice to train and trim your tree or shrub when it is young, as it grows, than to let things get out of hand and have to go back and hack out large diameter branches.
So what you want to do is make your cut close to, but not into, the special collar cells where a branch meets another branch or the trunk.