Training young shade trees - East Idaho News
In the Garden

Training young shade trees

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The pruning of young shade trees to enable development of strong, healthy tree structure is a frequently overlooked practice. Here are a few tips to help you improve the life and longevity of your trees.

The most common reason large trees require expensive, professional pruning is to reduce the risk of tree failure. These types of operations are needed to remove defective branches and those damaged by storm. Proper training of a young tree often eliminates the need for this pruning later in life. A little time invested now will pay for itself years into the future.

Late winter and early spring are typically the best time to prune. Leaves are gone, allowing a better view of the tree. Minor pruning does not stop tree growth. Instead, it redirects where new growth will occur.

There are two kinds of pruning cuts that send different signals to the tree.

Heading cuts remove a larger or major growth back to a minor growth or bud. These encourage new branches to form below the cut. They are used to correct shape problems and develop a denser growth habit. They can be used to control tree size to a limited extent, as well.

Heading and Thinning Cuts
Heading and thinning cuts | Bracken Henderson, University of Idaho Extension

Thinning cuts remove a smaller growth back to a larger growth. These are used to improve light and air penetration and retain a desirable form. In training young shade trees, thinning cuts allow you to establish strong scaffold branches and remove branches with undesirable crotch angles.

When pruning a young shade tree, there are two main issues you want to eliminate: codominant leaders and branches with narrow crotch angles. These need to be removed for essentially the same reason. They both lead to a condition called included bark. This occurs when the bark becomes trapped between the growing layers of the branch and trunk. A weak connection develops that worsens as the tree grows.

Your goal is to create a strong central trunk with scaffold branches that have crotch angles between 45 and 60 degrees.

Leader Narrow
Bracken Henderson, University of Idaho Extension

When removing a branch, cut in the right place to ensure a healthy recovery. The right cut is on a slight angle, away from the trunk, cutting downward. Avoid leaving branch stubs as well as cutting flush with the trunk. Both will lengthen the time needed for recovery, increasing the chance of disease.

One last point to make is to never remove branches from more than one third of the tree height. This is called “lion tailing” and it creates a weak trunk. Instead, remove the lower branches over a period of years until you eventually reach the height of what you decide to be your lowest permanent branch.

Bracken Henderson, University of Idaho Extension