Training Young Shade Trees
Why Prune My Shade Trees?
The most common reason older trees require professional (and likely expensive) pruning is structural flaws that developed when the tree was young. Professional arborists can remove defective branches, but this can leave a misshapen tree for years. You can reduce the need to hire an arborist when trees are older by pruning your trees when they are young. Indeed, investing a little time early on will likely pay dividends years into the future.
The most common reason older trees require professional (and likely expensive) pruning is structural flaws that developed when the tree was young. Professional arborists can remove defective branches, but this can leave a misshapen tree for years. You can reduce the need to hire an arborist when trees are older by pruning your trees when they are young. Indeed, investing a little time early on will likely pay dividends years into the future.
Appropriate Pruning Tools
When it comes to training young shade trees, the right tools are important:
- Bypass hand pruners (a pruning tool with blades that pass each other like scissors, a design that creates clean cuts that heal quickly)
- Long-handled loppers (bypass type)
- Pruning handsaw
- Pole lopper/saw for reaching high branches (optional)
- Stepladder (optional)
Note: All tools should be clean, sharp, and in good working condition to minimize pruning injury to the tree. For work requiring a chain saw or that is beyond the reach of a pole lopper/saw, hire a certified arborist.
When to Prune
Most pruning is done while trees are dormant. Late winter/early spring is the best period to carry out the primary pruning of most species. This is when it least impacts the tree and it is easier to assess needs when branches are leafless. Minor trimming and pruning can be done in the summer. Summer pruning of maple species also avoids excessive bleeding. Removing dead, diseased, or damaged branches is okay to perform year-round.
- The size of pruning wounds affects the speed at which they heal.
- Trees don’t heal wounds in the same way animals do; they slowly grow new tissue that covers the wound from the outside edges inward. Trees can’t repair damaged tissue, they instead seal off wounds.
- Pruning does not stop growth; rather, it redirects where growth occurs.
- As trees grow in height, each limb will always be the same distance from the ground.
- Removing more than 20% of the foliage during a single pruning event can cause loss of vigor and reduce tree health.
- Because treating wounds with sealant or paint may increase disease issues, leave pruning wounds exposed to allow optimal healing.
Types of Cuts
Each time you cut a branch you are telling a tree where/how you want it to grow. Be sure you are sending the right message.
- Thinning cuts (Figure 1)
- Improve light and air penetration
- Help a tree retain a healthier form
- Remove suckers
- Heading cuts (Figure 2)
- Correct shape problems
- Control size (to a limited extent)
- Encourage dense growth habit
Also, important to conducting successful pruning is knowing where and how to make the cuts. Figures 3–6 illustrate the right and wrong ways to make pruning cuts. Correctly positioned cuts allow the tree to recover quickly. Identifying the branch collar (the swollen area of trunk tissue that forms around a branch base) is part of pruning a tree properly.
Note that the bud just below a cut produces a branch’s dominant growth. In most cases this bud should face away from the center of the tree.
Let’s Start Pruning
Let’s Start Pruning
- Remove damaged, diseased, and dead branches.
- Select and maintain a strong central leader. Remove codominant leaders and remove or reduce competing branches.
- Select temporary branches below the lowest permanent branch (if the tree is small). Temporary branches are left on the tree for a few years but will eventually be removed. These may be reduced to keep them from competing with permanent branches.
- Select lowest permanent branch (if the tree is tall enough for this action). When you identify the lowest permanent branch, you are defining the height at which the tree canopy will begin. Mark this branch with water-based paint for reference.
- Select the scaffold branches. These are permanent branches that will form the canopy of your tree. Competing branches should be removed or reduced. Scaffold branches should be at least one foot from each other and be distributed radially around the center of the trunk.
Completion of these pruning steps assumes repeated pruning and training over a period of years. The walk-around initial assessment and steps 1 and 2 should be completed annually or every other year until the tree is large enough to exhibit a mature growth habit. Step 3 should be completed when the tree is small and still lacks mature form. Begin steps 4–5 when the tree is tall enough to grow permanent branches and repeat them until the tree exhibits a mature growth form.
Training your trees should begin as early as possible. The following guidelines will help you know when you should expect to conduct pruning/training. These are general guidelines. Actual timing depends on the tree species and growth response.
- 1–3 years after planting, remove only dead and damaged branches and retain trunk branches.
- 3–5 years after planting, remove one branch of a double trunk, if needed.
- 5–6 years after planting, begin removing lower (temporary) branches and identifying and training permanent ones.
Other guiding principles to consider when developing a pruning plan:
- Maintain a central leader (Figure 7).
- Over time, build a scaffold with both horizonal and lateral balance (5–10 branches).
- Avoid creating sharp crotch angles at the juncture of trunk and branch (45°–60° degrees is best; see Figure 7).
- To raise the crown, remove branches only from the bottom third of the tree (Figure 8).
- For large branches, use the 3-cut rule to avoid ripping the bark (Figure 9).
About the Author
Bracken Henderson—University of Idaho Extension, Franklin County
BUL 994 | Published September 2021 | © 2022 by the University of Idaho