Making the Cut: Proper Pruning Techniques to Give Young Trees a Strong Start
As we begin another annual pruning cycle at the Arboretum, it’s a good time to highlight the importance of proper pruning—especially for young trees. Most of our pruning work takes place during the dormant season, when tree structure is easiest to see and disease risk is minimized.
Poor pruning practices—or waiting too long to prune—can have lifelong impacts on a tree’s health. Before you pick up your tools, it’s important to understand the basics.
Choose the Right Tools
For young trees, a bypass hand pruner and a quality handsaw will handle most jobs. Selecting the correct tool ensures a clean cut that seals quickly.
- Use a handsaw for cuts over ½ inch.
- Use pruners for smaller cuts.
- A pole saw or pole pruner comes in handy for cuts out of reach.
- Sharp tools reduce strain on both you and the tree, producing smooth cuts that close more efficiently.
Sanitize Between Trees
Sanitizing tools when moving from tree to tree helps prevent the spread of disease—especially in high-value collections like oaks, where threats such as oak wilt and bacterial leaf scorch may be present but not yet visible.
Pruning in the dormant season reduces risk, but we take additional precautions by misting tools with concentrated isopropyl alcohol between trees. Bleach and other cleaners are effective but can be corrosive.
Small Cuts Are Best
Trees do not “heal” wounds. Instead, they compartmentalize them—isolating damaged tissue and sealing over the surface with new growth. Small cuts are sealed and compartmentalized quickly, reducing the likelihood of decay. Large cuts, even when made correctly, may take years to close and often result in significant internal decay.
The takeaway: prune early, when branches are small.
What to Remove—And Why
Before making any cuts, take a moment to assess the tree’s structure. Our rule of thumb is to remove branches that have no future, ensuring that what remains contributes to a strong, stable scaffold.
Start with the basics:
- Dead, diseased, or damaged wood
- Suckers and vertical sprouts, which are weakly attached and disrupt structure
- Crossing or rubbing branches, which will worsen over time
Then make selective cuts to improve the tree’s long-term form:
- Remove double leaders and branches with included bark
- Thin crowded areas, reducing clusters of branches at the same height
- Maintain well-spaced permanent branches around the trunk
If needed, you can gradually raise the crown for clearance. Low branches that will eventually be removed may be shortened instead of removed, allowing them to contribute to trunk strength while discouraging deer rubs.
Avoid over-pruning: never remove more than 25% of the canopy in a single year. Mature trees should have even less removed to prevent stress and decline.
Make Cuts Just Outside the Branch Collar
The branch collar is the swollen area where a branch meets the trunk. Cutting just outside this area allows the tree to form a complete ring of callus wood that seals the wound properly.
- Flush cuts remove the branch collar and prevent proper sealing.
- Stubs also interfere with callus formation and invite decay, insects, and disease.
The photo labeled Year 2 in the examples shows excellent, even callus formation around a correctly made pruning cut.
Prevent Tear-Outs With the Three-Cut Method
To avoid tearing bark when removing larger branches (1 inch or more):
- Make an undercut partway through the branch, six inches or more from the final cut.
- Make a top cut a few inches beyond the undercut to remove most of the branch.
- Make the final cut just outside the branch collar to remove the remaining stub.
This technique prevents the weight of the falling branch from ripping bark down the trunk, which can permanently damage the tree and hinder callus formation.
Photo Examples
The three oak examples below demonstrate proper pruning over time:
- Year 1: A clean cut made just outside the branch collar.
- Year 2: A full ring of callus wood forming around the wound, with a small fresh sucker removed below. Vigorous sprouts are common after pruning and vary by species, tree health, and pruning intensity.
- Year 3: The wound is fully sealed. While internal decay may be present at the original cut, healthy wound wood has sealed the site, protecting the tree from insects, pathogens, and further decay.
Proper pruning is one of the most valuable early investments you can make in a tree’s long-term health. With sharp tools, thoughtful cuts, and an understanding of tree biology, you can set young trees up for decades of strong, healthy growth.