Why prune trees?
- Health: Remove dead, diseased, or dangerous branches.
- Convenience: Keep trees from interfering with pedestrians, vehicles, or structures.
- Longevity: Correct a tree’s structure so branches and limbs are less prone to damage.
When to prune trees?
- Evergreens: Anytime.
- Deciduous: It’s best to prune deciduous trees when they are dormant. Their store of energy is in the roots, not in limbs and leaves you’re removing. And it’s easier to see their structure, too.
- Exceptions: Dead, diseased, and potentially harmful branches should be removed at your earliest convenience.
Here’s a look at some tree-pruning basics.
MAKE THREE CUTS
To prevent injury to the tree, remove large branches in three steps: with an undercut, overcut, and finished cut.
1) Undercut. Starting about 4–6 inches from the trunk, cut about one-fourth of the way through the underside of the branch with a handheld saw, such as this bow saw.
2) Overcut. Move out 1–2 inches from the undercut and cut off the branch. As the branch falls, the undercut prevents the bark from tearing down the side of the trunk.
3) Finished cut. Remove the remainder of the limb. Cut close to — not flush with — the trunk. Leave a 1/4-inch stub. This preserves the branch collar, a barely perceptible swelling near the trunk. It contains hormones that will speed callusing as the tree seals the wound.
Good to Know: Avoid pruning oak trees while they’re actively growing — fresh wounds can attract beetles that carry oak-wilt disease.
With trees, the narrower the angle, the weaker the limb. This V-shaped crotch could pose a problem as the tree grows larger — perhaps tearing off in a storm. Better to use a handsaw now than a chainsaw later.
Here’s what the tree should look like after the limb is removed. Note the angle of the cut, which results in a smaller wound that will heal quicker than a flush cut.
WATER SPROUTS AND SUCKER SHOOTS
Some species send out rapid-growing juvenile shoots wherever bark is injured or previous pruning has occurred. Water sprouts grow on limbs and branches, sucker shoots from the base of the tree. They are unsightly (and unnecessary to the tree).
Use pruners or loppers to remove water sprouts and sucker shoots early — before they grow into larger branches — to safeguard the tree’s natural shape. This also keeps the crowded shoots from rubbing together and causing wounds that invite pests or disease.
GOOD CUT/BAD CUT
A common pruning mistake is to leave a stub. It not only looks unattractive but the stub will eventually die, becoming a home to insects as it disintegrates.
This is the proper cut, mirroring the angle of the included bark (see arrow). Included bark, seen here as a dark, slightly ridged seam, forms when two or more branches grow closely together. It’s usually a sign of a weak joint.
Some smaller trees, such as Japanese maple or smoketree, look good with multiple leaders. But it can be a recipe for disaster with trees that grow large, such as this elm. As the limbs become larger and heavier, the connection to the tree will become weaker. Eventually, wind, ice, or some other outside force will cause the trunk to split and the tree will likely be lost.
Take care of the problem early, before there’s any damage. Choose the taller and straighter of the co-dominant stems and remove the other.