Table of Contents

What Is Pruning?

Pruning is the deliberate removal of specific parts of a plant — branches, buds, roots, or dead material — to improve the plant’s health, structure, appearance, or productivity. It’s one of the most important horticultural practices, and also one of the most commonly done wrong. Bad pruning can damage or kill plants that would have been perfectly fine left alone.

Why Prune at All

Plants grow on their own. They’ve been doing it for hundreds of millions of years without human help. So why cut them?

Health. Removing dead, diseased, or damaged branches prevents disease from spreading and eliminates entry points for pests. A dead limb left on a tree can harbor fungi that eventually infect healthy wood.

Safety. Overhanging branches near power lines, walkways, or structures can be hazardous, especially during storms. A branch that falls on a roof or car can cause thousands in damage. Removing hazardous limbs is the most urgent reason to prune.

Structure. Trees and shrubs with poor structure — multiple competing main trunks, narrow branch angles, crossing branches that rub against each other — are more likely to fail in storms. Structural pruning, especially when trees are young, prevents problems that are expensive or impossible to fix later.

Productivity. Fruit trees and flowering shrubs produce better when pruned correctly. Removing excess branches allows more light and air to reach the interior, encouraging fruit development and reducing disease pressure. An unpruned apple tree produces more but smaller, lower-quality fruit; a properly pruned one produces fewer but larger, better apples.

Aesthetics. Hedges, topiaries, and formal gardens require regular pruning to maintain their shape. Even informal gardens benefit from selective pruning to manage size, maintain views, and keep plants in proportion.

The Basic Principles

Cut to the branch collar. When removing a branch, cut just outside the branch collar — the slightly swollen area where the branch meets the trunk or parent branch. The branch collar contains specialized cells that seal the wound. Cutting into it (a flush cut) damages the tree’s healing mechanism. Leaving a long stub prevents the wound from closing properly.

Use the three-cut method for large branches. To prevent bark tearing:

1. Make an undercut 12-18 inches from the trunk, cutting about one-third through the branch from below
2. Make a top cut slightly farther from the trunk than the undercut — the branch will snap cleanly between the two cuts
3. Remove the remaining stub with a clean cut at the branch collar

Don’t top trees. Topping — cutting main branches back to stubs — is the worst thing you can do to a tree. It removes the tree’s food-producing capacity, triggers a flush of weak, poorly attached shoots (water sprouts), creates large wounds prone to decay, and destroys the tree’s natural form. A topped tree is weaker, uglier, and more expensive to maintain than an unpruned one. Every arborist organization condemns topping.

Thin, don’t shear. Thinning cuts remove entire branches at their point of origin, maintaining natural form and allowing light into the interior. Heading cuts (shearing) cut branches partway, stimulating dense growth at the cut point. Shearing is appropriate for formal hedges. For most trees and shrubs, thinning is far better.

Tools of the Trade

Hand pruners (secateurs) handle branches up to about 3/4 inch diameter. Bypass pruners (scissor-action) make cleaner cuts than anvil pruners (which can crush stems). This is your most-used tool.

Loppers are long-handled pruners for branches up to about 2 inches. The long handles provide use and reach.

Pruning saws handle branches over 2 inches. Curved-blade pull saws cut faster and more cleanly than bow saws for most pruning work.

Hedge shears — manual or powered — are for hedges and formal shapes only. Don’t use them on trees.

Chainsaws are for large branches and tree removal. If you need a chainsaw for pruning, you might need a professional arborist instead.

Keep tools clean and sharp. Dull tools crush rather than cut, causing more damage. Clean blades with rubbing alcohol between plants if you’re working with diseased material, to avoid spreading pathogens.

When to Prune

Timing depends on the plant:

Late winter/early spring (while dormant) — best for most deciduous trees and summer-flowering shrubs. The plant is inactive, diseases are dormant, and the coming spring growth will quickly begin healing wounds.

After flowering — for spring-blooming shrubs (lilac, forsythia, azalea). These set their flower buds the previous year, so pruning in winter removes the blooms. Prune right after flowers fade, before new buds form.

Anytime — dead, diseased, or hazardous branches. Don’t wait for the “right” season to address safety issues.

Avoid late summer/early fall. Pruning stimulates new growth. New growth that hasn’t hardened before winter can be killed by frost, stressing the plant.

Common Mistakes

Topping trees (already mentioned — just don’t do it). Pruning too much at once. Leaving long stubs. Using dull tools. Pruning at the wrong time. Removing lower branches from trees that are too young (removing all low branches creates a weak, top-heavy structure). Lion-tailing (stripping interior branches while leaving only tufts at branch ends — this creates wind-sail effects and increases breakage risk).

The biggest mistake of all? Pruning when it’s not needed. If a tree or shrub is healthy, well-structured, and appropriately sized for its location, leave it alone. The best pruning is the pruning you don’t have to do — because you planted the right plant in the right place to begin with.

Frequently Asked Questions

When is the best time to prune trees?

Late winter to early spring (while trees are dormant) is ideal for most deciduous trees. The tree is less stressed, diseases are less active, and you can see the branch structure clearly without leaves. Spring-flowering shrubs should be pruned right after they bloom. Dead, diseased, or dangerous branches can and should be removed any time of year. Avoid heavy pruning in late summer or early fall, as new growth may not harden before frost.

How much of a tree can you safely prune at once?

The general rule is never remove more than 25% of a tree's canopy in a single year. Removing more stresses the tree, reduces its ability to produce energy through photosynthesis, and can trigger excessive water sprout growth. For mature trees, 10-15% per year is often safer. Young trees being trained to a specific shape can tolerate slightly more aggressive pruning.

Should you seal pruning cuts with paint or wound dressing?

No. Research has consistently shown that tree wound sealants and pruning paints do not prevent decay and may actually slow the tree's natural healing process. Trees naturally compartmentalize wounds — sealing off damaged tissue with chemical and physical barriers. Wound dressings can trap moisture and create conditions favorable for decay organisms. The best practice is to make clean cuts at the proper location and let the tree heal itself.

Further Reading

• USDA Forest Service — Pruning Trees
• University of Minnesota Extension — Pruning
• Royal Horticultural Society — Pruning