When and How to Prune Native Trees

The best pruning is light, well timed and done with a clear reason for every cut.

Every cut is a wound the tree has to seal off. Done right, pruning makes a tree safer and stronger. Done wrong, it invites decay and weak regrowth.

When to Prune

• Most trees: Late winter during dormancy, roughly December through February. Without leaves you can see the branch structure, and wounds start sealing as soon as spring growth begins.
• Oaks: Virginia Cooperative Extension recommends pruning oaks in November and December and avoiding pruning from March through August. Fresh wounds in the growing season attract sap-feeding beetles that can spread disease. If storm damage forces a cut in spring or summer, cover the fresh wound with a tree wound dressing or latex paint.
• Spring-flowering trees like dogwood, redbud, serviceberry and fringetree: Prune right after they finish blooming. Pruning in winter removes the flower buds already set for spring.
• Maples and birches: They "bleed" sap if cut in late winter. It's harmless, but you can avoid it by pruning in early summer once the leaves are fully out.
• Dead, broken or hazardous limbs: Remove any time of year.

What to Remove

1. Dead, damaged and diseased branches
2. Branches that cross and rub against each other
3. Water sprouts (fast, straight shoots from branches) and suckers from the base
4. On young trees, competing leaders, so the tree grows one strong central trunk
5. Limbs growing toward the roof, siding or driveway. Keep limbs 6 to 10 feet off the roof.

How Much Is Too Much

Remove no more than about a quarter of a young tree's leafy canopy in one year, and less on mature trees. Older trees have less energy to recover. It's better to spread big corrective work over several years.

How to Make a Proper Cut

Look for the branch collar, the slightly swollen ring where a branch joins the trunk or a larger limb. Cut just outside it.

• Don't cut flush against the trunk. That removes the tissue the tree uses to seal the wound.
• Don't leave long stubs. They die back and rot.
• Wound paint isn't needed on most trees. Oaks cut during the growing season are the exception.

For any branch too heavy to hold in one hand, use the three-cut method so the bark doesn't tear:

1. Make an undercut about a third of the way through the branch, 12 to 18 inches out from the trunk.
2. Make a top cut a few inches farther out than the undercut, cutting until the branch drops.
3. Cut the remaining stub just outside the branch collar.

Never Top a Tree

Topping means cutting the main branches back to stubs to shorten a tree. It is one of the most damaging things you can do to a tree. It starves the tree, the large stubs rot, and the tree responds with a thicket of weakly attached sprouts that grow back fast and break easily in storms. A topped tree usually ends up more dangerous than it was before. If a tree is too big for its spot, reduce specific limbs back to healthy side branches, or consider removal and a better-suited replacement.

Avoid Lion-Tailing

Stripping all the inner branches and leaving tufts of leaves at the ends of long limbs is called lion-tailing. It puts all the weight at the tips and makes limbs more likely to snap in wind.

When to Call a Professional

• Any cut that needs a ladder, a pole saw overhead or a chainsaw
• Large limbs over the house, fence, driveway or neighbor's property
• Structural problems like cracks or weak, V-shaped branch unions
• Branches near power lines. Those belong to the power company, so call them first.

Pruning young trees for good structure is one of the best investments you can make. A few well-placed cuts at five years old can prevent a split trunk at forty.