Pruning a tree is a combination of aethetics, scientific technique, and common sense. All pruning comes from simple principles that must be understood before any activity takes place. Because every cut you make has the potential to change the growth of the tree --and could even cause permanent damage-- make sure you know why you are doing it, and have a plan, before you cut. When in doubt, consult with a professional arborist. 

Remember the following principals before you begin pruning any tree:

Think it through. Every cut you make has the potential to change the growth of the tree. Before you cut, know why you are doing it.

Prune correctly. You must always use proper technique. Understand where and how to make cuts before you act. Poor pruning can cause permanent damage to the tree.

Trees can’t heal. When a tree is wounded, a callus must grow over the wound. Trees will compartmentalize a cut, but they do not "heal" and the wound is contained within the tree forever.

Small cuts do less damage to the tree than larger ones. It is best to prune when trees are young because the cuts will be smaller and easier for the tree to close. Pruning mature trees can create the need for large cuts that the tree cannot close easily.

Reasons to prune 

• To remove dangerous limbs that can fall and injure pedestrians and damage property.

• To remove diseased limbs or limbs infested by insects, fungi, or bacteria that might result in failure and death for the limb.

• To develop a stronger branching structure that is more resistant to damage and breakage.

• To improve the tree's aesthetics and increase light penetration into the canopy.

• To provide clearance for streets and sidewalks.

What to Prune:

• Dead and damaged branches: Remove dead and damaged branches first. After removing these branches, other problems become apparent. Damaged living branches include broken, dangling or fractured branches.

• Stubs: Protruding ends of a branch that have been broken off or improperly pruned. These must be pruned back to a node or connecting branch.

• Suckers and watersprouts: Rapidly growing, vertical shoots that sprout from the roots or along the trunk and main branches. Eventually these shoots will destroy the shape of the tree. Suckers (shoots growing from the base or roots of the tree) and watersprouts (shoots growing from the trunk or branches) are often a sign of a tree under stress. They should be removed at the point of origin.

• Low Branches: Low branches do not allow pedestrians and vehicles to pass underneath unimpeded. They should be limbed up along street rights-of-ways.

• Branches with narrow crotch angles: The crotch angle is where the branch meets the trunk. Angles of 20 degrees (approx. 1 o'clock) or less are too narrow for a strong joint to form. Such narrow joints will be very prone to breakage in ice storms, high winds, and hurricanes. A strong joint is made when the branch angle is at 10 o’clock or 2 o’clock position. Branches with narrow crotch angles should be pruned selectively, especially with trees that are prone to this form of branching habit. 

• Rubbing branches: When two branches are rubbing against each other, the stronger branch is usually saved and the lesser one removed, but only if the larger branch is healthy and has a superior branch angle.

• Crowded branches: Keep in mind that in time branches will increase in diameter. Branches that will eventually grow into each other must be thinned out. Remove the weaker branch, but as with rubbing branches, only if the larger branch is healthy and has a superior branch angle.

• Branches that are a hazard: Branches that obscure the visibility of street signs such as school crossing, stop, or caution signs and traffic lights should be pruned.

When to Prune

Pruning is probably the most misused and misunderstood tree maintenance practice. Incorrect pruning may even kill a tree.

The best time to prune live limbs is during late winter or early spring before leaves emerge. Avoid pruning when leaves are expanding, since this is more likely to cause heavy sap flow. Prune dead, diseased and broken limbs as soon as you notice them; prompt pruning prevents the spread of decay and cavity development within the tree.

How to Prune

After you've carefully planned what you will prune, observe these steps:

	1.  Cut through 1/2 of the branch from underneath about a foot from the trunk. This will prevent stripping or peeling the bark off of the trunk.
	2.  A few inches further from the first cut, make the cut from the top of the branch downward. This will remove the entire branch.
	3.  Locate the branch collar (a layer of wrinkled bark where the branch attaches to the trunk) and the branch bark ridge (a raised area of bark at the branch/trunk union). Make the final cut just outside of the branch collar and the branch bark ridge, at the slight downward and outward angle.  Do not cut into the collar or leave a stub.

To cut small twigs, use a set of hand pruners. For small branches, use loppers. For large limbs, use a hand-saw. All tools should have sharp blades, since clean cut wood closes (forms callus tissue) faster than jagged wood. Hand tools with by-pass blades are preferred. Anvil type blades, where the blades meet, should be avoided as they crush plant tissue.

To shorten a branch, or reduce tree height or tree spread, use the reduction pruning method. This method can redirect tree growth without severely damaging or topping the tree. Begin by removing the portion of the branch or terminal leader back to a side branch that is at least 1/3 to 1/2 the diameter of the removed portion of wood. This will help ensure that there are enough leaves to make food for the tree and prevent stub-cuts, which can lead to wood decay.

Avoid making a cut that leaves a wound over 4" in diameter, since these take longer to callus over. Do not paint the pruning cut. Research shows that wound dressings are not effective in preventing decay.

Never remove more than 25% of the live crown or branches. This ensures that the tree has enough leaves to manufacture its own food.

PLEASE DO NOT TOP TREES!

Topped crape myrtle, an unfortunate occurence throughout Atlanta.

 "Topping" is the reduction in size of a tree by severely cutting

  back the branches. Topping weakens the tree and leaves large

  wounds. Topping usually occurs when the tree is too large for

  the available above ground space. This situation is best avoided

  by selecting the correct size tree for the space initially. If a site

  placement mistake exists and a tree must be shortened, begin to

  prune while the tree is young, and make Reduction Pruning cuts

  where branches fork.

  We know you're excited, but don't go too crazy!

  Do not prune more than 30% of a tree's canopy at once.

  Because of this, you must plan your cuts out before you begin

  Always prune off branches that most obviously need to be

  removed.

  Be conservative. Do not prune live wood excessively. Be

  thoughtful when you plan your cuts.

Trees Atlanta can teach you how to prune trees correctly and provide hands-on practice through our pruning classes. Classes occur in 3 part series twice a year. Please sign up for our weekly email to learn when the next  pruning class will be.