Guidelines for Correct Pruning, by Dr. Alex Shigo

Excerpted from Homeowner's Guide for Beautiful, Safe, and Healthy Trees, NE-INF-58-84. Note that Dr. Shigo is widely considered the greatest mind in the field of arboriculture, and the following guidelines, distributed to members of the ISA, are the highest standard in the field. For more in-depth information, I would recommend writing to the International Society of Arboriculture, PO Box GG, Savoy, Illinois, 61874-9902.

Correct pruning is the best thing you can do for your tree. Here are the guidelines:

Natural Target Pruning

1. Locate the branch bark ridge (BBR)
2. Find target A - outside BBR
3. Find target B - where branch meets collar
4. If B cannot be found, drop an imaginary line at AX. Angle XAC equals XAB.
5. Stub cut the branch.
6. Make final cut at line AB (with powersaws make final cut on upstroke.)

DO NOT:

• make flush cuts behind the BBR
• leave living or dead stubs
• injure or remove the branch collar
• paint cuts

The best time to prune living branches is late in the dormant season or very early in spring before leaves form. Dead and dying branches can be pruned anytime. Use sharp tools! Make clean cuts. Be careful with all tools. Safety first!

Wound Dressings

Wound dressings do not stop rot!!!

DO NOT:

• apply house paints or wood preservatives
• apply heavy coats of any material

Research shows that wound dressings do not stop decay or stall rot. Trees have been responding effectively to their wounds for over 200 million years. Do not interfere with this natural process. Keep your tree healthy and it will take care of its wounds. In a short time the wound surface will blend perfectly with the tree bark.

Tree Treatments

Tree Wounds

If trees are wounded, remove injured bark with a sharp knife. Make cuts as shallow as possible. Forming an elongated ellipse is not necessary. Make all margins rounded; do not point tips. Do not enlarge the wound. Do not paint. Do everything possible to maintain health -- water, fertilize, prune.

If cavities are filled, do not clean so thoroughly that the boundary between decayed wood and sound wood is broken. Fill with nonabrasive materials. Leave for professionals.

Injections and Implants

If you plan to have chemicals injected or implanted in your trees, make certain that it is done only by highly skilled professionals. Check injection and implant holes after one season to make certain they are closed. Injection and implant holes should be very small and shallow at the tree base, not in the roots.

Addendum (from me, and also elaborated on by Shigo in other works):

NEVER TOP TREES!

It is better to remove and replace a tree than to top it.

If you have any questions or are not certain about what is best for your tree, contact an ISA-certified arborist. Listings are usually available in the Yellow Pages; or, if you contact me I'd be happy to send you a list of qualified arborists in your area.

TREE MYTH #1: Trees are deeply-rooted; the root system of a tree looks virtually like a mirror image of the above-ground system.

FALSE!!! All trees are shallow-rooted. To see what a tree's root system really looks like, look at this picture. (THIS IS ESPECIALLY IMPORTANT FOR ANYONE WHO IS PLANNING TO DIG NEAR A TREE.)

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