Pruning Objectives
Crown Thinning to increase light penetration and air circulation through the crown.

• Do not remove more than 15-20% (5-10% is preferred) of the living crown at any one time and, if necessary, stagger greater removal over successive years.
• Branches with U-shaped unions are more stable.
• Those with V-shaped unions often develop included bark, which prevents strong branch attachment.
• If you discover codominant leaders – stems that of same size and some position – select the one that will provide the best tree structure and eliminate the other.
• Co-dominants form included bark causing a structural weak point, that in large trees, may increase the risk for personal injury and property damage.
• Ideally, lateral branches should be evenly spaced on the main stem of young trees
• To discourage development of codominant stems, lateral branches should be no larger than ½ to ¾ the diameter of the stem.

Crown Raising from the under-canopy of a tree to provide pedestrian, traffic, vehicle, building or line-of-sight clearing. Make every effort to maintain at least 60% live crown ratio, measured against the height of the tree (for examples a 10' tree ideally would maintain 6' of live crown against crown raising to 4').

Crown Reduction when a tree has overgrown its permitted space, such as when it begins to interfere with overhead utility lines. This should be used only as a last resort, since crown reduction cuts often results in large wounds that encourage decay and infestation.

Prime Cut
For effective sealing of pruning wounds and to reduce the risk of decay, remove only branch tissue and avoid damage to stem tissue. To target your cut, locate the branch bark ridge and branch collar of the branch to be pruned. Your cut should not damage either. Cutting too close to the bark ridge risks injury to the stem tissue. Cutting too far from the bark ridge leaves a branch stub that will delay seal growth.

For small branches, use hand pruners honed sharp enough to make clean (and not tearing) cuts. For branches large enough to require hand saws, make certain to support the branch during cutting. Branches too large to support should be pruned using a three-cut method:

1. First, a shallow notch on the underside of the branch, outside the branch collar. This will prevent branch tears.
2. The second cut should be outside the first, through the entire branch. A short branch stub will result.
3. The last cut is to shorter the branch stub to just outside the bark ridge-branch collar.

Dead branches are pruned using the same methods as for live branches.

Drop Crotch Cuts are often used for crown reduction, using the three-cut method outlined above to remove lateral branches. To avoid unstable spourt growth from a cut, select lateral branches that are no less than 1/3 the diameter of the stem to which they are attached.

Common Cuts That Harm Trees

No Topping!
This improper pruning of large, upright branches between nodes removes upper crown, retards photosynthesis and proportionately starves the tree. To compensate, trees will quickly generate sprouts or suckers, branches distinguished by their weak stem attachments.

No Tipping
The practice of topping applied to lateral rather than upright branches. Both practices cause a proliferation of weakly attached sprouts, and often result in the decay and death of the cut branch back to the next lateral branch below.

Lions-Tailing is the removal of all branches in the interior portion of the canopy, leaving tufts of leaf growth at the branch tips, instead of graduated distribution of branches and leaves along the full length of the limb. This practice removes photosynthesis vectors and starves the limb of carbohydrate production and storage. In addition, the interior of the tree structure, particularly concentrating where the trunk stems off into lateral branches, is the tree’s primary food storage vector. Lions-tailing also displaces weight to the end of limbs. Common effects of lions-tailing include branch sunburn, watersprout growth, weakened branch structure and limb breakage.

Flush Cuts made inside the branch bark ridge or branch collar create excessive development of woundwood along the perimeter of the cut. This injures stem tissue and promotes decay.