What do I need to know about tree pruning?

Pruning is the removal of dead or living parts from a plant.

Tree pruning is both an art and a science. Trees are pruned to achieve a certain look or produce an effect in the landscape - that's the art side of pruning. Understanding the tree’s growth and health response to pruning is the science side.

Proper pruning can improve a tree's healthy appearance, as well as increase the life expectancy of the tree. Proper pruning opens the canopy of the tree to permit more air movement and sunlight penetration.

Improper pruning can create hazards, decrease a tree’s life expectancy, or even kill it. Because trees are living organisms, they can be profoundly affected by pruning practices. Tree care professionals adhere to accepted industry standards of practice when pruning trees.

The American National Standard for tree pruning, designated as ANSI A300, has been in existence since 1995. Its development was approved by the American National Standards Institute. This pruning standard should be followed in all pruning situations and all geographic areas. Knowing how certain tree species grow within a given environment may alter how the recommendations of A300 are interpreted.

The National Arborist Association is the Secretariat for the ANSI A300 Standard, and assists arborists and consumers with the interpretation and application of the standard.

In California, Government Code Section 53067 recognizes tree industry pruning standards, and, in effect makes them the legal standard.

Pruning Treatments:

Crown Cleaning
Selective removal of dead, dying, diseased or weak branches and water spouts from a tree's crown.
Crown Thinning
Selective removal of branches to increase light penetration, air movement and reduce branch end weight.
Crown Raising
Removal of the lower branches to provide clearance under the tree.
Crown Reduction
Reduction in the height and/or spread of the tree.
Crown Restoration
Pruning which improves the structure, form, and appearance of trees that have been severely topped, vandalized, or otherwise damaged.
Vista Pruning
Selective thinning of limbs to allow an improved view through the tree.



How to make proper branch cuts



Figure 1 - The first cut is the under cut, about 4" to 12" away from the branch collar. The top cut is made slightly further away. The under cut prevents the stripping of bark down the trunk. The final cut, or stub cut, is made just outside the branch collar.


Figure 2 When cutting back to a lateral, bisect the angle between the branch bark ridge and an imaginary line perpendicular to the leader or the branch being removed.


Figure 3 - When removing a branch with a narrow attachment, cut from the bottom upward.