If You’re Not Sure of
Your Motives For
Pruning An Oak Tree
Don’t Do It

May 12 , 2005

When do you prune oaks? Simple answer—never! Oaks have evolved in Southern
California without the help of certified arborists or tree workers thinning or
cleaning their crowns or removing deadwood. Oaks do not need pruning. However,
people may need to prune oaks to obtain specific pruning based objectives.
Pruning should accomplish predetermined goals while striving to limit the formation
of decay columns within the tree’s major branches and stems. For most
trees and especially oaks, decay limits the life span of the tree. When new wood
production falls behind the rate of destruction by decay fungi, the tree loses
structural integrity and starts to fall apart. Limb loss, and main stem loss due to
decay eventually kills large oak trees. To prevent these large decay problems,
large limbs should not be removed but should be cabled to stabilize the upper
structure to prevent collapse and insure safety. Any pruning protocol for oaks
should consider the entry of decay and its long-term implications.

Pruning is the removal of branches, shoots and buds to achieve specific
goals. This usually means removal of living branches. To understand how to
prune oaks, two basic principles need to be reviewed. First, pruning retards or
slows tree growth. The more you prune a branch or tree, the less its trunk will
grow. The other basic pruning principle to remember is that pruning is a bud
invigorating process. When branches are removed from trees, buds on the remaining
branches are invigorated.

In many ways the best oak tree is the unpruned tree. It has fewer wounds
and therefore less decay than a heavily pruned tree. Curiously, the more frequently
a tree is pruned, assuming that it is properly pruned, the smaller the cuts
will be needed, so ideally, an oak is pruned frequently during its establishment
period. Another reason to prune is for crown restoration. Crown restoration
pruning seeks to solve some of the problems that have occurred in the canopy of
a tree due to storm damage or loss of natural structure caused by previous poor
pruning practices. Often crown restoration involves making large cuts to deal
with poorly attached, diseased or broken branches.

For further information, please contact your local tree specialist at

Western Arborist Article Spring 2005, “Pruning oak trees in Southern
California” By Dr. James Downer


Santa Ynez Valley Tree Care
P.O. Box 1147, Santa Ynez, California 93460

(805) 688-5580

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