In order to avoid spreading the pathogen Sudden Oak Death, also known as phytophthora ramora, it is best to prune your canyon live oak in the dry months of June, July or August. Oaks do not tolerate heavy pruning and should never be topped. Oak trees are protected in many parts of California and their pruning is controlled. If in doubt, contact your local county agent for pruning guidelines specific to your area.
Remove all dead branches and any that appear diseased. When removing large branches that require a saw, use the three-cut method. Approximately 4 inches from the trunk, make a 1/2-inch-deep cut on the underside of the branch. Then make a cut on the top side of the branch approximately 6 inches from the trunk and cut all the way through the branch at this 6-inch mark. This causes the branch to break off smoothly rather than cause a long tear in the bark.
Once the primary branch has been removed, the small stump can be cut off approximately 1 inch from the trunk of the tree.
Remove branches that cross and touch each other. Remove branches that grow across the canopy. Where possible, use loppers to cut branches off approximately 1 inch from the trunk, leaving the smallest scar possible. If branches are large enough to require a saw, use the three-cut method described in Step 1. The idea is to open the canopy to light and air. This helps reduce the chance of a viral infection of the tree. Do not remove more than 15 percent of the green wood of the tree in any one pruning.
Remove all suckers that have sprouted from the lower trunk, or which are growing from the roots. Suckers have a smooth skin and no bark. Many suckers can be broken off by hand, but where necessary use shears or loppers and cut as close to the trunk of the tree or as close to the roots as possible.