Live Oak Pruning Problems

Q. When is the proper time of year to trim a Coast Live Oak tree? And,is a permit required? My neighbor is having his tree trimmed today, May 14 and I'm concerned about the tree. Lisa

A. Sorry I wasn't able to get back to you before the tree was trimmed. What is the situation? Exactly where is the oak in question? As far as trimming, generally you should only trim live oaks if it is absolutely necessary, otherwise you’re just damaging their chances of surviving. What town do you live in? Could you send me a picture of the tree as it was and as it is now?

Q. Hi Frank, Thanks for getting back to me.  Sorry, I don't have pictures to forward, but I can tell you that the tree in question is a huge, old tree which has been here for all the 43 years we've lived in our E. Pasadena home.  The tree can be seen from the corner, where it is located in the backyard of that house.  It has been severely trimmed, in my estimation and according to the trimmers, they had a permit.  I'm just hoping it will survive.  Thanks for your input.  Lisa

A. You might want to mention to the owners that:

1.       The main thing keeping any tree up is its own weight acting through the force of friction. The heavier the tree the more likely it is to stand up to storms and winds.

2.       The fine structure of oaks and other trees helps dissipate the winds force on them, leading to greater stability and less chance of failure.

3.       Trimming a tree degrades the above two factors and causes a tree to be MORE likely to fail.

4.       Tree canopy density is proportional to the amount of nutrients a tree receives via photosynthesis (it has no other way to make energy), so when you trim your trees you starve them as well.

5.       The new growth that trees put on after trimming relies mostly on their stored food reserves –it further robs the trees of nutrition and puts them in danger of disease, insect infestations and ultimately, failure.

Q. Hi Frank, Thanks so much for the info...wish more people knew that!  I'm sharing w/ folks I know.  One Q. about Coast Live Oak trimming remains: Is there a correct season for trimming them?  Regards, Lisa

A. Yes, live oak trees, like Quercus agrifolia the California live oak, are best pruned when dormant in the late summer and early fall.

Resources:

1. Living Among the Oaks: This University of California Agriculture and Natural Resources booklet describes the special needs of California native oaks. A must read if you have an oak tree. Many people are killing their oak trees with kindness and the landscaping they have surrounding the trees -this pamphlet tells you if you are doing just that. 
2. Pruning California Live Oaks: Published by the Ventura County Agricultural Extension. Goes over the how when where and why of pruning oak trees (no surprise; states that the best pruning is often no pruning at all).