FAQ - Answer
I am not aware of any reasonable method of estimating age of oaks from visual measurements. Blue oaks in particular grow over such a large geographic area and under such extreme edaphic (soil and weather) conditions that it has not been possible to develop the type of graphic that you are asking for. The only approach would be to “core” local trees and count the rings (no easy task with oaks due to the hardness of their wood) or to count the rings of a tree once it has been cut. Another way may be “poll” local residents who may know a history of the site and see if they can help you determine if the trees have been present during their collective memory or if some historical event comes to mind to help estimate the age of the trees.