Answer

FAQ - Answer

Less is more when it comes to fertilizing mature oaks. I wouldn’t fertilize unless there was a significant reason for doing so --- such as a lab report that says an element is deficient. You may want to check chapter 5 in UC publication #3518 “Oaks in the Urban Landscape” - there is a section on fertilization. Here’s the link for the publication: http://anrcatalog.ucdavis.edu/Items/3518.aspx