What Is The Small Gourd On A Live Oak Tree

Question

I live in Orange County California. I have four live Oak trees and all of them have a small green gourds growing. These are not acorns

Answer 1

These are called "galls," and are relatively harmless. Here's an article that
explains the condition:
https://www.gardeningknowhow.com/ornamental/trees/oak/oak-apple-gall-info.htm