Q.Why is my Oak tree turning yellow with brown?
My 21 y/o oak tree is not looking well. Half a side of the tree is turning yellow green with brownish leaves. I can’t figure this out. The branches look just fine. We had a lot of rain storms throughout the season. We have clay soil.

Certified GKH Gardening Expert
Uh oh. This is a massive problem. You will want to have tree professionals remove that tree immediately before it affects others in the area.
Sudden oak death is not able to be treated and spreads to other trees very rapidly.
This article will offer more information: https://www.gardeningknowhow.com/ornamental/trees/oak/sudden-oak-tree-death.htm