Oak should be fine as long as you don`t have herbicide drift from anywhere else. Oak are only slightly acidic which is perfect for Azaleas. Black Walnut trees, on the other hand, produce a chemical called juglone which is toxic to many plants, especially to tomatoes and should be avoided, leaves and all.
Thanks for the information about oaks. Where I live there are native white oaks all over the place. We also have a lot of fir and pine trees. We have a very large red oak in the front yard. In the fall, the leaves are abundant. I don't compost them at all. I put them in the yard debris recycle. If I were to recycle them I would need a separate lot to do this on because there would be so many recycle containers. I mostly just recycle grass clippings and spent annuals. Our soil tends to be very acidic. You are right that Azaleas do well in acidic soil. Every fall I spread lime on the the grass otherwise the PH gets off and moss takes over.
