SOLVED! Dr. Robert Wyatt (UGA Prof. of Botany & Ecology, Ret’d) writes: I have examined the Òmystery fruitsÓ that you found in your backyard under water oaks, and I have come to the radical conclusion that they are not fruits at all! I think that they are oak galls, probably caused by Cynipid wasps. When I sectioned one of the Òballs,Ó it had none of the internal structure of a fruit such as a pome (i.e., a fruit like an apple or a pear). Moreover, the external surface lacked any evidence of floral partsÑnot even a stalk. There are thousands of species of gall wasps, and oak trees are among their favorite hosts. Galls can take on many different shapes, sizes, and textures. Yours seem to be Òimmature,Ó but they contain living larvae (or ÒmaggotsÓ) inside. A less likely possibility is that these galls were caused by flies. It is easy to see why someone might think these are Bradford Pear fruits, but I believe that the resemblance is only superficial. I hope this clears things up.

I found one of those under the oaks here too, in Peachtree Corners. Kinda looked like a tiny apple or immature persimmon. I thought it was an offering from the squirrels too, but may it is an immature aborted acorn.

PS: It’s dried and wrinkly 24 hours after picking up off the ground…