This has an eerie resemblance to osage orange, Maclura pomifera. Alternate foliage, shiny leaves. However, I have this same weed (tree, whatever) popping up in several of my beds here. I thought that it was osage orange. This plant is a common invasive here. But, if you research it says that 1) the wood is yellow and 2) the sap is milky. I know both of these traits to be true from OLDER specimens. After seeing your picture I cut off one of my identical volunteers. No milky sap and had greenish-tan wood. Perhaps it is too young to show the common traits, but sure the heck looks exactly like your post. Confused! Will be interested to see what others say.
hortster

Thanks Hortster,

I think you are right, it is Osage Orange and I looked it up on Daves Garden and sure looks the same. My neighbor thought it was some sort of tree. Guess I will let one of them grow for fun. I have no milky sap either. Strange, never had this before in my yard.