Rost,
The name "Horse Apple" came about due to the fruit the tree produces. It is green, knobby and about 4 inches in diameter, and as hard as a rock. It was said that horses will eat them, but the ones in a pasture that I knew of, none of the horses would touch them. They're great for chasing cockroaches out of a house. Put one in a aluminum pie tin and put it in a cupboard. (The juices will stain). They last about a month. Farmers in Illinois planted them in fence rows. A thick row of them with their thorns would make a great cattle fence. (The trees originally came from the southern mississippi valley.)

Russ