Q: I found a small tree with weird looking fruit behind my neighborhood library. It is growing in a tangle with other small trees and has thorns on the branches. Any ideas?
A: You found a che tree, Cudrania tricuspidata, also known as Chinese mulberry and mandarin melon. There’s no telling where it came from. Someone in the neighborhood must have one and a bird may have dropped seed behind the library. The fruit is sweet and edible, though chewy. A couple of online catalogs offer the tree, including Edible Landscaping.
See these sources for a discussion of its characteristics.