In New Jersey we had wild cherry trees and wild blackberries growing within
10 feet of some very large (40 ft. tall) wild black walnut trees along a
fence row. This was 25 years ago so I can't remember anything else except
that I had some hyacinths planted over my dead pet rabbit under one of the
trees and they naturalized. Could you try experimenting with some seedling
trees/shrubs to see what happens?