I plant under Hickory trees and haven't had any problems with the hostas growing. This be is all hickory trees. The biggest problems I have are the nuts falling on the plants, and squirrels burying the nuts in the beds. Do I dare mention that I hate those bushy-tailed little varmints?
Hosta was the first plant that lived in my shady north garden under black walnut trees. The chemical they produce is called juglone. Hostas are immune. I have hostas and tiger lilies - I call it my tiger garden. I started black hollyhocks from seed to add. I am going to try heuchera and astilbe when I thin my plants this week.
I hate squirrels also, especially when they get in the building. My neighbor has an air pistol...nuff said.