Actually, Black Walnut trees are ideal for growing hosta under. They have a tap root so there isn't very many surface roots to compete with the hostas. BW's get a bad rap by people for things not being able to grow under them, but I've never really had a problem. Mostly you can't grow tomatoes or things in the tomato family under them. I grow hosta, lily, daylily, peony, clematis, tulips, poppies, ligularia, brunaria, pulmunaria and lord knows tons of things I've forgot about. LOL
