I have many black walnut trees in and around my yard. To the question about the effective range of their "weed control", in my experience the jugalone effect is mostly in the roots, which extend well beyond the drip line in a mature black walnut tree.
Plants I've seen tolerate black walnut include chives and garlic, blackcaps (wild black raspberry), raspberry, sour cherry trees (Montmorency), peony, and strawberry.
Plants that I'm certain can't tolerate black walnut include rhubarb and tomato. There's plenty of others with mixed results I'm not sure enough to list.
