black walnut trees
I know my tomatoes hated to be in the same area as my black walnut tree. What about sunflower plants? do they mind being in the area of a black walnut?
I think it would be fine to plant sunflowers near your walnut. Here is a link to plants that tolerate juglone and the ones that don't. http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/toxicity-of-black-walnuts-towards-other... . http://hort.uwex.edu/articles/black-walnut-toxicity/