Toni, do you know if glads will grow under black walnut trees, or in the presence of juglone in some mulch? (I don't find it on any list I have of juglone tolerant nor intolerant plants and I have lots of corms to plant.)
Darius: without doing some research, I can't answer this with any authority. My understanding is that very little will grow under black walnut trees; however, I have 12 on my property, and the previous owner planted irises around the base of each many years ago. The iris seem to do fine and some of them bloom. I believe the ones that don't bloom have become covered with mulch and grass clippings over the years and the tubers don't get the sun.