I really like Japanese Iris and I understand some folks have trouble growing it. Maybe I hold my mouth right or think enough positive thoughts about this plant (or maybe I even grow it properly) but I have not had much trouble with it. Here are the instructions for growing this delightful plant.
As with many specialized plants, I note the care instructions are really clear. Full sun, adequate moisture (constant moisture), the right soil pH (acid) and good feeding will produce plants. Mess up one of these things and your plant will respond with a gradual decline and small flowers.
Given this is one of the largest flowering iris in our garden with spectacular colours, having it decline is a shame.
In any case, it is blooming away happily in my own garden right now. And I have to divide it this spring and figure out where to plant a bunch of offsets (no problem - as I have a lot of wet spots for it to conquer)
Oh and the leaf behind the flower is a potted Philodendron that I put out in the garden for the summer.