Welcome Idahofam! I ususally mix bone meal into the hole before planting the rhizome. I'm in agreement with Paul, in that it takes a while before the bonemeal breaks down to become available for the plant. I doubt that you can give it too much. It's kind of late I'm guessing to be planting irises. No doubt you won't get much bloom next spring, but there's a good chance they will make it for the following spring bloom. I planted some last year very late, and they mostly lived, but no bloom. Good luck!
