My granddaughters divided irises I had in containers last year and planted them in a bed in front of my house. They absolutely love where they are and will have to be divided again this coming Fall. I need advice on what to do to keep the bloom stalks from falling down. They get tall and then fall down. That does not happen with the irises in containers, and I have no idea what to do to keep them upright. Any thoughts/suggestions will be appreciated. My granddaughters want to "fix" the problem for me. TIA.