A couple of volunteers and I are in the process of planning a memorial bench that we are going to build to place at the library for a little girl who was killed by her step father. We are trying to figure out what plants and flowers we want. The little girl's favorite color was purple, so it was suggested to look for purple knockouts due to their long bloom time. I cannot find a such thing. Does anyone know if these exist or have any other suggestions? I live in zone 5 and have very cold winters and do not want to place any plants or flowers that will need a lot of maintenance (as in digging bulbs up every fall). THANKS IN ADVANCE!!