Parrots feather does survive zone 5 for me. No dirt, just stuck in rocks in waterfall, around the edge etc.
My iris, I use clay, and water up to top rim of pot. Again survive zone 5.
My cattails will grow with or without dirt/clay. I have some in pots. I have some in my stream held down with rocks - but either way will spread outside your pot so be careful. Survives zone 5.
I don't do well with Taro. I stuck some in my stream held down my a rock. DId very little growing. Had some planted in a pot, pot covered half way with water. Did very little growing. Had another bunch planted in a pot with clay. Pot covered all the way with water. Still very little growing, but did the best. Just bought more this year. Not sure yet how I'll plant this time. Does NOT survive zone 5. Must be brought inside in the fall/winter.