From my experience this year I have several growing in pots, I wanted to see the blooms before I placed them in the ground, they started looking bad but after I stepped them up they flourished and many are giving me buds forming. I have pizzazz in a small pot and I can tell it's time to step it up or plant it, I keep it watered but it's dropping leaves. I don't know if our summers are too warm and a plant that is all roots in a pot start to heat up and affects the roots(we are in the 90's with feels like temps in the 100's). I would think if you were going to try for keeping it in the same pot you would trim the roots back each spring and give fresh soil , but that is a guess on my part. I don't know if this helps and hopefully someone that grows exclusively in pots can give you some input. Sinking the pots in the ground will help keep the roots cooler and prevents them from blowing over in our summer storms.
