I picked up a rather spent-looking canna today for free (some kind of white and light green variegated)and would like to have as a houseplant this winter. It was soaking in water at the store. Should I wash the current soil off and repot in sterile indoor soil? Should I cut it back? I can see new shoots coming up next to the main plant which is about 3 feet tall. I'd like to use it in the center of a big pot and plant other houseplants around it in the same soil, such as spider plant, coleus, etc... Is this a good or bad idea?