Deb, I was just thinking about your question about protecting your calla during the winter. I'll bet that if your pond doesn't freeze solid you might be safe. The reason I ended up with callas along that part of the house was because each year I dug the same bloody plant up, for about five years.
Eventually I got it all out of the initial spot, but it took awhile. With that kind of tenacity a calla that enjoys pond living will be a happy camper as long as its deep roots aren't frozen...maybe.