Rsieminski, I am in zone 6 which means that I cant leave the cannas in the ground over the winter. I have found that leaving them to grow as long as possible before our first heavy frost results in bigger rhizomes, therefore I never cut them down after they flower. I also dont dead head untill every last flower is produced. If your zone is warmer then maybe you dont have to pull the rhizomes, unless you want to divide them for more plants. Best Wishes, Sagapo

Thanks! I figured they must be doing something, and if thy're not producing flowers, and they're not getting visably bigger, they must be making bigger rhizomes.