I had good luck growing water loving tropical cannas this year, thanks to all the rain. I liked the new colors of Tropicanna cannas. I have many more than I started with because they multiply, and though they are not winter hardy in Boston, they create tubers that are easy to store in my basement over the winter.
If you are growing these tall imposing Victorian foliage plants in containers in New England, cut the tops off to about 4” and move the containers to a heated space or a space that gets no cooler than about 60 degrees and keep them barely moist. In the spring, you can move them back outside after the nights are 50 degrees or warmer and all danger of frost has passed. Water them and fertilize with controlled release fertilizer.
After 1-2 years in the same pot, unless the pot is huge they’ll probably get root-bound as the rhizomes continue to reproduce, so another option is to follow the directions above but instead of leaving them in the pot, lift everything out of the container and place it in a plastic bag. Then, in the spring, break the rhizomes apart (better to break than to cut) and replant the best looking ones (ones that look as healthy as a potato that you would keep) and discard the rest.
When replanting new rhizomes in the spring, keep the soil only slightly moist until you see new shoots coming up; otherwise the rhizomes can drown and rot. If your cannas were planted in the ground, cut off tops to about 4” and dig them up in clumps. Place these clumps in a large plastic bag—store at 60+ degrees over winter. Don’t seal the bag up—the clumps must stay moist but not wet.
In spring, break clumps apart, discard spent rhizomes and replant the healthy ones
If you want to get a jump start on the season, you can start new plants indoors, then transplant out after all danger of frost has passed and evening temps are 50 degrees or warmer. When replanting new rhizomes in the spring, keep the soil only slightly moist until you see new shoots coming up; otherwise the rhizomes can drown and rot.