Dig around in your planter; chances are that the rhizomes are no longer any good. Cannas can't take the cold, especially the kind we had this year.

But stranger things have happened ........

All of my Cannas I forgot to dig up out of there pots were mush this spring when I dug around in the pots. My mom was kind enough to give me three more to replace the ones I lost. Last year I bought a bag of cannas from Home Depot and while they never bloomed, they did look pretty my $10 bought me 8 cannas, so I wasn't out all that much.

Good luck!!
Shannon