Some canna will grow seed pods...so if you're in to keeping the seeds, you can let them develop. They are large and black, and very easy to plant. However, some varieties of canna are sterile and do not set seed. Once blooing is done, you can cut the stack down to the ground. I usually do it as I see another one emerging. Remember, they are all connected underground, to the same tuber. I usually let the older plant feed the tuber a bit until I see the new sprouts of the next round.
I dead head mine... for aesthetic reasons... but if you do be very careful. More often than not there will be another bloom forming next to the one you dead head that you may not see without close inspection. Be careful not to cut it off. I also do not cut mine down to the ground because I enjoy all the foliage. I let mother nature do it for me... example during a freeze etc.
i think i feel better with that. i reallydont want to cut them down to ground, and this is my first year for them, so i am really enjoying the flowers, along with the hummingbirds that are coming to them. if there is no reason to deadhead then i dont think i will. i just thought maybe there might be a specific reason to do it, like it wouldnt bloom again or something.
i just love my cannas. they are blooming and thriving under conditions that have killed a lot of other things i have planted. (mostly the heat) and, i think i did just about everything wrong and i still have wonderful blooming plants. i am learning as i go and think i will invest in other colors for next year. mostly i have reds, which the hummers flock to. makes this senior very happy !