Cut the stalks down to the ground. Then fertilize and keep them watered and you should see new growth.

Jenna

Whatever you do don't cut the stalks down to the ground really bad advise its way too late in the season. Dead head the existing dead flowers blooms, water often and fertilize wait till the fall to dig them up or chop them down

I usually cut mine to the first set of leaves below the bloom.

Irish, I think it depends on where you live. Here the canna stalks are cut to the ground because they die back rapidly anyway. I constantly have new growth coming up from the ground and have flowering cannas well into December at least.

My numerous canna stands are large and we have lots of new growth coming up and there's no point in keeping a stalk that is going to wither and die when the energy of the rhizomes can go into producing new growth. If someone is trying to 'refresh' a neglected stand, then I stand by cutting them to the ground, fertilizing, and watering well.

Jenna