I often start canna seed in the late Summer/early Fall and let them overwinter in pots in a protected place. However, if you start them in late Winter/very early Spring, you'll still have flowering cannas the same year.

But pot 'em up in at least one gallon pots to give their new root system and rhizomes space to develope thru the cold months, and more importantly, during the Spring months when they start to put all their energy into producing plants. Just make sure that your pots don't freeze during the Winter months, however.

Jenna