Question
I live in zone 5a in Iowa, (-20F), and have to dig up my cannas.  I formerly lived in NC and never had to do this.  One variety (I don't know the name.  They were a gift.) is red, grows very tall and has tiny petals, green foliage.  I have no trouble with these as the tubers are quite huge and they multiply many, many times over.  My problem is with the canna that I love, "The President," which is a shorter ( 36") variety and has huge red flower petals.  When I dig these, the tubers are much smaller.  Except for the original tubers that I planted this year, the tubers seem to be very small and hard to distinguish from a sprouting stalk.  I am never certain if I have divided them properly.  In addition, though we have had freezes, the stalks aren't as "melted" as I like them, and I have had to dig them up this weekend due to some frigid weather that is on the way this week.  I am not certain how close to cut the stalks away on these small tubers, or if leaving too much will lead to rot. Thanks for your help

Answer
Hi Tess,
Thanx for your question.  One thing I did in the past was to cut the stalk of the canna off about 6 inches above ground, take them into a dry, cool (not freezing) basement and stand them up against the wall.  In a month they will be dry enough where you can cut off an additional 4 inches and store them in a plastic tray or a netted bag where air can circulate around them.  You will always lose a few of the small ones but you'll be surprised how even the small ones will make it through the storage period.  I hope this helps.  Next, year, remember that Zone 5a doesn't have the same type of hot summers that cannas adore like your North Carolina or even my Kansas City, blisteringly hot and humid summers.  You can put black mulch which helps absorb heat and heat up your soil.  Cannas first love heat, next, periodic watering and, they can be heavy feeders.  Not too much nitrogen or all you're going to get is leaves.  Get a fertilizer higher in phosphorus and potassium so you'll get lush growth and plenty of blooms.  I hope this helps.
Tom