Hi Eric....
I also Live in Ohio..near the Indiana border...so you know I am totally Z5! I have a friend...who threw cannas across the fence last year..down near a creek..because she didn' know what to do with them..she had so many! Lo and behold...they survived!!! Came up on their own! And of course...bloomed!
So based on that...I would say..it's definitely worth a try! Good luck!

You must have a woman from the coven spread a thick layer of mulch over the cannas in order for them to bear flowers the following year.

Mulch. Lots of mulch. Mounds of mulch. Better yet, put a couple of bales of hay over them as soon as they die down. With plenty of protection and a mild winter, they just might make it. But in your zone, it's probably easier (and certainly more reliable) to just dig them up to overwinter indoors and replant in the spring.

Thanks for the responses (even the mystic voodoo one).

Having spent several hours over a couple of days digging up tubers, removing attached soil, allowing them to dry, filling plastic bags with peat and soil mix, adding tubers, attaching labels and hauling them over to the cool cellar crawl space area to overwinter (I grew a lot of cannas this year), I question the "easy" part of the equation - reliable, yes, except for certain fussy types like 'Australia'.
So when I was left with just a big clump of 'Crimson Beauty' to dig up, I decided enough was enough and it was time to experiment. They'll get a good thick blanket of mulch and will just have to tough it out. If they don't make it, I'm out one inexpensive, misnamed variety ('Crimson Beauty', or at least what I have, is actually orange-red).

I also suspect that there is variability in hardiness among canna varieties, although I have seen little to nothing about this in print.

I live on the border of zone 6/7. I have not had luck overwintering them outdoors, probably because of our very clay soil. I suspect they get too wet and rot. I've had problems with a lot of other types of bulbs rotting too. If I ever get enough soil amendment in there, maybe I'll have better luck. I do see other gardens in my area where cannas do overwinter fine.

I have had luck with the red species type. But I moved this year and am up higher in elevation but do have much drier less clayey soil (good and bads) so I am gonna dig up parts of some and leave some, along with my hedychiums, I hope to god they make it!! I still haven't had a frost yet so maybe there is a warm halo around my house!

Some varieties seem to be more rot-prone than others. It's hard to keep them over winter in 7-a in clay soil and marginal with sandy loam, except near the house. I've found hedychium to be more moisture tolerant.

Last fall I performed several experiments leaving all my cannas in the ground and using several different levels of protection. The Cannas closest to my house fared the best. Everything else had 6-8 inches of mulch and it seemed the only parts that survived were in the center-most part of what I mulched. My soil is heavy clay although it was a very wet winter, but I think it was the cold rather than moisture that killed them. There also seemed to be a higher percentage of survival in areas that received more sunlight throughout the day. This year I will add even more mulch extending it outward more and hope for more survivors. On a side note I always collect several hundred canna seeds throughout the summer in case of a hard winter and to see if I can generate any new variations.

Don't know if this will help but it works here in SE MO. When you cut the leaves from your cannas, just lay them on top of the bulbs. You can add some straw mulch if you're going to have a hard winter. Don't know what the leaves have to do with it, but this has worked when heavy mulch without the leaves didn't. Got this tip from an old time canna grower that said she never dug a canna....

I have a neighbor who has left his in the ground for many years. They are on the south-facing wall, against the house, and come back each spring. I asked him how he mulched them, to keep them from freezing, and he stated he didn't mulch them. They are yellow-blooming ones that he originally planted about 12" deep.

I grow my cannas in pots...I cut them back and put them in the garage(no light) They are regrowing and are about 12 inches! Should I cut them back again or let them grow? I live in Chicago!

Well, this is a golden oldie/zombie.

judy, I'd cut down the shoots so that no more tuber energy goes into growth and let the pots dry out. Assuming your garage is unheated, the cold temperatures should promote dormancy.

As an update - I've long since stopped trying to overwinter cannas in the ground. Since we had a couple of nice warm days yesterday and today I followed the time-honored routine of digging the tubers out of the ground, trimming off frost-killed stalks, letting the tubers dry out for a day in the sun, and then loading them in layers into large tubs, covered with peat moss. The tubs go into the garage, where they get a modest amount of water a few times over the course of the winter, and do fine (temps get down to maybe 30F at the coldest).

I'm amazed that a zone makes that much difference, I've been 6b (NE Oklahoma) and 7 (Arkansas) (as well as hotter zones) and cannas seem to be weeds here. I've WISHED mine would die...and actually pulled (still pulling continuing growth) up a bed this late summer.

At my previous house, they invaded the lawn....and were most difficult to get rid of (because they kept coming..almost like bamboo).

Just goes to show that one man's weed is anothers coveted beauty :)

Don't get me wrong, cannas are great, just that mine weren't in a good place (a place along entry way where big bushy leaves are a problem).

I am in a zone 6B/7A and I leave most of them out all winter..I use the 1 cu yard bags of mulch. cut them down dump half the mulch on top. Lay an empty bag on top of this then cover with the remainder in the bag. seems to keep them dryish and they do ok. you won't get 100% coming up but they grow so fast it won't matter. a little bit of leaf litter raked on top dosen't hurt either.

Okay Miketropic, Since you listed zone 6b, not purely zone 7, and anyone who may have tried the stay in the ground method, and you are a zone 6b or 6a, how has your overwintering in the ground gone? I am planning on mulching well, and covering my cannas with a mini-greenhouse, to keep excess moisture from the crowns. I know, winter is a long ways off, that's a good thing! But, anyways, when it comes I'll try covering them etc. I just wondered if anyone had anything good to add about their wintering in the ground protected in zone 6 or 6b this past winter. later guys.

Bill zone 7 .I'm in Cheverly Md. Outside of Washington DC And I tried over wintering Cannas for forst time last Winter and had great success . I used about 8 inches of mulch per mound . Before that I had gone through the mess of storing them inside. I'm thrilled I don't have to do that again.

Hi Pheasantrun, I'm in zone 6a so I may need to lift mine, but, I have overwintered some Calla lillies that are said to be zone 8a, in some raised beds with some good mulch. But, I will need to divide my Cannas anyway, so maybe I should just leave some bits in the ground and mulch, but remove many plants too, so I can see of the few I've left intact in the soil do overwinter okay, and if not those I overwinter in my basement will be planted again in the spring. I will add that those Calla lillies were planted in a raised bed up against my brick house and that's likely why they did fine coming onto 3 years now, and they were mulched well, so that's likely why.