i finally got my act together to post some quotes about hot water soaking.
i found several sources siting it and that's why i decided to try it.
the last one (and the first here for those who prefer to watch :)) :
british gardener on youtube...about 1 minute in: he dunks for 20 sec in boiling water
https://www.youtube.com/watch?...

in english, but seems to be a Russian site: quick scalding and long soak in thermos!
https://floristics.info/en/gar...
Canna seeds have a very hard shell that must be softened before sowing. Scald the seeds with boiling water and keep them in a thermos with warm water for 3-4 hours

this one is a pdf...with informative pics of seeds with a little lid that pops after dunking
to allow water in (same as filing, I guess): soaking for 1 min! in boiling water
http://admin.ipps.org/uploads/...
Another example of a temperature-sensitive water gap structure is the imbibition lid that forms in Canna seeds after being submerged in boiling water for 1 min (Fig. 2). The lid separates from the seed again allowing water to enter the seed.
...there's more about imbibitional lid :O...(new word!)..

There is a roughly circular spot on the seed called the "imbibition lid" near the hilum slit (the scar where the seed was attached to the fruit), which is slightly raised above the surface of the seed. The imbibition lid is the spot that naturally decomposes, falls off, and allows water to enter the seed. If you can find it, the imbibi-tion lid is the best place to scarify canna seed.
An alternative to scarifying the seed is the hot water method. Place the seeds in a cup and pour very hot (nearly boiling) water over them. The temperature shock causes micro-fissures in the seed coat which al-lows imbibition. Let the water cool naturally and soak the seeds in it for 24 hours. Warm water above 122°F (50°C) for 24 hours helps to loosen the imbibition lid.
...
unfortunately i don't remember when my lid popped ( )...on the first scolding or after 2nd soak..
but i modified as follows (being scared as i was experimenting):
i waited 1 min after water boiled, then poured about 1/2" of water over seeds, pouring over metal spoon in pint glass jar in order to cool off faster and not break the glass.. left them to cool in jar for 24 hours. had 2 batches: the seeds did not seem to swell ..or just barely..
i also read that the water amount is important: not too much not too little.
so after 2 days since i did not see much swelling i decided to also file off a tiny spot on each. and then 4 seeds got scolded the 2nd time (and left to cool). the second batch (main 7 seeds) i soaked in hot water comfortable to touch.
and continued to keep them all in 1/2" of water until the roots were visible (germination).
as i always do for soaking seeds i added a few drops of 3% peroxide in water (to keep it sterile and prevent bacterial/fungal growth): you don't need to change water, just put a few drops in every day: the little bubbles will form on seeds providing oxygen..and preventing rotting.
as i said before: double boiling dunking did not damage the seeds, the roots grew 5 days ahead of the other batch, but the leaf growth stalled: of 4 only 2 are showing first leaves, while in the other batch i have 2 largish leaves on each on 3 seeds and 2 more starting up.
i am planning to grow them only in pots (and not too big) on my balcony to use as shading for other plants.
So if those slow to start seeds will stunt the plants i won't complain, as i would prefer to keep them smaller. but it's too early to talk about that..we'll see if they catch up or not.
now i am ready to pop 3 champions into tiny pots by themselves.
the other note for those who do not dare to scold the seeds: they need to be on a heat mat and moist until sprouting (read that best for canna to keep them flooded while on heat mat).
quote:
The soil temperature range should be 80 - 90° F. and there must not be much variation in this.
Most varieties of slow germinating seeds will turn black and rot if
there is not sufficient heat in the soil (75 to 90 degrees F for most species) or if the soil dries out or is allowed to remain too wet, which will encourage the growth of one or another of the varieties of fungus or mold.

i hope that this info is useful for future sprouters :).

skylark said:If they have grown enough, they should've formed a rhizome. Then you can resprout them in spring.
Are they dormant now? Do you still have some leaves?

yeah they did and once I brought them inside, they completely dried up. and some were molded too. I guess I just didn't know how to take care of them once they were inside. so I decided instead, to leave them in a pot all winter and kept them growing in the living room. They are now outside in the ground again.

I observed that plants in So FL in botanical garden have gone dormant over winter in dry season in ground. Even though the night temps never dropped below 55F or so. And dailies were perhaps 65F for a short period only.
So indoors they prolly should be allowed to dry up like Caladiums for a few months.
My seedlings though continued to grow slowly indoors: best 3 in 4" pot. I finally split them up and put outside a few weeks ago: it's reaching mid 80's here and 70's at nite: now they should take off.
The tallest one is about 1 foot. The other 2 are about 6" inches high. Once they planted individually and outside they should speed up.

My canna seedling is blooming! So excited. I'll be back with pictures.

here are some in my garden

I always plant a few cannas every year. Seems like I always have seedlings coming up on their own after spending the winter outdoors.... and you never know where they will come up! This year I had a few seeds on Red King Humbert rather than the old fashioned green leaf kind. I intend to plant them in spring to see if I get something other than the old kind. Don't grow the pretty ones because most are just so short, but I am thinking about getting a few next year just to play with.

Beautiful, Mike!!

Now I'm curious what happened to @JayZeke and @skylark 's plants?

The one time I tried to mess with Canna seeds, I stabbed myself trying to "nick" the outer shell. The rhizomes multiply so fast, I never felt the need to try again.

Living in FL my cannas are still lush and blooming. However, I am getting ready to move to a colder climate and would like to take a few canna rhizomes. Can I dig them now and just cut off the foliage or do I have to let it dry?

Are you moving to where they can go back in the ground or will you need to store over winter?

On the line between 7a 7b.

the rhizomes are super easy to start, the seeds not so. On my part it was just an experiment to see if i can do it. I wanted to grow them from seed in a smallish pot not in the ground and bring it from FL to NJ. then cut it down in fall and bring it back to FL to continue growing.
And i did just that. I need taller plants to give some shade relief in FL on my balcony and help support other plants in the wind.
They are still growing in the same 1 gal pots, so instead of being 5' tall they reach to the railing or so. Growing non-stop until now, but they do slow down in Jan-Fab when it drops to mid-50F at night. No blooms: my are indica grown for edible tubers, leaves can be used for wraps too. Although i never use them that way.
here they are in 21


and in 23:

i am thinking of giving them a rest (drying up in a pot until spring).

Beautiful, Sky! : )

Alice, if you are going to re-ground them this fall, I would leave longer stumps on the stalks so they will stick out of the ground a few inches, reminding me where they are and placing the wound above ground.

If you are going o store them, I would cut the stalk as close to the rhizome as possible just to save space and weight.

Tiffany, I'll try and figure it out. I might try it both ways as insurance.

Skylark, which variety of cannas are you growing? Right now I have some smallish ones, under 30" but I have grown 7' ones in the past. The Horn Canna catalog lists the height of different varieties.

Happy to reply. Best luck with the Cannas & the move overall! When is the big event?

Who knows, We have bought a home closer to one of our sons but have not put our present one the market yet.

@ardesia ,
we lived for a short time in Charlotte quite close to SC border and my cannas didnot survive; but they were not mulched well. Closer to the mountains at elevation it will be cooler still. So i think you'll need to dig them up for winter.
As far as St.Johns you can keep them going into 40F nites and cut the stalks and dig them up into pots for xfer. I would put them on the side to dry up somewhat to kick the dirt off and just pack the rhizomes.

oh, forgot:
mine are species C. indica, edible Canna; flowers are tiny. Mine never flowered in 3 years, but they are super constricted in 1 gal pots, while normally they are at 5' and spreading like wild fire.
the dwarf hybrid that i got flowered on 3-4 stalks, then produced 3-4 more, etc and keeps going in the same 1 gal pot. I'm taking it to FL for winter for the balcony. It is a shorty, just 18" with blooms from the pot.
It can probably bloom in sunroom too thru winter.

Thanks Skylark. We will be in Flat Rock at an elevation of 2750' and if yours did not make it in Charlotte they certainly won't survive in WNC. Guess I will try just a couple in a pot like you suggested.

Alice, plan to store them. All mine in ground freeeze over winter. I think they will be fine anytime you dig and cut tops, and store above freezing until you plant out in spring. I have almost every one grow again after storage.

Good to know, thanks, Sally. I am beginning to think maybe I should just leave them for the next homeowner here. Not sure I want to get into digging and storing. At my age I am trying to simplify matters. Just hauling pots indoors for the winter is going to be plenty.