I bought my canna(stuttgart)off e-bay late in the season,I have them planted indoors in front of a south window as they were already growing when I bought them,they will probably dry out a little this winter when it gets really cold and inside air is extremely dry but I think they will continue to grow untill they are able to go outside again next spring.All you can do is try.

Scott-

I had 2 little sprigs that I rescued from a sentimental place and put in a pot last year around September. I wanted to keep them inside to make sure they were going to make it. I just kept them in a south facing window and made sure to keep the soil moist. I set them out this spring and had to re-pot since they grew so robustly. They multiplied like crazy and look very healthy but sadly, did not bloom a single time. I wonder if they do need to rest in order to bloom? They will live though!

The first pic was at the end of December last year (they are in the small pot in the middle) and the second was taken just last week:

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Hope this helps!

-Frank

They don't need a period of dormancy in order to bloom, but there are some disadvantages to consider in keeping them growing indoors during the winter.

They need full sunlight for an average of 6 hours per day in order to build the energy required for blooming. They won't get that indoors.

In most indoor situations, they probably won't get enough light for sturdy growth either. They will have to rely on stored energy, which means they will be weaker plants by the time spring rolls around. They will also be acclimated to lower light levels, so when they go back outside, the foliage may burn.

Then they will have to use more stored energy to put out new growth. All this will set them back and delay the production of their next flowers. In a climate zone with a short growing season, they might not recover in time to flower before it gets cold again.