You don't just put it outside and leave it to harden off. It has probably burned and in shock. If you want it to live you should at least brace it from falling over so it can get some circulation. I would suggest reading up on plants in general.

Randi,
Chances are that even in the greenhouse your plants were not receiving enough sunlight. Could be overcrowded or simply short days. Lack of sufficient light is the normal cause. You may want to take the quick remedy and simply remove the weak foliage about four inches above the ground. Chances are that your plants have established a good root system and will regrow quickly. As long as the weather is good I would leave them outside.
Regards,
Kent

Thanks Kent. Your reply was a bit nicer than the previous person's. I am an experienced gardner, but new to cannas. Everyone else seemed to harden off nicely, except for the canna, which I thought was strange.

Kent's correct. It's just from have been growing 'soft' in the greenhouse.

Just cut off the bent stalks. New stalks will emerge which will be much more sturdy. This happened to my Stuttgart. It was unsightly. I just cut them off near ground level and new shoots quickly created a nice looking clump.

Dave,

Thanks for the follow up to your thread. It hopefully will be beneficial to others with the same problem and knowing a solution that may likely solve their problem.

Regards,
Kent

You can probably stiffen newly grown stems of potted cannas by feeding them potassium silicate (~ 1 g/gal) from a bottom saucer. In fact, cannas are big siliconphiles.

Sorry if I sounded rude but even a novice knows that many plants will burn to a crisp if put out in a full days sun. I put all my plants on the east side of the house to harden off where they only get 4 hours of direct sun in my location and even that is too much for some plants.

"Sorry if I sounded rude but even a novice knows that many plants will burn to a crisp if put out in a full days sun. I put all my plants on the east side of the house to harden off where they only get 4 hours of direct sun in my location and even that is too much for some plants."

Sorry if I sounded rude but even a novice knows that the Original Poster didn't complain about sunburn. Furthermore, cannas from an unshaded greenhouse rarely burn when put outside.

The lanky potted Tropicanna pictured below has withstood several windy storms with only one stalk falling over. As with the OP, it was started in a greenhouse, but it was moved to its present location without any hardening off.

The fact that it has withstood 30-40 mph winds has even surprised me and I can only suspect that it was because, last year, I fed it potassium silicate and calcium nitrate at different times from the bottom saucer. That would form a reservoir of semi-soluble calcium silicate in the growing medium. Both calcium and silicon are constituents of canna cell walls. Typically, both silicon and calcium are plentiful in soil but deficient in potting media.

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