Anyway, I have a ton of Cannas in storage, and absolutely no where to put them into the light when they come out, as all my shop lights are busy with seedlings.

We are averaging just above freezing temperatures now, but they are not falling much below that at night. Of course, a Canna cannot freeze! I would bring them in at night, but the greenhouse is a little warmer no matter what, and heats up with the least bit of sun.

So... what temps do I need to get them out?

You are in Brampton are you not? I think I saw it in other posts. I'm in Brampton also so I know the weather here.

Now your greenhouse, if I'm picturing it correctly, doesn't seem like it would hold much heat in over night. That's typical for plastic sheeting I would suggest that your cannas need to be at 10C minimum temperature to grow. At this temp, growth will be slow.

I usually don't try to get my cannas outside until the middle of April depending on the type of spring we are having and I have an unheated glass greenhouse. I end up throwing portable heaters in on the cold nights.

Generally though, it isn't until the beginning of May that I'm comfortable in putting them out with minimal protection.

The surprise "frostings" cause me a great amount of stress. I wouldn't be in too much of a hurry as you may stress your tubers too much.

Yes, they are a plastic type of unheated greenhouse. I was thinking though that I would bring them in at night into our family room. The temps are cool if the gas fireplace is not on, but decidedly warmer then 10 degrees ;-)

Basically, in the greenhouse during the day to take advantage of the sun, then wipped inside to go to bed when the sun goes down and the greenhouse cools... Knowing they can tolerate 10 degrees C is good though, gives me a rough idea that anything warmer, and we should be golden... ;-) I would love to start them in my basement underlights, but DH said no!