Going from inside to outside into direct sun easily kills them and does so quickly. They need to be gradually hardened off so first you need to read about hardening off and how it is a gradual process done over several days.

Try your plants, in the bag if you wish with the top open, first in full shade for a couple of hours and monitor them closely for wilting. Then you can gradually move them into partial shade/sun and over the next few days - depending on the temps - and finally into full sun.

Dave

Hi Dave,

Do you think that they can be hardened off with temps in the fifties? Is this too cool for them or should they be fine? Temps at night are above freezing FYI, even though I'd be bringing in them long before overnight lows. Why don't most people grow their seedlings like this instead of buying shoplights and using electricity? Hardening them off seems like the biggest inconvenience, but it sounds like it beats having to keep a perfect light environment indoors (which seems nearly unattainable for me). Is it possible that the seedlings will stretch outside once hardened off in full sun or is that rare (assuming not cloudy skies)?

This would be very convenient if it did actually work.