seeds Greenhouse seedlings - Hardening off ???

I have been starting plants indoors, then moving them into a high tunnel with shade.  I pull black plastic over the thing to harden off, then gradually pull it back.  Challenge is with all that black, I can go over 100 degrees in the spring.  Also, it is pain in the rear to keep adjusting the plastic.

So am wondering, if a plant goes from seed to a foot or so tall all within a green house does it still need to be hardened for solar.  Sure for wind and temperature, but what about the sun?  I am sure there is a difference between green house plastic and direct sunlight, but not sure how much.  Heck, for that matter is there a degree of solar protection advised for hardening off.  Thought about shade cloth over a green house but seems awfully redundant.

Can't say I have the full answer... but I've heard that 3rd or 4th sets of leaves are hardier that the early ones as far as the sun goes.
 
What I can say is that I move my plants directly from the indoor grow to the fully sunlit world using burlap as a shade cloth (do not have patients to move them out, then in, then out....arrrgh !). I use the burlap as a cover for a few weeks. Seems to work here in Minnesota. We don't get the 100 degree days that you do in KY. Maybe one or two a year but that's it.
 
I do know that if I move the plants directly to the outside from my indoor grow room, the sun will literally burn my plants to death..... nothing left  of them but a skeleton of brown !!!  Shade them for a while for sure.
 
Good luck,
 
Jeff
 

I do about the same but into the barn an onto the car port where they get indirect sunlight.  Minimum of a week later but prefer two weeks, they go into direct sunlight in the ground.  They dont get burns that way, but I do think it might shock them a bit.  Sometimes they will droop for a day or two.

Trying to decide how to expand for next year.  If a heated green house has the side benefit of no real hardening off period, that would be a major plus.  Instead of grow room to barn, to ground I could just go green house to ground.  Grow room is in basement and those stairs are frigging killing me more and more each year.