I have some rockcress (aubrieta) seedlings that I started to try to harden off. I put them outside in the shade and brought them back in at night. On the first day, everything was fine. When I brought them in the second evening, they appeared wilted. On both days, temps were in the fifties. I kept them inside on third day and they still are wilted. Is there any way to save them?
They'll be fine, though the transition may be a tough one if all they know is indoors. It will just take some patience and closer attention to get them acclimated. Here's what I would do:
1a) Make sure it's getting enough water. I would poke holes into the surface of the soil with your finger before watering.
1) Try to match the humidity while your plant adjusts to the temperature. Plants lose moisture through their leaves, even if it isn't scorching hot. If there is less moisture in the outdoor atmosphere than there is in its typical environment, transpiration will occur more quickly. Consider winterizing it, even during the day until you see that it's managing alright.
2) Once it's fine with the temperature, take off the winterization and let it get used to the temperature. As a hardy species it should be able to withstand 50 degrees, but you might want to watch out if it dips lower.
3) Let it be. Moving it in and out is not what you want to do. There are too many variables to consider between indoor and outdoor. Set it outside, and maybe put it in more sun than you have been to match what it was receiving indoors.
Wilting is always normal when moving a plant. Sometimes I'll move cilantro into a bit more shade and the next day it'll be drooping and pathetic. After waiting 48 hours it's back to normal. Aubrieta is much sturdier (though I'm not sure how it'll do in Maryland winters).