For this it would be nice to have one of those 'frigs from a grocery store!
They have lighting fixtures in them.
However that is not possible, so I am thinking to wait until the weather is cool , but above freezing during the day. Then move the plants back and forth from house. And move under lights at night.
A greenhouse might work depending on weather too , but here would not give long day lighting. I want to try growing Laurentia ( Isotoma axillaris) , but to get good flowering it requires chilling and long day lengths. I am not trying for Florist quality plants---jut reasonably good flowering. What thoughts has anyone else on this?

I've not grown them from seed, but I've grown Laurentia (Isotoma axillaris) plants here in the hot and steamy southeastern USA and it did great. When they got a little spent looking, I just cut them back really hard and fertilized. They would start blooming again within a few weeks. They didn't like to get over-watered. I lost them the year that we had non-stop rain and cool temperatures.

However, it sounds like you are trying to shift the seedlings from juvenile growth to flowering with vernalization, so I can't offer much help on that. I do have some old seeds that I might try so I'll be watching with you for any good advice.

How cool are they supposed to be?

Karen

I think below 12 º C or below about 50º F.
What I am wondering is that:--- the way I described would warm them up at night,--- so would that not wreck the effect of the chill? Vernalization should involve continuous cool temperatures? Or can it be oscillating temperatures? I may have to rig a light fixture into the unheated car port.

I don't know, but I would guess that the cold rx. should be 24/7. Do you have a greenhouse or access to one? If so, I'd go for the chill and hope the lengthening days would help with the photoperiod as spring progresses. Do you have a cold attic or basement? You might have to just put them in your coldest room with a lamp with a cfl.

Karen

I guess it needs to be chill for several weeks, then long days.
I just have a tent greenhouse.
I might be able to close off one room, and open the window to get a cool room.
The commercial florist growers keep them cool for ten weeks, and then long day for ten weeks.
We shall see, how they turn out! The seeds are not even sown yet.