When do I transplant my cabbage seedlings?

I do all the germinations in my bathroom with the heat turned on 24 hours. All seedlings grow taller and taller with tiny leaves. When can I put the seedlings out in the open air after I first sow the seeds? FYI, it is chilly outside.
When do I transplant my cabbage seedlings?
I already have mine in a cold frame hardening off. You need to harden them off for about a week before transplanting. Essentially hardening off it the period when the plants get used to sun and wind. Put them in a protected place out of direct sun and wind for a few hours the first day and increase this a couple of hours each day until the plants are out 24 hours. This is best done in a cold frame which can easily be made with 4 bales of straw or hay and a couple of windows. Put the bales in a square leaving the middle open (this is where the seedlings will go) and place a window or two over top (the amount of windows you use depends on size of the window) Put the seedlings in the cold frame, window(s) over top and you are set. Be sure to open the window (I use a short stick to prop them up) on sunny days (even if it is cold/cool) or the cold frame will heat up and cook the seedlings and kill them. With a cold frame you can put the plants out and leave them for a week (or more) and they will be fine. The instructions for putting them out for a few hours and increasing daily is for unprotected plants



Transplant before they are 8 weeks old or root bound.