Unsure when to transplant - ideas welcome
I am new at gardening (this is only my second year) and this winter was my first time at wintersowing. I've had great luck so far with germination, only a few of my flats aren't germinating. But at any rate, the flat that sprouted earliest (bachelor buttons) are now growing like crazy and soon will outgrow the top of the container. They have about four leaves, all of which I think are true leaves not seed leaves.
They seem pretty happy right now but I'm afraid they won't be happy if I keep them in their flat too much longer.
They seem ready to transplant, in other words. But my problem is we are still about a month away from our average first frost date. I could transplant them and put them down in the basement (I'm growing tomatoes from seed for the first time this year also, so I have a small grow light setup). But that seems like it's defeating part of the purpose of wintersowing which is to have plants that are already hardened off.
I'm worried if I transplant them and just leave them out with the rest of the flats that they'll get caught in a freeze. The next week forecast lows are mostly in the mid-30s but we do have one day next week forecast to be 30.
So, given those choices, what would you do? Keep them in the flats a little longer until they start appearing stressed? Transplant and put under lights for a month? Or transplant and put outside and hope they don't get frosted?