QUESTION
Im curious about this too. I have mutiple ~2-4 seedlings per pot. They are about 15 days old since they broke ground. They are all growing awesome and are about 6"-9" tall from soil.

I have some mature females in flower right now. I'd like to toss above said 15day seedlings in the 12/12 chamber. Cut males and take the remaining fems to harvest.

I would like to put them in flower as soon as realistically possible. I have more plants behind the seedlings. Can i put them in there when they hit 1 foot tall? They all have at least 5 fingers per fan leaf on the canopy. As long as they produce at least 1/2 an ounce per plant, i'm fine with that. Anyone give me advice?