It's recommended that your plants show pre-flowers before switching to 12/12, however this can take from 4 to 8+ weeks. You pretty much have to guess according to their size and the room size. When they fill 1/3 of the grow area, switch to 12/12.

Here's a nice guide that has pretty much all you need to know: Cannabis.com Growing Index
bigtopsfinn Reviewed by bigtopsfinn on . Rookie grower Hey guys, I'm new to the community. I am growing strictly for personal usage so as you read this realize that i do not care about 6+ ounces per plant. I want a minimal ounce per plant simply because i will probably smoke an ounce in a month and i will be rotating 4 plants flowering....2 veg...and 2 germ. The 4 Flowering will be a month a part. Currently i was waiting about one week before i transplant. And currently all i have is 4 plants with a batch germinating now. And the plants Rating: 5