Wait until you see preflowers.....usually around the 4th node.this is my first time and i cant figure out when to switch to 12-12... They have been in the soul 13 days. I am growing under a 1000w HPS light, on an 18-6 right now. please let me know if i can switch.
Listen to Dfunk. If they're clones you can flower anytime. If they are from beans I wouldn't go to 12/12 before preflowers show. In some cases they even triple in size too so consider your ceiling height/light fixture arrangement if you can't LSTI've come to the conclusion that his plants are clones. Flower when YOU want to & remember they will double in size so if you started 12/12 now they would probably be around 3' tall when finished.