when i have to set the timer and how manny hower's must be dark to start the flowering,my plants are 4 week's old 75 santimeters big and verry nice leaf's
start on a 12/12 cycle whenever you're ready to start producing buds/finding out the sex of your plants. I flowered at approx 1ft tall. you have to take into account the amount of space you have in your grow area because the plants will double or triple in size during the flowering period. so i mean if you got plenty of height then you could keep flowering. dont start 12/12 till you're ready. theres no set time. some people start after 3 weeks (which i did) others flower after 2 months or so. its really up to you and how much space you have!
my room is 3 m/2 and have not ventilation but have fan when is dark is necesery to have fresh air???when the light is on have fresh air....in the room have 6 plants,4 jack herrer and 2 withe widow....