Can be anytime you want. Some people switch to 12/12 when the plants are 3ft in height, some when it's 1ft in height. I have flowered a plant as small as 5inches when I switched to 12/12.

It all depends on your height restrictions, and if time is a factor or not, but of course, shorter veg. time means less yeild, so it's all up to the growers personal prefrences.
Nochowderforyou Reviewed by Nochowderforyou on . Average Time? on average how long to you vegitate before you switch over to 12/12 for flowering? i was thinking around 30 days or untill the plant was 1ft tall, once its in the flowering stage how long does it need 12/12 on average? Rating: 5