Hi, I'm a new grower just going through materials before I start my first grow. I read at various places that giving light for 12 hours and then darkness for the rest right from the seedling will make the plant short , tiny and give very small yields whereas a 18-24 hour light during vegetative growth will make it bigger . But I've seen plenty of marijuana fields in the wild ( acres of it growing freely in the mountains ) and they seem to receive the same 12 hour light. Yet they are tall , bushy and give great yields. Why this difference between indoor and outdoors ? Does it have to do something with the strains ?
12 light 12 dark puts the typical cannabis into flower. It can grow like a mad raped ape, or stay short. 16-24 hours of light tends to make the plant grow a lot but light spectrum helps determine if the stems grow and the plant is tall of the leaves grow and the plant stays short. Cannabis Indica is commonly grown indoors and is a shorter plant. Cannabis Sativa is a taller plant and is well suited for outdoor growth.
What you need to remember about the plants you see outside is that they aren't under 12/12. With the changing of the seasons the days and nights change as well. Nights are longer in winter shorter in summer and depending on where you live the growing seasons can be super long or super short. For example.... most people in the northern hemisphere will put plants outside in April or May as the days start to get longer as spring kicks in and gradually turn to summer. These long days will promote vegetative growth causing plants to get big and reach for the sun as long as conditions allow. Around early to mid August days will start to go down hill and get shorter eventually hitting the 12/12 mark forcing the plant to flower and continue to do so until harvest. Indoors you control the changing of the seasons by controlling the photoperiod. So to answer your question. .. in theory yes if you put a plant immediately into 12/12 it should remain smaller than if you veg it for a month first. You still have to consider the genetics of the plant. Some plants will still stretch and gain size during flowering but I wouldnt count on it being anything that will get to out of hand.
12/12 from seed will work with a sativa as there from the equator where an indica wont enjoy it as much. Even with a sativa it wont yeild as much as if you gave it 18/6for 3-whenever weeks then flipped to 12/12 when shes 1/3rd on ya total height as plants can strectch 2-3times there height when ya flip http://forum.grasscity.com/index.php?/topic/1275211-Dutch-passion-Think-Different-and-an-auto-purple