What amount of days should I leave my light for the full 24 hours? At what point do I shift to 18/6 and then 12/12 for the marijuana plants to flower?
Marijuana plants in your indoor garden (and any garden) are all short-day plants. They enter the flowering stage when the amount of uninterrupted darkness reaches a tipping point (around 8 to 12 hours), which mimics the onset of autumn. If the marijuana plants don’t achieve this number of hours, they will stay in vegetative growth.
You can force flowering at virtually any time. So, there’s really no universal time schedule to start cutting back the light. Instead, you can determine on your own depending on their size. After forcing, you can expect to see an increase in height of about 1/3 to 2/3 depending on the variety.
You don’t really have to have an 18/6 regimen. This only serves to slow growth because a mere 25% reduction in light doesn’t encourage flowering. When the marijuana plants achieve an ideal size for forcing, shift the on-off schedule to 12/12.