The amount of non-light hours or hours of darkness that you are providing to your marijuana plants depends a lot upon the phase of growth these plants are in. During the early stages, you can provide up to 2-3 hours of darkness, during peak vegetative phase, you can provide about 6 hours of darkness, pre-flowering would require 8 to 10 hours of darkness while flowering phase needs 12 to 14 hours of darkness. rn