Chapter 3

Know Your Light Cycles

Light cycles are a big part of your home grow, but thankfully they get automated with the use a light-timer connected to your grow lights. You only need to remember two light cycles: 18/6 for VEG and 12/12 for FLOWER.


In VEG phase, use the 18/6 Light Cycle (24/7 lighting is OK, but expensive.)

18/6 means 18 hours of lights on and 6 hours of lights off. 24/7 means lights are always on and never turn off. I think the plants prefer 18/6, but don’t ask me for proof. While running your grow lights 24/7 in VEG is permissible, it’s also more costly. 18/6 light cycle is your best bet. 


In FLOWER phase, use the 12/12 light cycle.

12/12 means 12 hours of lights on and 12 hours of lights off. During the lights off hours, do not expose plants to light under any circumstances! Once you put your plants to bed with 12 hours of darkness, it must stay dark the entire time. However, it turns out that green LED lights are OK around cannabis flowers during their dark time. So, some growers keep green LED headlamps around just in case they need to be in their grow space during lights out, which mind you is a rare occurrence. During lights out in FLOWER, leave the flowers be. 


PLEASE NOTE: If you’re growing “autoflowering” cannabis plants from seed, only use an 18/6 light cycle in both VEG and FLOWER. The above mentioned lighting schedules are for clones, feminized seeds and regular seeds. Autoflowering cannabis seeds have started to gain in popularity over the past few years, but the vast majority of growers prefer feminized and regular seeds. 


As for HARVEST phase, there’s no light needed, as you should try to dry cannabis flowers in a grow tent or area without any light, or a room in your home that is dimly lit. Complete darkness is ideal, but not an absolute requirement. 


Marc Eden’s DIY Cannabis Cultivation Book For Beginners
Published by Green Carpet Growing, Inc.
San Diego, CA 92103
© 2021 Green Carpet Growing, Inc
All Rights Reserved

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