Cannabis Autoflower Light Schedule

autoflower light schedule

Most cannabis growers agree that the ideal number of light to give to autoflowering cannabis strain is somewhere in the middle of 18 to 24 hours of light each day. But, as a cannabis grower, you must change the light schedule based on the strain you are growing. There’ only 3 life cycles or light schedules; 12/12, 24/0, and 18/6 (the first number is hours of light, and the second is hours of darkness). You could always change the cycle as long as they’re receiving over 12-hours of light every day. For instance, 22/2, 19/5, and 16/8. There are cannabis growers who are trying new schedules like 6/18, however, if you are a newbie grower you must stick to the simple schedule. Keep reading if you want to know more about autoflower light schedule, best grow lights for autoflowering plants, what is the best light schedule for autoflower, and when to start light schedule autoflower.

Best light schedule for autoflowers

What is the best light schedule for autoflower? Cannabis growers who are growing autoflowers don’t need to set the lighting time to 18 hours manually in the growing stage and adjust it to 12 hours daylight for flowering. This makes marijuana bloom automatically because of its genetics. And because autoflowering marijuana begins flowering only for 20-28 days after germinating and still in the flowering stage for the rest of its life cycle, it needs a different kind of lighting and adjusts at different times, unlike photoperiod marijuana plants. The preferred light cycle of growers of autoflowering cannabis strains is 20 hours of daylight and 4 hours of darkness every day. And the short growing period makes it needed time as effectively as possible and to boost the growing of the plants. Still, you might prefer to save money by adopting the autoflower light schedule which is 18 hours of light and 6 hours of darkness. This would also provide you a good outcome, particularly if you live in a location where it’s naturally sunny and hot as you would be allowed to turn off the lights in the hottest part of the day. 

Autoflower Light Schedule

18/6 Hours Light Cycle

Marijuana is a C3 plant, which means it could absorb CO2 for photosynthesis even during the light hours. You will normally wait to give your autos at least 18 hours of light, since autoflowering plants have a short period of vegetative stage and sometimes grow shorter than photoperiod cannabis strain. Without overspending on the energy, this allows for a fast growth. The autoflower loves light as much as the regular photoperiod cannabis strain, they don’t depend on it to start blooming. 

24 Hours Light Cycle

Some cannabis growers would even give their autoflowers a full 24 hours light, saying that it helps maximize the vegetative growth. Cannabis growers who withstand an 18 hours light cycle, in some cases, argue that this gives their cannabis plants a short “recovery” period that is important for healthy growing. There is no real harmony on whether autoflower grows better on 18 or 24 hours of light, and we have seen cannabis growers achieve great outcomes with both methods.

12/12 Light Cycle

Some cannabis growers still keep their autoflowers under a 12/12 light cycle during the flowering period, which is fine as autoflower grown in these conditions could still generate a fine harvest. Just keep in mind that the buds you are harvesting under a 12 hours autoflower light schedule would be smaller than what you would get under a 12 to 24 hours cycle.

Best Grow Lights for Autoflowering Plants

Fluorescent lights

One of the best grow lights for autoflowering plants, there’s a lot of fluorescent lighting choice from which to choose.


CFL are those twisting bulbs you possibly already have in your house. These can be bought at any hardware store. Their ability makes them a perfect solution for a stealth cannabis grower who does not want growing supplies on their card statement. The only negative here is that while every bulb has likely low power usage, you would need some bulbs to give enough light to grow cannabis. Power usage may reach more than 400 watts to produce enough illumination. 


T5s were being used for autoflower light cycles for a long time. Marijuana responds perfectly to the T5 light spectrum unlike CFL, and they are strong enough to grow a cannabis plant from seed to harvest. They are a little bit more easily seen than CFL, but it is not new for people to have houses ignited by T5 lights, particularly in East Asia. 


HID bulbs give a large quantity of light, and you will see it in your plants if you try to use them. They use the perfect scale of marijuana cultivation, and they also produce massive amounts of heat and use a great deal of more electricity than other alternatives. 

Metal Halide

Metal halide lights give the perfect blue scale for vegging marijuana plants, and it is often used for the length of a full-grown season, but many cannabis growers shift to HPS come flowering. 


Cannabis growers would sometimes shift to high-pressure salt lights for flowering after vegging under the metal halide. With regards to electricity used in every unit of energy for the marijuana plant, the HPS/MH blend is a great option. But, either of these lights is cheap, while they might be effective in comparative terms, they’d still use a good deal of power on the way, and you will see it on your electric bill. 


Growing autoflower with LED lights is best lights for autoflowering. LED is the perfect low-power solution for cannabis growers with small tents and growers with a stealth mind. Low-power consumption means you will hardly see an uptick on your electricity bills, and if you are only using one or two lights. Standard LEDs are giant arrangements of bluish purple lights that look like something from a movie. They’re not as effective as HID bulbs, but they’re low-power usage. The negative here is that the purple light ruins the havoc cameras, which means you will have to turn them off to get amazing pictures of your hard work. 


A chip on board grow lights are small LEDs that give an intense white light, this is one of the best grow lights for autoflowering. A single 100 watts cob light is sufficient to power a tiny grow room by itself and you would only spend $100. And if you are searching to grow on the cheap, COB is better than CFL in regards to power usage and just a little bit expensive. 


There’s really no proven best autoflower light cycle. But before going to any autoflower light cycle, consider thinking about the electricity bills and the climate you will be growing in. And if you’re in doubt, begin with an 18/6 autoflower light schedule. This schedule is mostly used by the autoflower growers. Once growing outdoors, you have to work with what you have because obviously you can’t control the sun. Outside growers must be aware that with the change of season the number of daylight might decrease or increase but autoflowers musht grow fine in all kinds of season.

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