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Best Light Schedule for Your Autoflower Strain

You decided to try grow autoflowers, and need a bit more information about the specific lighting they need. Or maybe you’ve already tried experimenting with these wonderful strains and need a booster to start making progress again.

Whatever your reason, rest assured you’ve found the right guide and we’re here to help. Today, we plan to cover all the lighting types, light cycles, and necessities that best suit your strain and cultivar. We want to make sure your plant is growing healthy and ready to harvest in no time!

Are there any lights that are better suited for autoflowers?

When it comes to autoflowers, there is generally no “best light” for these specific strains. We’ve discussed in previous guides the resilience of these guys. And if you wish, you are fully capable of growing them with just sunlight and whatever light cycle you choose.
Perhaps you have experience with photoperiod cannabis and its sometimes strict regimes. It might not be too much to consider providing your autoflower with the specific spectrum it needs at each stage of growth.
When a daytime plant is in the vegetative stage, growers typically use blue lights (400-550nm). And when she enters the flowering stage, growers will turn her into reddish-yellow lights (550-700nm).
It is perfectly acceptable to apply the same lighting techniques used on photoperiod strains, with autoflowering strains.
The advantage of providing blue light during the vegetative period is that it helps their growth. This process helps produce a shorter, stockier healthy plant. During the flowering phase, providing your plant with the reddish-yellow lights promotes budding and results in larger, denser flowers.

Which light cycle is best for autoflowers?

When it comes to autoflowers, the consensus with most growers is that the optimal light range is between 18 and 24 hours. Light cycles are determined by hours of light versus dark. An example would look like: 18 hours of light and 6 hours of darkness (18/6).
With autoflowering plants, there are four basic light schedules commonly used by most growers depending on their cultivar:

We’ll dive deeper into these light cycles and the benefits each brings. But keep in mind that although these are the most common cycles, what works best for your plants may differ.
Feel free to choose or adjust a lighting schedule at your discretion. Remember though that if you decide to adjust from cycle to cycle, be sure to do so gradually. You don’t want to stress your plant or plants too much. As long as your autoflowers are given at least 12 hours, you are sure to receive the best results.

Do autoflowers need darkness?

Before we dive into the types of lighting schedules, there’s one topic we’d like to discuss. In some of our other guides we have explained how autoflowering strains are derived from the ruderalis variety.
However, they have been crossed with either a sativa or an indica, making them stronger than their ruderalis line. And due to their genetic makeup, autoflowers don’t rely on darkness to flower. So some growers think a 24/0 cycle works just fine.
In contrast, other growers claim that not providing a dark period will reduce overall plant health. This in turn can lead to shorter plants and reduce their overall harvest.


Types of light cycles

We now know a little more about the types of lighting that are best suited for our autoflowering friends. Likewise, we learned the potential impact of the amount of darkness you provide them.
Next, we have the 4 basic light schedules growers recommend for autoflowering strains.


24/0 light cycle

If you are growing your autoflowers in a colder climate, a 24/0 light schedule is recommended. This means you will leave your HPS or LED lights on 24/7. Which, in turn, keeps your plants warm and eliminates the need for a timer.
As a general rule, the more light a plant is exposed to, the faster it grows. Thus, this process allows your plant to grow faster and decreases the time spent regulating the light cycle. Since you will keep your lights on until harvest time.
With that in mind, this particular light cycle may tend to be a bit more expensive. That is why it is recommended for growers who use it out of necessity.


  • No timer needed
  • Potential for higher returns

The inconvenients

  • Can be expensive due to higher electricity consumption

20/4 light cycle

The 20/4 light cycle is quickly becoming the most favorable among autoflower growers. Indeed, it offers support between the 18/6 cycle and the 24/0 cycle.
What makes this lighting program ideal is that you don’t spend as much on electricity as with a 24/0 cycle. You’re also giving your plants some rest they wouldn’t get on a 24/0 cycle.
Compared to the 18/6 cycle, the 20/4 program gives your plants more light time. And as we just said, more light means faster growth. So if you put your autos on a 20/4, you’re likely to get optimal yield results.


  • Reported better results compared to the 18/6 cycle
  • Allows your plants to rest

The inconvenients

  • Higher power consumption compared to 18/6

18/6 light cycle

The 18/6 light schedule is the most frequently used cycle when it comes to autoflowering strains. It is also recommended for growers who are new to growing with autoflowers.
Probably one of the best things about this cycle is that it is ideal for growers who live in warmer climates. Those with experience with 18/6 suggest keeping your lights on at night. And to save energy, you can keep your lights off for the hottest six hours of the day.
Growers have reported that this lighting program uses up to 25% less electricity compared to the previously mentioned cycles. With minimal electricity consumption and more rest time for your plants. The 18/6 method seems to be one of the most effective and healthy ways to grow autoflowers.


  • Sufficient rest time for your autoflowers
  • Saves the most electricity of the cycles mentioned so far

The inconvenients

  • Having a timer is essential for this light cycle

12/12 light cycle

Traditionally, the 12/12 light schedule is used for photoperiod plants. Growers tend to use the 12/12 method if they are growing photoperiods alongside their autoflowers.
That being said, if you are only growing autoflowering strains, this cycle is not recommended. We mentioned earlier that at a minimum your autoflowers should receive 18 hours of light per day. If you don’t provide your plants with at least the bare minimum, they won’t grow to their full potential.
Remember that the more your plant is exposed to light, the more it will grow. On a 12/12 cycle, autos will end up being smaller and producing lower yields.


  • Ideal for growing photoperiod and autoflowering strains together
  • Less electricity consumption, good for low budget growers

The inconvenients

Your autoflowers will not grow to their full capacity and will produce less overall

Things to Consider When Choosing a Light Cycle


We’ve looked at the pros and cons of each cycle discussed today. It’s not hard to see why the most recommended cycles for automobiles are 18/6 and 20/4.
Even so, there are still other things to consider when deciding which light cycle is best for your needs. Let’s take a closer look at some that we have mentioned below.

Temperature issues

When deciding on a light cycle, keep in mind the typical climatic temperatures of your location. As mentioned in the 24/0 cycle, it is best suited to colder climates. And again, the 18/6 cycle is best suited for warmer climates.

Total cost

With the light cycles discussed today, we’ve touched on a few that have higher energy costs. Experienced growers know that energy costs are just one of many things to factor into your overall budget.
Therefore, keeping your budget in mind is always a good rule of thumb. It’s important to factor in any costs that might arise, both before and during your grow operation.

Your schedule and your time management

If your decided light cycle doesn’t require a timer, your schedule plays a big role here. Time management is a necessity for all producers. Be sure to prepare whatever your daily schedule is with the tasks that come with growing.

Conclusion of our guide to the best autoflower light cycle


All in all, there is no “best light cycle” for your autoflowers. Certainly, there are some that will inevitably provide you with the best results for your plants. But as you can see, it all depends on your needs and desires as a grower. Likewise, the autoflower strain you choose can play a role.

Now that you have this knowledge under your belt, it’s time to put it into practice. Experiment with what light cycles work best for your plants. Heed our tips while you’re doing it, so you don’t stress out the tension. Who knows, an unusual light cycle may be the best fit for you.

Warning: This content is intended for educational purposes only. It has been compiled with research from external sources. it is not intended to replace medical or legal advice. Please consult your local laws for the legality of cannabis consumption.

#Light #Schedule #Autoflower #Strain

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