Autoflower Strain

You've decided to try out growing autoflowers and need more information on what specific lighting they require. Or, possibly, you've already tried experimenting with these beautiful strains and need a refresher to start progressing again.

Whatever your reason, rest assured you've found the right guide, and we're here to lend a helping hand. Today, we plan to cover all types of lighting, lighting cycles, and necessities that best suit your strain and cultivar. In addition, we want to ensure your plant grows healthy and is ready to harvest quickly!

Are there lights that are better for autoflowers?

Regarding autoflowers, generally, there isn't a "best light" for these specific strains. However, we discussed in previous guides how resilient these guys are. And if you so desire, you can grow them with only sunlight and on whichever lighting cycle you choose.
Maybe you have experience with photoperiod cannabis and its sometimes strict regimens. It may not be too far of a stretch to consider providing your autoflower with the specific spectrum it needs during each growth stage.
When a daily plant is vegetative, growers typically use blue lights (400 to 550nm). And when it enters the flowering stage, growers will transition it to reddish-yellow lights (550 to 700nm).
Applying the same lighting techniques used on photoperiod strains with autoflowering strains is perfectly acceptable.
The benefit of providing blue light during the vegetative period is that it aids in their growth. This process helps produce a shorter and stocky healthy plant. In addition, offering your plant reddish-yellow lights during the flowering stage promotes budding and results in larger dense flowers.

Which light cycle is best for autoflowers?

Regarding autoflowers, the consensus with most growers is that the optimum lighting range is between 18 to 24 hours. This is because light cycles are determined by hours of light versus darkness. An example would look like this: 18 hours of light and 6 hours of darkness (18/6).
With autoflowering plants, there are four basic lighting schedules routinely used by most growers depending on their cultivar:

  • 24/0
  • 20/4
  • 18/6
  • 12/12

We will go more in-depth about these lighting cycles and the benefits each provides. But remember that though these are the more common cycles, what works best for your plants may differ.
Feel free to choose or adjust a lighting schedule at your discretion. But remember, if you decide to adjust from one cycle to another, be sure to do it gradually. You don't want to overly stress your plant or plants. As long as your autoflowers receive 12 hours at minimum, you will receive the best results.

Do autoflowers require darkness?

Before we dive into the types of light schedules, there is one topic we would like to discuss. In some of our other guides, we talked about how autoflower strains are a derivative of the strain ruderalis.
However, they were bred with either a sativa or an indica, making them stronger than their ruderalis lineage. And autoflowers do not rely on darkness to flower due to their genetic makeup. So some growers believe a 24/0 cycle works just fine.
In contrast, other growers claim that not providing a dark period will decrease the plants' overall health. This, in turn, can lead to shorter plants and lessen their overall harvest.

Types of lighting cycles

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

24/0 lighting cycle

If you will grow your autos in a colder climate, a 24/0 lighting schedule is recommended. You will leave your HPS or LED lights on 24/7. Which, in turn, keeps your plants warm and removes the need for a timer.
Typically, the more light a plant is exposed to, the faster it grows. So this process allows your plant to develop quicker and diminishes 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 can tend to be a bit more pricey. However, this is why it is suggested for growers who use it out of necessity.


  • No need for a timer
  • Potential for higher yields


  • It can be expensive due to higher electricity usage

20/4 lighting cycle

Quickly becoming the more favorable amongst autoflower growers is the 20/4 lighting cycle. This is because it offers a medium between the 18/6 and 24/0 cycles.
This lighting schedule is ideal while you're not spending as much on electricity as you would with a 24/0 cycle. You also give your plants some rest they wouldn't receive on a 24/0 cycle.
Compared to the 18/6 cycle, the 20/4 schedule gives your plants more light time. And as we just discussed, more light means faster growth. So if you place your autos on a 20/4, you will likely experience optimal yield results.


  • Reported better results in comparison to the 18/6 cycle
  • Allows your plants time for rest


  • Higher energy usage in contrast to 18/6

18/6 lighting cycle

The 18/6 lighting schedule is the most frequently used cycle for autoflowering strains. It is also recommended for growers new to growing with autoflowers.
Probably one of the best things about this cycle is that it's great for growers who live in hotter climates. Those with experience using the 18/6 suggest keeping your lights on during the night. And to save on energy, you can keep your lights off during the six hottest hours of the day.
Growers have reported that this lighting schedule uses up to 25% less electricity than previously mentioned cycles, with minimal electricity use and more rest time for your plants. The 18/6 method seems to be one of the most economically efficient and healthy ways to grow autoflowers.


  • Ample rest time for your autoflowers
  • Saves the most on electricity out of the cycles mentioned thus far


  • Having a timer is essential for this lighting cycle

12/12 lighting cycle

Traditionally, the 12/12 lighting schedule is used for photoperiod plants. Growers use the 12/12 method to grow photoperiods alongside their autoflowers.
That said, this cycle is not recommended if you're solely growing autoflower strains. We previously mentioned that, at minimum, your autoflowers should receive 18 hours of light daily. If you're not provided your plants with at least the bare minimum, they will not grow to their full potential.
Remember, the lighter your plant is exposed, the more it will grow. So on a 12/12 cycle, autos will end up smaller and produce lesser yields.


  • Great for when growing both photoperiod and autoflower strains together
  • Least amount of electricity usage, suitable for growers on a budget


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

Things to consider when deciding on a light cycle

We've discussed the pros and cons for each cycle discussed today. However, it's not hard to see why the top-recommended cycles for autos are the 18/6 and the 20/4.
Even so, there are still some other topics to consider when deciding which light cycle best suits your needs. So let's take a closer look at some we've mentioned below.

Temperature concerns

Remember your location's typical climate temperatures when deciding on a lighting cycle. As mentioned in the 24/0 cycle, it best suits colder climates. And again, the 18/6 cycle is best suited for hotter climates.

Overall cost

The light cycles discussed today touched on a few with higher energy costs. Growers with experience know that energy costs are just one of the many things to consider in your overall budget.
Keeping your budget in mind is always a good rule. In addition, it's essential to factor in any costs that might occur before and during your growth op.

Your schedule & time management

If your decided lighting cycle doesn't require a timer, your schedule plays a significant role here. Time management is a necessity for all growers. Be sure to prepare whatever your day-to-day schedule might be with the tasks that come with growing.

Wrapping up our guide on the best autoflower light cycle

Overall, there is no "best lighting cycle" for your autoflowers. Accurate, some 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've got this knowledge under your belt, it's time to put it into practice. Experiment with which lighting cycles work best for your plants. Heed our advice while you do so that you don't stress the strain. Who knows -- an uncommon lighting cycle may be the most ideal for you.