Photoperiod vs. Autoflowers - Which One's Better?

If you've wondered whether to grow photoperiods or autoflower plants, here's an article explaining why autoflowers are certainly better.
19 May 2021
9 min read
Photoperiod vs. Autoflowers - Which Ones Better?

  • 1. ¿qué son las plantas de cannabis fotoperiódicas?
  • 2. What are autoflowering cannabis plants?
  • 3. What are the differences between photoperiod and autoflowering cannabis strains?
  • 4. In conclusion

La industria del cannabis está evolucionando más de lo que cualquiera podría haber imaginado. Con las nuevas variedades, concentrados y aceites que salen al mercado cada día, tienes muchas opciones. Pero una pregunta que surge constantemente en la mente de todo cultivador es: ¿fotoperiódica o autofloreciente? ¿Cuál debería elegir?

El debate entre las fotos y las autos no es nuevo. Los cultivadores han tomado partido y las discusiones se suceden por todas partes. Aunque puedes cultivar ambos tipos, el objetivo es elegir algo más eficiente. Y este artículo te ayudará a hacerlo. Las automáticas rendían muy poco, pero hoy en día se pueden encontrar variedades automáticas que pueden rendir y producir tanta resina como las fotos en poco menos de 9 semanas, lo que permite cultivar en exterior durante todo el año.

1. ¿Qué son las plantas de cannabis fotoperiódicas?

El término "fotoperiódico" aparece en cualquier sitio de venta de semillas de cannabis. En pocas palabras, el fotoperiodismo es la medida de la luz a la que está expuesta la planta. Cuando se habla de una planta fotoperiódica, se tienen en cuenta los ciclos de luz y oscuridad. Esto sucede porque las plantas de cannabis fotoperiódico sólo empezarán a florecer cuando tengan al menos 12 horas de oscuridad, lo que suele ocurrir en el exterior cuando llega el invierno o cuando se cambia a 12/12 en el interior. So, when you see a number such as 24/0, for instance, it typically means that the plant gets 24 hours of light and 0 hours of darkness.


Photoperiods vs autoflowers: what are photos?

Main characteristics of photoperiodic cannabis.

In other words, it’s as simple as the sun rising and setting. Most photoperiod cannabis strains will flower when they receive at least 12 hours of darkness as it happens in the wild. Growers let the plants grow for a certain duration in the vegetative stage. Usually, the plants run on an 18/6 cycle with 18 hours of light and 6 hours of darkness. However, the plant will continue to grow and refuse to flower until the season or light cycle changes. And this is why growers alter the light cycles and switch to 12/12 with 12 hours of light and 12 hours of darkness. The plants start flowering only when they receive a signal indicating that the season is changing.

2. What Are Autoflowering Cannabis Plants?

Unlike photoperiod plants, autoflowers don’t depend on seasonal changes to begin flowering. After the plant develops a few branches, it begins to flower “automatically”, which is why they are named autoflowers. Suffice it to say that autoflowers will flower no matter what conditions you provide. Getting only 12 hours of sunlight? No problem – autos will still flower. Wanna complete the entire grow with a 12/12 cycle from start to finish? Sure! Autos will perform the same.


Photoperiods vs autoflowers: what are autos?

Main characteristics of autoflowering cannabis.

Although autoflowers tend to grow fine with less light, they use light to produce food. Therefore, autos grown in an 18/6 cycle generate more yields than those grown with minimal light. This means that you can grow autoflowers indoors under any light cycle you prefer or outdoors all year long but the quality and quantity of your harvest will be affected by the amount of light your autos get. Now, you can grow autos under the following light cycles:

  • 12hrs of light and 12hrs of darkness:
  • Or 18hrs of light and 8hrs of darkness;
  • Or 20hrs of light and 4hrs of darkness.

But have in mind that you will definitely have better yields and more resinous buds when growing under 18/6 or 20/4 but you can still get a decent harvest if your plants get 8, 10 or 12 hours of light per day.

3. What Are The Differences Between Photoperiod And Autoflowering Cannabis Strains?

The primary difference between photoperiod and autoflowering plants is the exposure to light where autos flower automatically. We already got that out of the way. But, there are other differences and we will discuss them below.

Autoflowers are fast

Autoflowers are regarded for their speed. Most autoflowers take only 2 months from seed to harvest whereas photoperiod strains need at least 4 months to complete their cycle. This is one of the reasons beginners choose autoflowers. For example, if you grow a photoperiod strain, it needs at least 8 weeks in the vegetative period to grow to a certain extent. Once the grower is satisfied with the growth of the plant, he can shift the plant from the vegetative to the flowering phase by altering the light cycle.


Photoperiods vs autoflowers: seed to harvest time

Autoflowers usually take between 7-11 weeks from seed to harvest while photos can take up to 16 weeks!

Autoflowers, on the other hand, start flowering as soon as they turn 4-5 weeks old. They are so fast that the grower needs to keep up with it; however, after a few harvests, it becomes incredibly easy because it’s as simple as sowing the seeds and forgetting about it. So, given a choice between smoking the buds in 3 and 5 months (including curing period) which one would you choose? Autoflowers take 3 months and photoperiod plants need 5 months, and if you need something fast, autoflowers strains are definitely ideal for you.


Photoperiod plants take a long time to flower. They take more time to grow, and naturally, they grow bigger. On average, they grow up to 5-6 feet indoors. Outdoors, they grow as big as 9-10 feet. This is one reason why they need to be trained mandatorily. For instance, if your Grow Room lacks vertical height, growing photoperiod plants is not an option unless you train them using several training techniques.


Photoperiods vs autoflowers: size

Autoflower and photperiod cannabis plant size comparison.

Even if your Grow Room is about 8 feet in height, lights and other equipment will reduce the height, thereby forcing you to choose smaller plants. Autoflowers are genetically smaller. With such rapid flowering, an autoflower can grow up to 2-3 feet indoors while growing up to 5 feet outdoors. For growers with small grow rooms, autoflowers can be a blessing in disguise. Since the plants are smaller, they are perfect for stealth grows as well. Training techniques such as LST and topping can be used to get better yields.


Photoperiod plants need to be maintained right from altering the light cycle to training the size to prevent uncontrolled growth. It can be maddening if you don’t install a timer. Also, photoperiod plants cannot handle light leaks at all. This is why some growers hesitate to make their own Grow Rooms because it’s a little difficult to build a grow room with absolutely no light leaks at all. But, what happens if there’s a light leak, you ask? Well, for one, a light leak can stress the plant and force it to turn into a hermaphrodite full of seeds. Since you want sensimilla buds with no seeds, a light leak is out of the question. As you can understand, you need to be precise with photoperiods and there’s no margin of error especially when it comes to the lighting.


Photoperiods vs autoflowers: manteinance

How well photos and autos handle training.

Also, the plant reduces yields considerably if it’s stressed, so it forces the grower to constantly worry about light leaks and other factors that stress the plant. Coming to autoflowers, they are super hardy. Although every single day matters when they grow, they don’t need to be maintained much. Yes, it’s true that it’s easy to stunt an autoflower if something goes wrong early in the vegetative stage because they have a limited number of days, but they don’t mind light leaks at all. In fact, autoflowers can be set with one light cycle – preferably 18/6 hours – and they will simply do their thing even if you leave them alone.


There was a big difference in photoperiod and autoflowers when the first autoflower called Lowryder was released. Photoperiod cannabis strains boasted of at least 15 percent THC back then and autoflowers were no match for them.


Photoperiods vs autoflowers: potency

Nowadays you can find autos that are as potent or even stronger than photos.

However, things have changed, and how! The autoflowers released in recent years are every bit as potent as photoperiods. Take our Strawberry Banana Auto, for example. With over 27 percent THC, they are certainly as good as photoperiod plants. Some autoflowers exceed photoperiod strains in potency now! Yeah, that’s how far autoflowers have progressed!

Strawberry Banana Auto
4 out of 5
Delivery was a bit slow.... other than that I'm satisfied with the buying process. EVen got some freebies with my order which is always nice.
Verified customer
Reviewed 13 April 2021


Photoperiod plants are bigger – we have already established that. Obviously, the yields are more compared to autoflowers. However, don’t write off autos just yet because you can grow two autoflowering strains in the time required to grow one photoperiod plant. To understand this in detail, let’s go a little deeper. Most photoperiod plants produce an average of 600-700 grams per meter square whereas autoflowers generate about 450-550 grams per meter square. The yields increase if you grow them outdoors, regardless of whether they are photos or autos.


Photoperiods vs autoflowers: yields

Despite photos yielding a bit more, autos finish faster so, considering the time they take, it's pretty much the same.

Some photoperiod plants produce at least 400 grams per plant while autos yield up to 250-300 grams per plant. As you can see, photoperiod plants produce a bigger yield. However, if you consider the time required to harvest a photoperiod plant and compare the two, the yields are pretty much the same. Let’s say you grow photoperiod plants and yield 700 grams per meter square in 4 months. Within the same time duration, you can grow two batches of autoflowers yielding 550 grams per meter square per harvest. So, if you consider the time, the yields of the autos are higher than the photoperiod plants! Also, the size of the autos allows you to stuff more plants in smaller grow rooms, thereby producing more yields in the process.


Cloning is the process of creating another cannabis plant using one cannabis plant as the mother. Photoperiods have an advantage over autoflowers where they can be cloned several times. Therefore, a single seed can produce as many plants as you want.


Photoperiods vs autoflowers: cloning

Although you can clone autoflowers it's not recommended because the clones will remain tiny.

Autoflowers can be cloned too, but it’s a waste of time and effort since the clone is of the same age as the mother. So, even if you clone an autoflower, the resulting plant will begin flowering immediately and you’ll be left with a tiny plant yielding almost nothing.

Perpetual harvests

Autoflowers have an advantage over photoperiods where they can be harvested perpetually, as long as you want to. Sure, you can try the same with photoperiods but you will need two separate rooms for vegetative and flowering phases because the light cycles need to be matched appropriately. The same applies to cloning too. Even if you clone a mother plant, you’ll need to wait until the clones grow well to put them in the flowering stage. Why? Because you can’t push the clones into flowering stage immediately, and both the mother and clone will need to wait in the vegetative phase in an 18/6 cycle. This is why growers separate the clones and use different rooms for flowering and vegetative stages.


Photoperiods vs autoflowers: perpetual harvest

Autoflowers make it easier to have a perpetual harvest because you only need one tent to veg and flower autos.

On the other hand, autos don’t need separate rooms since they don’t need specific light cycles. You can sow seeds and tend to the seedlings just as one batch is about to be harvested, thereby saving you loads of time. Comparing both photoperiod and autoflowers, it’s easy to see that autoflowers match photoperiod plants in every aspect. Whether it’s potency or yield or speed, autoflowers have an edge over their counterparts. Having said that, it’s a matter of personal choice, but if you love smoking buds quickly, autoflowers beat photoperiods by a long stretch.

Differences Between Photos And Autos

 Average SizeSeed to harvestVeg. Light CycleFlowering light Cycle
Autoflowers60-100cm7-10 weeks18/6, 20/418/6, 20/4
Photoperiods80-200cm10-16 weeks18/612/12

4.  In Conclusion

What used to be low-yielding small plants have now evolved and improved a lot. Autoflowers had a bad reputation due to the first autoflowering strains such as the Low Ryder not being at the same level as photoperiod strains but nowadays you can find autos that are up to par with photos or even better. Good autoflowering genetics can grow super resinous flowers with huge yields, with THC levels reaching up to 27%, this plants allow you to grow top-quality flowers outdoors all year long and with a seed to harvest time of as littles as 7 weeks, making them a great choice for those who suffer with challenging climates or those who just want a quick turnaround time without sacrificing yields of bud quality. If you’re looking for good autoflowering genetics make sure you take a look at our catalog, with over 50 different strains that vary in size, potency and terpene profile, you will surely find what you’re looking for.

If you’ve grown autos and photos before and want to share your experience with fellow growers, feel free to leave a comment in the comment section below!


This post was most recently updated on May 18, 2021.

19 May 2021