A Basic Guide to Autoflowers

A Basic Guide to Autoflowers

What is an Autoflower?
An autoflower is a plant that flowers regardless of the light cycles it receives - if you give it 24hr of light with no dark period it will still flower.

Autoflower plants came about from the introduction of cross breeding cannabis ruderalis to the beloved cannabis sativas and cannabis indicas that we enjoy. At first, most of the plants were small and lacked enough THC and CBD production to be considered ‘potent’ but they had the advantage of being able to autoflower. This changed with the introduction of the original LowRyder strain by The Joint Doctor. After its introduction, growers and consumers came to the realization that this new breed of autoflowering plants was capable of producing a decently potent product and decent yields (although still being relatively small plants). However, there was still room for improvement especially in order be accepted by mainstream growers of the time and subsequently a group of breeders dedicated work towards the improvement of autoflowers. Nowadays, there are plenty of autoflower genetics that can regularly produce upwards 20+% THC, and some even in the 25-27+% range, and plants that can easily get upwards of 6feet/1.8m in as little as 9-10 weeks from seed. Needless to say we have come a long way from some humble beginnings.

Pros and Cons
There are some advantages to a plant that flowers regardless of the light schedule it is given. When growing indoors, plants can be grown to harvest in a veg space, grown without the need for light timers, or grown in spaces that are not light tight (which would prevent photoperiods from flowering or cause stress to the plant to the point of unwanted hermaphroditism). Autoflowers typically finish in less time than photoperiods, with quite a few breeds finishing in 8-9.5 weeks from seed. Lastly, there can be a higher yield achieved in the same amount of time compared to photoperiods because autoflowers can be grown on longer light schedules (ie more energy can be provided to the plant). When growing outdoors, autoflowers can be harvested earlier due to there set lifespan, be planted at any point during a season (so long as they have time to finish), and provide for a couple of harvests per season. Autoflowers can also be grown in regions that are not conducive for outdoor photoperiod growth due to the shorter growing season (ie balance of light and dark periods).

One of the limitations of autoflowers is that it runs on a genetic clock. As such, there is less opportunity to resolve a problem during its growth period whereas issues arising from photoperiods can be resolved during the vegetative growth period. The genetic clock also limits the ability to veg a plant to fill a space or size before inducing flowering. Another limitation of autoflowers is mother plants and clones cannot be created due to the genetic clock. Clones or mother plants that are created would finish on the same time schedule as the original plant - autoflowers can only be grown from seed. As such, growers would need to either acquire more seeds or create their own seed (which I see as a good thing).

Growing autoflowers is the same as growing photoperiod plants but there are some helpful tips on how to get the most out of your autoflower plants. Autoflowers should be grown as smoothly as possible to avoid any growth issues. It is easier to adversely affect an autoflower due to its short lifespan, so it may be best to start new if there is an issue in the first couple of weeks. Autoflowers can take a punishment but the end yield and product will suffer.

Autoflower plants also should be started in their final container size in order to avoid transplanting. Transplanting can happen but, if it is not done early on, the plant can stall out due to limited root space which can result in a reduced yield or quality. Pruning and training can be done when needed but only sparingly, as any drastic changes can stunt the plants.

The standard light cycles for autoflowers range from 18/6, 20/4, to 24 hours. Plants will still flower with 10 or 12 hours of light however the yield will be reduced.

Seed Making, Breeding, and Different Autos
Autoflowers’ genetic trait is a recessive gene and this impacts seed creation. When breeding an auto with another auto, the recessive gene is carried over. However, when an auto is crossed with a photoperiod, 100% of the offspring from those pairings will carry both the dominant and recessive gene. The offsprings are crossed again and, in this second crossing, roughly 25% of those plants will be true autoflower plants.

There are two way to breed seeds. The standard is with Regular Auto genetics by using the pollen from a male plant to fertilize a female plant to produce seeds. Only a few breeders actually sell regular auto seeds, due to the lesser demand for regular autoflower seeds and because feminized seeds are more profitable.

The second and more common method is to make feminized seeds through the use of Colloidal Silver, Silver ThioSulfate “STS”, or other feminizing agent to force a female plant to produce pollen. This is different than natural hermaphroditism (do some research on the subject if you want to know more).

With the modern advent of autos, there are a few crosses or types that you should be aware of that are different than straight autos. “SuperAutos” are autoflowering genetics that have been bred to flower over a longer period of time thus allowing them to grow massive plants. These plants still retain the autoflowering gene which allows for longer light cycles.

Another breed, which is not actually an Autoflowers but use their genetics, are “Fast” versions that utilize the quick flowering rate to have photoperiods finish in a shorter time span than they otherwise (for example, 8 weeks instead of 10 weeks).

Choosing Reputable Breeders and Seedbanks
Reputable breeders and seedbanks are important and not all breeders are equal. Quite a few ‘breeders’ enter the autoflower market to try and grab market shares with bulk market seeds and seeds that they have had little part in breeding, typically with genetics that are random at best. Customers expecting autoflower plants may run their plants for 8-10+ weeks before realizing that their plant is not an auto and thus having to induce flowering like a photoperiod plant.

My opinion, you should support the companies and breeders who actually put the work and dedication into breeding their own auto genetic lines and not just an auto version of their Photoperiod counterpart. I would recommend Mephisto Genetics, Sweet Seeds, and some Dutch Passion Auto’s. I haven’t tried every breeder out there but I am confident in saying that they are excellent places to start.


Autoflowers and my personal story on why i made the switch.

Quite a few years back, I wanted to re-approach this hobby of growing with open eyes and without biased opinions that I once held. I set about learning anew or at least refreshing my knowledge on the subject as things change over time.

I had a veg chamber about 80% the size of my flower chamber but it was starting to nag at the back of my mind that it was only ever full when I had multiple mother plants, clones that were vegging, and new seed runs just going through the first couple weeks of veg. I consistently had left over space that wasn’t being used while keeping my flower space full. I started thinking about how I could use that space more efficiently and figured this would be an excellent time for me to try my hand at some modern autos.

I started to run a bunch of freebie autos that I had with mixed results. Some were straight up junk and others didn’t do well due to my own fault. Eventually after trying a few different breeders I went out and did some research on genetic lines that people were having good results with and decided to pick up a couple packs. I wasn’t disappointed, first plant that surprised me was a Dark Devil by Sweet Seeds. It sat off in the corner of my veg space and it proceeded to grow and finish in 8.5 weeks from seed and ended up yielding 25-35% more than the photoperiods I was running at the time such as C99, Bubblegum, Lemon Kush, Diesel hybrids, DP Blueberry, ect. I was intrigued, so after I got a decent cure on those buds, I did some sampling. They were good and the potency was no different than my photoperiods.

At that point I knew they were onto something and that got me thinking. I was on a genetic hunt at the time with the eventual goal of making my own crosses of the plant that suited me best. Realizing that that I could run plants 2-3 weeks quicker from seed than I could with photoperiods and yield more in that time. I said screw it and ran one of my spaces almost purely with autos apart from some mothers I was keeping. I was sold after that harvest.

To finish this out here are a couple shots of some of my micro grown autos I have done. Don’t shy off because they are micro grown, that’s just the way I choose to grow for my consumption.


So feel free to add your own info, history, or results that you have achieved. But lets keep this on topic and keep the basic questions unless they need to be asked to their own “basic growing” thread


some nice plants what was the best ?

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What’s best by one person opinion versus another person preferences can be very different. Whole reason why i recommended breeders, not specific strains, also i haven’t tried any where near all that’s available out there.

But a few of the ones i do like are Dark Devil, and Cream Mandarine by Sweet Seeds, Think Different by Dutch Passion when used in crosses i made but i didn’t enjoy it as much by itself, and Sour Crinkle by Mephisto currently, i need to make some more purchases, and will be making some crosses shortly.


you could always try an autoflowering version of a strain you’ve previously enjoyed.

@Mr.Sparkle have you ever ran an autoflower and photo version of the same strain (not necessarily simultaneously) and if so was there a noticeable difference besides expected variation in phenos ?

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I have not… actually maybe a cherry bomb, and i guess diesel hybrids but they wouldn’t of been the same either way with being hybrids.

There will be minor differences though just due to the introduction of an autoflowering plant that will pass over it genes, but how much of a difference that is ultimately dictated by the skill of the breeder and how many subsequent generations they bred that line out too in order to get the qualities they want.

From what i’ve read though of the ones that were bred well, there is very little difference between photoperiod and auto.


Yo @Mr.Sparkle how did the Dark Devil smoked man? I got some of those too i wanna grow…


It’s one of my regulars in rotation to say the least, i can not actually say qualities at the moment just cause i have been sampling a lot of other stuff i’ve run recently. It’s just a good base strain for myself that at least allows me to go out and do stuff and be constructive while still being somewhat level headed, not a knock you on your ass type, well unless i consume a lot, but its just a good strain for what i like and need, and has a nice smell to me, not your standard skunky weed smell which is good.

I have made a couple hundred * R1 * seeds in order to have it around for awhile, but i need to do some selective breeding with them to refine the pheno expression i want to keep.

Definitely worth the look for the price.

Edit: Ment R1 seeds not F1


I didn’t know they had Dark Devil in regulars… I thought only feminized autos…

EDIT, corrected the autos to fem autos.

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@MadScientist no they don’t have regular autos, i reversed a couple of the feminized seeds to provide pollen for their siblings, the horror i know lol


iv had the dark devil and bloody skunk the 2nd one i like better the dark devil smelled and tasted to much like lavenda but fk the colour that was the same on both my favs so far are the more mango and super skunk sort stuff i had humbodlt em dog didnt like it still havnt cracked the blue dream and green crack yet cant wait

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R1, did you just make that up? I assume you mean you reversed it. Technically still a F1, but I get your point. Any experience with Afterthough autos? Airbud seems like a pretty cool guy with my experience, but never ran his gear.


haha no i didn’t come up with that it’s just what some use to designate their seeds sometimes even though not correct terminology, and yes F1 “filial” is still correct , but labeling S1’s “selfed”, R1’s “reversed filial”, or BX1’s “backcross” or whatever on my own labels it at least helps me remember what the seeds are and how they came about without going back through my grow journals to know exactly the cross.

And i don’t know of that breeder, i’ll have to take a look


Moved the thread over to the Grow FAQ section.

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If growing say a regular common strain such as northern lights, from an original breeder; would CS still make regular auto seeds? Or would the seeds created be a regular seed mix 50/50 male/female?

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Colloidal Silver or other options are used to force a “Female” plant to produce pollen whether auto’s, photoperiods, regular, or feminized that doesn’t matter. But any other plants which would have to be female that are pollinated with that pollen will produce seeds that will be strictly female when grown out. Barring possible latent hermaphroditic issues that may be present in the original genetics.


Well said @Mr.Sparkle. Thanks bro!


it would make female seeds as they don’t have a Y chromosome in the pollen. it would not make auto seeds unless you were pollinating an auto with auto pollen


Crossing a reversed auto with a photo-period strain will result in some (roughly 25%) auto plants, some 'fast versions and mostly fem regs… hope this helps. Happy growing