If you’ve ever been interested in breeding your own cannabis, there’s no doubt you’ve come across terms like F1 strains, F2 strains, F3, and so on. So what is an F1 strain? What does it mean when you are getting a cannabis breeding program started and have F1 or F2 seeds? It seems like a confusing concept at first, but Wikileaf is here to take the mystery out of the terms and get you on a confident path to create your own stable strains. 

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Understanding F1, F2, F3 Generations

First off, what the hell does this F mean anyway? It stands for filial, which is of latin origin and means “the offspring of two parents”. We call the parents the P1 generation and their offspring the F1 generation.

different types of cannabis plants growing by a windowsill The offspring of 2 parent plants is called the F1 generation in the cannabis industry. Photo Credit: Shutterstock
When you cross two individuals from the F1 generation, you create an F2 generation. Two F2 individuals crossed together gets you an F3 generation and so on for F4, F5..etc. It's just a label breeders use to keep track of how many generations a cross has been bred down in an attempt to stabilize its traits. But what do these labels mean when you are growing them? At the most basic level you can think of it like puppies, as cannabis and canines are pretty similar... in terms of breeding. The momma dog and the daddy dog are the P1 generation and their batch of puppies would be the F1 generation. The puppies come out looking either more like the mom or more like the dad, or a mix of both. This is true for cannabis as well, for the most part. To better understand what F1, F2 generation seeds are, let’s take a look at old school cannabis in the Netherlands. 

Cannabis Breeding 

When the first Dutch cannabis seed banks started getting serious about breeding cannabis around the 1970s, they started with landrace strains. Cannabis indica from the mountains of the Middle East, and Cannabis sativa varieties from Africa and Asia as well as Central and South America. When used in breeding projects, these landrace strains represented the true P1 generation; they were from genetically isolated populations that had been inbreeding for a very long time. 

a large nug of Afghan Kush cannabis on a black background Afghan Kush, pictured here, is a very popular landrace strain.
If you had a batch of these landrace seeds, they would grow with similar traits like the plants you picked them from. These plants evolved for a millennia and adapted to their specific region's climate, making their genes dominant for the traits that help them survive. The Dutch were breeding true F1 hybrids by taking Cannabis sativa and Cannabis indica and crossing them together to make strains like Skunk #1

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F1 Strains

These F1 hybrids inherited the dominant genes from both their P1 parents. This is a genetic condition called heterosis, also known as hybrid vigor or overdominance. The result is a stronger, more robust plant with a higher potency and yield than the parents used to create it.  This original F1 generation is actually quite stable with little variation in traits, meaning if you planted seeds of Skunk #1, you knew all the plants from those seeds would have highly potent buds that smelled like they got sprayed by a skunk. It would be a relatively uniform and genetically stable batch of seeds. 

a small cannabis seedling sitting in a small black plastic container of soil F1 plants typically look pretty similar to one another. Photo Credit: Shutterstock
To help explain all this let's imagine a scenario: You’re stranded alone on a beautiful tropical island with ten of those original Skunk #1 seeds. With nothing else to do, you plant them all and get to growing. As those first buds appear under the tropical sun you notice how similar they look next to each other, in terms of structure, height and aroma.  Since you planted all the seeds you’ll have to make more for your next round. You cut out the males, but leave the strongest looking one to pollinate a few female plants. When harvest time comes, you get to enjoy some of the finest, most pungent and potent pot on the planet. You save the seeds and start to grow another crop. 

F2 Strains

Since you crossed a male and a female from Skunk #1 which is an F1 hybrid, you created an F2 generation. When you grow these seeds out you notice the plants look drastically different from one another. Some are way taller, some more short and stocky. They smell different from one another too. Some have that skunky funk aroma and some are more sweet and fruity. So what's going on here? Why are all these F2 generation plants so drastically different? 

two different cannabis plants next to each other, one green and one purple F2 plants tend to vary more in appearance to one another. Photo Credit: Shutterstock
In the F2 generation, a genetic process called “recombination” takes effect which remixes, in a sense, all the traits present that were passed on from the P1 generation. Where you had plants in the F1 generation that were relatively similar looking, the F2s are all over the place. Some are tall, lanky and take longer to ripen, a distinct trait from their sativa heritage. Others are short and stocky, and their flowers finish fast, a trait inherited from their indica lineage. Then other plants exhibit a new combination of these traits, tall and lanky but ripen quickly. Or a medium sized plant with larger buds with a longer flowering period that packs an aroma mixed of fruity sativa traits and musky indica funk. In this case, the existing traits from the P1s have been recombined in a new way, creating a unique phenotype. This is where the magic happens if you are trying to create a new cultivar. Just remember, in the F2 generation you are not creating new traits, just recombining existing traits in new and novel ways. Growing F2 generation seeds could be bad if you are not trying to breed your own cannabis. If you are trying to just grow a solid crop of buds that look more consistent, you’d want that original F1 hybrid generation seed. The F2 generation bud will just be too inconsistent due to recombination.  Some seed breeders used this to their advantage, knowing it's easier for someone to just buy their seeds again than it is to take the time to rebreed the genetics. But a dedicated and true cannabis breeder knows that after the F2 generation is where the selection work begins. 

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F3 and Beyond

Back to our tropical ganja paradise scenario, let's say you make F3 seeds by selecting the most THC potent male and female. In the F3 generation you see more uniformity in the traits between plants, with a handful of exceptions. If you took the highest THC plants from the F3 generation, and bred them together to make an F4 generation, you’d notice almost all of the plants were very potent. You have essentially created seed that bred true for high potency.  

Cannabis Breeding Take Away

This much inbreeding doesn’t come without some consequences though. While only concentrating on breeding plants with high potency, you might have neglected the fact that the higher potency plants yielded less and were more susceptible to diseases and mold. 

a green cannabis plant leaf, with orange hairs, with a spot of white mildew Breeding this way can potentially lead to consequences like powdery mildew on your cannabis plants. Photo Credit: Shutterstock
What's happening is a genetic condition called “inbred depression” when a population has been inbred enough that detrimental recessive traits like high susceptibility to disease start to surface. While creating a plant that breeds true for one trait, you might have unintentionally created seed that also breeds true for something unwanted. This is why it takes a keen eye with a wide lens to breed good, stable cannabis strains. There are lots of variables at play and unexpected surprises could possibly arise with every new cross. Today’s cannabis genetics situation makes it even harder to gauge breeding outcomes, as we are mostly breeding with the hybrids of hybrids.  Most F1 crosses made today have considerably more variation than those original F1 hybrids the Dutch made, because a large percentage of today’s cannabis strains share common parents in their lineage. If you’ve ever crossed two of your favorite strains you might have noticed the crazy variation and non uniformity of traits in the seeds produced in the F1 generation. This is because we are not using true P1 landrace parents, but rather breeding hybrids with hybrids. 

Wrap Up

For the aspiring cannabis breeder all these labels and terms can be a little daunting at first, but fear not. If you’re like most of us and don’t have access to landrace genetics, one way to insure a successful breeding program is to use seeds from reputable and experienced breeders that diligently track their strains' pedigrees. This way you can get a strong start down the path to creating your own amazing cannabis genetics.