s1 seeds

F1, F2, S1, IBL And BX: Deciding Which Plants Are Best To Breed Through Decoding The Genetics Of Cannabis

For cannabis cultivators everywhere, finding the best genetic composition and keeping those traits throughout the generations is the ultimate goal. It’s also the goal of cannabis growers to experiment with their plants by cross-breeding them, creating new strains with completely different attributes and psychotropic abilities. But how exactly is this done, and how can you benefit from understanding the basic genetics and nomenclature of cannabis?

How Do You Breed Cannabis Plants?

Cannabis breeding is usually a step left for experienced growers, so let’s start with the basics first. Cannabis seeds are bred when a male cannabis plant of one strain pollinates a female cannabis plant of a different strain. The genetics of the male plant are then crossed with the genetics of a female plant, producing seeds of what we refer to as a hybrid strain. To do this, you’ll need to set up a pollination chamber away from your other plants so there is no cross-pollination occurring. Your male plant will be guaranteed to pollinate the female plant, which will continue producing buds but will also be producing seeds as well.

Easy-To-Grow Cannabis Strains

The Basics Of Cannabis Genetics

If you want to breed cannabis strains into new hybrid seed types, it’s important to know what specific terminology is used when describing cannabis genetics and lineages. If you’re buying cannabis seeds to grow, this is also useful information to know so you can identify the exact strains from which your seeds have descended.

What Is Meant By F1?

F1 simply stands for “first-generation hybrid,” or the first generation of offspring from your initial mother and father plants. F1 cannabis seeds are the first generation of seeds produced from initial pollination. These are considered to be the most stable of hybrid seeds, as they haven’t yet been crossed with another breed of cannabis. This subsequent generation is what’s referred to as F2.

Pure Indica Cannabis Strains

The Difference Between F1 And F2

F2, or “second-generation hybrid,” is the second generation of seeds that are produced after your F1 cannabis seeds have flowered and had the chance to breed with its brother and sister plants of the same generation. Two F1 strains that have been bred together create the F2 seed hybrids, two F2 strains that are bred create F3 seed hybrids, and so on.

How Selfing Produces S1 Seeds

Female plants can produce S1 seeds through a process called “selfing”. Selfing is a chemically-induced process by breeders that causes female plants a certain amount of stress, resulting in them producing male flowers. These male flowers will then produce pollen, which pollinates the rest of the plant through self-pollination. Female plants that have self-pollinated will then produce what is known as stable S1 seeds, or seeds that have been “selfed”.

What Are IBL Seeds?

IBL seeds, or “inbred line” seeds, are in-bred descendants of the original F1 cannabis seed hybrids. The term IBL is typically adopted after the F line has reached F5. Successful IBL breeding occurs after so much hybridization between plants of the same lineage that the IBL becomes almost like a strain of its own variety, having been bred from plants with near-identical genetics. IBL seeds have most likely been bred together to preserve and maximize certain desired traits, such as the pungency of the Skunk family.

Skunk Cannabis Strains

BX: Explaining The Process of Backcrossing

Backcrossing in cannabis breeding is the process of taking an F1 hybrid strain and breeding it with the original parent plant. The genetics of the F1 strain are crossed with the parent plant’s genetics, and the resulting seeds are referred to as BX1. Backcrossing cannabis plants is essentially how to stabilize a strain – in other words, how to preserve and guarantee certain desired traits that are shown in a particular plant.

What Are Fast Versions Of Seeds?

Certain strains have been bred to possess the stable and reliable qualities of autoflowers, which are known as “fast versions” or “early versions” seeds. These are F1 plants that have been bred with a strain of Ruderalis, which is known to be a very sturdy family of cannabis. Fast versions are best for growers who are new to growing, or who want something that will produce cannabis very quickly.

Fast Flowering Cannabis Seeds

What Should I Pick?

In the end, you should choose the seed that is the most stable, meaning a seed with reliable genetics where you know exactly what you’re going to get when you plant it, such as an F1, S1 or BX. If you’re looking at breeding cannabis yourself, it all depends on what types of strains you’re looking to grow more of or whether you want to experiment with breeding plants through cross-pollination. Regardless, it’s important to know how each type of cannabis strain is formed and its genetic history so you can be aware of exactly what you’re smoking.

Making Sense Of Cannabis Terminology

Although it seems confusing on the surface with so many letters and numbers, understanding the basics of cannabis genetics and cross-breeding will help you in the future to decide what you want to smoke, what you want to grow and if ever necessary, how and what you’ll want to breed together to get exactly what you’re looking for.

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Have you ever seen F1, F2, S1 symbols while reading about cannabis? Do you know what all that letters and digitals mean? Actually, it is really important while choosing the best genetics (and that is what everyone wants). It’s also will be helpful if you want to experiment with your plants by cross-breeding them, creating new strains with completely different attributes and psychotropic abilities.

Basic Genetics Terminology For Cannabis

Our beloved marijuana strains are produced using several different breeding methods. Check out the terminology used to describe the unique genetics of different cannabis varieties.


Breeding cannabis is a complicated art that can be performed in plenty of ways. Here, we describe the common terms surrounding various cannabis genetics and how they came to be. We decided to keep it short and concise, as all the scientific minutiae can be very complex.


Landrace varieties originate from regions where cannabis plants have been growing for a very long time in the wild—centuries, or even millennia. This naturally creates stable, robust genetics that produce a homogeneous offspring. This means that the landrace strains from a particular area will develop very similar growth patterns, appearance, and chemical composition. Hindu Kush or China Yunnan are examples of pure landrace strains.

F1 stands for a “first generation hybrid”. When two strains with completely different genotypes breed, for example, a Master Kush with Durban Poison, their offspring will be an F1 hybrid. When this hybrid is bred together with another F1 hybrid from the same batch (a sister or a brother), it creates an F2 hybrid. When this process is repeated, it creates an F3, then F4, and so on. After F5, the plants can be considered as IBL.

IBL stands for “inbred line”, meaning that after several generations of hybridising a specific lineage, the strains become almost like a different family of strains. Skunks were hybridised and selected for their very pungent and potent nature, and after many generations, they developed into the Cheese family, which can be called an IBL.


Poly-hybrids derive from mixing completely different hybrids with each other. For example, Master Kush and Durban Poison produce offspring called F1(A); AK-47 and White Widow produce an offspring called F1(B). When F1(A) and F1(B) have a lovechild, it will be coined as a poly-hybrid.


Backcrossing refers to taking a hybrid strain and breeding it back with the original parent. For example, a male Chocolope and a female Jack Herer develop an F1 hybrid. When this F1 hybrid is hybridised with the original female Jack Herer, the resulting strain will be coined as BX1. When this BX1 gets backcrossed again with the original female Jack Herer, it will be coined as BX2, and so on. The genetics of the original female strain can be retained by keeping the plant in the vegetative stage as a mother, keeping the cuttings as clones or using tissue culture propagation.


Selfing is when a mother plant is pollinated by herself. Breeders use special chemicals on female plants to induce stress, which results in the plants producing male flowers, which produce pollen. When this pollen in used on the female flowers of the same plant or a clone from the same mother, the resulting seeds will be “selfed” or coined as S1. When the S1 seeds are backcrossed with the original parent, they’re called S2, S3, and so on. Breeders often do this to preserve the genetics of the strain, and to feminize the seeds.

Cannabis genetics are not all the same. We are here to clear up any confusion surrounding breeding terminology, from landraces to IBL.