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

Last updated: 26 February 2024

f1 genetics

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.

fast flowering cannabis seeds

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 strain
F1 stands for "First-generation"

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.

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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

How Selfing Produces S1 Seeds
S1 stands for "Selfed”

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?

are s1 seeds stable
IBL stands for "Inbred line”

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.

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BX: Explaining The Process of Backcrossing

what does f1 generation mean
BX stands for "Backrossed”

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?

f1 weed

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.

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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Joh Carlos
Wow, cool information, top.
Hello Jon Carlos! Thank you for the comment - it's nice to hear you've liked the article :)
Sammy Nona
So once I am happy with my own IBL, I can send off a sample to some companies and they will test it and tell me all about it. Do you have any idea how much of a sample they will require and approximately how much it might cost? (They don't seem to want to reply to emails from a lowly bum like me.)
start reading
Hello Sammy Nova! Unfortunately, we won't be able to advise you on this matter, however we can recommend contacting a particular company and asking them for instructions, as we believe it all depends
Hi! Good info. Can you recommend a good book for a hobbyist interested in breeding, or even something more technical\ academic? Both? : ) Thanks!
Hello Jojo, here's the list of books you can find interesting: "The Bible of Grower" by Jorge Cervantes, "Marijuana Botany: An Advanced Study" by Robert Connell Clarke, "The Cannabis Breeder’s Bible: The Definitive Guide to Marijuana Genetics, Cannabis Botany and Creating Strains for the Seed Market" by Greg Green. We believe you'll find these books enjoyable
I sincerely appreciate your answer. I'll certainly check them out.
Thanks for the information
Herbies Seeds
Hello Husain,We're glad to hear you enoyed the article. We wish you the best of luck in your hobby!
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