Inbred cannabis strain seeds

Cannabis Breeding Techniques (Advanced)

Are you interested in breeding your own cannabis strains? With all the incredible genetics available today, there are more opportunities than ever for breeding new strains.

Evolution of the Cannabis Plant Through Selective Breeding

Let’s take a look at an example of the power of selective breeding.

Here’s some of the top 40 strains according to High Times magazine in 1977

Here’s an assortment of some of today’s strains

Now some of these changes are because of different growing practices, but a lot of the changes have to do with genetics and what people have been breeding for over the last several decades.

Over the last few decades, many growers have been selecting for high-THC and “psychedelic” effects, big plump buds with big yields, shorter flowering periods, pretty colors and overall looks. Recently there’s also been many people breeding high-CBD strains for medical users.

But in addition to the percentage of THC or CBD, there’s a lot more to the overall effects of cannabis. There are many cannabinoids and terpenoids that we haven’t studied, and these all can change what effects the buds will produce. Some growers are starting to breed for other traits besides color or THC/CBD levels, paying more attention to the nuances of different strains and their effects.

For example, some cannabis enthusiasts enjoyed the cannabis they got back in the 60s or 70s, and miss certain effects from older strains. While these strains may not have been as high in THC or as “pretty” as famous strains today, they had other pleasant mental or body effects.

Luckily for breeders, many heirloom and landrace genetics have been preserved through seeds. Some seed breeders like ACE Seeds and Cannabiogen offer some interesting genetics from landrace and heirloom strains.

These days, there’s so much opportunity to grow buds that produce the exact effects you want. Growers everywhere have access to huge seed banks full of diverse genetics, both new and old.

Landrace & Heirloom Strains

Generations of growers before us have traveled the world finding landrace strains of cannabis, so that we all get to benefit from a huge pool of genetics for our breeding programs.

A landrace strain is a local cultivated strain; a strain which has been developed by local residents of that area.

So a grower might visit an area where the local growers have a unique strain of cannabis. Sometimes their local strain has new desirable traits you haven’t seen before (a particular color, taste, smell, potency, etc).

Many growers will take seeds to grow themselves. A landrace strain collector might bring back dozens of seed so the genetics of these local strains are preserved. These seeds are then mixed with other breeding stock to capture those traits in new plants.

Many famous cannabis breeders travel around the world to find unique landrace strains to bring into their breeding programs.

The strain Panama (shown below) is made from three heirloom strains:
Panama ’74, Green Panama & Colombian “Punto Rojo”

There are many phenotypes that show up in mixed heirloom strains like this, and unique genetics you may not be able to find in most modern strains.

Case Study: The Ruderalis Plant

A famous example a local plant that rocked growing world is the “Ruderalis” plant. People might not consider it a landrace since it doesn’t seem to be actively cultivated by local growers, but it is a local plant that’s been mixed into many breeding programs around the world.

In the wild, Ruderalis is a small, scraggly wild cannabis plant that grows in extremely cold climates with short summers. The buds aren’t potent and the plants are scrawny, but these plants had one very important trait – the ability to “auto-flower” after just a few short weeks, regardless of light schedules.

Here’s an example of two Ruderalis plants in the wild (pic taken in Russia)

this amazing pic is from the Canada CannabisClub™

Unlike most other strains, auto-flowering strains are not dependent on light schedules. Instead, they start growing buds and are ready to harvest in just a few months no matter what happens.

At some point, an enlightened grower realized that this auto-flowering trait could be useful to growers. Yet the wild Ruderalis strain would never be useful to growers in its original form, as it had low levels of THC and the buds were tiny. So breeders began crossing auto-flowering strains with quality high-potency cannabis strains.

Original crosses created relatively small plants with low potency, but growers have continued to refine and stabilize auto-flowering strains. Over the last decade or so, many breeders from around the world have been working together to isolate the auto-flowering trait in plants that produce high-potency buds and big yields. By continuously breeding the Ruderalis plants back to potent cannabis strains, we now have strains that have kept that auto-flowering characteristic, but are just as potent as modern strains (we managed to “breed out” the phenotypes that didn’t produce good buds or growth patterns).

Now there are numerous stabilized auto-flowering strains that are just as potent and beautiful as any other strains, and several breeders now also carry an auto-flowering version of their regular strains.

Here’s an example of a modern auto-flowering plant (Dutch Passion AutoMazar ↗) about 2.5 months from seed. This pic is just after harvest and the plant ended up producing about 4 ounces of high-quality bud.

It doesn’t look anything like it’s wild cousin anymore, does it? And the potency and effects of high-quality modern auto-flowering strains are now about the same as photoperiod strains.

In just a few years, breeders were able to take a scraggly hemp plant and breed out everything except the auto-flowering trait. This gave breederd the power to create potent auto-flowering strains around the world.

As a breeder, you have the power to identify specific traits and then incorporate them into your strains, leaving behind everything you don’t want.

Overview: Breeding New Cannabis Strains

First off, why make new strains? Because each new strain has the potential to bring something new to the growing world which has never been seen before.

Just like many strains now have different effects than popular strains from years ago, you could create strains that are better for you than anything available today. You can even take older heirloom strains and create unique strains that no one has ever experienced.

Every plant is a little different, and when someone grows a seed, the resulting seedlings will have a mix of traits from each of their parent plants. As different plants are bred together, people can select to cross only their favorite plants. They can create new combinations that produce unique and wonderful effects.

Over a few generations of picking the most desirable plants for breeding, new seedlings will show more of the specific traits you’ve selected for, and less of the traits you’ve selected against.

This is basically how new strains are born, though there are several special techniques (explained below) to help you get to your goals as quickly and efficiently as possible.

Traits to possibly select for when breeding

One of the first things to consider is “what am I trying to achieve by breeding?” There’s millions of breeding combinations that could produce all kinds of crazy buds, but each breeder has different goals.

Growth Patterns – does the plant grow tall or short, long & lanky, short & bushy, how long until harvest (length of flowering stage), yields, etc

Hardiness – how fast plants tend to grow, resistance to mold or root problems, whether it can stand heat or cold, how strong the stems are, etc

Buds – Smell, Color, Appearance, Perceived Effects, Potency, THC or CBD levels, etc

The bigger your pool of genetics (the more plants you have to choose from), the easier it becomes to find specific traits that you want to include in your breeding program.

For breeders, it’s exciting to live in a time when there is an abundance of genetics available to anyone with a mailing address, whether you want to try the new popular strains or find an old heirloom strain to create something new.

This is Nepal Jam, a strain carrying heirloom genetics; it was made from a cross between a Nepalese Highland sativa x Jamaica ’85 strain

Unfortunately most breeders can’t grow dozens or hundreds of plants at a time, so it’s helpful if you have other growers willing to grow your seeds out and let you know how the plants turn out.

As growers breed together plants of known strains, they are able to develop new and interesting strains that carry the best traits from the parents. As time goes on, this process of artificial selection creates plants that look nothing like their ancestors.

Growth Patterns & Hardiness

Figuring out the hardiness and vegetative growth patterns of a plant is relatively easy. You simply need to observe plants while they’re growing.

But some traits are much more difficult to stabilize than others, especially when it comes to the buds themselves.

Unfortunately, the more you focus on one particular trait, the less you can pay attention to other traits. Color is a great example of a trait that’s somewhat difficult to breed for because of this reason.


Colored strains are very popular these days. Purple and pink buds are especially popular, but when it comes to color of buds, it’s difficult to stabilize a strain so that 100% of offspring are the same color as desired.

One problem with trying to stabilize a color, is it can cause breeders to pay less attention to how the plant grows, how buds smell, and what the effects will be.

That’s why it’s important to pay attention to all traits in a breeding program! Don’t only pay attention to color.

In order to preserve the other desired effects (potency, smell, etc), growers may sometimes include genetics that don’t produce colored buds. As a result, many colored strains that you get today will have some plants that produce color, while other plants of the same strain will make buds that grow green. Some strains are stabilized to almost always produce color, but sometimes these strains are lacking in other ways because the breeder paid more attention to color than effects.

When it comes to color, it’s important to understand that the color of buds doesn’t have anything to do with cannabis potency. It’s simply a visible trait, just like how many flowers come in different colors. Purple cannabis buds can be ultra-potent, or they can be “meh.” The effects produced have to do with the breeding/genetics and growing style, not the color.


Smell is a subjective thing. Each person has a different reaction to different smells.

And to make things more confusing, every cannabis bud produces a bouquet of many different smells. Because of this complexity, it can be difficult to “lock in” a certain smell in a strain, especially smells that are recessive traits. Without any way to actually “measure” the smell, you have to rely more on your personal feelings and gut instinct.

It can several generations of trying different crosses and seeing the results before growers are able to produce plants that tend to smell like something new.

Yet we’ve got strains that people agree smell like pineapple, blueberry, strawberry, bubble gum, sandlewood and more. It’s definitely possible to breed cannabis strains that produce unique new smells that add to the whole cannabis experience.


Some growers test for THC and CBD levels, and these can be very important traits for medical cannabis patients.

But in addition to THC and CBD, there’s a lot of other aspects that contribute to the perceived potency and effects a strain will have on you. There are dozens of cannabinoids that we haven’t studied (and therefore don’t test for); there’s also terpenoids and other bud factors that likely affect the experience from using cannabis. Because of this, there’s no one factor that all growers should be paying attention to. What’s most important is creating a strain that you like.

When it comes to selecting for potency, I recommend choosing to breed the plants that produce the mental and physical effects you like. If you’re only breeding plants that you like, the potency will take care of itself and you’ll end up with better and better buds over time.

You don’t necessarily need to know the THC and CBD levels to know what you like

Terms & Tools of the Trade


Phenotype = Genetics + Environment

A “phenotype” is simply a list of all the various traits that you observe in a plant (how a plant grows, how the buds turn out, etc). You’ll likely hear this word a lot when talking about breeding cannabis strains.

People might talk about how a strain has a “tall” or “short” phenotype, or perhaps that some of the plants display a “pink” phenotype that grows pink buds.

Phenotypes are like the traits children get from their parents. Each child is a different phenotype. So YOU are a phenotype made from your parents, and each of your siblings (if you have any) would be a different phenotype.

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Imagine two parents; one is very tall and the other is very short. Each of their children could be tall or short. But if both parents and everyone in their family are tall, chances are their children will be tall too.

This is similar to how phenotypes work with plants.

Here’s a small sample of some ways cannabis buds can form – each displays a different phenotype

Here’s an example of two plants with completely different growth patterns in the flowering stage. Each of these plants displays a different phenotype in this environment due to the differences in their genetics.

“Unstabilized” strains carry more than one common phenotype (sometimes many). What that means is you can get two plants of the same strain, but they can display different phenotypes (they may look and grow completely differently from each other).

Some strains are more “stabilized” which means that all the seeds of that strain display the same phenotype. All plants grow the same way. This stabilization is accomplished by careful breeding to ensure that all seeds only carry genes for the desired phenotype.

But genetics isn’t the only thing that affects how your plants grow. Both the plant’s genes and the environment influence the phenotype that you see.

In fact, the environment plays a really big role in how your plants turn out.

Let’s say you take a clone of a plant (an exact genetic copy of the original). These plants will grow similarly in the same environment, but they often grow very differently in different growing environments.

For example if one environment tends to be cold, it might slow down the plant or even kill it, but that same plant might thrive in a warmer temperature. Some plants might do well with lower levels of nutrients, but have all kinds of problems with higher levels of nutrients. It depends on the genetics the plant inherited from its parents. A good breeder will know the environment their strain tends to perform best, and can help you understand how to get the most from each strain.

From now on, I’m just going to talk about specific traits that help make up the phenotype of a plant, since these are what most breeders are paying attention to.

Dominant & Recessive Traits

Some traits are “dominant” and some are “recessive”. This means that your plants can sometimes be carrying “hidden” traits which won’t show up unless you breed together two plants that both carry a copy of the hidden gene.

So for example, you could take two plants that grow green buds, but some of their offspring could produce pink buds. This means that the parents were carrying genes that can make pink buds and this recessive “pink” trait was brought out in their offspring.

Ultra-Quick Rundown of Mendelian Genetics & Inheritance

Knowing a little bit about genetics and inheritance will give you a huge advantage in your breeding program.

The first thing you need to know is that all plants (and animals) get two version of each gene, one from each of their parents. The interaction between the two versions of a gene can have a huge effect on your plant.

Mendelian genetics examines how plants and animals show different phenotypes depending on their genes.

So lets start by looking at dominant and recessive genes. Certain genes have complete dominance, which means they always “take over” if the plant has even one copy of the gene. Recessive genes will only show up in the phenotype if the plant got two copies of the same recessive gene from each of its parents.

The figures below show examples of Mendelian inheritance. This is super-simplified, but could help you get a better understanding of dominant and recessive genes.

Complete Dominance – Let’s say that cannabis plants can have a “red” or “white” version of a gene that controls bud color. The red version is completely dominant, and the white version is recessive. That means that (with these genes) the plant can only shows buds that are either red or white. It doesn’t “mix” them.

Let me give you an example with a diagram. “R” is the dominant gene in the diagram below. What that means is if a plant carries any copy of the “R” (red) gene than the buds will be red. The buds will only be white if the plant gets two copies of the “W” (white) gene. Let’s look at what happens over 3 generations if a plant with two “R” genes is bred with a plant that has two “W” genes.

Mendelian Inheritance Example – Complete Dominance

(1) Parent generation
(2) F1 generation
(3) F2 generation

You can see that the first generation (F1) above would produce only red flowers since all the offspring would get at least one copy of the “R” gene. But if you crossed those F1 plants together, you would get about 3 reds to every 1 white since you’d start getting plants that received two copies of the “W” gene.

But in many cases, genetics are not that simple. Not all genes follow the dominant-recessive pattern. Often it’s not a case of genes being only “on” or “off.” They may interact with each other to form new combinations. And to add to the confusion, certain traits are produced by the interaction of dozens or even hundreds of genes.

Incomplete Dominance – Let’s look at an example where the genes have incomplete dominance over each other. In these cases neither version of a gene is “dominant.” Instead they partially affect each other.

So what does that look like in practice? The next diagram shows an example of incomplete dominance.

Just like the above example, we start with two plants, one with two version of “R” (buds turn red), and the other with two “W” genes (buds turn white).

But this time both genes display “incomplete” dominance – it’s not that the offspring will show just one version or the other, but actually a mix of the two.

This time, when a plant gets one copy of “R” and one copy of “W,” the flowers will actually turn pink.

Neither version of the gene is completely dominant, so they influence each other creating a “mix” of the two versions of the gene.

Mendelian Inheritance Example – Incomplete Dominance

(1) Parent generation
(2) F1 generation
(3) F2 generation

In this case, the first generation above would produce only pink flowers since all offspring would get one version of each gene. But if you crossed those F1 plants together, you would get a 25% chance of getting white or red, and a 50% chance of getting pink flowers.

But so much more can be affected by genes than just the color of cannabis buds. Smell, taste, mental effects and more are all affected greatly by the genetics of a plant.

One of the best ways to discover interesting hidden or recessive genes in your gene pool is to first cross your starting plants, and then cross their offspring together or “backcross” with their parents to see if new traits appear.

Once you’ve identified a trait you’d like to keep, then you can start crossing that plant with other members of its “family” until you’ve figured out which plants you need to breed together for their offspring to always show that particular trait.

Over time, growers can develop a whole “suite” of new traits that can be consistently bred from their genetic stock.

You may enjoy learning more about genetic inheritance. A great tool to help you visualize dominant and recessive traits is the Punnett Square (shown above) to help you predict how a particular plant cross might turn out. There are other inheritance factors, such as non-medelian inheritance and epigenetics, that can also affect how your plants grow.

Stabilizing Strains, Back-Crossing & Inbreeding

A stabilized strain produces consistent results from all its seeds. To accomplish this, you must manipulate your genetic stock via breeding and back-crossing until you get a set of parents that consistently produce offspring that all grow the same – almost like being able to deliver clones in seed form. With a stabilized strain, growers know exactly what to expect when growing a strain since all seeds grow the same way.

“Back-crossing” is a powerful technique to help breeders stabilize strains. Back-crossing is when you take a plant or animal and cross it with one of its parents (or possibly another closely related family member). The idea is to create offspring which are genetically similar to the desired parent. Each offspring from a backcross is more likely to carry two versions of the desired parent’s genes.

So for example, let’s say you cross two cannabis plants. The mother plant has a trait you like (like a great body “stone”). You can take the male plants from her offspring and cross them back with the mother plant. This gives you offspring that are more like the mother (have more versions of her genes), and therefore are more likely to pass the trait (great body “stone”) to the next generation.

Some growers refer to the back-crossing process as “BC” or “BX” (B = back and X = cross).

As a result of back-crossing, you can “lock in” desirable traits from a specific plant so the strain consistently produces plants that grow the way you want.

Heavy back-crossing causes heavily inbred plants. This can sometimes result in bad recessive genes getting locked in (if a plant gets two versions of a “bad” gene, than it will suffer since it doesn’t have a “better” version of the gene to fall back on). This is how inbreeding can go wrong.

Inbreeding can also result in healthy uniform plants which tend to produce consistent offspring. The “good” type of inbred plant is an asset to breeding programs because you can easily predict some of the traits that will be passed on to the next generation. Heavily inbred plants carry two identical versions of many of their genes, and therefore will consistently pass only their particular version of each gene to all their offspring. If a plant has two identical versions of the “W” gene, for example, than that means all their children will get at least one version of the same “W” gene. This can be used to predict traits in the offspring before you even cross your plants.

When to backcross? If you like how a particular plant grows, that’s when you backcross. You’re trying to “lock in” certain traits into your genetic pool. By backcrossing, the offspring become more like the parent, and more likely to pass those traits on to the next generation.

Unless you plan on creating heavily inbred plants, you generally only need to backcross once or twice to get the genetic stability needed to start developing a new strain.

Excited yet? Let’s talk about your own breeding program.

How to Select Male & Female Plants for a Breeding Program

Female Plants – It’s relatively easy to select for female plants in a cannabis breeding program. You simply grow the female plants out and wait for the results. If the plant grows well and buds are good, keep it! If you didn’t like how this particular female plant turned out, trash it!

Note: Some growers will take a great female plant and cross it with itself via feminization to back-cross the single plant more effectively and quickly than by using its offspring. Some growers will also cross two different female plants, skipping the process of finding males altogether. Some growers are against using feminization as part of the selection process of a breeding program. These growers believe that by forcing female plants to make pollen sacs for feminization, you may be unintentionally selecting for hermies (plants that show both male and female plants). The jury is still out on what’s best, though many breeders have strong feelings either way. Most growers seem to agree that male plants are an important part of every long-term breeding program.

…But it’s a lot tougher to know what genes are carried by male plants since they don’t produce buds. You can’t know what “bud traits” a male plant will produce until you start breeding it with several different female plants and look at the offspring.

Through the slow process of breeding males and looking at the offspring, breeders can identify particular male plants that are great at producing certain traits in their female offspring.

Male Plants – Proven male plants are probably some of the most prized and important parts of any cannabis breeding program. The reason is that male plants are “silent carriers” for the genes that produce buds. The only way to know for sure what traits a male plant will pass onto female offspring is to breed it with different known female plants and see how the offspring turn out. After a lot of testing, a grower can create or find a male plant that is known to give desirable traits to its offspring.

For example, you could find a male plant that tends to make offspring whose buds smell like blackberries. Even though the male plant never grows buds at all, it is silently carrying the bud trait of smelling like blackberries. This type of knowledge can be extremely useful if you’re trying to cross a male with your female plants.

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The process of picking males for a breeding program is time-consuming and you’ll need to keep great notes about each offspring of a male plant in order to learn what silent traits the male plant is carrying for its female offspring.

Harness the Power of Hybrid Vigor (Heterosis) & “F1” Crosses

When you take two unrelated, heavily inbred plants and breed them together, you end up with something known as “heterosis” in the offspring.

Heterosis happens when breeding two plants that are…

Heavily inbred (gone thorough several generations of back-crossing and/or breeding between closely related plants)

Unrelated to each other (they don’t share any known ancestors)

Heterosis can sometimes be used to increase yields, uniformity, and vigor of the plants. When this happens, the result is known as “hybrid vigor.” Offspring from the same parents with hybrid vigor tend to grow the same as each other; plus they can grow faster, be stronger, and/or produce bigger yields than either of their parents.

This effect will only happen for the first generation (“F1”) cross between the two inbred plants. If you breed F1 crosses together, they will no longer experience hybrid vigor. It only happens with the first cross between two heavily inbred plants.

Sometimes an F1 cross between two unrelated inbred plants can produce undesirable or surprising results, but growers are often rewarded with better vigor and uniformity from F1 crosses.

You can use hybrid vigor to your advantage once you’ve identified a great F1 cross. If two parent plants create an awesome F1 cross, some growers will keep the “mother” and “father” plant so they can use them repeatedly to breed and make more seeds of the same F1 cross. This ensures that all the offspring get to benefit from hybrid vigor, plus they’ll all grow the same as each other. Some “strains” are actually a specific F1 cross between two parents that produces a desirable result every time.

For example, the strain “Aurora Indica” (↗) is actually an F1 cross between a specific Afghan x Northern Light plant. These same two plants are bred over and over again to make more Aurora Indica seeds. As an F1 cross, all Aurora Indica plants get to benefit from hybrid vigor.

The “hybrid vigor” technique is used in many types of plant cultivation, not just for growing cannabis. A familiar example is with corn. Most of the corn people eat today is an F1 cross. Since the 1940s, many of the most popular “strains” of corn are actually the first-generation hybrids made from inbred strains. Each F1 cross has been chosen because it produces specific traits, for example yield, appearance and hardiness. The F1 attribute helps ensure that all the resulting corn looks/tastes the same, and is ready to harvest at the same time.

The growers of corn have found a great F1 cross that produces better results than any individual strain on the market. Notice how the F1 offspring seems to be better than its parents in almost every measurable way. By crossing the same two “parents” every time, corn breeders know that every one of the F1 offspring will perform the same way, get similar yields, and be ready to harvest at the same time. That’s the power of hybrid vigor!

Are you ready to start searching for your own perfect F1 cannabis cross?

Breeding New Cannabis Strains – Step-By-Step

Important! Always label every plant or clone! It’s surprisingly easy to lose track of which plant is which, especially if you are working with a lot of plants

Choose Your Male & Female Plants – whether you’re backcrossing, creating an F1 hybrid, or just crossing two great plants together, you need to first decide which two plants will become your “parent” plants. The rest of this article should help give you ideas on how to choose the best parent plants for your goals.

Separate Males & Females – After you’ve decided which plants you want to breed together, keep males separate from females throughout the grow process (or remove males at beginning of the flowering stage). No matter what, make sure males are separated from females as soon as male pre-flowers (small pollen sacs) appear. Make sure that no pollen from the male makes it to the females without you doing it yourself, or you will end up with seedy buds of unknown genetics.

Collect Pollen from Males – Wait until pollen sacs are well-developed before collecting pollen from the desired male plant.

• Not sure when to collect pollen? This picture will show you what mature pollen sacs look like, as well as what the pollen will look like.

• You can take a ziplock bag, place it around the stem and shake to get the plant to release pollen into the bag. If you can’t use it right away, save any pollen in a sealed ziploc bag in the freezer. Fresher pollen is better, and many growers recommend throwing pollen away after a month.

Pollinate Females – Female cannabis plants are ready to be pollinated a few weeks after they first show signs of white pistils. At this point there will be individual buds forming, but the hairs/pistils will still be white. It’s important to avoid pollinating the wrong plant, so before you start, isolate the female plant from other plants and turn off any fans. Take the ziplock bag full of pollen and gently place over a stem with several buds forming. Seal it at the base so no pollen can get out. Carefully rotate and shake the bag to cover buds with pollen. Leave bag on for an hour or two, then carefully rotate and shake bag again. Wait two more hours then carefully remove the bag.

Care for “Pregnant” Mother Plants – Make sure to provide mother plants with a good source of nutrients, including more nitrogen than what’s included in most “bloom” nutrient formulas. It may be helpful to switch to a “vegetative” nutrient schedule to make sure seeds get what they need during the seed formation process. Seeds should start forming a few weeks after pollination, and will be busting out of their heavy calyxes several weeks after that. If you need to keep the seeds for a while, save them in a cool dark place (but don’t freeze them).

Plant Seeds – Germinate your seeds and see how they grow. Do they grow fast or slow? How do the buds develop? How long is the flowering stage? Smell? Taste? Potency? It may be helpful to keep clones of all your plants just in case one of them happens to be a real winner. That way you can use it as part of your breeding program indefinitely.

Keep Records! To breed successfully, one of the most important things is to keep great records. Write down which plants were bred together and how their offspring turned out. This lets you keep track of traits that show up in the parents and offspring. This will also help you create new strains because you’ll be able to know what traits to expect when breeding certain plants.

“Making stable hybrids relies on the ability to test-grow as many offspring as possible in each new generation, in order to assess how desired qualities are passed on and decide whether a strain is ready or needs more fine-tuning.”

~Sensi Seeds

To help keep track of what genetics are contained in each plant, many breeders have several growers testing out their strains and crosses. This helps provide valuable information about what phenotypes are showing up for particular crosses. It’s difficult for most breeders to grow and study hundreds of plants in different environments, so having people to grow out your strains and report back gives valuable information for your breeding program.

No matter how you choose to do it, always be testing your plants and getting feedback from other growers! This helps alert you to any negative phenotypes that must be “bred out”. For example if certain plants produce offspring that don’t smell/taste/give effects the way you want, you’ll know that the parent plants carry a phenotype that should be bred out of the gene pool so that no growers unexpectedly get those traits.

On the flip side, you might learn about wonderful new traits that you didn’t realize were there in the genetics of your parent plants.

Most importantly, breed plants you like!

You are now armed with the information you need to create your breeding program and develop your own strains! You could be the next famous breeder and cannabis cup winner!

Bonus! Neat example showing recessive traits.

From source kamyo: “This is a cross consisting of Ducksfoot/AfghanErdpurt x Ducksfoot/Pakistani Chitral Kush. The webbed leaf trait of ducksfoot is recessive and will rarely show in F1 hybrids of ducksfoot/non-webbed plants. In this case, two F1 hybrids were crossed, and it was estimated that maybe 25% would show webbed traits. That estimate seems pretty accurate, but it might even be more than that. Just thought it was worth showing different phenotypes that can show from the same parents.”

Cannabis Genetics 101: Stabilising a strain

Procedures to stabilise cannabis strains are poorly understood, even by breeders producing commercial strains. Stability refers to the variability and predictability found in the offspring of a parent generation: when a strain is unstable, variability will be high and predictability low; with a stable strain, the reverse is true.

Variability & predictability

Variability in this case refers to the range of different phenotypes that will express when hybridising two different strains; predictability refers to the expected distribution ratio of the different phenotypes. When crossing stable parents, Mendelian inheritance dictates that: 50% of the offspring will resemble both parents equally, 25% will express traits closer to the mother and 25% closer to the father.

Usually, breeders will stabilise a strain over several generations. First, a healthy mother and father are selected, and bred to produce hybrid offspring that will be of varying predictability depending on parent stability. Hence, if the mother and father are both considered stable, their offspring would be expected to express three phenotypes as outlined above.

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Stable vs. true-breeding

It is important to note that ‘stable’ does not equate to ‘true-breeding’. A true-breeding strain is one that will produce consistent offspring of one dominant phenotype (with few to no specimens unlike their siblings); in cannabis, these are usually found among the landraces and traditional cultivars. Further, breeders may use the term true-breeding to refer to single traits that will always recur (such as purpling or webbed leaves), rather than for overall phenotypic expression.

Mendelian inheritance at its most simple – 25% of offspring have the type AA, 25% are aa and 50% are Aa

Stable parents usually produce predictable, homozygous offspring, although with a greater degree of variation than found in true-breeding strains. However, if one or more parents is unstable, crossing them together results in a range of heterozygous offspring that can express any number of unpredictable traits, and which will not correspond to predictable Mendelian ratios.

The traits that are dominant in each parent are recombined to provide the genetic basis for the next generation. The initial crossing of two unrelated parents is known as the filial-1 (f1) hybrid. Usually, the best examples of the f1 hybrids will be crossed to produce the f2 generation, which is usually even more unstable than the f1.

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Crossing & back-crossing

With several generations of crossing together brothers and sisters from the same parents—selecting on the basis of desirable traits—a greater degree of consistency and therefore predictability can be achieved. Desired traits become dominant and will always appear, while undesirable traits are gradually eliminated from the gene pool and are no longer expressed.

For some traits, back-crossing plants to previous generations allows traits to become stabilised more quickly. Many breeders erroneously believe that some degree of back-crossing is necessary to stabilise any strain, but in reality this technique is only required for certain characteristics.

Inbreeding depression

After crossing and possibly back-crossing for several generations, the desired traits should begin to express in all individuals. However, after many generations of essentially limiting and reducing the gene pool so that only desired traits express, the resulting paucity of genetic material can lead to a level of inbreeding that is detrimental to the overall health and sustainability of the strain.

Put simply, if two related parents both carry the same recessive allele, which happens to be defective or otherwise deleterious, the chances of two identical copies passing to the offspring are far higher than with unrelated parents. If two individuals carrying these faulty alleles then breed with each other, the undesirable trait will be dominant and breed true in all subsequent generations of the lineage.

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Outbreeding for improved diversity

For this reason, when strains begin to experience such severe inbreeding (known as inbreeding depression), it is common to introduce a new, unrelated father in a process known as outbreeding.

Inbreeding depression will occur more slowly if there is an abundance of genetic material from which to form new offspring. Therefore, with smaller population sizes, inbreeding depression can occur rapidly. This is especially common in countries with a strong cannabis-using culture that have not decriminalised the means of production, such as the Netherlands where small libraries are maintained due to risk of discovery.

Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.


47 thoughts on “Cannabis Genetics 101: Stabilising a strain”

Thank you so much for sharing this wonderful post with us.

Good afternoon Salvador!

Thanks for your kind words, you are very welcome!
You might also enjoy our article on Selecting Phenotypes: From Seed to Mother Plant

Thanks again, and have a great day!

You really do not understand the breeding process Do you.

This article explains a lot about why European cannabis strains SUCK.. They have no idea what they are doing!!

Good morning Wolf,

Thank you for your comment,

Really fantastic information can be found on site.

I’m commenting to let you be aware of what a amazing experience my friend’s child experienced checking your blog. She learned such a lot of things, including what it is like to have an amazing helping nature to let other individuals very easily know precisely some hard to do topics. You truly exceeded people’s expectations. Many thanks for supplying these warm and friendly, trusted, informative as well as unique tips on that topic to Tanya.

Well sounds like true going with mother nature and jamaica

99% of everything written here is crap. Get your facts straight.

Well said! Kudos

Wouldn’t feminized seed production count as back-crossing? Of course it would. How many generations before inbreeding depression sets in? 3? 5? Some growers are headed toward a brick wall.

Thanks for sharing this knowledge. Just getting a grasp on breeding. Lots to consider, track and log and “TIME”
Cant help but hear @MotherNatures points about Sun Rain wind Organic outdoor altruism but science doesn’t stop.

thanks for a great article

as far as breeding goes,can feminized plants pollen if there sprayed with the silver collidal spray and collected and then used to pollinate another feminized plant create only female seeds?in theory ..

Imagine that the plants are people.
First, you have sex with a sibling. F1.
Then, your inbred offspring do the same. F2.
And then those even more inbred offspring do the same again. F3.
Imagine how genetically superior we could all be, completely severed from Nature.
How beautiful. How potent. Really ??
Stabilized hybrid horticulture is a good example of how myopic, greedy and sick humans have become.
And yes, stabilized hybrid cannabis culture started here at Sensi Seed Bank. Yes, you are the experts.
I have been growing organic, open pollinated cannabis outdoors for 40 years, growing with Nature, not against it.
My weed is sweeter, higher and genetically stronger than any inbred mutant will ever be.
When you take away the Sun, take away the earth and the wind and the rain and abuse the sexual integrity of the medicine, all you have left is a drug that makes you even more stupid than you already are.
Nature knows best, You can work with it, selective breeding is natural, progressive. Engineering a genetic cul-de-sac is not.

So true. Nature took care, is taking care, and will always take care. Humans only pollute.

you are a toxic person

you are too…..if you think your not, think again.

Well said! Kudos

Working outdoors with landraces, with nature, is my preference – predictability, surprise, variation, observation, selection all satisfy and reward. Explore the flow.

Coot? is that you…? LoL love alonee

this article helped a lot towards my knowledge of breeding and creating a reliable strain with only the best genetics, I had a general idea but wasn’t sure. I’m going to be crossing some really bomb strains, like cup material

Talking of genetics becomes very complex. Although the mendelian square is a good ground to start, we are truly opening up a diverse selection of many different allele that are either closely related or situated upon differing loci upon the DNA strand. The combinations of these allele in pairing can either be expressed or switched off depending upon the allele itself. The back crossing becomes the stabilizing element, and even introducing a completely different strain can produce a hybrid of stronger growth and bigger yield. Creating a phenotype that breeds true having characteristics that are desired is a very lengthy process and careful thought along with detailed notes to review so as to deeper understand the process involved which is hidden in the genetic coding. Letting natural selection to take place without any human intervention then the phenotypes revert back to their original strains. I learn this from breeding show guppies.

I dont think ANY of you know what youre talking about. Great speculation though!!

send me your email bro, if you really do this and you’re good at it and you know about it we can help each other out. I breed the best strains and select only the best phenomes, mostly the afghan indica dominant phenomtypes of all my strains

Tony I have some landraces Afghani s there beautys,,also got an indica dominate strain thats insane Blueberry headband x Green Poison indica dominate..I m still learning the whole breeding thing but always looking to talk to good people..

Successive selfing and selection of desirable phenotypes that are as identical to the founding mother as possible works toward stabilizing a strain.

Each generation will carry less and less undesirable genetic characteristics as those that do show up are removed from the breeding project.

Once the strain is reduced to as near a true breeding line as one desires the project can be called complete.

If the breeder desires the near true breeding phenotype can be then back crossed to the original mother plant and the process completed again as many times as desired.

It should be noted that any out breeding or back cross to the original and desired phenotype will result in an increase in genetic diversity requiring additional breeder selection and removal of undesirable traits.

While this process involves much inbreeding, any negative results are likely to be easily identified and removed from future use. Once bad genetics are found and removed they are gone, this is ultimately a good thing.

hi Dear . i have question
if we have 2 Clones from 1 Single (superStrain)
and Trying to polinate one of them with using collodial silver for sexing with other one ? what is future results ? can this seeds apear Exactly as mother-father plants?
can seeds have genetics problems?

Thank you for your comment ? Unfortunately we cannot respond to grow questions on the blog, but we do have the Sensi Seeds Forum where you can ask a thriving community of gardening fans for advice, share your experiences, and see if your question has already been covered. I hope this helps.

With best wishes

I have been growing cannabis for 15 years, received
about 30 seeds from a breeder friend o mine, most crap
seeds or died, 1 damped off small runt to darn, but the
3 seedlings I did grow are as follows. Plant#1 I broke the tap
root unfortunately, but has been fed organic liquid karma
i think has built a new tap root now, she is the best cannabis
strain i have ever seen in 15 years now, but is secret will not tell,
But i did name the strain CLEOPATRA is a pure indica though,with long fuzzy white hairs, at only 7 inches tall and
STINKS, will post up some photos
on the forums sometime, I AM THE ONLY PERSON WITH THIS INDICA
LIKELY EVEN THE NATIVE COUNTRY IT IS FROM DUE TO WARS ETC. Plant #2 She is a BERRY cocktail odor.they have been growin in 50% perlite,
and a 50% vermiculite mix I make myself, for ex. drainage,
Plant number #3 is a burnt rubber ORANGE, and is a MALE PLANT
I TRIM THESE WITH MY CLIPPERS, and they seedlings
start growing some what more normal for themselves.
I will take cuts of all 3 strains, Cleopatra is my favorite,
because of the plants odor which as i said is a secret,
and is the strain i have been searching for 15 years now,
i have never seen so much resin in a cannabis plant like
these 3 strains just really old clone INDICA STRAINS,


I couldn’t get through the first few sentences before realizing this dude is delusional. Lol.

I think it was one long run on sentence, i didnt see any periods.

I sure hope that,” secret strain ” didn’t cause the psychosis


Reading that tells me why my Cali connection GSC seeds are all so different. 6 seeds. 1 never cracked. 1 damped off (my fault), the other 4 are all totally different. CCs GSC seeds are crap! Beware!

I had a similar experience with Cali connection green crack. Phenos were all over the place. Most breeders don’t bother stabilizing their work and expect you to do the pheno hunting and cloning. I have only really had good luck with OG18 reserva privada. I’ve grown dozens of strains from seed and practically all of them have had multiple phenos.

It is so funny you guys actually arguing about stability, assuming the heredity mechanism is Mendelian.
~99% of the desired traits are quantitative, breeding and stabilizing is relevant in terms of populations, GWA, and is usually acquired by mass selection.

I am a grower out of oregon.Been growing for 20 years. Study cannabis botany for 5 years or more.I understood ur breeding medellain scale and it was thefirst time i saw that scale.u guys explained things well! Thank you!

Also this for ‘Why’. F2 is highly unpredictable n varied because it shows phenos of parents, grandparents plus great grandparents. F3-F5 wil also show recessive genes, once 7th generation is reached it should be fairly true-breeding providing good practice and selection is involved. If trying to create an IBL note taking and photos are a huge help.

Hey there, awesome read for those starting on a breeding project. Myself; i already understand most of that as am in the feild of horticulture, already have the basics of crossing and inbreeding and have successfuly done both producing both an F1 and linebreeding from stable IBL. Would like to see bit more on the outcrossing (namely using hybrids or ‘double-crossing’) and also on top crossing or ‘3-ways’.

How is an f2 that you choose a selected mother that will pass on desired traits become more unstable…..I’m sorry you choose a male that has similar traits then you would have a much more stable strain. “F2″&”F3” …..etc. Along with natural selection is how mother nature stabilizes strains…..wake up ppl and just observe nature

F2 and even subsequent offspring can easily be more unstable because that’s when recessive genes will appear. The first offspring of an unrelated pairing are F1 and if only one side carries a recessive gene it will carry on to a small percentage of the F2 generation. If both original patents carry a recessive gene it will show in a F2 generation but if only oneof the originals carries the recessive gene it won’t show in the F2 generation. So you’d have what you think to be a more stable strain until F3 and subsequent generations with low percentage of plants with wild genetic variants. It’s also a good way to find “hidden” recessive traits that you may desire in your strain but there is a give and take in every breeding between becoming more stable and inbreeding more recessive unwanted traits.