How to Crossbreed Cannabis and Create New Weed Strains (2024)

One of the best traits of cannabis is that it has thousands of different strains to choose from.

And there’s at least one that’s bound to be your favorite. This wouldn’t be possible without experts that knew how to crossbreed cannabis.

They not only created new cannabis strains they also improved its genetics. It’s through cannabis breeding that we now have high-yielding and potent plants.

And while marijuana breeding is a laborious process, it’s also rewarding.

Depending on the reason, you’re either rewarded with an improved strain or a new hybrid you can call your own.

Crossbreeding marijuana plants: How new strains are created

Before we answer the question of how to crossbreed cannabis, we need to understand why we crossbreed weed plants in the first place.

We breed cannabis genetics together to introduce unique strains. Many passionate growers try to learn how to crossbreed plants simply for the honor of creating something new.

Growers want to improve upon the strains of yesteryear. While it’s not a way to make last year’s top strain obsolete, a new strain can sometimes become the new favorite.

This is because most new strains offer different effects than previous strains. New strains can also introduce new and unique blends of flavor and aroma.

Outside of that, breeders also crossbreed cannabis to create robust strains.

By only breeding the most desirable plants, growers can introduce strains that are more resistant to diseases.

They can also use crossbreeding to create marijuana plants that yield more and have stronger effects.

Lastly, cannabis breeders will produce new strains simply because they want to. Often, new strains offer a unique experience when smoking and growing.

Creating new strains is also a good way of practicing cannabis breeding techniques.

It gives you a way to play around with genetics. Try crossbreeding an heirloom strain with a strain we have today to create a new and unique plant.

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Marijuana crossbreeding: Terms to know

Phenotypes

When talking about breeding cannabis plants, the word you’ll hear the most is “phenotype.” It refers to the list of traits that you can observe on a strain.

These traits range from how tall your weed plants grow to how much they yield.

Important note: phenotypes can either be unstable or stable. Unstable ones carry more than one common phenotype. You’ll see these as plants that grow with varying traits.

Backcross

To stabilize phenotypes, a breeder practices backcrossing. This process involves breeding a hybrid offspring with one of its parents. Doing so stabilizes the phenotype.

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Backcrossing is a repetitive process that takes a couple of generations before you see any results.

But, the time and effort it takes to backcross cannabis are well worth it. The resulting seeds will produce plants with uniform traits as if they were clones.

Stabilizing

Stabilizing and backcrossing are hand-in-hand with each other. Once you backcross your strain, it leads to a stabilized phenotype.

This means your strain will produce consistent results from all its seeds.

What can you stabilize? It can range from the usual traits such as how tall your plants will grow to the average yield they produce.

But, stabilizing a strain can also mean making unique traits (e.g., purpling) more consistent.

Why backcrossing is important for cannabis plants

When it comes to crossbreeding weed strains, backcrossing is a necessary process.

Without it, the hybrid you produce from its two parent strains will have an unstable phenotype.

This means you’ll have inconsistent results due to not having a common phenotype locked in.

And while it’s fun to see what different phenotypes your strain will produce, you’ll need to lock in your desired phenotype – especially if you plan to grow the hybrid you created.

Important: heavy backcrossing can backfire. Breeders can accidentally lock in undesirable traits into their hybrids.

This is because you’re using the same parent and crossbreeding it with its offspring. At one point, an offspring will carry a bad gene which continues in the next generation.

Dominant and recessive cannabis genetics

There is much to be said about genetics, but the important thing to consider is the presence of alleles.

They are DNA sequences that carry dominant and recessive traits. They mean your plants can have hidden traits outside of their visible phenotype.

For example, you cross two strains that produce blue buds but only 3 out of the 4 offspring grew blue buds.

The last one instead grew purple buds. Why did this happen? The parent strains both had purple buds as a recessive trait.

For dominant traits, it’s pretty simple. They take over the entire appearance of the plant if it even has one copy of the gene.

But, it’s not always the case. In some situations, the dominant gene instead has incomplete dominance over the plant. This leads to the dominant trait mixing with the recessive one.

When talking to breeders, you might hear them mention F1 and F2 generations when they’re discussing crossbreeding.

F1 is short for first filial while F2 means second filial. These terms refer to generations of crossbred plants, with F1 being the first generation from true-breeding parents.

On the other hand, F2 is the second generation produced by the first generation through self-pollination.

F1 usually has plants that express dominant traits more. In comparison, F2 may have more plants that express their recessive traits.

When backcrossing a strain, use your F1 plants to avoid locking in recessive traits.

How to breed cannabis strains

1) Select parents for your strain

Male Plants

Choosing the ideal male plant for crossbreeding is a laborious process requiring much testing.

There’s more to it than picking a robust male plant with an attractive aroma.

You also need to consider the ‘hidden’ traits that they possess. Male plants are often called silent carriers because of this.

The hidden traits are recessive genes. They will only appear if bred with a female plant that shares a copy of the recessive gene.

This is why selecting the perfect male plant takes a lot of time and effort – the only way to know the recessive traits of the male plant is by breeding it with females and growing the seeds produced from it.

You also need to factor in flowering time. When you’re mixing weed strains, you must choose a male plant that’s late blooming.

Fast-flowering males are often dominant when passing on their genes.

This is not ideal as it would produce offspring that resemble its male parent rather than the female.

Female Plants

Selecting the ideal female plant for crossbreeding isn’t as difficult as males.

You should prioritize females with a robust structure, large buds, and a healthy root system.

When selecting a female, you can also consider things such as aroma, flowering time, and taste.

And, of course, the effect and potency of the buds are also factors to include.

Desirable traits when crossbreeding

Potency

Potency is the most important trait when crossbreeding cannabis. The best way to achieve high potency is to select a female plant that produces flowers with high THC.

Appearance

When choosing traits for crossbreeding, appearance and potency are often at odds with each other.

Focusing too much on the color and shape of your buds might result in a less potent strain.

But, focusing solely on potency can result in a plant that produces unappealing buds. You need to strike a balance between the two when breeding cannabis.

Durability

Plant durability refers to how resistant a strain is to mold and pests. But it can also mean how strong the stalk and stems are.

Generally, you would want to crossbreed hardy plants together to produce robust offspring.

That way, they can handle high-stress and low-stress training, which are common practices when growing weed.

Growing behavior

It is the most important trait for your cannabis – second only to potency.

Growing behavior determines how much you yield per plant and how long the flowering period will last.

It also determines the kind of plant your hybrid will produce, such as whether you’ll get tall and skinny plants or short and bushy ones.

2) Collect pollen from male cannabis plants

The easiest part of crossbreeding is collecting the pollen from the selected male cannabis plant.

Because cannabis is wind-pollinated, you only need to shake the branch with male flowers.

Do this above a plastic tray or sheet of paper to catch the pollen. Be sure to wear a mask to avoid inhaling any of the pollen.

When gathering pollen from male plants, ensure that there are no open vents or windows for it to travel.

Once collected, store your pollen in a container. You should also avoid going near your female plants right after gathering pollen.
It can stick to your hair and clothes and accidentally pollinate your plants.

Remember: keep male and female plants separated.

3) Fertilize female weed plants

After gathering the pollen, dust it onto the flowers of your female plants – literally. The best way to apply pollen to your female plants is with a paintbrush.

How to pollinate your females:

• Select one of your female weed plants
• Paint the branches of your female plant with the pollen-covered brush.

Note: Do this process carefully if you’re trying to leave some colas unpollinated for sinsemilla.

The best time to pollinate your female plants is when they’re 3 to 5 weeks into flowering. By that point, the flowers of your female weed plants have fully matured.

Remove and plant the seeds

Once your female plants have been fertilized, let them finish flowering. When your buds are ready for harvest, the seeds in them will have fully developed.

And on harvest, you can either collect the seeds or keep them in the buds while you hang them dry.

When you have all the seeds collected from the buds, don’t plant them immediately.

They need another month before they’re truly ready to germinate. After waiting a month, you can now germinate and plant your seeds – which are now normal cannabis seeds.

That means male plants will also grow along female plants. Remember to keep those males plants to stabilize your new strain further.

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In summary

Seed breeding can take a lot of time (and effort) to perfect. But, by understanding the essentials of how to crossbreed cannabis plants, you have taken a step closer to making your own weed strain.

One last note, you’ll want to give your plants plenty of love – fertilized mother plants require extra nutrients if you want them to produce healthy seeds.

Not interested in all of that work? Why not purchase feminized marijuana seeds at my online store, ILGM.com.

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Confidently grow potent, proven strains or cross them with a male plant to create your own unique strain. Our forum can help with all your questions.

FAQs about cannabis breeding

What happens if my cannabis gets pollinated?

Rather intentional or unintentional, you’ll end up with cannabis buds with seeds. To prevent this, you must isolate male plants once you see one growing with your female plants. The same goes for hermied cannabis plants.

Can a male cannabis plant pollinate a female in veg?

No, there are no accounts of a flowering male pollinating a female marijuana plant that was still vegging. However, a male plant’s pre-flowers can pollinate a female in her flowering phase, which is why it’s important to distinguish the sex of your cannabis early on.