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how to crossbreed cannabis seeds

Breeding cannabis requires quite a lot of space. You need a nursery and propagation area and different rooms for male and female specimens to avoid unwanted cross-pollination. Even more space is needed if you intend to start breeding polyhybrids over multiple generations starting with four inbred cultivars. If you intend to begin this process, you’ll need to learn how to pollinate your flowers in the correct way.

However, if an F1 hybrid cultivar is bred with an F1 hybrid cultivar from a different genetic line, a polyhybrid is formed. F1 hybrids already possess varying genetic traits from both parent strains, meaning polyhybrids are even more diverse and unpredictable in the traits they possess. Creating polyhybrids is a great breeding method as it allows you to combine unique traits from a wide spectrum of cultivars. Although, as you can imagine, these strains are quite unstable and heterozygous. It takes some solid work to stabilise these varieties and ensure that their offspring are more uniform.


Seeing as you’re considering breeding, you are probably already well aware of this fact, but it’s always worth reiterating: Keep your males away from your females! This is especially important when looking to breed a polyhybrid because of the increased chances of breeding the wrong varieties together.

Female plants are ready for breeding during the early flowering phase when small, white pistils start forming. These “pre-bud” structures are basically little hairs that protrude from the calyx to catch pollen. Next, isolate the chosen female plant to further prevent any unwanted fertilisation. Consider setting up a specific fertilisation area to avoid any mishaps.

Differences in phenotypes can manifest as variability in size, resin production, colour, and so on. Strains can also vary in their chemotype. This refers to the chemical constituents that they manufacture. One plant might have higher levels of a specific terpene, whereas another may have slightly higher levels of CBD. If you germinated a bag of seeds that all shared the same lineage and noticed a large difference between the phenotype of each plant, this would mean that the strain is unstable, and that the seeds are heterozygous. Although this isn’t necessarily an issue for hobby growers, it can become problematic for commercial growers looking for strict consistency among their crop.

Growers visiting regions such as the Hindu Kush Mountains would have been greeted with strains of cannabis with traits they had never seen before. They brought back dozens of seeds and evaded law enforcement in the process! Next, they mixed the seeds with other breeding stock to grow ‘new’ strains that had many of the traits found in the landrace strain.

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Germinate your seeds in the usual manner and take notes on how they grow. This means keeping a journal which highlights details such as flowering time, potency, color, taste, and scent. If you’re feeling confident, keep clones of all the plants in case one of them turns out to be exceptional.

Once you have the male and female plants, keep them separate during the growing process. Always ensure that males are separated from females as soon as the small pollen sacs on males (their pre-flowers) show. Otherwise, the males will pollinate the females, and you end up with unknown genetics.

Unstabilized strains often carry several phenotypes, which means that two plants of the same strain are likely to exhibit different traits. Stabilized strains display the same phenotype, which means plants of the same strain will grow in the same way. You can achieve this by manipulating your genetic stock through breeding and back-crossing until you end up with parents that consistently produce offspring that grow the same. This is essentially cloning in seed form.