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How to Breed Your Own Cannabis Strain

By Luis Cordova | Last updated: June 22, 2021
Key Takeaways

There are many reasons why growers may want to breed their own cannabis strain. Whatever the reason, follow these steps from Luis Cordova to breed the best strain for your needs.

So, why do we and why should we breed cannabis? That may be a hard question for breeders to answer. Breeding can be a hobby, preserve genetic linage, improve health, or for developing new species. Breeding can improve flavor, cannabinoids, shape, yields, or many different genetics.

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Currently, the breeding community has become increasingly interested in breeding for terpenes. Terpenes are the aroma-producing compounds of the plant that give it smell and taste. Understanding the terpene profile of the plant allows for improved terpene development. As more is understood of the plant, it has been found that terpenes play a vital role in the entourage effect and the sale of product. Let’s take a look at the key basic components of breeding.

Strain and Soil Choice

Following some easy steps can allow anyone to create a breeding program. Before putting seed into soil, it is important to first choose your strain or strains. Choice can be based on plant size, terpenes, yield, or any factor you choose. Whatever your choice, you will need some regular seeds. Female-only plants can be used, but you will have to force them to be hermaphrodites, which is not the best choice for a home breeder.

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Soil choice should be considered at this point. A good soil mix should have a balanced ratio of macro- and micronutrients. The soil should also have a balance of beneficial microbes. Microbes are the secret to improving the plant’s health and feed the plant the nutrients it needs. Healthy soil encourages healthy cannabis plants with higher production, strength, and quality seeds.

Cycle and Pollen Collection

So now we have our seeds and our soil: now for the long part. The next two months will be letting your plants grow while keeping them healthy. Most breeders will let their plants veg for at least two months, sometimes longer depending on the size of the plant, growroom size, and plant vigor. This is really a personal choice, but a bigger, well-defined plant will give bigger flowers and more seeds. I like to aim for a two-month veg cycle. Of course, this is for a plant that is growing faster than its pots can keep up and shows potential. If the plant isn’t performing as well as I expect but still has some potential, I like to give it two to four weeks extra growth to see if it is worth keeping. Usually, I aim to finish in a seven- to 15-gallon (26-57 liter) fabric pot due to my own grow limitations.

After veg, we go into the flower phase. Usually, when a male plant is in pre-flower you have about three to four weeks till the flowers will begin to be mature enough to open and drop pollen. Alternatively, you can cut clones from the plants and place them under 12/12 light. In about two weeks they will begin to sex. This will tell you which plants are male or female. Isolate the males so no unwanted crossbreeding occurs. Some breeders will isolate males from each other to decrease pollen contamination.

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Male cannabis plantCannabis plants are dioecious, meaning that there are separate male and female plants.

Now, we need to collect pollen. There are two commonly used methods of collecting pollen. The first method is collecting pollen in bottles, bags, or small jars. The collected pollen is stored with desiccate material in the freezer until the females are ready. Prior to storage make sure no plant material is mixed in with the pollen. Plant material and water will destroy pollen so keep the pollen in a low moisture environment.

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The second and possibly easiest method is using a nylon screen. I find the best screens to use are the kind that are used in silk-screen printing. Any mesh screen will work but I find that higher mesh counts are easier to work with. However, common 110 or 156 mesh counts work just as well. Place the screen preferably in a frame and over a clean, dry container. Now, begin to cut the stalks of your male flowers one at a time. We can begin to shake them or trim them over the screen. Pollen will fall through the screen and all plant material will remain on the screen. The pollen can then be stored and used later on.

Pollination

Now that we have our pollen collected, it’s time to start pollinating the females. It is best to pollinate females between 21-29 days of flower. This is common because the flowers’ pistils are white and standing up. Pollinating at this time will also give you enough time for the seeds to fully mature and reduce other issues that can happen. There are three main methods of pollinating females that all get the job done.

The first method is to take the pollen out of storage and let it warm up to room temperature. Take any fine toothbrush and dip it into the pollen. Then paint the female pistils with the pollen. I like to start from the top of the female and work my way down. That way I can ensure the whole flower has been pollinated. Try not to disturb the plant after pollination so the pollen can be absorbed by the flower.

The second method is introducing a male into a room of females and shaking it. This method will coat everything, so some preparation is needed. After a male is selected, place the females into a separate closed room. Place the male in the center of the room if possible. Tie a rope or string onto the male’s main stem. With the rope in hand walk out of the room and try to close the door. You can also add a sheet of plastic to the inside door frame to keep pollen from escaping. Now shake the hell out of the rope.

You will see a cloud of Armageddon-like pollen cover everything in the room. Leave the pollen to settle for at least 30 minutes to one hour. Now the females can be removed from the room. Alternatively, take individual male flowers that have just opened or are about to open and sprinkle the pollen on the female flower. You can cut the entire stalk of flowers off and shake it above all the flowers.

The third method is to take a brown paper bag with pollen in it and cover the female flowers with it. Shake the bag and let it set for five to 10 minutes. This method will allow you to cross different males on one female. Be sure to label the cross and attach it to the stem.

Now that everything is pollinated the waiting game begins. During this time, the white hairs will begin to turn red or orange and little seeds will begin to form. If the hairs do not turn color this may mean the pollen was not viable. Every calyx that has been pollinated will start to form seeds. Seeds will begin to get bigger and the outside husk may begin to split. A mature seed should be dark brown with brown stripes. If the husk holding the seed is still green hold off on harvesting. I would suggest that you wait until the entire husk is brown and fragile. Doing so allows for all the sugars to be absorbed and ensure the seeds are higher quality.

Seed Removal

Now for the messy part: removing the seeds from the flowers. There are different procedures to remove the seeds, each one very time consuming. First, cut your plants down. It doesn’t really matter how you cut your plants. I usually cut the entire plant as it allows me to control the drying process. At this step I do not do any trimming. Now remember, when those seed pods split any trimming can let the seeds fall out. The sugar leaves and fan leaves will create a protective shell around those seeds, preventing them from falling out. As they dry, I like to use nylon silk screen mesh to wrap around the plant. The mesh catches any seeds that fall during the drying process.

Seed forming in cannabis plantSeeds vary widely in shape, size, and color, and can look different depending on the variety.

After drying, branches can be cut off. At this point you can pick the seeds out one by one with tweezers or gloved hands. This procedure takes a long time but saves time on the sorting process. Alternatively, you can rub the flowers together and let everything fall into a container. My go-to method is rubbing the flowers on a nylon screen and let everything fall into a bin. The seeds will stay above the screen with all plant material falling into the bin. Other mechanical methods exist which make the process much quicker.

Drum machines shred the flowers and separate the seeds automatically. If you can afford the machine this is the way to go. It will sort plant material, inviable seeds, small seeds, and larger seeds into separate bins.

Seed Sorting

The seeds are now ready to be sorted. Various methods are available for this step. For small batches, a tray and a small fan can be used. Put all the material on one side of the tray and tilt it slightly. Begin to shake the material slowly down the tray and let the fan blow the plant material off the good seeds. Next you can remove inviable seeds by hand.

A faster method is to buy or build a zig-zag blower. This box uses a vacuum and angled ledges to separate the seeds by weight. This machine does work well but extra separating is needed. Another machine that can be built or bought is a shaker table. The shaker has different sized mesh screens. The screen separates seeds by size making sorting quick and easy. Other more advanced machines use the same concept but have a computerized system that helps sort by seed size and color. If the seeds do not meet a standard they are rejected.

Seed Storage

Now that our seeds are graded by quality, storage and germination rate are the last step. Storage is straight forward with the overall goal being not to let any water onto the seeds. Water will promote mold and destroy all your work. The best option is to place the seeds in a vacuum-sealed container. I use vacuum-sealed mylar bags for this. Place the mylar bag into a bigger clear bag with desiccate material and vacuum seal. Make sure no desiccate material contacts the seeds as this will destroy them. Now you can place in a refrigerator or freezer for up to three years. Depending on the strain I have created I take the extra step of using a glass vacuum container to add another layer of protection.

The very last step is germination rate. Most growers will pop up to 100 seeds to calculate the average germination rate. If sorting has been done properly an average of 95 percent is achievable. However, different factors can affect germination and cause the germination to be 80 percent. Germination rate indicates a seed’s viability and quality, and allows for adjusting planting rates for a determined plant population.

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Written by Luis Cordova | Plant Biotechnician, Pharmaceutical Scientist

Profile Picture of Luis Cordova

Luis holds a M.S. in Plant biotechnology and Pharmaceutical Science. He is a long-time cannabis grower He has put his focus on breeding cannabis and development of organic soils for tropical regions. He loves how much the industry has grown and changed. He hopes to pass on new and old knowledge to all growers across the world.

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