Introduction to cannabis breeding for beginners

Published Feb 20, 2019 02:29 p.m. ET

If some of the more scientific type phrasing used to discuss cannabis breeding and cannabis genetics is a bit too overwhelming for you than know that you are in the right place. You are not alone, many get excited at the idea of playing with different weed strains to create something new and unique but get lost in all the technical jargon and give up. Here we will cover how to breed cannabis, how to cross strains, and cannabis genetics in a way that anyone can understand and benefit from.

How to breed cannabis

Marijuana seed breeders often resort to tactics that cannot be reproduced at home to yield as many seeds as possible. Luckily, a home grower only requires enough plants needed for personal use, there are simpler ways to get into cannabis breeding that don’t need a science lab, or anything fancy for that matter. To begin you need to focus on preserving the cannabis genetics that is found in the plants you start with. Cloning is one of the easiest ways to obtain and maintain the cannabis genetics of the plants you start with. When a clone is taken from a female plant, it will be a replica of the mother plant and carry the same genes.

Step 1 - Select a strain with cannabis genetics that most benefit you

The evolution of marijuana over the last several decades has taken place mostly due to private growers who choose plants for specific qualities. Marijuana seed breeders do the same and will focus on one of several points when making their selections.

Plant Size - Some marijuana strains carry genetics that enables them to maintain a smaller size. This comes down to basic efficiency as wasted space isn’t always an expense that can be afforded.

Potency - Individual strains are often chosen specifically for their ability to produce high quantities of either THC or CBD depending on what the end product is used for. Rare pot strains will provide both which is a more recent focus as many learn the benefits of CBD that aren’t always immediately felt but can now be proven.

Flowering Period - Many new growers assume that all marijuana will take about the same amount of time to grow to full maturity, but that isn’t the case. Some autoflowering strains can be finished in as little as 40 days while others can take upwards of 90 days or fall somewhere in between. The length of a flowering period tends to have the most significant impact on the grower themselves as the expense of maintaining lights, hydro, and nutrients over a more extended period can add up quickly.

  • The expected yield of a plant is often one of the most important genetic factors growers, and breeders look for. This is for obvious reasons, and more is almost always better for those looking at the short term. However, some of the best weed in the world doesn’t provide the highest yield so consider this one, but it’s not recommended to make a full decision based on this alone.

Bud Size - If the end product is more for show or resale than it is for personal use than this quality may also come into play.

Terpenes - Terpenes are one of the least understood chemical components of the cannabis plant. Each strain will carry genetics that will produce various levels of different terpenes, and there are no two exactly alike. Terpenes are microscopic and cannot be seen by the human eye, but they do provide both the smell and the taste that each strain produces. While the science behind terpenes and their specific benefits is lacking, we do know that fragrances have aromatic qualities that can enhance the experience of consuming cannabis. Terpenes are generally labeled by scent, for example, pine or citrus which are self-explanatory will taste and or smell like pine trees and oranges. It’s a bit more technical is it breaks down from there but since the taste is such a large part of the overall experience specific terpenes may be a quality you want to pay attention to.

Step 2 - How cannabis genetics is passed down

The dominance of the genetics each marijuana strain carries will affect the rate at which specific qualities are passed down.

Dominant- Dominant strains are those that make up more than 50% of cannabis plants genetics. The strain that holds more than 50% of the cannabis genetics will almost always pass down its genetic traits to its offspring. This guarantees at least some of the characteristics you are seeking from cross-breeding will show through in the offspring.

Incomplete Dominance - Incomplete dominance means that the genetics are either equally divided. In this case, both strains being used will affect the outcome which can be a bit trickier to work with when selectively breeding to create a new strain.

Stabilized Strains- A stabilized cannabis strain will always produce the same results from its seeds. To achieve this, you must either begin with one or stabilize your plants with selective breeding until you have two parents that consistently show they can produce the same offspring. A stabilized strain can be multiplied using cloning and used for breeding.

Step 3 - How to select parent plants

Female plants are easy to choose once you have one that gives you a result you like. If you don’t like the bud, size, growing cycle, etc. of your female plant than it is easier to throw it out and start again than it is to get rid of those qualities. Male plants, on the other hand, are a bit more difficult since the only way you will know for certain if it will pass on its genetics to its offspring is to try it. Male plants tend not to exhibit the same qualities we see in a female like the buds or the smell making it difficult to guess what genes it’s secretly carrying within it until it’s offspring flowers.

Step 4 - Separate males and females

To keep control over the process, you will need to start by separating the males and females so that when pollination happens when you choose otherwise you could end up with a room full of random genetics. Males should be removed the moment they begin to produce pollen sacks and should be separated from that point on.

Step 5 - Collecting Pollen

Pollen should be harvested once a male plant has completely matured. Do so by using a ziplock bag placed underneath each stem and shaking it gently. Male pollen should not be stored for any more than one month before it is usedand during that time should be kept in a freezer in a sealed container.

Step 6 - How to pollinate

A female cannabis plant will be ready to be pollinated three to four weeks after they begin to show white pistil growth and buds are forming. If you are only wanting to breed one female and have others in the room, it is safest to do this away from the rest. Take the baggie full of pollen from earlier and wrap it around one of the branches formed closest to the stem of the plant. Use an elastic or string to seal it at the bottom to prevent the pollen from escaping. The bag should stay on for 4 hours and should be turned once every hour for the best results.

Step 7 - Caring for pregnant mother plants

For the best seeds, you will want to ensure the pregnant plants are receiving an optimal amount of light, water, and nutrition. If you follow a nutrient schedule, it is recommended to switch to one suitable for vegetative growth to help the seeds develop. You will begin to see seeds 2-4 weeks after pollinating.

Step 8 - Harvesting seeds

You will know the seeds are ready when their outer shells begin to dry up and break open exposing the seed. At this point, you can pull them out gently by hand. If they will be stored for a while before they will be used then it is best to keep them in a paper envelope in a cool dark place to keep them fresh.

At this point, you have made it through the entire process of cross breeding and will hopefully have seeds that obtained some of the cannabis genetics you were hoping to pass on. The only way to know for sure is to plant one and see how it turns out. It is always best to remember that cross-breeding cannabis this way is not an exact science and can be a time-consuming adventure or trial and error before you get the results you want. If at first, you don’t succeed, then try again. During the process keeping well-documented notes to refer to later can help you to build confidence as you garner experience that will improve your ability to grow.  

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