Breeding Cannabis Seeds

Ever wonder where all of those cannabis strains come from? Cannabis breeding is how new strains are created. Here's how cannabis strains are bred! Learn how cannabis breeders combine strains to enhance, strengthen, or combine traits & effects of cannabis to create the perfect experience. Follow these steps from Luis Cordova to breed the best cannabis strain for your needs.

How Cannabis Strains Are Bred

For the average cannabis consumer, keeping track of cannabis strains can be a real headache. It may seem like there are new strains popping up all the time – because there are! But just where are all of these strains coming from?

Why Breed New Cannabis Strains?

Breeding new cannabis strains allows growers to explore new combinations of cannabis genetics. Combining two strains with unique genetics can reveal new flavors and aromas, alter cannabinoid levels, and boost total yields.

Strains have also been crossed with close relatives or other versions of themselves for improved health and fortification. This process can create new varieties of a strain that are nearly identical to the original plant but feature improved resistance to fungus, bugs, and other potential threats.

Each cannabis strain available today is derived from the breeding and crossbreeding of landrace and heirloom strains that once were native to very specific regions of the world such as Africa, The Middle East, Asia, and Latin America. Thanks to previous generations of growers that once traveled the world to collect these seeds, we now have a range of cannabis strains that have been crossbred many times over giving them unique flavors and effects.

How Does Cannabis Breeding Work?

Cannabis plants can grow to be either male or female. While only female plants are capable of producing buds, male plants produce pollination sacs that are critical to cannabis breeding.

In order to breed a new strain, you will need to have a male plant of one variety, and a female plant of another. A couple of weeks into their flowering stage, male plants will develop pollen sacs that can be easily identified with the naked eye. When these sacs are matured, they drop onto the ground and release pollen that spreads over the female plants, fertilizing them.

Typically, growers place one male plant in a grow chamber with several females, to ensure multiple plants can grow from one breeding attempt. A single male plant can pollinate tens of females. Growers typically only introduce one healthy male into the cannabis breeding environment in order to guarantee more stable genetics for all of the new seeds.

Once a female plant is pollinated, it does not produce the sticky buds that it would if left to grow on its own. Instead, pollinated female plants produce seeds that are a genetic expression of both their mother plant and their father plant.

Oftentimes, the traits and characteristics of the female plant tend to carry over more dominantly to the new progeny. Nevertheless, the traits of the male plant are still obvious in the genes of the new breed. Each seed carries a unique set of characteristics passed down from its mother and father resulting in many different ‘phenotypes’ of a single strain.

Breeding Strains Forwards And Backwards

The strains you are likely to pick up at your local dispensary are unlikely to have just gone through one single round of breeding. Most of the time, new strains go through several series of breeding in order to develop a consistent phenotype of high quality. Growers then select the best phenotype to carry on the genetic line.

Strains can also be bred backward. Once a grower has settled on a phenotype, they may then backcross that strain by breeding it with one of its original parents or another phenotype in order to strengthen its genetics and obtain more desired characteristics.

Cannabis breeding is often a long and strenuous process, but well worth it. With legalization, new strains and phenotypes are now being bred by both industrial and home growers. Expect to see more unique cannabis strains in the future!

Looking to see what strains are available now? Check out our Seattle dispensary online menu.

Cannabis Breeding: How Are New Strains Created?

While browsing Leafly’s strain database, you may wonder what a cross of this and that strain is, what a hybrid or a backcross is, or what a parent strain is. All of these have to do with plant breeding—essentially, breeding a male and female plant to combine or refine the genetics of two plants or strains. Breeding two different strains often results in a new strain, or hybrid.

Cannabis breeders typically breed to purify and strengthen strains, combine strain traits, or enhance specific characteristics.

Cannabis breeders typically breed to purify and strengthen strains, combine strain traits, or enhance specific characteristics like higher yields, specific aromas, potency, and many other things.

When growing and breeding, it’s important to know where your seeds come from and what kind of genetics they have. If the seed breeder can’t give you a detailed history of how a packet of seeds was bred or what they were crossed with, you never really know what you’re getting.

Plant breeding is a fundamental process of growing cannabis. Breeding is highly technical and typically done on a commercial scale, but with legalization increasing, breeding is becoming more popular. You can even do it yourself.

The Basics of Breeding

Cannabis plants can be either male or female. Cannabis consumers are mainly concerned with female plants, because only females produce the sticky buds that we all know and love. But male cannabis plants are important for the breeding process, as they are needed to pollinate the bud-producing females.

Take the strain Super Lemon Haze as an example. It’s a hybrid (or a “cross”) of Super Silver Haze and Lemon Skunk—these are the parent strains. At some point, the breeder decided that they liked some attributes of Super Silver Haze and some of Lemon Skunk and decided to combine the two.

To do this, you need a male of one strain to pollinate a female of the other. Once pollinated, the female will then produce seeds that express the genes of both the male and female plant. Those seeds will be harvested and grown separately, and voilà: You have created a hybrid.

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So how do you know whether to pick a male or a female of each strain that you’re crossing?

“Often in cannabis, the traits of the female carry over to progeny (seeds) more than the male. That said, the traits of the male are often obvious to the discerning grower so one should definitely choose a male that will complement the traits of the female,” says Nat Pennington, founder and CEO of Humboldt Seed Company who’s been breeding cannabis for 20 years. “So much is possible with truly intentional breeding strategies.”

How to Breed Cannabis Plants

After two parent strains are selected for breeding, a male and several females are put into a breeding chamber to contain the pollen. A breeding chamber can be as simple as an enclosed environment with plastic sheeting on the sides, or a specially designed sterile environment for large-scale breeding.

“A healthy male can pollinate up to 20 females, and by pollinate, I mean absolutely cover the plant with seeds.”

A single male plant can pollinate tens of females. “It’s always a good idea to have only one male, genetically speaking, per pollination effort,” says Pennington. “A healthy male can pollinate up to 20 females, and by pollinate, I mean absolutely cover the plant with seeds.”

This is intentional breeding—any grower who’s accidentally grown a male and pollinated a crop will know that one male can easy pollinate hundreds of females, filling your whole crop with seeds.

Once in the breeding chamber, you can grow the plants vegetatively for a few weeks to let them get bigger, but it’s not necessary. Put them on a flowering light cycle: 12 hours of light, 12 hours of dark.

The mature male will grow pollen sacs within the first couple weeks of its flowering phase. Pollen will release from the sacs, move through the air, and land on the female plants, pollinating them. Having an enclosed breeding chamber is important to contain the pollen and also to prevent outside pollen from getting in.

You can also help along the pollination effort by shaking pollen from the male onto the females, or by collecting pollen from the male and directly applying it to the females. These female plants will continue to grow and flower, during which they’ll grow seeds (as well as buds). These seeds will express the genetics of both the male and female plant.

When the seeds are mature, they are harvested and stratified (or dried). “The secondary process of maturation happens after the plant is dead, and the seed needs to be stratified before it will germinate,” says Pennington. “In general, harvest for flower takes place three to four weeks before harvest for seed.”

These seeds—now a hybrid of the two parent strains—will be grown on their own, outside of the breeding environment.

Phenotypes

But the process doesn’t end there. The hybrid strain that you buy at the dispensary has likely gone through many rounds—or generations—of breeding to strengthen its genes and to ensure that its descendants are healthy and consistent.

Just as you and your sibling might have different physical attributes from your parents, each seed created from a round of cross-pollination will have different attributes from its parent strains. Maybe you have your father’s eyes and your mother’s hair, but your sister has your mother’s eyes and hair. Each cannabis seed is unique and will express different traits, and different combinations of traits, from one or both of the parent strains. These seeds with various expressions are called phenotypes.

Homozygosity ensures that a plant will consistently produce the same seeds with the same genetic makeup over and over again.

A plant that produces a set of phenotypes that have a lot of variety are said to be heterozygous. With cannabis, you typically want seeds that are homozygous—ones that have the same set of genes. Homozygosity ensures that a plant will consistently produce the same seeds with the same genetic makeup over and over again, ensuring that buyers and consumers will get the same plant or seed time and again.

After a strain is crossed, a breeder will then have to select which phenotype of the new strain they like best. For large-scale growers, they want to choose the best phenotype for mass production.

Back to the Super Lemon Haze example: This strain takes a lot of its bud structure, trichome and resin production, and overall appearance from Super Silver Haze. But it takes its flavors and aromas from Lemon Skunk.

Lemon Skunk also tends to grow extremely tall and has loose buds, whereas Super Silver Haze grows smaller and has denser buds. Through selecting specific phenotypes, a breeder can pick one that has the attributes they want to keep. In this case, a phenotype that has the structure and bud density of Super Silver Haze and the flavors and aromas of Lemon Skunk.

Most likely, there were early phenotypes of Super Lemon Haze that grew tall and loose like Lemon Skunk, or tasted more like Super Silver Haze. But the breeder discarded those phenotypes and keep growing the ones that have the attributes of what we now know is Super Lemon Haze.

Backcrossing

High-quality breeding still doesn’t stop there. Once a breeder has crossed a strain and narrowed down a phenotype and finally has the one, they will usually backcross that strain to strengthen its genetics.

Backcrossing is a practice where a breeder will cross-pollinate the new strain with itself or a parent—essentially, inbreeding the strain. This makes the strain more homozygous, and strengthens its genetics and desirable characteristics, and also ensures that those genes continue to pass down from generation to generation.

The hybrid that you bought from the dispensary has gone through months and even years of growing, crossing, and backcrossing, as well as a selection process to pick the best phenotype of that strain.

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Breeding is about time and patience. Says Pennington: “To be a breeder, you have to be willing to accept the fact that you won’t have uniformity in the offspring, [you’ll get] lots of ugly ducklings in the hunt for your golden goose. To make seeds that will actually reflect the golden goose takes time, and it takes more than just a one-off cross. Even after you found your golden goose, expect to have to do a whole number of stabilizing backcrosses to reproduce your golden goose in seed form.”

How to Breed Your Own Cannabis Strain

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.

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.

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.

Cannabis 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.

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.

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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.

Seeds 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.