Ever wondered how those marijuana seed banks make feminized seeds? Learn how to create your own feminized seeds at home using two female plants! Explore how to begin growing marijuana plants by comparing seeds versus cuttings, and learn how to acquire the seeds you need. Can’t fully get rid of that cannabis strain you grew for so long? Learn how to store seeds and pollen to clear space in your garden and hang onto those favorite genetics for another day.
How to Make Feminized Seeds at Home
First of all, what are “feminized” marijuana seeds? Although male and female plants look the same when young, only female cannabis plants make buds. Male cannabis plants grow non-potent pollen sacs instead. Male plants also lower yields and cause seedy buds if they’re left among your female plants for too long. Because male plants don’t make buds and their presence reduces the quality of buds, most growers toss male plants the moment they see pollen sacs forming. However, since about half of regular cannabis seeds end up being male, that means you end up tossing half your plants once they start flowering.
Feminized seeds come from two female plants being bred together, causing all offspring to be female (which means every plant makes buds)
While regular seeds make female plants about half the time, feminized seeds only create female plants. That means you won’t need to toss half the plants once they start flowering. But how are feminized seeds made and can you make them at home?
Feminized seeds are created by breeding two female plants together. Because there are no male parents, all the resulting seeds end up being bud-bearing female plants. With feminized seeds, you can count on every plant to produce buds. Learn more about male vs female plants and feminized cannabis seeds.
Feminized seeds are available from seed banks for nearly every popular or famous strain. Breeders understand that a lot of people just want to grow plants for buds, and don’t care about making a robust breeding program (which is one of the main reasons growers want male plants).
You can’t see the difference between male and female plants until they start flowering (unless you do a genetic test). Feminized seeds ensure all plants are female so you don’t need to worry about it. You know that every plant is female from germination.
So how do seed banks feminize their seeds? How do you breed two female plants together?
The main idea is to force a female plant to produce pollen sacs like a male plant. These flowers (growing on a female plant) create pollen, which can be harvested and used to pollinate another female cannabis plant. The resulting seeds will all end up being female. Can feminizing seeds cause hermaphrodite plants?
Growers can force a female plant to make pollen sacs, and the “feminized” pollen produced can be used to fertilize another female plant. The resulting seeds will only produce female plants.
How do you force a female plant to make pollen?
There are two main ways to make feminized pollen:
- Induce feminized pollen chemically (Recommended) – This is the professional way to feminize seeds and is how reputable seed banks and breeders create feminized seeds to sell to the public. Substances that interact with plant processes such as colloidal silver or gibberellic acid are applied to bud sites of a female plant when they start flowering. Bud sites are drenched daily for the first 3-4 weeks after the switch to 12/12. This causes a female plant to produce pollen sacs which release feminized pollen when they open up. This pollen is used on another female plant to produce feminized seeds. This article will give you step-by-step instructions on how to feminize cannabis seeds using this method.
- Rhodelization (Not Recommended!) – In some cases, a female cannabis plant may naturally start making male pollen sacs or bananas, which can self-pollinate the plant. This happens if the plant is stressed, or if the plant is not harvested in time and buds start to die of old age. The plant is basically doing everything it can to make seeds and save the next generation. This method is “natural” and these seeds end up being mostly female. The problem with this method is you’re selecting for plants that naturally turn into hermies (grow both male and female sex organs) without any chemical induction. This means the resulting seeds are much more likely to turn hermie in natural conditions, too. That’s a problem if you don’t want seedy buds every time you harvest. For that reason, it’s highly recommended you don’t feminize seeds this way. It’s also a good idea to toss any and all seeds that are the result of natural herming (for example seeds you find in your buds even though you didn’t grow any male plants).
Read this article for more in-depth discussion about the pros and cons of each method, and how to avoid hermaphrodite plants when producing your own feminized seeds.
Overview: How to Make Feminized Seeds
This is a quick overview of the process, and then I’ll give the full details and steps below.
1.) Buy or Make Colloidal Silver – The article below will teach you how to make colloidal silver at home, as well as show you where to buy it if you don’t want to make it (it’s actually pretty cheap). It’s basically a solution of silver suspended in water and is available online and in health stores as a dietary supplement.
What about gibberellic acid? From what I understand it can be used exactly the same way as colloidal silver to induce female plants to produce pollen, but I don’t know the recipe for an effective gibberellic acid solution. On the other hand, I know that this exact colloidal silver method works for making feminized seeds. That’s why I’ve only included instructions for colloidal silver. If you’ve used gibberellic acid to make feminized seeds; we’d love to hear from you.
2.) Spray the bud sites of your known female plant daily during the first 3-4 weeks of the flowering stage (until pollen sacs form and start splitting open) – After switching to a 12/12 light schedule to initiate the flowering stage, choose bud sites on your known female plant, and spray/drench them daily with colloidal silver (or gibberellic acid). As the treated flowers develop, they will form into male pollen sacs instead of regular buds. Untreated bud sites on the plant will form into female buds as usual; however, these buds are unsafe to smoke unless you’ve been very careful to make sure they didn’t come into contact with colloidal silver or gibberellic acid during the feminization process as these are unsafe for smoking.
3.) Harvest “Feminized” Pollen – When pollen sacs are ready to be harvested they swell like a balloon and start to open up. Don’t harvest early! Keep spraying the bud sites daily until pollen sacs open or you might end up with empty pollen sacs. When the pollen sacs are ready, the leaf section protecting the pollen will start to crack. At this point, it’s time to collect the feminized pollen. One of the easiest ways to do this is to collect the pollen sacs directly and let them dry for a week. At that point, they can be placed in a bag and shaken to collect all the pollen.
4.) Pollinate Another Female Plant – At this point, take the feminized pollen you’ve collected and use it to pollinate a female plant that has been flowering for about 2-3 weeks (full detailed instructions with a video on how to do this below). Although it’s possible to pollinate the same plant as the original, it’s not recommended in part because the timing doesn’t match up (pollinating buds late in the flowering stage doesn’t produce many seeds). It’s best to pollinate a different female plant that you started budding a few weeks after the original. This increases the number of seeds produced as well as gives the new female plant enough time to develop them to maturity. It also increases genetic diversity compared to self-pollination.
5.) Wait ~6 Weeks After Pollination to Harvest Seeds – After about 6 weeks from pollination, the calyxes on the buds of your female plant will be swollen and fat. You know it’s time to harvest your seeds when they start bursting out. At this point, it’s time to congratulate yourself because you’ve got feminized seeds!
Now that you’ve gotten the overview, here’s the feminization process with detailed step-by-step instructions…
Step-By-Step Instructions (with pics!)
1.) Buy or Make Colloidal Silver (or Gibberellic Acid)
Where to get Colloidal Silver (your options):
Buy Ready-To-Use Colloidal Silver: Colloidal silver is sometimes used as a dietary supplement, so it’s relatively easy to find (never take it without talking to a doctor first though!). If you’re purchasing colloidal silver, try to find a solution that has at least 30 PPM (parts per million) of silver or higher.
- Buy A Colloidal Silver Generator Kit: If you plan on feminizing a lot of seeds, you may want to invest in a generator kit so you can easily make your own endless supply of colloidal silver. This is cheaper in the long run compared to buying it ready-to-use.
- Make Your Own: You can make your own colloidal silver generator at home. The following diagram illustrates what you need to do.
Note: You can purchase gibberellic acid online (a gibberellic acid solution can be used the same way as colloidal silver for feminizing seeds). However, I do not have experience with the gibberellic acid method and don’t know the best way to prepare the solution.
2.) Spray the bud sites of your known female plant daily during the first 3-4 weeks of the flowering stage (until pollen sacs form and start splitting open)
Wait until your plant is 5-6 weeks old before initiating the flowering stage. Some young plants seem to have trouble (and take much longer) to go through the feminization process, and their pollen may not be as fertile, so start with a more mature plant.
When plants are ready, change to a 12/12 light schedule to initiate flower formation and put cannabis plants in the flowering stage. Note: If you’re feminizing an auto-flowering plant, start spraying daily when the plant is about 20 days old from seed. This is when most auto-flowering cannabis strains start making flowers.
As soon as you change the light schedule (and maybe even a day or two before) start spraying your plants thoroughly with colloidal silver at every bud site you want to form into pollen sacs.
Spray bud sites thoroughly, drenching them with colloidal silver every single day. Bud sites are located wherever leaves meet stems.
The above pic shows you where pollen sacs form on the plant (the same places female buds form).
Important! Keep spraying daily until pollen sacs open up. Don’t stop spraying early, even if pollen sacs appear to be already formed, otherwise they may not produce much pollen
A spray bottle / mister is really helpful for spraying bud sites evenly and thoroughly
You can choose to treat a single bud site or all the bud sites on the plant. Any untreated bud sites will develop into female buds as usual. If you want to smoke these buds, it’s incredibly important to avoid letting them come into contact with colloidal silver because silver is not safe to smoke. (Don’t worry, feminized seeds don’t contain any silver). I highly recommend letting the whole plant be your test subject so you don’t have to worry about that
3.) Harvest Your Feminized Pollen
When pollen sacs are starting to crack and look like they’re about to open up (or if you can see one has already opened) then your pollen is ready for harvest!
When pollen sacs are cracking and opening up, you’re ready to harvest your pollen!
Pollen spilling onto a nearby leaf
One way to harvest your pollen is to gently and carefully remove all the pollen sacs. Let them dry in open air for a week, and then put them in a resealable bag. If you shake the bag the pollen should easily spill out. You may need to cut a few open yourself.
How to Store Feminized Pollen: Moisture is your main enemy when storing pollen. It can help to double the mass of the pollen collected by adding regular cooking flour. This absorbs moisture during storage and as an added bonus, it increases the volume to make application easier when you get to pollinating. If pollen is totally dry and you triple-bag the pollen-flour mixture and stick it in the freezer (with a good nametag so you know where the pollen came from), your pollen can be stored for a year or longer. You can add a few silica packs (which suck out any remaining moisture) in the bag to make extra sure that the pollen stays totally dry.
4.) Pollinate Another Female Plant
When your chosen mother is 2-3 weeks into the flowering stage, take a small paintbrush or powder brush and ‘paint’ your feminized pollen on the developing bud sites you want to pollinate. Bud sites (for both male and female plants) are located wherever you can see leaves meet a stem.
Buds are ready to get pollinated when they look like little bunches of white hairs
Only the buds that come in contact with pollen will grow seeds. You can choose to pollinate all of your buds or just a few on the plant.
Here’s a video by Ed Rosenthal on Youtube showing you how to pollinate buds with pollen. Make sure to touch all the female pistils/hairs with your pollen.
5.) Wait About 6 Weeks Then Harvest Seeds
It usually takes about 6 weeks for your feminized seeds to fully develop. Some plants are literally dying right as the seeds become ready, so to get the most viable seeds, you need to try to keep it alive until the seeds actually start dropping. The seeds can be used right away, or stored in a cool, dry place for a few years. Don’t forget to label them with the date.
This seed is about to burst out of its calyx
This is what it looks like when the seed is exposed
Picture Journal of Making Feminized Pollen with Colloidal Silver
This grower initiated the feminization process on a seedling that was only a few weeks old. As a result, the plant wasn’t able to get big enough to produce many pollen sacs. You will get even better results if you start with a plant that is at least 5 weeks old
October 18 – Plant right before the switch to 12/12
October 27 – After being drenched with colloidal silver daily for a little over a week
October 30 – Pollen sacs are forming
November 15 – Pollen sacs appear to be almost fully formed and are swelling in size, but haven’t opened up yet. Don’t stop spraying colloidal silver or you may end up with empty sacs!
November 27 – Pollen sacs are opening up! Collect the pollen before they’re all open!
FAQs – Frequently Asked Questions
How can I identify plant gender before the plant actually starts flowering?
There are a few ways to identify plant gender before the plant actually starts flowering, and each is helpful in different situations.
- Use feminized seeds – All your plants will be female if you start with pre-made feminized seeds.
- Start with a clone – A clone is an exact copy of another plant. If the “mother” of the clone is a female plant, it means the clone is also female
- Look at preflowers (identify plants when they’re 3-6 weeks from seed) – If you know where to look, cannabis plants will actually reveal their gender in the vegetative stage when they’re just 3-6 weeks from seeds. Male plants usually show their gender by 3-6 weeks and female plants usually show their gender around week 4-8 from seed. Learn how to determine the sex in the veg stage by looking at preflowers.
- Test the leaves of your seedling in a lab – It’s possible to send in a leaf from a young cannabis plant to a specialized testing company, and they will be able to determine the gender as soon as 3 weeks from seed! Although I haven’t used any of these companies and can’t recommend any in particular, here’s a link to one example just so you can see what I’m talking about. From talking to other growers who use this method, it appears to be accurate.
- Take a clone and force it to start flowering – if you take a clone from a vegetative plant, you can force that clone to start flowering and reveal its gender. You’ll know the sex of the “parent” plant by the sex expressed by the clone. This is what I do to determine the sex. I cut off a piece of the plant, stick it in a glass of water (don’t forget to label it with the strain), and give it a 12/12 light schedule until the little piece starts forming either pollen sacs or buds.
The easiest way to identify sex with unknown seedlings? Cut off a small branch of the plant, stick it in a cup of water with a label, and keep it in a sunny window on a 12/12 light schedule until buds or pollen sacs start forming. As long as the plant is getting bright light in the day and long dark nights, it will reveal its sex in just a few weeks (you don’t even need to wait for roots to form).
Can I Make a Breeding Program Using Just Female Plants and Feminized Seeds?
Yes, it’s possible to use just female plants and feminized seeds for further breeding, with one major caveat.
Without careful and thorough testing, it may be possible to accidentally select cannabis plants that tend to herm (make male flowers or pollen) and cause seedy buds when you don’t want them to.
For each possible “mother,” clones should be grown in several different environments and tested thoroughly to make sure that the mother plant does not have any tendency to make pollen naturally in normal or stressful conditions. It’s okay if plants grow pollen sacs if induced chemically since that is very unlikely to happen in someone’s garden on accident, but you don’t want plants that will start growing male flowers on their own without chemical induction. Thorough testing of plant hardiness is always important when breeding, but it may be especially important when breeding feminized seeds together.
Are there other reasons I should avoid breeding seeds without males?
The most common reason growers say you shouldn’t do this is because it’s “unnatural” or doesn’t “seem right.” Some growers say you need male plants for genetic diversity. I’ve also heard growers say that the resulting plants will be weaker, sterile, and less potent. Someone once even told me that resulting plants “will be worse in every way.”
As of yet, I haven’t seen any of these claims backed by actual personal experience, or any real-life examples showing why using feminized seeds is not a viable way to breed new strains.
To those who say this type of reproduction just doesn’t seem right, the evolutionary strategy of plants using only female and hermaphrodite plants to breed is actually pretty common and is known as gynodioecy. One example of a plant that only reproduces this way is a flower found in Canada and the US called Lobelia siphilitica, also known as the Great Lobelia. Obviously, this reproduction method isn’t exactly the same as artificial feminization since the pollen production is caused naturally instead of induced chemically, but examples of gynodioecy show that a female flower-based breeding population can exist in the wild even when no plants are purely male.
The Great Lobelia naturally reproduces using only female and hermaphrodite plants. This is similar to the cannabis feminization process because it results in a population of plants that all primarily grow female flowers, with no pure male plants
When it comes to genetic diversity, the ability to cross out to thousands of different cannabis strains allows you to dramatically increase the gene pool without using male plants. So those are my answers to the common objections of a feminized seed-based breeding program, however I am just a theory-crafter when it comes to this topic. It certainly seems possible that a feminized-only breeding program could run into unforeseen problems down the road, but as far as I know there isn’t any evidence of that so far.
Although I have a few anecdotes from growers who have used only feminized seeds for a few generations, it would be much better to share information from someone who has conducted plenty of testing over several generations. We’d love to hear from you if you have bred more than a few generations using only feminized seeds and want to share your experience.
What are the positive aspects of breeding two feminized seeds together?
Besides not having to worry about male plants in the next generation, the main advantage of doing this is you have a much better idea of what you’re working with when it comes to producing the type of buds you’re looking for. When you’re growing a male plant, it has several genes it will pass to its offspring that has to do with how buds develop, but since it’s a male plant those genes aren’t expressed and it’s hard to figure out what they are.
Historically, the way to learn more about the “hidden genes” contained in a male plant is to breed it to several well-known female plants and see how the offspring compare to each other. The genes that don’t come from the known mother plant are assumed to come from the male. Another way of going about this is to take several clones of the same well-known female plant and breed them with many different male plants to see which ones produce the best offspring.
After testing with several pairings, you start to get an idea of the hidden genes a male plant has to offer to its female offspring. This time-consuming process of documenting and identifying good male plants is why proven stud male plants are one of the most valuable and closely guarded types of clones available today.
But the process of finding the right “father” is a little different when you start with two female plants. In this case, you already know quite a bit about the genes of both parents because you can just look at and test the buds of both plants directly. This allows you to pinpoint desirable genes with less guessing and much less time spent growing out and cataloging plants.
Breeding two female plants together offer hints about what kind of buds their genes will produce
Why even have male plants then?
In nature, male plants are effective at increasing genetic diversity by ensuring cross-pollination. With only purely male and purely female plants, every resulting seed will have two different parents.
Another big advantage in the wild of having separate female and male plants is sexual specialization. In other words, plants are able to evolve male and female traits separately, so each type of flower can become more specialized at its unique “job.”
However, this isn’t the only successful breeding strategy for plants. In fact, only 6-7% of plants have completely separate male and female plants like cannabis plants do (known as dioecious plants). Most plants grow some mix of male and female flowers on each plant, with different combinations offering different evolutionary benefits.
You might enjoy this scientific article if you want to learn more about the evolution of sex determination in plants and animals: Sex Determination: Why So Many Ways of Doing It?
And although most cannabis strains (at least the good ones) display either purely male or purely female flowers, there are some wild populations (and some strains of hemp) that regularly produce plants with male and female parts on the same plant.
When it comes to artificial selection for breeding new strains, the grower is in charge of cross-pollination, so there’s no need for the plant to specialize in male parts. Pretty much the only thing most growers care about is how female flowers develop. So (unlike in nature) growers have the freedom to choose plants that improve female buds without even having to consider how it might affect male plants.
Only a small percentage of plant species produce male plants like cannabis.
Can feminizing seeds result in hermaphrodite plants?
The answer is yes. If you do it the wrong way then feminization can lead to plants with an increased chance of herming. However, with a well-tested and well-bred feminization program, one of the main goals is to breed out any plants with hermaphroditic tendencies that show up under normal conditions. When you buy feminized seeds from trustworthy breeders, you can count on the fact that every plant will end up growing only female flowers and that’s it.
This is a relatively big topic with a lot of opposing opinions so I wrote a whole article about it.
Feminizing seeds the wrong way can result in hermaphrodite plants.
Can I pollinate the same plant I collected the pollen from?
Yes, it’s possible. However, it’s not really recommended because, for one, the timing doesn’t match up. By the time your pollen is ready to use, your original plant will already be several weeks past the optimum pollination point. It’s best to pollinate a female plant that has only been flowering about 2-3 weeks, but pollen sacs need more time before pollen is ready to use. It’s also possible to run into unwanted side effects from self-pollination/in-breeding.
One thing to keep in mind is even if you pollinate a plant to itself, the resulting seeds are likely not going to be exact copies of the original (unless the original plant is extremely inbred). The resulting seeds include not just the mother’s expressed genes but also her hidden ones.
How to Grow Marijuana from Seed
If you’re in a location where cannabis (another term for marijuana; short for the plant cannabis sativa) is illegal, growing it is probably illegal too. Bringing in seeds or cuttings to your location can very well be a felony, and reputable sellers won’t ship to you.
You can probably purchase and grow hemp seeds and plants, which have a negligible amount of THC, but these plants won’t produce the psychoactive effects of plants that contain higher levels of THC. Check with your seller to be certain you’re getting what you think you’re purchasing. If you buy seeds for CBD-only hemp plants by mistake, you can end up being very disappointed post-harvest.
How to acquire seeds or cuttings
You can usually find cannabis seeds for sale at most dispensaries in areas where growing cannabis for personal use is legal. You may also find growers who sell cuttings/clones. You can expect to pay $50 to $100 for a pack of ten seeds. When shopping for seeds or cuttings, read the labels and any other information the manufacturer provides on its website or in its catalog to make sure you’re getting the right seeds or cuttings (the strain) for the plants you want to grow.
One way to get your mitts on some seeds is to collect seeds when you find them in flowers you purchased, or get some from friends if they’re collecting.
- Feminized seeds: Nearly all seeds sold by reputable companies are feminized, but make sure they are. These seeds are specially treated to grow into female plants.
- Auto-flowering or photoperiod: Auto-flowering plants are easier, because they enter the flower stage after a certain number of weeks regardless of the light/dark cycle. If you’re a beginner, seriously consider going with auto-flowering plants.
- Genetic background: If seeds are from a well-established strain, such as O.G. Kush, Bubble Gum, or a cross-breed, the genetic background should be stated.
- Blend: The blend represents the percentage of the three species — sativa, indica, and ruderalis. All auto-flower strains contain some percentage of ruderalis, which is responsible for the auto-flowering nature of the plant.
- Yield indoors: The number of grams of bud per square meter of plant when grown indoors.
- Yield outdoors: The number of grams of bud per plant (after drying) when grown outdoors.
- Plant height indoors: Shorter than when grown outdoors.
- Plant height outdoors: Taller than when grown indoors.
- Time to harvest: Approximate number of weeks after germination the flower should be ready to harvest.
- Potency: Percentages of CBD and THC.
- Effect: The type of experience you can expect when consuming product from the plant.
Know the laws about buying cannabis
- In some European countries, laws prohibit growing cannabis, but seed is legal, which is quite confusing. You’re allowed to buy and eat cannabis seeds because they’re non-psychotropic, but you can’t buy them to grow cannabis. Other countries in Europe, such as Germany, have their own seed laws.
- In Canada, where cannabis is federally legal, seeds can be shipped across provincial lines.
- In the U.S., in some states in which cannabis is legal, you can purchase seeds from some dispensaries or other locations to grow plants as long as you keep them in the state. Other states may bar selling to non-licensed growers. Shipping or transporting seeds across state or international borders is illegal, although a few reputable online seed stores ship to individuals with success.
Cuttings are typically treated in a similar manner as seeds in legalized locations. They may be available from some dispensaries or outlets for pick up or delivery with a fee. They’re prohibited from crossing U.S. state lines or international borders. You can buy individual plants and mix and match strains. Prices vary and are often determined by plant size.
Buy cuttings (clones) only from a reputable source who understands proper back-crossing of strains for stability. Back-crossing involves pollinating a plant with one of its parent plants to promote sexual stability, so that when you have a female it won’t hermaphrodite into a male during flowering.
Both seeds and clones are often able to be purchased from commercial locations already in your state.
In the U.S., transporting any part of the cannabis plant over state lines is illegal. This applies to seeds and clones and, technically, even to tissue samples.
How to germinate cannabis seeds
Germinating seeds requires a dark environment that is around 70 degrees. There are many ways to germinate seeds (in soil, in a wet paper towel, in starter plugs) You can also sow them directly into soil in a garden or container, as long as the soil is light and fluffy, so the roots can easily grow down and the stalk can break through the soil. Plant the seeds about 1/4- to 1/2-inch deep and cover them loosely with soil.
Most importantly, seeds need a moist environment; they won’t germinate if they get too dry. You can use a heat mat to increase the success of germination in colder climates.
How to transplant marijuana plants
When transplanting any plant, whether it started from seed or a clone, handle it gently, being very careful not to damage the roots. Center the plant in the pot, and plant it deep enough to cover the root ball completely in soil. If the plant is root bound, you can gently tease the roots apart to encourage outward growth.
Pack your soil or other grow medium down around the roots well enough to support the plant while new roots grow, but not so tight that the soil restricts outward root growth. Water the soil around the roots.
About This Article
This article is from the book:
About the book authors:
Kim Ronkin Casey has been a communications professional for more than 20 years and recently took a year-long leap into the world of cannabis as the communications manager for one of the leading dispensaries in North America. She now consults for companies in the industry on internal and external communications. Joe Kraynak is a professional writer who has contributed to numerous For Dummies books.
Preserving Cannabis Genetics: How to Collect and Store Seeds and Pollen
Sometimes a grower has to move on from a certain strain. Maybe you’ve been growing the same strain for a long time and it no longer makes as much money as it used to, or maybe you just want to mix it up and start growing something else and don’t have the space for it.
It can be bittersweet saying goodbye to old genetics, but sometimes it’s unavoidable. You can take clones or keep a mother plant, but those aren’t ideal because they require a lot of care and maintenance, especially if they aren’t producing flower.
Fortunately, preserving genetics for long-term storage is easy and will save time, money, and space in the long run. Through seed and pollen collection, you can hang onto those genetics that you can’t fully get rid of and safely store them for future use.
The Benefits of Long-Term Storage
Cannabis genetics are often sourced from external companies and organizations such as nurseries and seed banks. For the individual grower, saving seeds and pollen removes this reliance on external companies. This is especially true with pollen, as very few (if any) companies offer pollen to the public.
Saving space is a big reason to consider long-term storage of seeds and pollen. Mother plants lay dormant in a vegetative state and take up lots of space. Maintaining this extra space is time-consuming and takes extra resources like water, soil, nutrients, light, and other costly elements, all for something that doesn’t produce flower. Even keeping clones of an old strain around will take up space and resources.
A grower or breeder can also freeze the progress of a breeding project for months or years without losing any of the long, hard work. Endeavors such as phenotype hunting and maintaining desired mothers for breeding and cloning can all be saved for later through genetic preservation. This process is like backing up work on a hard drive.
How to Collect Seeds
Cannabis is for the most part dioecious, meaning that the male and female reproductive organs exist on two separate plants (although hermaphroditic plants do occur). It is also a wind-pollinated plant, so pollen must be transferred from a male stamen to a female pistil via the air in order for pollination to occur and seeds to form.
A female cannabis plant that has received pollen from a male will produce many seeds over the course of its maturation cycle. Upon senescence, when the female plant is fully mature and ready for harvest, its seeds will be ready for stratification and collection.
To collect seeds, it’s important to wait until they are fully mature and ready for harvest. Cannabis with seeds takes longer to mature than cannabis that only produces flower.
To tell if a seed is mature, take a look at its shape and color. Premature seeds will be small and light in color, taking on a beige hue. Fully mature cannabis seeds are more full in shape and size and have a much darker brown hue, sometimes accented by black tiger stripes.
Deseeding cannabis can be done by hand or machine. This process typically takes place after the plant has been dried for one to two weeks after harvest. This way, seeds will have reached their maximum maturity and plant material will be brittle enough to break apart with minimal effort.
When collecting seed by hand, use a fine screen to help catch trichomes that will break off during the process. This material is valuable and it would be a shame to waste.
To release the seeds, simply break up the dried buds over a screen and they will fall out. You can release the seeds en masse by rubbing the flower between your fingers and lightly breaking it apart.
Separate or sift seeds over the screen to remove any unwanted plant matter from the seeds themselves. Brush off the seeds—they should be completely free of any remaining plant material such as leaves, stem, or trichomes, as these elements put seeds at a higher risk for contamination and spoilage during long-term storage.
Male cannabis plants will produce pollen several weeks into their flowering cycle. Once their pollen sacs have opened up and released, the plant will begin to senesce and eventually die. It is important to collect pollen right as the sacs are beginning to open up, as this is the time pollen is most viable.
The best way to harvest pollen for storage is to remove an entire male flower cluster and place it in a sealed storage container for several days. After the cluster has dried, place it over a micron screen with parchment or wax paper underneath, and give it a light shake. This will allow the pollen to separate from any remaining plant matter and fall through the screen and onto the wax paper.
Moisture is a death sentence for pollen viability. Because of this, many breeders opt to mix flour into their pollen at a ratio of 4:1 (flour to pollen) when storing it long-term. This additional step will help keep pollen dry for a longer period of time.
Seed and Pollen Storage
Long-term storage requirements for seeds and pollen are similar. Both require cool, dark, dry, and oxygen-deprived environments for optimal preservation.
When storing seeds, place them in an air-sealed container that doesn’t have any light leaks. Film canisters, medicine bottles (non-translucent), and any sealable storage jar will work fine. The idea is to reduce the amount of oxygen present in the storage space as much as possible. You can also add uncooked rice to the storage container, which acts as an absorbent, to reduce moisture content.
For a cool environment, store seeds in either the refrigerator or freezer. Seeds need a consistent temperature without fluctuation to remain dormant long-term.
As mentioned above, the best way to reduce moisture in pollen is to mix it with flour. For long-term storage, it can be kept in a sealed vial or freezer bag. You can keep it in the refrigerator or freezer, though for optimal long-term storage, the colder the better.
The Shelf Life of Seeds and Pollen
You can expect cannabis seeds that have been sealed and properly stored to last for several years, and in many cases, longer. Seeds may be dormant, but they are still alive. Over enough time, they will lose their viability.
It’s important to continually practice germination testing to be sure your stored seeds haven’t lost all viability. To test this, periodically plant a seed and document its ability to germinate.
Fresh seeds should have a germination rate close to a 100%, whereas older seeds will see a significant drop off over time in their ability to germinate.
Out in the open, pollen may be viable for one or two weeks under normal conditions. However, when frozen and sealed, it can last up to a year and even longer. Pollen is more unstable than seed and even under the most optimal conditions, it isn’t expected to have as long of a shelf life.
For both seeds and pollen that have been frozen long-term, it’s important to avoid defrosting until they are ready to be used. Fluctuations in temperature and moisture content will quickly destroy their viability, so maintain a steady temperature for as long as possible. Warming and freezing multiple times isn’t good.
When it comes time to use frozen seeds, remove them from their container and let them sit out on a dry surface for several hours. Letting the seeds reach room temperature will help ensure a successful germination.
Pollen should also be placed at room temperature before using. Since pollen can be much messier to handle, it’s best to carefully transfer a sample from its long-term storage container to a fresh container before using it to pollinate a plant. This way, you don’t have to use all of the pollen and saved pollen can go back in the freezer with minimal exposure to warm air.