How to make feminised cannabis seeds

Until the 1990s, any cannabis cultivator was aware that, at some point, they had to separate the male and female plants if they didn't want the first ones to pollinate the latter, which results in plants completely full of seeds. However, those were the days when pioneering seed banks like Dutch Passion were revolutionizing the cannabis scene with the birth of the first feminized cannabis strains, or in other words, seeds that only develop into female plants. At the beginning of the 20th century, many seeds banks were offering this type of seeds, feminized versions of classics strains that had been cultivated during many years as regular plants.

We are sure that by now you?d probably have grown some feminized seeds, maybe even though you are a purist and the fiercest defender of regular seeds. But... do you know where feminized seeds come from? Are you familiar with the processes used by both breeders and growers to obtain them? In this article we explain everything!

Feminized cannabis seeds quality control
Feminized cannabis seeds quality control

Advantages of growing feminised seeds

Indeed, the advent of feminized seeds brought about a genuine revolution within the cannabis sector. Growers were now sure that all their plants would be females, without the need to differentiate between male and female plants or having to remove the males before they could ruin the crops, which offers a number of benefits of significant importance:

  • Space and resources saving: no more growing plants which eventually will be removed for being males.
  • Reliability: it?s not that most plants are female, or that they are genetically more likely to produce female plants. The plants grown from feminized seeds have only female chromosomes (XX), therefore this method is 99% reliable.
  • Sinsemilla plants: by not having males in the grow room, your female plants won't be pollinated, so they won't produce any seeds during the flowering period (something that every cultivator wants, unless they want to obtain seeds)

These advantages were of great interest for the growers, and soon feminised seeds accounted for a large portion of the seeds available in the market. In addition, being able to use only female plants (generally known and selected clones) to produce seeds had another great advantage for seed producers and breeders of new varieties: they no longer need to keep males in their gene pools! And not only that... from that moment on, any female plant they could get their hands on could be used as a male to pollinate other plants, thus exponentially increasing the possibilities of creating new crosses.

Outstanding Orange Candy feminized from Philosopher Seeds
Outstanding Orange Candy feminised from Philosopher Seeds

It is not surprising, therefore, that at present, feminized seeds represent virtually all the seeds in the market, since they offer a number of significant advantages for both professional and home growers and breeders, for photoperiod and autoflowering plants. The main disadvantage of this method is a well known and hotly debated issue: the growers who buy this type of seeds cannot produce their own seeds in the absence of male plants, so the only way they can manage it it?s using the same process to obtain this type of seeds. But... what are these processes and what are they based on?

Female crosses: feminised cannabis seeds are born

As we?ve already mentioned, feminized seeds are the result of a process that reverses the sex of a female plant, that is, she is forced to produce male flowers. This way, and once into flowering, the female chosen will start to develop what we know as male flowers (stamens and anthers), which, just like male plants, will release the pollen that will pollinate the female plants. What is then the difference between a male plant and a reverted female plant?

The sex of cannabis plants is determined in the same way as ours, through the so-called sex chromosomes or genosomes. Male plants have a couple of different sex chromosomes called "XY" or heterogametic, while female plants have two chromosomes called "XX" or homogametic. When crossing a male (XY) with a female (XX), we will obtain around half of the plants of each type in their offspring. In other words, when a breeder uses a male and a female plant, the seeds produced by them will be approximately 50% males and 50% females.

After this explanation, many of you will have already figured out that if we cross two female plants (reversing the sex of one of them to force it to produce pollen), the result will be seeds that will produce female plants, as there are only female sex chromosomes in the equation. If crossing XY with XX produced 50% of each class (male and female), crossing XX with XX will produce plants that only exhibit chromosomes XX, that is to say, female plants. No matter how many times we "transform" a female plant into a male plant, we won´t be changing their genetic composition, which will still be female or XX. This way, the pollen produced by this plant will pass down female sex chromosomes exclusively.

Feminized seeds indoor grow, 100% females plants
Feminised seeds grown indoors, 100% female plants

As you can see, and although we normally use the expression "reversing the plant sex", that is not exactly what is done, because the sex chromosomes of the female plant (XX) have not changed, even if we managed to produce male flowers. This "sex change" of female plants can be achieved in a number of ways, but usually with the same goal: to reduce the level of ethylene in plant tissues and/or inhibit the ethylene action, which makes the plant develop male flowers on entering the flowering period, as if it were a male from regular seeds. This is because ethylene is a natural regulator of the sex expression in plants!

Let's see now the most popular ways to reverse the sex of a female plant in order to produce feminized seeds.

Methods used to produce feminized cannabis seeds

There are several ways to secure that a female plant produces pollen, and almost all of them require some type of chemical that is often sprayed on the plant. Once sprinkled with the chosen product and under a flowering photoperiod, the plant will flower normally, but as a male instead of female, producing 'feminized' pollen (which only contains chromosomes XX) that can be used to pollinate other females in order to produce seeds. These are some of the most commonly used techniques:

Stress or rodelization

One of the first methods used to obtain seeds that produce female plants was stress or rodelization. There are several ways to stress the cannabis plants to make sure they develop male flowers, such as through temperature, nutrition, photoperiod, and pH. However, supporters of this technique often prefer something as simple as delaying the harvest 2-3 weeks in order to force the plants to develop a few male flowers without stressing them as much as with any of the other methods we have mentioned.

Although this action will produce far less pollen than other techniques like STS, it will be enough to obtain a handful of seeds for the domestic growers to try to create their own feminized crosses. Also, the great advantage of this technique is that is 100% natural, and it doesn´t use any chemicals. It is an excellent alternative for anyone who just wants a few seeds and wishes to keep it simple without any formulas or laboratory products. However, bear in mind that this is the only method listed in this post that may produce some plants with hermaphroditic traits.

Male flower produced by rodelization
Male flower produced by rodelization

STS or silver thiosulfate solution

Without any doubt, one of the most commonly used methods for both producers and seed banks. This is a solution made of distilled water, silver nitrate and sodium thiosulphate (sometimes called sodium hyposulphite) that, after being sprayed on the female plants, inhibits their ethylene action resulting in the formation of male flowers once flowering has been induced. STS is relatively easy to prepare, although its lifespan after combining the two components is quite limited, barely a few days as long as it´s well preserved (in a dark and cool place).

It is important to mention that you must not consume any part of the plants sprayed with this type of product, although that would be weird, as the plants have "become" males and won´t produce any buds. Nevertheless, you shouldn't use the reverted plants to make resin extracts; the best thing is to discard them after harvesting the pollen. Both components, sodium thiosulphate and silver nitrate, are also used for photo-development.

Colloidal silver

This is another way to revert the sex of the plants, but this time using a solution made of 30ppm colloidal silver (that you can easily find in many pharmacies and also online) and distilled water. The solution must be applied for a few days until the plant starts producing male flowers, something that it´s not necessary with STS, where in most cases one single application is enough.

Colloidal silver is formed by electrically charged silver nanoparticles and has antibacterial and antifungal properties. This product was introduced in the market in 1980 for therapeutic use. However, as with STS, you should get rid of the sprayed plants once their pollen is harvested, as colloidal silver is absorbed systemically by the plant and remains in its tissues.

This sativa plant treated with STS started flowering as a female but soon developed male flowers
This sativa plant treated with STS started flowering as a female but soon developed male flowers

Silver nitrate

This is a method researched by Mohan Ram, who also conducted extensive investigations on plant sex reversal with STS. According to his findings, sodium thiosulphate (STS) is more effective in producing male flowers and viable pollen in female plants. Probably because of this, silver nitrate is mixed with sodium thiosulphate, instead of using it in isolation.

Gibberellic acid

Gibberellins are plant hormones that help regulate various processes related to the development of the plants. There are several types of gibberellins available in the market, although the most common and effective is gibberellic acid or GA3 (Gibberellin GA3). This product is used in a very similar way to colloidal silver, sprayed on the plants during several days before switching the photoperiod over to flowering.

It is worth stating that one of the side effects of gibberellic acid is a significant stretching of the treated parts of the plant, so don't be surprised if this happens to your plants! The recommended dose to achieve the best results is approximately 100ppm.

Urban legends and lies about feminized seeds

Despite the fact that, after two decades of cannabis cultivation, many of the false myths surrounding feminized seeds have been debunked, from time to time we still hear some arguments like the ones shown below. As is often the case, many of these stories are spread by people who have never grown this type of seeds or have none or very limited experience with them. Ignorance is always a bad thing, and that's why we want to emphasize several points in relation to feminized seeds and the myths that often go with them; myths such as the following:

Feminized seeds produce hermaphrodite plants:

The problem with monoecious hermaphrodite plants has more to do with the parents used (and if they exhibit any hermaphrodite trait) rather than with the type of seeds produced. If to create a feminized seed you use a female plant with a tendency to produce male flowers, part of its offspring will likely inherit that characteristic, whether the said female plant is used as a pollen donor (after reversing its sex) or as a recipient of pollen (letting it flowering as usual).  Yet the same thing happens when producing regular seeds: if the male or female parents are not stable in this respect, neither will be their offspring (or at least part of it).

Marijuana and hermaphroditism

Many growers have been surprised to have hermaphroditic cannabis plants in their crops. In this post we explain how to detect them and what to do in the event that a hermaphrodite plant appears in your crop, as well as what are the causes that usually accompany this hermaphroditism.

Feminized seeds produce mutant plants:

Nothing could be further from the truth. It is true that sometimes some plants develop weird traits or mutations, although this also happens with regular seeds. Unfortunately, there seems to be not enough studies comparing the ratio of specimens with mutations of one or other type of seeds; however, given the millions of feminized seeds that have been germinated in the last 20 years, if mutations would pose a problem, the quantity of feminized seeds sold would certainly not be so high, and this would be a "public security" issue within the cannabis sector, both for the growers and the producers of the seeds.

Feminized seeds have chemicals:

This is another lie that some people believe. As it's been mentioned before, a female plant is sprayed with some chemicals in order to inhibit its ethylene action. After a few weeks of this and once in the flowering period, the plant will produce male flowers and pollen, which will be harvested to pollinate the female plants designated to produce seeds. Once the seeds are formed, they are collected and packed immediately, so they don't come into contact with any chemicals or the plants that produce seeds, nor, of course, with the seeds themselves. Also, to produce cannabis seeds, you normally need two separated indoor cultivation areas, one for the reverted plants (treated females) and the other for the females to be fertilized to produce the seeds, so the latter can?t get "contaminated" with any chemicals.

Feminized seeds are GMOs:

Once again, this is a false statement. We have already pointed out that by using these sex reversal techniques we inhibit the ethylene action in the female plant, and under no circumstances the seeds (or plants) are genetically modified. The sex chromosomes of the female plant converted into a male plant are still female (XX), nothing has changed at a genetic level.

We hope you found this article interesting; even today, many people are still unaware of the intriguing process behind this type of cannabis seeds. Do not hesitate to leave your comments; we will be delighted to answer them.



  • Marijuana Botany, Robert C. Clarke
  • The Cannabis breeder's Bible, Greg Green
  • The Cannabis grow Bible, Greg Green
  • Breed your own vegetable varieties, Carol Deppe
  • Induction of Fertile Male Flowers in Genetically Female Cannabis sativa Plants by Silver Nitrate and Silver Thiosulphate Anionic Complex, Mohan Ram, Sett R.

The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.

Comments in “How to make feminised cannabis seeds” (13)


Morgster 2023-09-07
Can you use the colloidal silver method in a greenhouse? And also what is the ratio of colloidal silver to distilled water thanks


Morgster 2023-09-07
Can you use the colloidal silver method in a greenhouse?


Ray 2023-02-15
Hi can you use Silver and GA3 together

Alchimia Staff

Dani Alchimia 2023-03-01
Hi Ray, First of all, sorry for the late reply. Honestly, I haven't tried and don't know whether it would work or not. But most people I know using Silver do not use GA3 at all. All the best!


Ken 2023-01-24
Can you apply silver colloidal to a female plant that it’s mother plant was feminized this would be a second generation feminizing

Alchimia Staff

Dani Alchimia 2023-01-26
Hi Ken, You can try it, most strains will reverse their sex no matter if they already come from feminized plants. Best!


Pgfb18 2022-09-20
how much solution to make GA3 is to apply to plants? to make autoflowering seeds? there is nowhere almost explaining how to make autoflowering feminized seeds

Alchimia Staff

Tim Alchimia 2022-09-20
Hi, thanks for your comment and question. As stated in the article, 100ppm (parts per million) is the recommended concentration of GA3 to achieve reversal. To make this, you'll need to mix 100mg (1/10 of a gram) of pure GA3 with 1 litre of distilled water. If the GA3 you have sourced isn't pure, you'll need to adjust the dilution to compensate, i.e. if it's GA3 with 50% purity, you'll need to use 200mg of it in 1 litre of water, and so on. Then you'll need to spray the target plant a number of times (sources vary from every day over ten days to only spraying a couple of times). It's worth pointing out that GA3 has been superseded by STS (Silver Thiosulphate Solution) which is what all commercial seed producers use to reverse females. Much of the reason for the clear lack of information available about these techniques is commercial interest - a breeder who has perfected his or her solution and application schedule for successfully reversing plants has little motivation to then release that precious data to the world as it could potentially threaten their business model. Another reason for the lack of clear instructions is that each cultivar will react differently to the treatment and a concentration of STS or GA3 that works really well on one plant may completely fail to get results on another different variety. It's best to experiment, take notes and find the ideal technique for the plants you want to reverse. I hope that helps. Best wishes and happy growing!


Art VandelayS 2022-06-09
Thnx a lot Tim... No, they were all female, normally. Their sexuality turned to hermaphrodite after GA3 application. So, if one of my reversed plants pollinates other reversed plant, their resulting seeds will be female?

Alchimia Staff

Tim Alchimia 2022-06-09
Hi Art, glad to be of help. Yes, that's correct, the seeds resulting from a reversed female pollinating another female will be feminised. This is because both parents only possess the X chromosome, meaning they cannot pass on any Y chromosomes to their offspring and therefore no males. Best wishes and happy growing!


Art VandelayS 2022-06-02
Hello... I practiced Gibberelic Acid on one of my plants, so many years ago. And All seeds were feminised. But i use this method for just 1 plant. Because of this, it breeded itself. I grow them later, and they are 100% female and have good uniformity. Now, i have 4 Green Poison F1 in my terrace. Last week, i started to use Gibberellic Acid on them. I can see GA3's effects in my plants. My question; if i put them together into the grow room, my final seeds will be full feminised? They are all hermaphrodites but... for example; if Plant A's male pollens breed Plant C's female flowers, Plant C's final seeds will be feminised or 50% Male / 50% Female??? Thanks a lot...

Alchimia Staff

Tim Alchimia 2022-06-07
Hi, thanks for your comment and question. There are a couple of things I don't quite understand. You say the 4 Green Poison F1 plants are all hermaphrodites, but do you mean that the GA3 is causing them to reverse sex or that they were already hermaphrodites before you applied the GA3? If the case is the latter, then I wouldn't recommend you make seeds with obvious hermaphrodites as these characteristics will most likely be carried on not the next generation. It's always best to eliminate the hermies from any breeding programme to ensure the best stability in the offspring. If, however, you mean that all of them have successfully produced male flowers after GA3 application, as desired, then there's no problem. The pollen from a reversed female (a female that has been treated with GA3 or STS to produce male flowers) will make female seeds 99.9% of the time. When you talk about Plant A's male pollen, do you mean it's a male plant or a reversed female? If it's a male then the resulting seeds will be (roughly) 50/50 male/female. If it's a reversed female, as explained above, the seeds will be female. I hope that helps, if I've misunderstood your question then please let me know. Best wishes and happy growing!


OwningYou 2022-04-01
You keep referring to pollen sacks on female plants as male flowers. This is false information. A true female plant can not and will not produce male flowers. A female plant can produce female pollen sacks. Male pollen sacks & female pollen sacks are two completely different things & look nothing alike.

Alchimia Staff

Tim Alchimia 2022-04-05
Hi, thanks for your comment. A female cannabis plant, when treated with STS, will produce male flowers that are indistinguishable from those produced by a regular male plant. Of course, a regular male will produce larger floral clusters and release more pollen than a reversed female, but the individual pollen sacks are, physiologically speaking, the same on a reversed female as they are on a regular male plant. There are always differences in the morphology of the flower clusters, but the pollen sacks themselves are exactly the same. Now, if we're talking about the pollen produced by these flowers then yes, it is indeed very different, with the reversed female pollen only containing the X chromosome while the regular male pollen carries both X and Y chromosomes. I hope that's helped to clear up any confusion. Best wishes and happy growing!


Buttersthecat 2020-11-17
Just there anything that can be used as an ethylene action catalyst? I'm just curious to see if anyone has ever tried changing the sex expression of a male plant. Wasn't sure if it was even possible, or what would happen if you did it.

Alchimia Staff

Tim Alchimia 2020-11-18
Hi and thanks for your comment and question. I believe that a PGR called Ethephon can be used to "feminise" or reverse male plants, although I have read that in many cases the resulting female flowers are not fertile, or that the resulting seed produced by these flowers is not fertile. Theoretically, if you only had clones of a male plant you could still produce seeds by reversing one to female flower expression and pollinating it with the other, un-feminised male. As I understand it, if it worked this would produce regular seeds, as both males would carry the X and Y chromosomes as opposed to reversed female pollen which only has two X chromosomes resulting in female seeds when used to pollinate a true female. I hope that helps, best wishes and happy growing!


captain kirk 2020-10-01
what are the amount of each item for the sts method. i am wanting to try to make fem. seeds. any help will be great. thanks

Alchimia Staff

Tim Alchimia 2020-10-02
Hi and thanks for your question. I'm afraid that the breeders we spoke with about this subject were all unwilling to reveal the exact formulas that they use for STS reversal, as each of them has spent a lot of time and money in perfecting their recipe. There are a few recipes available online that you can find by searching for "STS recipe", although you'll need to do some experimentation to make it suit the particular plants you're working with. Each plant will react slightly differently and some may need a less concentrated blend to avoid "burning" the plant upon application, while other plants may need a stronger concentration to trigger a reversal. Sorry that I'm unable to be more specific about this. All the best and happy growing!


ewrecc420 2020-07-12
I'm trying to make feminized seeds from a clone of a HUGE yielder.. I made the clone into a bit of a bonsai cluster fuck.. And sprayed one top with CS.. At beginning of flower it was producing pistils.. But im about 2 weeks (still spraying 2 - 3 times a day) and now Im seeing some balls.. Now, can I use the same pollen to pollinate the same plant that Im spraying CS to produce pollen? Sorry.. My exact question is.. Lol.. Can I have the seeds produce on the same plant the pollen was made from? All in one flower cycle? Also.. Will I need to backcross to have the desired traits?? Thanks in advance!

Alchimia Staff

Tim Alchimia 2020-07-13
Hi, thanks for the comment and question! Yes, you can certainly pollinate the same plant with feminised pollen in the same flower cycle. Even though the effects of the CS may mean the plant has some strange growth habits, it won't affect the developing seeds at all. To fix the traits I would select the examples that best represent what you want and either cross them to each other or use one of them to pollinate the original mother. A lot depends on the stability of the original genetics, a poly hybrid won't make it as easy to fix the traits as, say, an IBL. I hope that helps, best wishes and happy growing!


Fast Eddie 2020-06-16
Can you make FM seed outdoors

Alchimia Staff

Tim Alchimia 2020-06-17
Hi, thanks for the question. Yes, you can definitely make fem seeds outdoors, although you'll probably be best separating the plant that you want to reverse from all the others, just so there's no risk of any o the STS solution being sprayed on plants you want to pollinate to make the seeds. I hope that helps, best wishes and happy growing!


Eugene 2020-05-25
What method is the best, STS or colloidal silver? I never used STS method, but using colloidal silver sometimes I got no pollen on my hermy

Alchimia Staff

Tim Alchimia 2020-05-26
Hi Eugene, thanks for your question. All the breeders and seed makers that I know use STS without exception because it's way more reliable than colloidal silver for this purpose. The only real advantage of colloidal silver is its ready availability in health food shops while finding the ingredients for STS can sometimes be more of a challenge and mixing them must be done properly for it to work. I hope that helps, best wishes and happy growing!

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