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how to make feminized cannabis seeds

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

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 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.

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

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

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 by the presence of hermaphrodite plants in their marijuana crops. In this post we will tell you how to detect them and how to proceed if you find a hermaphrodite cannabis plant in your growing space. We will also discuss the causes of 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.

At this point in time, we all know what feminised seeds are, although even today there is some confusion regarding the most common methods to produce

How are feminized seeds made?

Image of a purple seed emerging from many others in black and white

Feminized seeds were a revolution when they came on the market more than 15 years ago. Nowadays they represent more than 75% of the worldwide sales of marijuana seeds, and this is no coincidence, as during this time they have proven to be just as good, or even better, than regular seeds. In this article we will see different ways to create 100% feminine seeds, are you in?👉

🔥 Is it easy to create feminized marijuana seeds?

If you have ever wondered how to feminize a cannabis seed and you imagined it was a difficult task I’ll tell you it wasn’t, creating a good regular variety can be as complicated as producing female cannabis seeds, because the greatest difficulty is in finding parents who transmit their best qualities to the offspring.

If you have already accomplished this step and your only concern is to know how to extract feminized seeds from a cannabis plant, I am going to explain it to you briefly.✍

Image where you can see the thin pollen produced by a reversed plant falling on female cannabis flowers*

🎯 How to make feminized seeds with STS step by step

  1. Prepare STS (Silver Thiosulphate), mixing silver nitrate with sodium sulphate.
  2. Spray the STS on the plants that we want to reverse their sex, these will act as “male” in pollination.
  3. Change the photoperiod to flowering and repeat the spray application of STS one week later and again 15 days after the first time.
  4. After the third application change the photoperiod of the receptors that will act as female during pollination, this will be the last application of STS, after the second one we already inhibit the production of ethylene, which causes the plant to flower as male instead of female.
  5. About 25 days after putting the receptors in bloom they will begin to be at their best to be pollinated, depending on the variety, this will happen at the time when the reversed ones start to release pollen.
  6. Pollinate for 2 or 3 weeks if you want to get a lot of seeds, if you want to get few and take advantage of the rest of buds to consume you can do a located pollination on a single branch.
  7. After the last pollen intake by the females it is time to ripen the feminized seeds, it is very simple, we only have to feed the plants for 30 days more as when we cultivate to produce flowers.

Requirements for parental selection

The females chosen to be reverted to male have to undergo a number of tests to prove that they are suitable for reversion. These tests are based on the resistance and sexual purity of the selected specimens and basically they try to induce different types of stress. Only plants that stay fully female will pass the test and then they can be considered good breeding tools.

When we choose the varieties we want to cross we have to look at the desirable qualities, such as taste, production, effect, speed, and so on. But it must be clear that these features are only useful if they are transmitted to the progeny, a good phenotype is only a good phenotype if its qualities are not transferred to its descendants. On the other hand, if it transmits those qualities, it can also be considered a good breeding tool.

Photograph of a hermaphrodite marijuana bud where you can see both male and female flowers*

🧐 Are there other ways to produce feminized cannabis seeds?

Yes, there are, although not as effective and reliable as with STS, so we do not recommend them. But if you want to know other ways to make 100% feminine seeds of your favorite weed I’ll tell you. First of all you have to understand that all techniques are based on stressing a female plant to revert its sex to male, so it can produce flowers with which it can pollinate another female.

The first feminized seeds on the market were made by naturally stressing a female to pull out male flowers with pollen. This is not a good method, since plants that revert under natural stress can easily transmit this trait to their offspring. It often happened that those feminized strains were hermaphrodites, so natural stress is not a good way to reverse cannabis females.

The most common technique used to cause stress to female plants was known as “Light Poisoningor light stress. It’s easy, you just have to use irregular photoperiods, or often interrupt the night cycle of female cannabis plants during flowering.

⚠️ What is Rodelization?

It is another stress process, in this case due to over-ripe, i.e. not harvesting in time or lengthening the flowering cycle of a female cannabis plant to produce male flowers. This method is not very good because of the small amount of pollen that is created, it is not worth it if you want to make many feminized seeds.

This is something they do naturally as a way of perpetuating the species. When a female guesses she’s going to die and hasn’t been pollinated, she spontaneously generates fertile male flowers to self-pollinate and continue with the lineage.

⛳ Making feminized seeds with colloidal silver

The technique for producing feminized marijuana seeds with colloidal silver is based on the same theory as the STS one. Both use silver to inhibit the production of ethylene in a female plant, and that this specimen blooms as a male and releases pollen.

With colloidal silver there are also several spray applications during the night cycle in some of the first days of the flowering cycle. The silver used in this method, or in the STS technique, is a heavy metal that can be toxic. It is therefore important to cover the substrate so that possible droplets from the sprayed leaves do not wet the soil.

👌 How are feminized seeds made with gibberellic acid?

This way of producing 100% feminine seeds with gibberellic acid was published by the great Robert Connell Clarke in his magnificent book “Marijuana Botany”. With this method several applications must be done during a period of 5 or 7 days. The biggest problem with gibberellic acid technique is its instability, since a very precise dose is needed to be effective, around 100 PPM. It is also common that each variety may need a different dose, so not many people use it nowadays.

👾 Conclusions

If you want to make your own feminized seeds, I recommend you the STS method, it is the most used for some reason. You have to be careful not to inhale the gases it produces, protecting yourself with a mask, safety goggles and gloves for its manipulation, but it is the most effective technique. It is surprising to see an elite clone bloom as a male after having grown it many times as a female, I invite you to try it.

If you liked this article you can help us if you share it, that way if a friend of yours is curious about how to get feminized seeds he/she can see it here.🤪

Do you want to know the best way to produce feminized cannabis seeds? ✨ In this article we will show you ❤️ See how easy you can create your 100% feminine.