How to Make Feminized Marijuana Seeds

cannabis seeds
November 05, 2020

On the modern cannabis seed market, feminized seeds are arguably the most popular choice among growers. Here’s how to make feminized marijuana seeds using proven methods.

Why would you even consider making feminized marijuana seeds? One reason is availability. How can you grow a strain you’ve come to love or need if the seed banks do not have its seeds on stock?

How Feminized Marijuana Seeds Are Made

There is no one way to create feminized seeds, and that is a good thing – you have choices. As someone doing this for the first time, you want to go with rodelization – a 100% beginner-friendly natural method. As you gain more experience, you may also want to try using chemical agents such as colloidal silver or sodium thiosulfate – the preferred method by professionals.

Each method has pros and cons. To know which technique you can consider using, then assess your needs, preferences, and budget, as well as the amount of time and effort you’re willing to invest.

To understand how the process of feminizing seeds works, you need to wrap your head around three concepts.

I. Sex chromosomes

Chromosomes determine the sex of cannabis plants. Females are homogametic and have XX chromosomes. Males, on the other hand, are heterogametic with two different sex chromosomes – XY.

Once a male plant (XY) pollinates a female (XX), you get a 1:1 male-to-female ratio. Simply put, half of the seeds produced will be males, while the remaining half will consist of females.

By forcing a female plant to produce pollen, and fertilizing another female, you only get female seeds. That is because only female sex chromosomes – XX – are involved.

II. Pollen production

Typically, only male plants produce pollen. When making feminized seeds, though, the goal is to induce the female to develop pollen sacs. Eventually, that pollen is collected and used to pollinate another female plant, which then produces the seeds.

III. Ethylene production

Ethylene is an aging hormone present in cannabis plants. It plays a crucial role in many processes, including flowering, chlorophyll loss, weakening of stems, and shedding of various plant parts, among others. More importantly, it also regulates the sex expression of plants. And by lowering the level of ethylene, the females are forced to grow male flowers.

Inhibiting ethylene production, in essence, is what these proven methods aim to do.

Option 1: Rodelization Method

Rodelization is an all-natural way of creating feminized seeds. It involves forcing the female plants to develop the stamen or the male pollen sac.

Being seedless – also called sensimilla – is an unnatural state for female cannabis plants. In the wild, when a plant remains unfertilized as the end of its life cycle approaches, it will develop male organs so it can self-pollinate to produce seeds. This is a last-ditch effort to propagate its genetics, ensuring the survival of the species.

In the grow room, you can replicate this condition by delaying the harvest period. After 2-3 weeks, the female plants will produce stamens. As long as they have never been exposed to the pollen of males, rest assured that the seeds produced will be feminized.

Rodelization is not only easy to do but also cheap. After all, it does not involve the use of chemicals and other special materials. All you need is extra time. This makes it ideal for home growers and those creating feminized seeds for the first time.

This technique, though, can be hit-or-miss. There is simply no guarantee that a plant will self-pollinate if you don’t harvest on time. And if it does, the pollen produced is much less compared to other methods. Also, its success may depend on the genetic makeup of the plant, as some strains will naturally produce more seeds than others.

Plants grown from this type of feminized seeds have hermaphroditic tendencies, so you’ll have to be vigilant.

Option 2: Colloidal Silver Method

Colloidal silver refers to the tiny silver particles suspended in a liquid. While often touted as a dietary supplement and even a cure-all, it has no proven health benefits. Worse, it can cause serious side effects.

At any rate, one thing is for sure. Colloidal silver is a godsend for cannabis growers who want to produce feminized seeds. Once applied, the silver ions inhibit ethylene production, forcing the female plants to grow male pollen sacs.

Colloidal silver is widely available and comes in varying strengths. 30 ppm offers the best results. 15 ppm will also do, but any less than that will produce little usable pollen. Alternatively, you can buy a generator and make your own solution. But for convenience, just go for a pre-made one.

Transfer the colloidal silver solution in an opaque spray bottle. Ensure that youkeep it away from light to preserve its potency. If the liquid has already turned dark gray, then it is no longer effective.

A warning. Plants that have been treated with colloidal silver are not suitable for use or consumption. You’ll have to toss them out after harvesting the pollen. As a workaround, some growers only spray on certain parts of the plant. You don’t want to risk it, though.

But, rest assured that the seeds produced are 100% safe.

How to make feminized marijuana seeds using colloidal silver:

The best time to use colloidal silver is 1-2 days before switching to the flowering period. Spray on the bud sites until they are fully drenched.

Continue misting the plants daily for the next 10-14 days – or until the male flowers appear. When this happens, keep the plant well-isolated from the rest of the females. The last thing you want is accidental pollination.

Option 3: Silver Thiosulfate Solution Method

The use of silver thiosulfate – STS for short – to make feminized seeds is a fairly recent technique. But, it is fast becoming the go-to option for many growers. After all, it is highly effective and guarantees that the seeds will be 100% feminized.

STS is a solution containing sodium thiosulphate, silver nitrate, and distilled water. When applied on the bud site, it halts ethylene production, forcing the female plant to develop male flowers.

Like colloidal silver, a plant that has been sprayed with STS is no longer viable for consumption. Make sure to discard it after collecting the pollen.

How to make feminized marijuana seeds using STS:

Creating feminized seeds using this method is straightforward and only takes about 20 minutes – or even less. Also, the main ingredients required – sodium thiosulfate and silver nitrate – can easily be bought online or in any local pharmacy.

STS is prepared as two separate solutions – A and B. The first one consists of distilled water and silver nitrate. And the second one consists of distilled water and sodium thiosulphate. They are placed in airtight, light-proof glass bottles, then kept inside the fridge. With proper storage, they may last for several years without going bad.

Before application, solutions A and B are combined, then diluted with water. Take note that the resulting solution has a short lifespan of about 15 days and loses potency over time. As such, try to prepare the STS solution as needed. The freshest possible batch can also help increase the success of the produce.

A word of caution:

Always wear protective equipment – such as a face mask, goggles, gloves – when handling the solutions. That is because STS can cause severe skin burns and damage the eyes. It is also toxic when inhaled.

Do not use metallic objects at any point in the procedure. Metal can affect the composition of STS, as well as reduce its efficiency. For best results, stick only to glass and plastic materials.

Gathering the supplies:

Before getting started, prepare all the materials that you’ll need so you can work without interruptions.

  • Silver nitrate
  • Sodium thiosulfate (anhydrous or pentahydrate)
  • Distilled or reverse osmosis (RO) water
  • Glass or plastic measuring cup
  • Digital scale
  • Plastic spoon
  • Two 500 ml brown glass bottles with lid
  • Two 60 cc syringe
  • 1000 ml brown glass sprayer bottle
  • Dishwashing liquid

Preparing solution A:

Start by adding half a liter of distilled or RO water into a measuring cup. If available, opt for Pyrex.

Add 0.5 grams of silver nitrate crystals into the water. Use a digital scale for accurate measurement. Stir the mix using a plastic spoon. Keep at it until the crystals finally dissolve. This should only take a few seconds.

After mixing, transfer the solution to a 500 ml brown glass bottle. Screw the lid tightly. Label the container “Solution A – Silver Nitrate.” You can refrigerate it for the time being.

Wash and thoroughly clean all the tools you used. Wipe them dry. You’ll need them for the next step.

Preparing solution B:

Pour half a liter of distilled or RO water into a clean glass or plastic measuring cup.

Measure 2.5 grams of sodium thiosulfate anhydrous. If using sodium thiosulfate pentahydrate, go for 3.9 grams. After obtaining the exact amount, add it into the cup of distilled water. Stir until it dissolves. This should take less than a minute.

Transfer the solution to a 500 ml brown glass bottle. Cover it tightly with the lid. Label the container “Solution B – Sodium Thiosulfate.” If you don’t plan on making the STS solution yet, keep it in the fridge.

Once done, rinse and clean all the materials you used.

Mixing STS:

Once ready to apply STS to the plants, take out the solutions from the fridge. It is time to combine and dilute them. As a rule of thumb, always add Solution B – the sodium thiosulfate solution – into the container first before pouring in Solution A – the silver nitrate solution.

Use a syringe to measure 50 ml of Solution B. Add it into a clean measuring cup. Grab the other syringe. This time, use it to draw 50 ml of Solution A.

Start whisking Solution B with a plastic spoon. As you do, slowly add Solution A into the measuring cup. This should take around 30 seconds.

After stirring, transfer the STS solution into the brown glass sprayer bottle. Fill it with 800 ml of distilled or RO water. Add about 6 to 10 drops of dishwashing liquid into the mix.

Cover the bottle with the sprayer top. Secure it tightly. Shake the solution well.

To test if the consistency of the blend is just right, spritz the STS solution on a leaf. It should stick onto the leaf surface – not form a blob or roll down. If so, add a couple more drops of dish soap. Shake it well before repeating the test.

The final solution – which has about 1:9 STS-to-water ratio – can be used on the plants every five days for a month. Consider covering the spray bottle with a black garbage bag to prolong the shelf life.

Applying STS:

Start spraying on the plants five days before shifting to the flowering stage. Remember, wait for another five days before misting again. By the second session, you should have flipped the switch already. Keep spraying every five days.

Make sure to protect the root zone before every application. Do this by covering the base of the cannabis plant with newspaper or other similar material. Remove it only when the STS solution has evaporated or dried out.

It is best to apply the solution right before turning off the grow lights. Don’t forget to switch off the fans, too. Separate the plants you’ll be using from the rest. You don’t want to contaminate the other females.

When spraying, focus on the cannabis plant’s leaves. Ensure that it is fully coated and dripping. Wait for it to dry before returning the plant alongside its sisters.

Watch out for any symptoms of yellowing or burning. It indicates that the solution is too strong and still needs to be diluted. If so, add about 1/3 cup of distilled or RO water into the mix. Discard some of the STS if there is not enough room on the bottle.

How to Collect Pollen

Timing is critical when collecting the pollen. Do it too late, and the sacs may have erupted already, pollinating the rest of the females. Monitoring the plants is key. In particular, wait until the pollen sacs swell and start splitting open. The leaves protecting the pollen may crack as well.

The easiest method is to carefully remove all the sacs. Keep them in a sealed container for a few days to let them dry.

After the drying period, dump the sacs on top of a micron sheet. Position parchment paper underneath. Shake the setup well. The pollen should pass through the filter onto the paper.

Alternatively, you can also place the sacs in a resealable bag. Shake it vigorously so that the pollen may spill out. You may have to slice open some of it. Afterward, pry out each sac, leaving the golden powder behind.

How to Store Pollen

Moisture is always something to avoid when storing cannabis. The same goes for pollen. Remember, if it gets wet, it is practically useless.

By adding cooking flour to the pollen, you can prevent moisture buildup. Stick to a 3:1 flour-to-pollen ratio.

After adding, wrap the paper around the pollen-flour mixture. Place it inside an opaque, airtight bottle. Keep the container as small as possible to reduce oxygen exposure – another factor that can degrade the pollen. Consider adding some uncooked rice to fill the space, lowering the volume of free air.

Place the bottle in one or two resealable bags before storing it inside the fridge for a few days. You can also keep it in the freezer for up to a year. Either way, make sure to avoid temperature fluctuations.

How to Pollinate the Plants

A female cannabis plant that is 2-3 weeks into the flowering stage is ready for pollination. There are a couple of ways to do so. It depends on how many seeds you want to produce.

First, you can use a paintbrush with soft bristles to dust the pollen onto the buds and the branches. If you want, you can pollinate the entire plant. Since the trichomes are sticky, the spores will glue onto them easily. Hence, you may have to dip the brush onto the pollen container a few times as you apply.

If you want to harvest a lot of seeds, place the pollen in a bag. Put it over a branch – or even the whole plant. Secure the loose ends of the bag with a zip-tie or a string, then shake well. Let it sit for 24 hours. Needless to say, for this method, you’ll also need an abundant pollen stash.

Typically, it takes about six weeks before the plant develops seeds. While waiting, make sure to provide optimal growing conditions.

When and How to Harvest Feminized Marijuana Seeds

In general, cannabis seeds ripen within 4-6 weeks upon pollination. By then, the seed should be structurally sound and appear tan or dark brown. You may also see some black or light tiger stripes on the outer shell. If not, let the seeds develop for a bit more until they sport the desired appearance.

Harvesting mature seeds is a piece of cake. Simply remove the fertilized flowers. Once dried, crush the buds over a fine screen. The seeds should drop through the mesh. You can also gently rub the flower between the fingers to release the seeds.

If you want to see some results from using colloidal silver in the cannabis breeding process, check out this Homegrown Forum post on colloidal silver.